Geochemical characteristics of the shale gas reservoirs in Guizhou Province, South China

Yuliang Mou; Peng Xia; Lijun Zhu; Yong Fu; Ke Wang; Lingyun Zhao; Chao Qin

doi:10.1016/j.arabjc.2024.105616

View/Download PDF

Buy Reprints

PDF

Translate this page into:

Review article

03 2024

:17;

105616

doi:

10.1016/j.arabjc.2024.105616

Geochemical characteristics of the shale gas reservoirs in Guizhou Province, South China

Yuliang Mou^{^a,^b}, Peng Xia^{^a,^b,^c,⁎}, Lijun Zhu^{^a,^b}, Yong Fu^{^a,^b}, Ke Wang^{^a,^b}, Lingyun Zhao^{^d,^e}, Chao Qin^{^a,^b}

a Resource and Environmental Engineering College, Guizhou University, Guiyang 550025, China

b Key Laboratory of Ministry of Education for Geological Resources and Environment, Guiyang 550025, China

c School of Geosciences, China University of Petroleum, Qingdao 266580, China

d Guizhou Academy of Petroleum Exploration and Development Engineering, Guiyang 550081, China

e Key Laboratory of Unconventional Natural Gas Evaluation and Development in Complex Tectonic Areas, Ministry of Natural Resources, Guiyang 550081, China

⁎Corresponding author. pxia@gzu.edu.cn (Peng Xia)

Received: 2023-10-22, Accepted: 2024-1-8,

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Abstract

The characteristics of prospective five shale gas reservoirs in Guizhou Province are significantly different.
Relationships among sedimentary environment, lithofacies, and reservoir properties can guide shale gas exploration and development.
Reservoir properties differ between the marine and the marine-continental transitional shale.

Abstract

We analyzed a large amount of published petrological, mineralogical, and geochemical data from the Niutitang, Wufeng-Longmaxi, Dawuba, Liangshan, and Longtan organic-rich shales. These include marine shales and marine-continental transitional shales. The main marine organic-rich shales include the Niutitang, Wufeng-Longmaxi, and Dawuba shales, while the main marine-continental organic-rich transitional shales include the Liangshan and Longtan shales. The marine organic-rich shales were generally deposited under anoxic conditions, and are generally brittle siliceous-rich lithofacies, which is a type I organic-matter dominated. In contrast to the marine organic-rich shales, the marine-continental transitional organic-rich shales were most likely deposited under dysoxic to oxic conditions. They are generally less brittle argillaceous-rich lithofacies, that are type III organic-matter dominated. Of the five organic-rich shales, the Niutitang and Wufeng-Longmaxi organic-rich shales are over-mature shales, and the Dawuba, Liangshan, and Longtan organic-rich shales are high-maturity to over-mature shales. The spots with siliceous rock floor on the western edge of the Xuefeng uplift is a favorable area for future exploration of shale gas in the Niutitang organic-rich shale. The Chishui terrestrial basin and center of the aulacogen are the faverable areaa for shale gas expolation and development of the Wufeng-Longmaxi and Dawuba organic-rich shales, respectively. More basic geological research work is needed to select favorable areas for the Liangshan and Longtan organic-rich shales. To accurately guide future shale gas exploration and development, more research is needed on the relationship between the sedimentary environment, the lithofacies, and the reservoir properties of the shales.

Keywords

Shale gas

Organic-rich shale

Organic matter

Marine shale

Marine-continental transitional shale

South China

Show Related Articles from PubMed

1 Introduction

In recent years, Chin’s annual natural gas imports have consistently exceeded 40 % of its consumption, indicating a high degree of external dependency. From 2012 to 2022, China’s shale gas production increased from 0.03 to 24.00 billion cubic meters, with its share in natural gas production exceeding 10 % for three consecutive years (https://www.nea.gov.cn/). China has achieved significant success in the exploration and development of shale gas, becoming the world’s second-largest producer of shale gas (Long et al., 2021), and shale gas in China primarily produced from the Sichuan Basin. However, it still falls short of meeting societal demands (Zou et al., 2022). Currently, shale gas exploration is expanding to the deep and ultra-deep shale gas reservoirs within the Sichuan Basin and to the peripheral regions, marking a pivotal period of significant breakthroughs. The peripheral regions have become important substitutes for increasing shale gas resource and production (Zhang et al., 2021a; Zhang et al., 2021b; Zou et al., 2021; Guo et al., 2022; Hu et al., 2022 ).

Guizhou Province is located in South China (Fig. 1a), and has been divided into 13 tectonic zones according to its complicated tectonic evolution (Fig. 1b). The Chishui craton basin zone belongs to the Sichuan Basin, while the remaining 12 tectonic units are all located on the periphery of the Sichuan Basin (Guizhou Geological Survey, 2017). The sedimentary strata of Guizhou Province are well-developed, encompassing formations from the Neoproterozoic to the Quaternary, with a cumulative sedimentary thickness reaching tens of thousands of meters (Guizhou Geological Survey, 2017). In these sedimentary rock formations, there are multiple sets of organic-rich shales with significant exploration potential, including both marine shale and marine-continental transitional shale (Fig. 2). Preliminary surveys and evaluations conducted from 2012 to 2013 revealed the substantial shale gas resources in Guizhou Province (Qin et al., 2012; Zhang, 2012; Yi and Zhao, 2014; Geng et al., 2018; Zhu et al., 2019; Zhao et al., 2022 ). Guizhou Province ranked third among the 34 Provincial-level Administrative Regions in China, based on shale gas resources data from the Ministry of Natural Resources of the People’s Republic of China (https://www.mnr.gov.cn). Subsequently, many geologists and engineers focused on shale gas exploration and development in this region (Wei et al., 2012; Sun et al., 2017; Zhang et al., 2016; Wu et al., 2017; Xia et al., 2018, 2020, 2021a, 2021b; Sun et al., 2019, 2021; Zhu et al., 2019; Li, 2020; Han et al., 2021; Zhao et al., 2021; Lan et al., 2022 ). However, the productivity of shale gas is still unsatisfactory. Compared to the Sichuan Basin, the sedimentary setting, developmental characteristics, and reservoir properties of organic-rich shale in Guizhou Province exhibit significant differences. The distribution of sedimentary strata is therefore highly heterogeneous in Guizhou Province, and contemporaneous heterotopic facies are common among organic-rich shales (Fig. 2, Guizhou Geological Survey, 2017; Fu et al., 2021; Xia et al., 2022 ). The characteristics of the minerals, lithofacies, and organic matter are also various among different organic-rich shales, and these varieties significantly affect the enrichment and recoverability of the shale gas. Thus, summarizing the distribution of the organic-rich shales, and characterizing their reservoir properties and exploration prospects, is therefore important.

Geological setting. a) The location of Guizhou Province in South China (after Guizhou Geological Survey, 2017), and b) The geological map of Guizhou Province showing its tectonic zones.

Lithostratigraphic correlation chart of the strata from the Sinian to the Quaternary in Guizhou Province, showing the Niutitang, Wufeng-Longmaxi, Dawuba, Liangshan, and Longtan organic-rich shales (after Guizhou Geological Survey, 2017). Fm is Formation.

This review considers the large volume of published petrological, mineralogical, and geochemical data, including data from the Lower Cambrian Niutitang, Ordovician-Silurian Wufeng-Longmaxi, Lower Carboniferous Dawuba, Lower Permian Liangshan, and Upper Permian Longtan organic-rich shales in Guizhou Province. The review also considers some experimental results to identify the differences between the different organic-rich shales. This study improves the understanding of the shale gas reservoirs and their properties in Guizhou Province, and can serve as a reference for shale gas evaluation in this province and other peripheral regions of the Sichuan Basin.

2 Organic-rich shales in Guizhou Province

The organic-rich shales in Guizhou Province occur in the Lower Ediacaran Doushantuo Formation, the Upper Ediacaran Laobao Formation, the Lower Cambrian Niutitang Formation (also called the Jiumenchong Formation or the Zhalagou Formation in Southeast Guizhou, and the Qiongzhusi Formation in Northwest Guizhou), the Ordovician-Silurian Wufeng-Longmaxi Formation, the Lower Carboniferous Dawuba Formation (which is also called the Xiangbai Formation in some regions), the Middle Carboniferous Jiusi Formation, the Lower Permian Liangshan Formation, and the Upper Permian Longtan Formation (Fig. 2). Of these organic-rich shales, the Niutitang, the Wufeng-Longmaxi, the Dawuba, the Liangshan, and the Longtan organic-rich shales are the main shale gas targets, see Fig. 2 (Cao et al., 2018; Zhu et al., 2019; Li, 2020; Han et al., 2021; Lu et al., 2021; Xia et al., 2021a; Zhao et al., 2021; Zou et al., 2021 ).

The Niutitang Formation unconformably overlies the dolomite of the Ediacaran Dengying Formation and conformably overlies the chert of the Ediacaran Laobao Formation (Fig. 2), while the Dengying and Laobao Formations are heterotopic deposits (Dai et al., 2013; Fu et al., 2016; Xia et al., 2022; Yang et al., 2022 ). The Niutitang Formation is overlain by the Canglangpu, Mingxinsi, Bianmachong, and Palang Formations. The Niutitang Formation’s burial depth ranges from 0 to 9900 m while its thickness ranges from 0 to 900 m. The burial depth of the Niutitang Formation increases from east to west in Guizhou Province and does not occur in the southeastern part of Guizhou Province (which includes the Tianzhu, Jianhe, Jingping, Liping, Rongjiang, and Congjiang counties), see Fig. 3a.

Burial depth of the shale gas exploration and development target formations (after Zhu et al., 2019). a) The Niutitang Formation, b) the Wufeng-Longmaxi Formation, c) the Dawuba Formation, d) the Liangshan Formation and e) the Longtan Formation.

The Wufeng-Longmaxi Formation conformably overlies the Baota Formation and is overlain by the Xintan Formation. The formation occurs in the northern parts of Guizhou Province, with a thickness ranging from 0 to 80 m. The Qianbei and Wuling depressions control the distribution and thickness of this formation (Guizhou Geological Survey, 2017). The burial depth of the Wufeng-Longmaxi Formation increases from east to west of North Guizhou, with its maximum burial depth being located in Chishui County (Fig. 3b).

The Dawuba Formation is conformably overlain by the Nandan, Weining, and Shanxi Formations, and it conformably overlies the Tangbagou and Muhua Formations (Fig. 2). This formation occurs only in Southwest Guizhou and not in the other regions in Guizhou Province (Fig. 3c). The maximum thickness of the Dawuba Formation reaches 550 m in the Weining and Luodian counties (Lu et al., 2019). Its burial depth, which ranges from 0 to 3500 m, increases from northeast to southwest in Southwestern Guizhou (Zhu et al., 2019). The maximum burial depth of the Dawuba Formation is located in the core of the Luodian syncline.

The Liangshan Formation unconformably overlies the Pingchuan and Longyin Formations, and it is conformably overlain by the Qixia Formation. The Liangshan Formation occurs in West Guizhou and South Guizhou, with a thickness ranging from 0 to 860 m (Xiao et al., 2021). The maximum thickness of the Liangshan Formation is also located in the Luodian syncline, similar to the Dawuba Formation (Fig. 3d). Its burial depth exceeds 4000 m in the Chishui, Luodian, and Xingyi counties.

The coal-bearing Longtan Formation unconformably overlies the Emeishan basalt Formation and the Maokou Formation (Zhu et al., 2019; Zhao et al., 2021). It mainly occurs in West Guizhou and Northwest Guizhou, with its thickness ranging between 170 and 360 m (Ma, 2017). The burial depth of the Longtan Formation is generally shallower than 2000 m. In Northeast Guizhou, its burial depth mainly ranges from 0 to 1000 m and ranges from 0 to 2000 m in Southwest Guizhou (Fig. 3e).

3 Distribution of the organic-rich shales

The organic-rich shale of the Niutitang Formation is located in the lower part of the formation (Xia et al., 2018; Xia et al., 2022), with a thickness ranging from 20 to 120 m. This organic-rich shale occurs in the whole province except for its southeastern corner and is mainly enriched in the Zunyi, Tongren, Duyun, and Bijie regions (Fig. 4a). The Niutitang and Wufeng-Longmaxi organic-rich shales are some of the most important marine shale gas reservoirs in South China. However, the shale gas resource volume in the Niutitang shale is poor compared to the Wufeng-Longmaxi shale (Zeng and Guo, 2015; Horsfield et al., 2021; Zou et al., 2021 ).

Distribution of organic-rich shales in Guizhou Province. a) The Niutitang organic-rich shale, b) the Wufeng-Longmaxi organic-rich shale, c) the Dawuba organic-rich shale, d) the Liangshan organic-rich shale and e) the Longtan organic-rich shale.

The organic-rich shale of the Wufeng-Longmaxi Formation is also called graptolite shale. This organic-rich shale is located in the lower part of the Wufeng-Longmaxi Formation with a thickness of less than 80 m (Liang et al., 2017; Lan et al., 2022). The Wufeng-Longmaxi organic-rich shale occurs in North Guizhou, and its thickness gradually decreases from north to south (Fig. 4b). Interestingly, the Wufeng-Longmaxi shale in the center of the Sichuan Basin contributes the most to shale gas production in China at present, with the majority being wells characterized by “high formation pressure and high production”. However, shale gas development from this shale has shown less promising results in North Guizhou, characterized by “low formation pressure low production” wells, and occurs on the southeast margin of the Sichuan Basin (Fig. 5b, Dai et al., 2014; Zou et al., 2016, 2021; Xia et al., 2021a ). The reason for the considerable difference in shale gas productivity from the margin compared to the central part of the formation may be that the basin margin (such as North Guizhou Province) has much more complicated tectonic movements and cannot preserve the gas resources as well as the central parts of the basin (such as the center of the Sichuan Basin) (Guo and Zeng, 2015; Zhu et al., 2019; Xu et al., 2020; Lan et al., 2022 ).

Schematic sketch illustrating the sedimentary environments of the organic-rich shales in Guizhou Province. a) The Niutitang organic-rich shale, b) the Wufeng-Longmaxi organic-rich shale, c) the Dawuba organic-rich shale, d) the Liangshan organic-rich shale and e) the Longtan organic-rich shale.

The Dawuba organic-rich shale occurs in the lower part of the Dawuba Formation (Lu, 2019) and can reach a thickness of 140 m, but is usually thicker than 40 m (Fig. 4c, Su, 2018; Lu et al., 2021). The Dawuba organic-rich shale is, in addition to the Niutitang and Wufeng-Longmaxi organic-rich shales, a significant marine shale gas reservoir (Zhu et al., 2019). Much less basic research has been done on this organic-rich shale in comparison to the Niutitang and Wufeng-Longmaxi organic-rich shales.

The Liangshan organic-rich shale in the Guizhou Province is a marine-continental transitional deposit (Xu, 2017). Unlike the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales, which occur in the lower parts of their respective formations, the Liangshan organic-rich shale can also occur in the middle and upper parts of the Liangshan Formation (Zhang et al., 2016). The thickness of the Liangshan organic-rich shale ranges from 0 to 201 m, while its sedimentary center occurs in Qinglong County (Fig. 4d, Zhu et al., 2019).

The Longtan Formation is the most significant coal-bearing strata in Guizhou Province (Qin et al., 2012; Yang, 2020). It not only contains shale gas reservoirs, but also coalbed methane reservoirs (Wu et al., 2010; Liu et al., 2022). The thickness of the marine-continental transitional organic-rich shale ranges from 20 to 55 m (Fig. 4e). Since this organic-rich shale is usually associated with coal, it is also called the coal-series shale (Zhao et al., 2021). The sedimentary center of this shale occurs in Qinglong and Zhongshan counties, where its thickness exceeds 50 m. Like the Liangshan shale, the Longtan shale can occur anywhere in the Longtan Formation (Zhao et al., 2021; Lou et al., 2022). This geographical occurrence of the Liangshan and Longtan organic-rich shales may be the result of their marine-continental transitional sedimentary environments (Qin et al., 2012; Xu, 2017).

4 Sedimentary environment of organic-rich shales in different strata

4.1

4.1 Sedimentary environment of the Niutitang organic-rich shale

The Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales are marine shales, while the Liangshan and Longtan organic-rich shales are marine-continental transitional shales (Fig. 5, Guizhou Geological Survey, 2017; Zhu et al., 2019; Lu et al., 2021; Xia et al., 2021a, 2022; Zou et al., 2021 ).

There was an open ocean between the Yangtze Block and Cathaysia Blocks during the initial stages of the Early Cambrian, during which an uplift, platform, slop, and deep basin occurred in the study area (Goldberg et al., 2007; Yeasmin et al., 2017; Li et al., 2020 ). The Niutitang organic-rich shale was deposited in the intra-platform basin, while the slop and the deep basin occurred from west to east (Fig. 5a). This organic-rich shale was deposited under suboxic to anoxic conditions, while a high paleo-productivity generated a large amount of organic matter, especially in the slop and deep basin settings (Fu et al., 2021; Xia et al., 2022). Before the depositional stage of the Niutitang organic-rich shale, upwelling currents and hydrothermal activities brought large volumes of nutrients such as P and Si, which caused bacterial and algal blooms (Usui and Someya, 1997; Wei et al., 2012; Jia et al., 2018; Xia et al., 2020; Tan et al., 2021 ). This stage is proven by the phosphorite (Fig. 6), phosphorus-rich rock, chert, and silicon-rich rock that are present in the Niutitang organic-rich shale (Han et al., 2021; Valetich et al., 2022; Zhang et al., 2022 ). The abnormal enrichment in certain trace elements (such as Ni, Mo, Cu, Pb, Zn, Au, Ag, Ru, Rh, Pd, Ir, and Pt) also indicates hydrothermal activities (Chen, 2006; Lehmann et al., 2016). These bacteria and algae enhanced the primary productivity of the ocean, while their decomposition consumed the oxygen in the seawater. These organisms, therefore, caused an organic matter-rich and oxygen-deficient environment (Fig. 7a), which controlled the enrichment and preservation of organic matter in the Niutitang organic-rich shale.

Field photos of the Niutitang Formation. a) Phosphorite in shale, Zhijin, b) the Niutitang Formation section in Songlin, c) the unconformity surface between the Ediacaran Dengying Formation and the Cambrian Niutitang Formation, Zhijin, and d) Chert in shale, Sansui.

Paleo environmental proxies of marine shales (Su, 2018; He, 2019, Zhu et al., 2019; Xia et al., 2020, 2022). a) U/Th versus V/(V + Ni) and b) TOC versus Mo.

4.2

4.2 Sedimentary environment of the Wufeng-Longmaxi organic-rich shale

During the initial stages of the Early Silurian, a restricted sea occurred between the Chuanxi and Qianzhong Uplifts (Fig. 5b). The Sichuan Basin was an intraplate basin located in the Yangtze Block between the Chuanxi and Qianzhong Uplifts (Liu et al., 2021; Zou et al., 2021). The seawater in the restricted Sichuan basin was anoxic (Fig. 7), which allowed for the preservation of large volumes of organic matter in the Wufeng-Longmaxi organic-rich shale of this basin. The sedimentary centers of the Sichuan Basin were located in the Mianyang-Chengdu and Yibin-Luzhou areas during the deposition of the Wufeng-Longmaxi organic-rich shale (Jin et al., 2009). Most of the Guizhou regions experienced paleo uplift during this stage, so the sedimentary strata were lost in these regions (Fig. 2). Only a part of North Guizhou Province was included in the Sichuan Basin, and today occurs on the margin of the Sichuan basin (Fig. 5b). The Wufeng-Longmaxi organic-rich shale therefore only occurs in North Guizhou Province (Fig. 4b). The thickness of this organic-rich shale in Northern Guizhou Province is however much thinner than that in central parts of the Sichuan Basin (Zou et al., 2021).

In contrast to the Niutitang shale, the development of the Wufeng-Longmaxi shale was not controlled by hydrothermal activities and upwelling currents. This is proven by the high concentration of rare earth element contents (REEs) and the high ratios of light REEs to heavy REEs (∑LREE/∑HREE) in the Wufeng-Longmaxi shale (Fig. 8).

Rare earth elements content of marine shales. a) REE and b) ∑LREE/∑HREE.

4.3

4.3 Sedimentary environment of the Dawuba organic-rich shale

Based on the sedimentary structure, sedimentary environment, and stratigraphic framework of the Dawuba Formation, its sedimentary facies can be divided into the following depositional zones: Two marginal slope facies on both sides of the aulacogen, a shallow semi-deep marine facies transiting to the aulacogen, a trough basin facies in the aulacogen, an uplift shallow marine facies in the Shuicheng area, and a tidal flat lagoon facies in the Weining area (He, 2019; Lu et al., 2021). Of these depositional zones, the most favorable environments for the development of the organic-rich shales were the semi-deep sea and the aulacogen depositional zones (Fig. 5c, Su, 2018). The relatively stable sedimentary environment of the detained shallow sea to semi-deep sea facies was entered from the slope facies to the aulacogen. The influence of the terrigenous debris is gradually weakened, which enhanced the reduction environment (Fig. 7). This environment allowed the enrichment of the black shale deposits, the reduction of carbonate minerals, the enrichment of pyrite, and the development of spicules. Basin facies sediments occur at the core of the aulacogen of the detention trough, where the fossils of plankton such as spicules and algae are developed. The influence of terrigenous detritus on the organic matter was weaker in the aulacogen, which promoted the enrichment of black shale deposits. The aulacogen was therefore the most significant environment for the deposition of the Dawuba organic-rich shale.

The Shuicheng-Ziyun fault zone mainly controlled the sedimentary facies of West Guizhou. The facies changed from the shore, through the shallow sea, to the semi-deep sea and aulacogen because of the effect of this fault zone (Fig. 5c and Fig. 9). The large fault zone served as a migration pathway for the deep hydrothermal fluid, and we can therefore deduce that the Dawuba organic-rich shale was affected by hydrothermal activities. This deduction is supported by the low ratios of ∑LREE/∑HREE (Fig. 8) and the abnormally high thermal maturity of the organic matter in this organic-rich shale (Fig. 10).

Field photos of the Lower Carboniferous Formation. a) The siliceous shale in the Dawuba Formation, Huishui, b) the siliceous shale in the Dawuba Formation, Luodian, c) the limestone in the Nandan Formation, Changshun, and d) the sandstone in the Xiangbai Formation, Wudang. The Dawuba, Nandan, and Xiangbai Formations are heterotopic deposits as shown in Fig. 2.

TOC content and Ro values of the different organic-rich shales (the value in brackets is the sample number of each organic-rich shale).

4.4

4.4 Sedimentary environment of the Liangshan organic-rich shale

Large areas of the Guizhou Province were uplifted into the land under the effects of the Qiangui movement at the end of the Late Carboniferous (Guizhou Geological Survey, 2017). East Guizhou was therefore land, and the Xuefeng and Qianbei Uplifts were located in Northeast and Southeast Guizhou, respectively (Fig. 5d). West Guizhou had a relatively lower altitude compared to East Guizhou, and mainly developed a marine-continental transitional facies group, which included a lagoon, a barrier island, a coast, and a shallow water shelf (Zhong et al., 2020; Liu et al., 2022). The Liangshan Formation was generally deposited in West Guizhou (Fig. 3d), where it unconformably overlies either the Pingchuan Formation or Longyin Formation (Fig. 2) because of the Qiangui upliftment (Zhang et al., 2014).

The organic-rich shale in the Liangshan Formation was generally deposited in the lagoon and shallow water shelf environments (Fig. 5d). Geochemical proxies, including V/Cr, Ni/Co, and V/(V + Ni), indicate that this organic-rich shale was deposited under oxic to dysoxic conditions, see Fig. 11 (Zhang et al., 2016; Zhu et al., 2019). This depositional environment was a much more oxygen-rich environment compared with the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales. In addition to the organic-rich shale, the Liangshan Formation mainly contains quartz sandstone and quartz siltstone, while the general lithological association for the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales are carbonate rocks and mudstone (Zhang et al., 2012). This means that the Liangshan organic-rich shale was more obviously affected by terrigenous input compared to the other three organic-rich marine shales, and the terrigenous influx was generally from the Kangdian ancient land and the Xuefeng ancient land (Guizhou Geological Survey, 2017; Zhu et al., 2019) (Fig. 5d).

Paleo environmental proxies of the marine-continental transitional shales and the Dawuba organic-rich shale (Zhang et al., 2016; Su, 2018; Ding et al., 2021). a) Ni/Co versus V/Cr and b) Ni/Co versus V/(V + Ni).

4.5

4.5 Sedimentary environment of the Longtan organic-rich shale

The Guizhou province contained continental, marine-continental transitional, and marine facies groups during the Late Permian, and the water depth increased from West Guizhou to East Guizhou. The Longtan Formation was deposited in West Guizhou mainly in the Bijie and Liupanshui regions under these conditions (Fig. 3e), while carbonate-rich strata (such as the Wujiaping Formation, Fig. 2) was deposited in East Guizhou during the same stage (Guizhou Geological Survey, 2017; Zhao et al., 2022). The Longtan Formation mainly contains coal, mudstone, sandstone, and limestone (Fig. 12), which means that West Guizhou experienced multiphase seawater intrusions and that the Kangdian ancient land provided large volumes of terrigenous debris during the sedimentary stage of this formation (Wang et al., 2020a; Shao et al., 2021; Li et al., 2022 ).

Drilling core photos of the Longtan Formation from well DHC-1 in the Zhongshan County. a) Organic-rich shale and limestone, b) Coal, organic-rich shale, mudstone, and limestone, c) Plant fossils, and d) Organic-rich shale and limestone.

The organic-rich shale in the Longtan Formation was deposited in a delta and a lagoon (Fig. 5e). Similar to the Liangshan shale, the Longtan shale was mainly deposited under oxic to dysoxic conditions (Fig. 11, Sun, 2014). The organic-rich shale can still exist in the context of an oxic sedimentary environment (Wang et al., 2022a). This means that the enrichment mechanism of the organic matter is controlled by primary productivity and terrigenous debris influx.

The sedimentary environments of the five organic-rich shales differ from each other (Fig. 5). We can deduce that the marine organic-rich shales (including the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales) were generally deposited under anoxic conditions. The marine-continental transitional organic-rich shales (including the Liangshan and Longtan organic-rich shales) were most likely deposited under oxic to dysoxic conditions. Upwelling currents and thermal activities caused the anoxic conditions of the Niutitang organic-rich shale, while that of the Wufeng-Longmaxi organic-rich shale was caused by the restricted ocean conditions. The Longtan organic-rich shale has a higher total organic carbon (TOC) content than the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales because of the abundant terrestrial plants that were present during Late Permian, even though it was deposited under oxic conditions.

5 Composition of the different shales

5.1

5.1 Geochemical characteristics of the organic-rich shales

5.1.1

5.1.1 Organic matter abundance

The organic geochemical characteristics of the organic-rich shale are described by the abundance, type, and thermal maturity of the organic matter (Hao et al., 2013). The TOC content is the most effective index to indicate organic matter abundance in shales. To serve as an effective source rock for hydrocarbon generation, the TOC content of the source rock must be no less than 0.5 %, while the “sweet spot” of the shale gas resource is usually at a TOC content above 2.0 % (Jarvie et al., 2007; Lu et al., 2019). Interestingly, the Lewis shale in the San Juan Basin has great shale gas productivity even though its TOC content is relatively low at 0.5 %–2.5 %, see Fig. 10. This is mainly because the effective thickness of this shale ranges from 60 to 90 m, which is much thicker than most shales in the USA with a higher TOC content (Li et al., 2012; Gentzis, 2013). The TOC content should therefore be combined with the effective thickness of shale to identify possible “sweet spots” for shale gas development (Zhu et al., 2019).

The TOC content in the Niutitang organic-rich shale ranges from 0.7 % to 14.6 %, with an average of 5.2 % (Fig. 10). About 69.1 % of 316 samples reported by our previous studies have a TOC content higher than 4.0 %, while 12.7 % of these range from 3.0 % to 4.0 % (Zhu et al., 2019; Ning et al., 2021; Xia et al., 2022 ). There are two high-value TOC areas (where the TOC content is greater than 8 %) in Guizhou Province, one which is located in the Tongren area of the East Guizhou region, and one in the Yuqing-Shibing area of the Southeast Guizhou region, (Fig. 13a). These two high-value areas developed due to the normal shelf slope sedimentation and the sedimentary center that formed under the influence of the Qianzhong Uplift (Fig. 5a). The TOC content decreases from the east to the west of Guizhou Province. The TOC content is, however, still greater than 3.0 % in the West Guizhou region, and still has relatively good hydrocarbon prospectivity.

Distribution of the TOC content of the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales (Zhu et al., 2019; Lu et al., 2021; Ning et al., 2021).

In the Wufeng-Longmaxi organic-rich shale in Guizhou Province, the TOC content is 0.6 %–7.2 %, with an average of 3.4 %. This shale has a lower TOC content compared to the Niutitang organic-rich shale in Guizhou Province and has a similar TOC content to the Wufeng-Longmaxi shale in the Sichuan Basin (Fig. 10). The Wufeng-Longmaxi organic-rich shale mainly occurs in the North Guizhou region because of the Qianzhong Uplift (Fig. 4b and 5b). In the Daozhen, Tongzi, and Yanhe areas, which occur in the northern part of this region, the TOC content of the Wufeng-Longmaxi organic-rich shale exceeds 3.0 % (Fig. 13b), which could be the case because these areas are close to the sedimentary center of the Sichuan Basin. The TOC content in the Wufeng-Longmaxi organic-rich shale gradually decreases from north to south.

The TOC conten of the Dawuba organic-rich shale ranges from 0.2 % to 5.8 %, with an average of 1.2 % (Fig. 10). The organic matter is mainly enriched in the Yadu-Ziyun aulacogen (Fig. 5c), while the TOC content in this aulacogen is generally greater than 1.5 % (Fig. 13c). The TOC content gradually decreased from the center of the aulacogen to its sides.

The Liangshan organic-rich shale has a TOC content of 0.1–4.1 %, with an average of 1.2 % (Fig. 10). This organic-rich shale has the lowest TOC of all of the five organic-rich shales. The high TOC content in the Liangshan organic-rich shale mainly occurs in the Yadu-Ziyun aulacogen, similar to the Dawuba organic-rich shale.

The Longtan organic-rich shale is the most significant source rock and reservoir for the marine-continental transitional shale gas facies ( Ma, 2017; Wang et al., 2022b). The TOC content in this organic-rich shale ranges from 0.1 % to 17.0 %, with an average of 3.3 % (Fig. 10). Approximately 60.01 % of the 236 samples reported by previous studies (Zhu et al., 2019; Zhao et al., 2021; Lou et al., 2022 ), have a TOC content higher than 4.0 %, and about 35.0 % have a TOC content less than 3.0 %. The organic matter in this organic-rich shale is mainly enriched in the Shuicheng, Panxian, Xingren, and Liuzhi areas, which are also the main coal-producing areas in Guizhou Province.

5.1.2

5.1.2 Organic matter type

The type of organic matter is a significant index that controls the hydrocarbon generation and preservation conditions of shale gas (Zou et al., 2021). Maceral compositions and δ¹³C_org in shale can be used to identify the organic matter type (Lu et al., 2019). The organic macerals compositions can be used to calculate the type index (TI) according to the following formula: $TI = (100 . a + 50 . b - 75 . c - 100 . d) / 100 .$ where a, b, c, and d are the sapropelinite, liptilite, vitrinite, and inertinite content, respectively. TI values above 80 indicate type I organic matter; TI values ranging from 40 to 80 indicate type II₁ organic matter; TI values ranging from 0 to 40 indicate type II₂ organic matter, and TI values less than 0 indicate type III organic matter.

In addition to the TI index, the δ¹³C_org is another significant parameter used to identify the organic matter type. Generally, when δ¹³C_org < -29 ‰ it indicates type I organic matter; when −29 ‰ < δ¹³C_org < -27.6 ‰ it indicates type II₁ organic matter; when −27.6 ‰ < δ¹³C_org < -26 ‰ it indicates type II₂ organic matter, and a δ¹³C_org above −26 ‰ indicates type III organic matter.

The results of the calculations can be seen in Figs. 14 and 15. The TI index and δ¹³C_org value of the Niutitang organic-rich shale range from 87.75 to 100.00 and −39.2 ‰–-30.7 ‰ (Zhu et al., 2019; Xia et al., 2020). Both these values indicate that the organic matter in this organic-rich shale can be classified as type I organic matter.

Ternary diagram showing the different organic matter types.

Organic matter type identification based on the data of the kerogen carbon isotope and the TI index (δ13Corg values is from Lin et al., 2014; Li, 2019; Zhu et al., 2019; Xia et al., 2020; Ma, 2017; Niu et al., 2021; Wang et al., 2022a; Zheng et al., 2022).

In comparison to the Niutitang organic-rich shale, the Wufeng-Longmaxi organic-rich shale contains both type I and type II₁ organic matter (Fig. 15). The TI index of this organic-rich shale ranges between 44.75 and 95.50, with a δ¹³C_org value of −30.98 ‰–-28.22 ‰ (Lin et al., 2014; Wang et al., 2022b).

The TI index and δ¹³C_org value of the Dawuba organic-rich shale range from −21.00 to 29.25, and from −26.87 ‰ to −24.19 ‰, respectively (Fig. 15, Niu et al., 2021; Zheng et al., 2022). Both these values indicate that the organic matter in the Dawuba organic-rich shale belongs to the type II₂ and type III organic matter classes.

The TI index of the Liangshan organic-rich shale ranges from −42.00 to 65.00 (Fig. 14), implying that there is a rich source of organic matter during the sedimentation stage of this shale (Jiang and Cha, 2006; Huang and Gao, 2017). According to the TI index, the Liangshan organic-rich shale contains the type II₁, type II₂, and type III organic matter. The reported δ¹³C_org value of this organic-rich shale is very limited, with only four values being collected. They range from −26.90 ‰––23.00 ‰, indicating type II₂ and type III organic matter (Fig. 15, Li, 2019).

Both the TI index (-82.00–-67.25) and the δ¹³C_org value (-24.90 ‰––23.20 ‰) indicate that the organic matter in the Longtan organic-rich shale can be classified as type III (Fig. 15, Ma, 2017). The organic matter in the Longtan organic-rich shale therefore mainly derives from terrestrial higher plants. In contrast to the Longtan organic-rich shale, the organic matter in the Niutitang and Wufeng-Longmaxi organic-rich shales came from lower organisms, such as algae and bacteria, while the organic matter in the Dawuba and Liangshan organic-rich shales are from both higher and lower organisms.

5.1.3

5.1.3 Organic matter maturity

Vitrinite reflectance (R_o) is an effective index that indicates the thermal maturity of organic matter (Lu et al., 2019; Huang and Gao, 2017). The R_o values of the Niutitang, Wufeng-Longmaxi, Dawuba, Liangshan, and Longtan organic-rich shales range from 1.4 % to 4.2 % (averaging 2.7 %), 1.5 %–4.0 % (averaging 2.5 %), 1.0 %–4.9 % (averaging 2.6 %), 1.0 %–2.7 % (averaging 1.6 %), and 0.8 %–3.3 % (averaging 2.1 %), respectively (Fig. 10).

Approximately 92.59 % of the 104 R_o values reported by Zhu et al. (2019), Ning et al., (2021), and Xia et al., (2022), have a R_o value higher than 2.0 %, indicating that the Niutitang organic-rich shale is over-mature (Jiang and Cha, 2006). Ninety percent of the 87 of the Wufeng-Longmaxi organic-rich shale that was recently reported (Cao et al., 2020; Sun et al., 2021a; Cao et al., 2022; Shi et al., 2022 ) have R_o values higher than 2.0 %, therefore the Wufeng-Longmaxi organic-rich shale can also be classified as an over-mature shale. In contrast to the Niutitang and Wufeng-Longmaxi organic-rich shales, the Dawuba, Liangsha, and Longtan organic-rich shales contain more high-maturity samples. The high-maturity shale samples are 28.57 % (56 samples in total), 35.29 % (45 samples in total), and 29.05 % (92 samples in total) in the Dawuba, Liangshan, and Longtan organic-rich shales, respectively.

Of the organic-rich shales in Guizhou Province, the Niutitang and Wufeng-Longmaxi organic-rich shales are classified as over-mature shales, and the Dawuba, Liangshan, and Longtan organic-rich shales are classified as high-mature to over-mature shales. During the high maturity to over-mature stages, the liquid hydrocarbons generated during the thermal evolution of organic matter are cracked into methane at high temperatures (Tilley et al., 2011; Cavelan et al., 2019), which explains why Guizhou Province is oil-poor.

5.2

5.2 Shale lithofacies

5.2.1

5.2.1 Mineralogical characteristics

In organic-rich shales, the main minerals include quartz, feldspar (includes K-feldspar and plagioclase), calcite, dolomite, pyrite, and clay minerals (such as smectite, illite, chlorite, and kaolinite) (Fan et al., 2004).

Quartz is the most significant mineral in the Niutitang organic-rich shale and accounts for 30 %–90 % of the mineral composition. Clay is another mineral that is enriched in this organic-rich shale. The clay mainly contains an illite and illite–smectite mixed layer. The clay in the Niutitang organic-rich shale can reach 68 % (Ning et al. (0 2 1). The mineral proportions of feldspar, calcite, and dolomite are generally lower than 30 %. Apart from these minerals, pyrite is another significant mineral in the Niutitang organic-rich shale, which is also helpful to analyze the paleo-environment (Xia et al., 2022).

In the Wufeng-Longmaxi shale, the quartz and clay contents are nearly equivalent, with average proportions for both the quartz and clay at about 40 %. Feldspar, calcite, and dolomite are common minerals, with percentages usually lower than 20 %. Pyrite is also common, but its content is generally lower than 5 %. The main clay minerals in this organic-rich shale are illite and illite–smectite mixed layers.

Clay has displaced quartz as the most enriched mineral in the Dawuba, Liangshan, and Longtan organic-rich shales. The proportions of clay minerals in the Dawuba, Liangshan, and Longtan organic-rich shales can reach up to 76.00 %, 73.00 %, and 83.00 %, respectively. The Liangshan and Longtan organic-rich shales have significantly lower contents of carbonate minerals and pyrite in contrast to the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales. This may be because the sedimentary environment of the Liangshan and Longtan organic-rich shale was a marine-continental transitional facies, such as a lagoon-tidal flat, which differs from the marine sedimentary environment of the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales (Guizhou Geological Survey, 2017; Zhu et al., 2019).

5.2.2

5.2.2 Lithofacies classification and features

The methods reported by Wang et al. (2016), Feng et al. (2020), and Ning et al. (2021), which take felsic minerals (quartz and feldspar), carbonate minerals (calcite and dolomite), and clay minerals as three end elements to carry out the shale naming division, were used to divide the shales into a total of 4 shale groups and 12 shale types. The 4 different groups are the Siliceous shale group (I), the Argillaceous shale group (II), the Calcareous shale group (III), and the Mixed shale group (IV). The 12 shale types include the siliceous shale (I-1), the carbonate-rich siliceous shale (I-2), the argillaceous-rich siliceous shale (I-3), the argillaceous shale (II-1), the silica-rich argillaceous shale (II-2), the carbonate-rich argillaceous shale (II-3), the calcareous shale (III-1), the silica-rich calcareous shale (III-2), the argillaceous-rich calcareous shale (III-3), the argillaceous/siliceous mixed shale (IV-1), the calcareous/argillaceous mixed shale (IV-2), and the siliceous/calcareous mixed shale (IV-3), see Table 1.

Table 1 Shale classification scheme of the marine shale (after Ning et al., 2021).

Shale groups	Shale types	Code	Minerals composition (%)
Shale groups	Shale types	Code	Felsic minerals	Carbonate minerals	Clay minerals
Siliceous shale group (I)	Siliceous shale	I-1	> 50	< 25	< 25
	Carbonate-rich siliceous shale	I-2	> 50	25–50	< 25
	Argillaceous-rich siliceous shale	I-3	> 50	< 25	25–50
Argillaceous shale group (II)	Argillaceous shale	II-1	< 25	< 25	> 50
	Silica-rich argillaceous shale	II-2	25–50	< 25	> 50
	Carbonate-rich argillaceous shale	II-3	< 25	25–50	> 50
Calcareous shale group (III)	Calcareous shale	III-1	< 25	> 50	< 25
	Silica-rich calcareous shale lithofacies	III-2	25–50	> 50	< 25
	Argillaceous-rich calcareous shale	III-3	< 25	> 50	25–50
Mixed shale group (IV)	Argillaceous/siliceous mixed shale	IV-1	25–50	< 30	25–50
	Calcareous/argillaceous mixed shale	IV-2	< 30	25–50	25–50
	Siliceous/calcareous mixed shale	IV-3	25–50	25–50	< 30

Based on the mineral composition, the Niutitang organic-rich mainly includes siliceous shale and argillaceous-rich siliceous shale (Fig. 16). The Wufeng-Longmaxi organic-rich shale is a mixture of an argillaceous-rich siliceous shale, an argillaceous/siliceous mixed shale, and a silica-rich argillaceous shale. Apart from also containing argillaceous-rich siliceous shale, argillaceous/siliceous mixed shale, and silica-rich argillaceous shale, the Dawuba organic-rich shale has large amounts of argillaceous shale, calcareous/argillaceous mixed shale, and siliceous/calcareous mixed shale. The Liangshan organic-rich shale includes a mixture of siliceous shale, argillaceous-rich siliceous shale, silica-rich calcareous shale, argillaceous/siliceous mixed shale, calcareous/argillaceous mixed shale, and siliceous/calcareous mixed shale. Lastly, the Longtan organic-rich shale mainly contains argillaceous shale, silica-rich argillaceous shale, argillaceous/siliceous mixed shale, and argillaceous-rich siliceous shale.

Ternary diagram showing the lithofacies of the organic-rich shales in Guizhou Province. I-1 is the siliceous shale lithofacies; I-2 is the carbonate-rich siliceous shale lithofacies; I-3 is the argillaceous-rich siliceous shale lithofacies; II-1 is the argillaceous shale lithofacies; II-2 is the silica-rich argillaceous shale lithofacies; II-3 is the carbonate-rich argillaceous shale lithofacies; III-1 is the calcareous shale lithofacies; III-2 is the silica-rich calcareous shale lithofacies; III-3 is the argillaceous-rich calcareous shale lithofacies; IV-1 is the argillaceous/siliceous mixed shale lithofacies; IV-2 is the calcareous/argillaceous mixed shale lithofacies, and IV-3 is the siliceous/calcareous mixed shale lithofacies.

5.3

5.3 Pore characteristics

5.3.1

5.3.1 Porosity and permeability

The porosity of the Niutitang, Wufeng-Longmaxi, Dawuba, Liangshan, and Longtan organic-rich shales range from 1.3 to 10.6 % (with an average of 6.96 %), 0.77–9.8 % (with an average of 6.77 %), 0.24–16.37 % (with an average of 10.50 %), 6.64–22.22 % (with an average of 13.34 %), and 0.13–22.00 % (with an average of 12.00 %), respectively (Lu et al., 2019, Zhu et al., 2019, Ma, 2017, Han et al., 2021, Xia et al., 2021a; Xia et al., 2021b; Zou et al., 2021; Zou et al., 2022 ). The permeability values of these five organic-rich shales range from 0.0022 × 10^-3–0.0172 × 10^-3 μm² (with an average of 0.0083 × 10^-3 μm²), 0.0014 × 10^-3–0.0667 × 10^-3 μm² (with an average of 0.0161 × 10^-3 μm²), 0.0011 × 10^-3–4.7100 × 10^-3 μm² (with an average of 0.5600 × 10^-3 μm²), 0.0056 × 10^-3–2.6500 × 10^-3 μm² (with an average of 0.1300 × 10^-3 μm²), 0.0008 × 10^-3–2.9100 × 10^-3 μm² (with an average of 0.2600 × 10^-3 μm²), respectively. Based on these results, the Dawuba, Liangshan, and Longtan organic-rich shales are much more heterogeneous, which may have been caused by their sedimentary environment.

5.3.2

5.3.2 Pore types

Based on the SEM images reflect, the pore types of the Niutitang shale samples mainly include organic matter pore, interparticle pore, intraparticle pore, intergranular pore, and dissolved pore (Xia et al., 2021b). The organic matter pore is a special kind of interparticle pore that develops within organic matter. These four kinds of pores have been observed in all five organic-rich shales (Fig. 17). Even though the Niutitang and Longtan shales are richer in organic matter than the Wufeng-Longmaxi shale (Fig. 10), the Wufeng-Longmaxi organic-rich shale has a much higher proportion of organic pores in contrast to the other four shales (Zhu et al. 2019, Fig. 18). In the Sichuan Basin, the relatively lower thermal maturity of the Wufeng-Longmaxi organic-rich shale (2.0 % < R_o < 2.8 %) compared to the Niutitang organic-rich shale (3.0 % < R_o < 4.2 %), is the main reason for the difference of organic pores between these two shales (Wang et al., 2020b). In Guizhou Province, the thermal maturity values of the Niutitang and Wufeng-Longmaxi organic-rich shales are however close to each other (Fig. 10). The reason for the differences in the organic pore between the Niutitang and Wufeng-Longmaxi organic-rich shales in the Guizhou Province is still controversial (Wang et al., 2017; Yu et al., 2022). The Liangshan and Longtan organic-rich shales have favorable thermal maturity for developing organic pores, but they have significantly lower organic pore proportions compared to the Wufeng-Longmaxi shale (Fig. 10). The most likely reason is that the organic matter type in the Liangshan and Wufeng-Longmaxi organic-rich shales is type III organic matter, which has fewer pores than type I and type II organic matter (Loucks et al., 2012; Zhang et al., 2020).

SEM images of pores in the organic-rich shales. (a)-(f) show the Longtan organic-rich shale. (g)-(i) show the Niutitang organic-rich shale (g is from Ning et al., 2023). (j)-(l) show the Wufeng-Longmaxi organic-rich shale.

Pore types of the different organic-rich shales in Guizhou Province (data from Zhu et al., 2019; Xia et al., 2021b).

The Dawuba, Liangshan, and Longtan shales have higher intraparticle pore proportions compared with the Niutitang and Wufeng-Longmaxi shales. A possible reason for this is their high clay and carbonate minerals content (Fig. 16).

It is important to note that (1) The organic matter in the Wufeng-Longmaxi organic-rich shale is much more porous than in the Niutitang organic-rich shale, even though they have nearly the same type (Figs. 14 and 15) and (2) Based on the thermal maturity (Figs. 10 and 15) the sedimentary environment of the shales gradually changed from marine to continental from the Niutitang shale, through the Wufeng-Longmaxi, Dawuba, and Liangshan shales, to the Longtan shale. At the same time, the organic matter gradually changed from type I to type III, resulting in different organic pores characteristics between these organic-rich shales.

5.3.3

5.3.3 Pore structure

The pore structures of the five sets of potential shale series are very similar (Fig. 19a). Based on the adsorption/desorption curves of the potential shale, the Longtan, Liangshan, and Dawuba shales with high clay mineral content are mainly characterized by parallel plates and sharp cleats (Zhu et al., 2019; Ma, 2017). The Niutitang and Wufeng-Longmaxi shales, in contrast, have a high content of brittle minerals with open pore structures, such as tubular pores with open ends, slit pores with parallel walls, and wedge pores with open sides (Zhu et al., 2019; Xia et al., 2021b). Based on the specific surface area and pore volume diagrams (Fig. 19b), the Wufeng-Longmaxi, Dawuba, and Longtan shales have high values, while the Niutitang shale has low values. The mesopore pore structures account for an absolute proportion of more than 50 % in all five of the potential shale targets in Guizhou Province (Fig. 19a). A possible reason is that most intercrystalline pores of clay minerals and organic pores are mesopores (Xia et al., 2023; Zhao et al., 2023).

Pore structure characteristics of organic-rich shales (data from Zhu et al., 2019; Xia et al., 2021b). a) Proportion of pores with different sizes and b) Pore volume and specific surface area.

6 Prospect of shale gas in Guizhou Province

6.1

6.1 Gas resources and origin

Zhu et al. (2019) evaluated the gas resources of the organic-rich shales in Guizhou Province using the volumetric method under conditional probability. The Niutitang organic-rich shale was found to be the most abundant shale gas-enriched reservoir of the five organic-rich shales. The geological resources and recoverable resources in the Niutitang organic-rich shale are 3.55 × 10¹² m³ and 0.64 × 10¹² m³, respectively. The Longtan organic-rich shale is next in line, in which the geological resources and recoverable resources are 1.73 × 10¹² m³ and 0.31 × 10¹² m³, respectively. The Wufeng-Longmaxi and Dawuba also have significant shale gas resources. Their geological resources are 1.48 × 10¹² m³ and 1.44 × 10¹² m³, with recoverable resources at 0.27 × 10¹² m³ and 0.26 × 10¹² m³, respectively. The shale gas in Guizhou Province does however have an abnormally high proportion of nitrogen gas (Xia et al., 2018; Zhu et al., 2019; Han et al., 2021 ). The geological conditions in Guizhou Province were complicated, as indicated by the distribution of folds and faults (Guizhou Geological Survey, 2017). Faults, folds, and erosion control the preservation and distribution of the shale gas reservoir (Fig. 20, Xia et al., 2021a). Air, carried by surface water, moved into shale gas reservoirs and displaced the shale gas in the pores (Fig. 21, Xia et al., 2018; Zhong et al., 2021). The proportion of nitrogen in the shale gas is therefore higher than the gas. This phenomenon had a significant influence, especially in the Niutitang organic-rich shale, because of an unconformity between it and the Late Ediacaran Dengying dolomite (Fig. 5). This unconformity served as a migration pathway for the surface water causing exchanges between the atmosphere and shale gas in most of the shale deposits of North Guizhou (Fig. 21, Xia et al., 2018).

The Seismic survey shows the structural characteristics of the Niutitang and the Wufeng-Longmaxi organic-rich shales (after Xia et al., 2021a).

Relational model of the circular geothermal system of the Niutitang shale gas reservoir in Guizhou Province.

Fig. 22 shows the C₁/(C₂ + C₃) and δ¹³C of methane (δ¹³C₁) which indicates the hydrocarbon gas origin. The hydrocarbon gas in the Niutitang and Wufeng-Longmaxi organic-rich shales mainly comes from associated gas and from cracking gas of crude oil (Xia et al., 2018; Zhong et al., 2021; Shi et al., 2022 ). The hydrocarbon gas in the Dawuba and Longtan organic-rich shales is from coal-derived gas (Zhu et al., 2019). These results agree with the sedimentary environment and organic matter type of the organic-rich shales. The sedimentary environment changed from marine to marine-continental transitional conditions from the Niutitang and Wufeng-Longmaxi, through the Dawuba, to the Liangshan and Longtan organic-rich shales, while the shale gas origin changed from crude oil to coal.

Diagram of C1/(C2 + C3) versus δ13C1 showing the hydrocarbon gas origin (data from Xia et al., 2018; Zhu et al., 2019; Zhong et al., 2021; Shi et al., 2022). I1 is biogas; I2 is biogenic gas and sub-biogenic gas; I3 is sub-biogenic gas; II1 is associated gas of crude oil; II2 is oil-type cracking gas; III1 is oil-type cracking gas and coal-formed gas; III2 is associated gas of condensate and coalbed methane; IV is coal derived gas; V1 is inorganic gas; V2 is inorganic gas and coal-derived gas.

6.2

6.2 Brittle index and compressibility

The brittle index evaluates the compressibility of shale gas reservoirs. The compressibility can be calculated by the methods of mineral compositions and mechanical parameters, following the Chinese Petroleum Natural Gas Profession Standard (NB/T 10248–2019). The mineral compositions (Fig. 16), were used to calculate the brittle index of each organic-rich shale. The brittle indexes (BI) of the Niutitang, Wufeng-Longmaxi, Dawuba, Liangshan, and Longtan organic-rich shales range from 59 to 96 (with an average of 80), 38–77 (with an average of 56), 24–89 (with an average of 58), 28–80 (with an average of 54), and 15–69 (with an average of 35), respectively. Based on the NB/T 10248–2019 grading standard, 70 < BI is perfect, 60 ≤ BI < 70 is good, 40 ≤ BI < 60 is medium, and BI < 40 is weak. The Niutitang organic-rich shale is very brittle and is favorable for hydraulic fracturing. The Longtan organic-rich shale is not very brittle and is unfavorable for hydraulic fracturing. Methods to improve the permeability of the Longtan organic-rich shale must be developed.

6.3

6.3 Prospect for exploration and development

The Niutitang, Wufeng-Longmaxi, Dawuba, Liangshan, and Longtan organic-rich shales are the main shale gas reservoirs in Guizhou Province (Xu et al., 2017; Zhu et al., 2019; Han et al., 2021; Lu et al., 2021; Ma, 2017; Xia et al., 2021a; Lan et al., 2022 ). These shale gas reservoirs have different sedimentary environments, reservoir properties, and shale gas resources (Guizhou Geological Survey, 2017; Zhu et al., 2019; Xia et al., 2020 ). Both the Niutitang and Wufeng-Longmaxi organic-rich shales are over-mature marine shales. However, the Niutitang organic-rich shale has a higher organic matter content but cannot preserve shale gas very well, in contrast to the Wufeng-Longmaxi organic-rich shale (Xia et al., 2018; Cao et al., 2022; Lan et al., 2022 ). The Dawuba organic-rich shale is also deposited in a marine system, but it is controlled by deep fault zones (such as the Yadu-Ziyun fault zone, Fig. 5c), and has a higher thermal maturity and a lower TOC content compared with the Niutitang and Wufeng-Longmaxi organic-rich shales (Fig. 10).

In comparison to the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales, the Liangshan and Longtan organic-rich shales have been deposited in marine-continental transitional environments, and are also called coal-series shales (Zhang et al., 2016; Xu et al., 2017; Zhao et al., 2021; Lou et al., 2022). Exploration and development of the Liangshan organic-rich shale are limited, and more fundamental geological research is needed in the future. The Longtan shale is rich in shale gas resources and has a high organic matter content. However, it is the least brittle of the five organic-rich shales, which complicates hydraulic fracturing. The Longtan organic-rich shale is associated with the coal seams of the Longtan Formation, which is the most significant coal-containing strata in Guizhou Province. The shale gas and coalbed methane in the Longtan Formation must therefore be explored and developed concurrently.

The relationship between the environment, the lithofacies, and the reservoir properties are close and would provide additional information for shale gas exploration and development (Ning et al., 2021; Yu et al., 2022). Fig. 23 shows the information on the sedimentary environment, the lithofacies, and some reservoir properties of a typical marine shale (the Niutitang organic-rich shale) and a typical marine-continental transitional shale (the Longtan organic-rich shale). There are significant differences between the sedimentary environment, the lithofacies, the organic matter type, and the reservoir properties of these two shales. The marine shale corresponds to anoxic conditions and is a siliceous-rich lithofacies that contains type I organic matter. In contrast to the marine shale, the marine-continental transitional shale generally corresponds to dysoxic to oxic conditions and is an argillaceous-rich lithofacies that contains type III organic matter. Therefore, the reservoir properties, such as the brittleness and the pore structure, differ between the marine and the marine-continental transitional shale. The marine shale is enriched in quartz because of the large amount of biogenic silicon it contains (Dong et al., 2021; Xia et al., 2022). The quartz content correlates positively with the TOC content (Fig. 24a). However, there is no notable positive or negative correlation between the quartz and the TOC content in the marine-continental transitional shale. This may be because of its terrigenous input, which brought in clay and plant residue. Samples with higher clay mineral content usually have a higher TOC content (Fig. 24b). These results imply that the relationships between the sedimentary environment, the lithofacies, and the reservoir properties are significant and can guide shale gas exploration and development. More research on these relationships is needed in the future.

Comparisons of the sedimentary environment, the lithofacies, and the reservoir properties between a typical marine shale and a typical marine-continental transitional shale. Here, SS is siliceous shale lithofacies; A-SS is argillaceous-rich siliceous shale lithofacies; AS is argillaceous shale lithofacies; S-AS is silica-rich argillaceous shale lithofacies, and AS-MS is argillaceous/siliceous mixed shale lithofacies.

Relationships between the minerals and the TOC content. a) Quartz content versus TOC content and b) clay content versus TOC content.

6.4

6.4 “Sweet spot” of shale gas

Based on the geochemical characteristics of shale gas reservoir discussed in this study, the enrichment of shale gas in the Niutitang organic-rich shale is controlled by its floor conditions. The spots with the floor of the Dengying Formation dolomite are characterized by low gas content and high nitrogen proportion, and those spots with the floor of the Laobao Formation siliceous rock usually has high gas content and low nitrogen proportion (Xia et al., 2018). Therefore, the the spots with siliceous rock floor on the western edge of the Xuefeng uplift is a favorable area for future exploration of shale gas in the Niutitang organic-rich shale.

Although the Wufeng-Longmaxi organic-rich shale has achieved significant breakthroughs in North Guizhou, the thickness of this shale has become thinner from north to south because of the changes of sedimentary facies (Zhu et al., 2019; Xia et al., 2021a). This organic-rich shale with a thickness greater than 20 m is only distributed in several synclines and Chishui terrestrial basins (Cao et al., 2022). The burial depth of this organic-rich shale in the Chishui terrestrial basin is greater than 4000 m (Fig. 4b), which can be selected as a “sweet spot” for deep to ultra deep shale gas exploration and development.

The Dawuba Formation has achieved breakthroughs in industrial airflow. Its organic-rich shale is mainly developed in the center of the aulacogen (Fig. 5c). Several wells in the center of the aulacogen have achieved good gas display (Lu et al., 2021), and thus this area is a favorable area for the shale gas exploration of the Dawuba Formation.

The exploration level of the Longtan and Liangshan formations is relatively low, and more basic geological research work is needed to select favorable areas.

7 Conclusions

Prospective shale gas reservoirs in Guizhou Province include marine shales and marine-continental transitional shales. The main marine shales are the Niutitang, Wufeng-Longmaxi, and Dawuba organic-rich shales, while the main marine-continental transitional shales include the Liangshan and Longtan organic-rich shales. These marine organic-rich shales were generally deposited under anoxic conditions, and are characterized as siliceous-rich lithofacies (including siliceous shale lithofacies and argillaceous-rich siliceous shale lithofacies), and are type I organic matter dominated with strong brittleness. In contrast to the marine organic-rich shales, the marine-continental transitional organic-rich shales were most likely deposited under dysoxic to oxic conditions, and they are generally characterized as argillaceous-rich lithofacies (including argillaceous shale lithofacies, silica-rich argillaceous shale lithofacies, and argillaceous/siliceous mixed shale lithofacies), and is type III organic matter dominated with weak brittleness. Of the five organic-rich shales, the Niutitang and Wufeng-Longmaxi organic-rich shales are classified as over-mature shales, and the Dawuba, Liangshan, and Longtan organic-rich shales are classified as highly mature to over-mature shales. The relationships between the sedimentary environment, the lithofacies, and the reservoir properties are significant and can guide shale gas exploration and development. However, more research on these relationships is needed in the future.

The spots with siliceous rock floor on the western edge of the Xuefeng uplift is a favorable area for future exploration of shale gas in the Niutitang organic-rich shale. The Chishui terrestrial basin is faverable area for shale gas expolation and development of the Wufeng-Longmaxi organic-rich shale. The center of the aulacogen is a favorable area for the shale gas exploration of the Dawuba Formation. More basic geological research work is needed to select favorable areas for the Liangshan and Longtan organic-rich shales.

Acknowledgements

This research was supported by the National Natural Science Foundation Project of China (Nos. 42002166, 42162016, 42063009), Guizhou Provincial Fund Project (No. ZK[2020]YIBAN106, (2022)ZD005, [2020]4Y037), and Geological Exploration Fund Project of Guizhou Province (No. 52000021MGQSE7S7K6PRP).

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

Cao T.T., Liu G.X., Gao Q.G., Deng M., . Influence of maceral composition on organic pore development in shale: a case study of transitional Longtan Formation shale in eastern Sichuan Basin. Oil Gas Geol.. 2018;39(1):40-53.
[Google Scholar]
Cao T.T., Liu H., Pan A.Y., Deng M., Cao Q.G., Yu Y., Huang Y.R., Xiao Z.H., . Marine shale gas occurrence and its influencing factors: a case study from the wufeng-longmaxi formation, northwestern guizhou China. Geofluids. 2022;2022:203651
[Google Scholar]
Cao T., Xu H., Liu G., Deng M., Cao Q., Yu Y., . Factors influencing microstructure and porosity in shales of the Wufeng-Longmaxi formations in northwestern Guizhou, China. J. Pet. Sci. Eng.. 2020;191:107181
[Google Scholar]
Cavelan A., Boussafir M., Rozenbaum O., Laggoun-Defarge F., . Organic petrography and pore structure characterization of low-mature and gas-mature marine organic-rich mudstones: Insights into porosity controls in gas shale systems. Mar. Pet. Geol.. 2019;103:331-350.
[Google Scholar]
Chen, L., 2006. Sedimentology and geochemistry of the Early Cambrian black rock series in the Hunan-Guizhou area, China. Doctor Thesis, Institute of Geochemistry, Chinese Academy of Sciences,Guiyang, Guizhou province, China.
Dai C.G., Zheng Q.Q., Chen J., Wang M., Zhang H., . The metallogenic geological background of the Xuefeng-Caledonian tectonic cycle in Guizhou. China.. 2013;20(6):219-225.
[Google Scholar]
Dai J.X., Zou C.N., Liao S.M., Dong D.Z., Ni Y.Y., Huang J.L., Wu W., Gong D.Y., Huang S.P., Hu G.Y., . Geochemistry of the extremely high thermal maturity Longmaxi shale gas, southern Sichuan Basin. Org Geochem.. 2014;74:3-12.
[Google Scholar]
Ding J.H., Zhang J.C., Shi G., Shen B.J., Tang X., Yang Z.H., Li X.Q., Li C.X., . Sedimentary environment and organic matter accumulation for the longtan formation shale in xuancheng area. Acta Sedimentol. Sin.. 2021;39(2):324-340.
[Google Scholar]
Fan D.L., Zhang X., Ye J., . China’s Black Rock System and Its Related Deposits. Beijing: Science Press; 2004.
Feng Z.Q., Hao F., Zhou S.W., Tian J.Q., Wu W., Xie C., Cai Y.W., . Pore systems of the different lithofacies of the Longmaxi formation at depths exceeding 3500 m in the Zigong area Sichuan Basin. Energy & Fuels. 2020;34(5):5733-5752.
[Google Scholar]
Fu Y., Dong L., Li C., Qu W.J., Pei H.X., Qiao W.L., Shen B., . New Re-Os isotopic constrains on the formation of the metalliferous deposits of the Lower Cambrian Niutitang formation. J. Earth Sci.. 2016;27(2):271-281.
[Google Scholar]
Fu Y., Xia P., Long Z., Zhang G.J., Qiao W.L., Guo C., Yang Z., . Continental weathering of Yangtze area during Edicaran (Sinian)—Cambrian transition stage: advances and prospects. Geological Review. 2021;67(4):1077-1094.
[Google Scholar]
Geng M., Chen H., Chen Y.P., Zeng L.J., Chen S.S., Jiang X.C., . Methods and results of the fourth round national CBM resources evaluation. Coal Science and Technology. 2018;46(6):64-68.
[Google Scholar]
Gentzis T., . A review of the thermal maturity and hydrocarbon potential of the Mancos and Lewis shales in parts of New Mexico, USA. Int. J. Coal Geol.. 2013;113:64-75.
[Google Scholar]
Goldberg T., Strauss H., Guo Q., Liu C., . Reconstructing marine redox conditions for the Early Cambrian Yangtze Platform: evidence from biogenic sulphur and organic carbon isotopes. Palaeogeogr. Palaeoclimatol. Palaeoecol.. 2007;254(1–2):175-193.
[Google Scholar]
Guo T.L., Zeng P., . The structural and preservation conditions for shale gas enrichment and high productivity in the Wufeng-Longmaxi Formation, Southeastern Sichuan Basin. Energy Explor. Exploit.. 2015;33(3):259-276.
[Google Scholar]
Guo X., Zhao Y.Q., Shen B.J., Wei X.F., Lu L.F., Pan A.Y., Li Y.P., . Marine shale gas exploration theory in southern China: review and prospects. Acta Geol. Sin.. 2022;96(1):172-182.
[Google Scholar]
Han S.B., Wan J.B., Sun M.D., Dang W., Lang Y., . Formation and Evaluation of High-Over Matured Shale Gas. Beijing: Science Press; 2021.
Hao F., Zou H.Y., Lu Y.C., . Mechanisms of shale gas storage: Implications for shale gas exploration in China. AAPG Bull.. 2013;97(8):1325-1346.
[Google Scholar]
He B., . The research of sedimentary environment of Dawuba Formation (lower carboniferous) in ZiYun, Guizhou aera. Guiyang: Guizhou University; 2019.
Horsfield B., Zou C.N., Li J., Yang S.Y., Mahlstedt N., Misch D., Gross D., Wei M., Wang Y.F., Tan J.Q., . Prediction of the gas-generating characteristics of the Qiongzhusi and Longmaxi Formations, Yangtze Platform, southern China, using analogues. AAPG Bull.. 2021;105(5):945-985.
[Google Scholar]
Hu T., Pang X.Q., Jiang F.J., Zhang C.X., . Dynamic continuous hydrocarbon accumulation (DCHA): existing theories and a new unified accumulation model. Earth Sci. Rev.. 2022;232:104109
[Google Scholar]
Huang Z., Gao G., . Comprehensive research methods of petroleum geology. Beijing: Petroleum Industry Press; 2017.
Guizhou Geological Survey Institute., 2017. Geological records of Guizhou Province. Beijing: Geology Press.
Jarvie D.M., Hill R.J., Ruble T.E., . Unconventional shale-gas systems: the Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment. AAPG Bull.. 2007;91(4):475-499.
[Google Scholar]
Jia Z., Hou D., Sun D., Jiang Y., Zhang H., Han X., Zhang Z., Hong M., Chang Z., . The intensity evaluation of the hydrothermal sedimentation and the relationship with the formation of organic-rich source rocks in the Lower Cambrian Niutitang Formation in Guizhou Province, China. Energy Sources Part A. 2018;40(12):1442-1451.
[Google Scholar]
Jiang Y.L., Cha M., . Oil and gas geology and exploration. Beijing: Petroleum Industry Press; 2006.
Jin W.Z., Tang L.J., Yang K.M., Wan G.M., Lu Z.Z., Yu Y.X., . Tectonic evolution of the middle frontal area of the Longmen Mountain thrust belt, western Sichuan basin China. Acta Geologica Sinica-English Edition. 2009;83(1):92-102.
[Google Scholar]
Lan, B.F., Zhao, F.P., Li, S.P., Jiang, H., Liu, S. and Zhang, Z.Y., 2022. Investigation of the enrichment and accumulation of normal pressure shale gas in Anchang syncline outside of Sichuan Basin. Advances in the Exploration and Development of Unconventional Oil and Gas: From the Integration of Geology and Engineering. Frontiers in Earth Science, 9: 802142.
Lehmann B., Frei R., Xu L.G., Mao J.W., . Early Cambrian black shale-hosted Mo-Ni and V mineralization on the rifted margin of the Yangtze Platform, China: reconnaissance chromium isotope data and a refined metallogenic model. Econ. Geol.. 2016;111(1):89-103.
[Google Scholar]
Li H., . Sedimentary Env ironment characteristics and Evolutionary Analysis of the late Permian-early Triassic in Dejiang area, Guizhou Province. Chengdu: Chengdu University of Technology; 2019.
Li X.J., . Guizhou Qianbei shale gas generation mechanism. Beijing: Science Press; 2020.
Li J.Z., Li D.H., Dong D.Z., Wang S.J., . Comparison and enlightenment on formation condition and distribution characteristics of shale gas between China and US. Strategic Study of CAE. 2012;14(6):56-63.
[Google Scholar]
Li Y., Pan S.Q., Ning S.Z., Shao L.Y., Jing Z.H., Wang Z.S., . Coal measure metallogeny: metallogenic system and implication for resource and environment. Sci. China Earth Sci.. 2022;65(7):1-18.
[Google Scholar]
Li C., Zhang Z.H., Jin C.S., Cheng M., Wang H.Y., Huang J.H., Algeo T.J., . Spatiotemporal evolution and causes of marine euxinia in the early Cambrian Nanhua Basin (South China) Palaeogeogr. Palaeoclimatol. Palaeoecol.. 2020;546:109676
[Google Scholar]
Liang C., Jiang Z.X., Cao Y.C., Zhang J.C., Guo L., . Sedimentary characteristics and paleoenvironment of shale in the Wufeng-Longmaxi Formation, North Guizhou Province, and its shale gas potential. J. Earth Sci.. 2017;28(6):1020-1031.
[Google Scholar]
Lin J.S., Liu J.Q., Feng W.M., Jing X.Y., . Organic geochemical signatures and palaeo-environmental implications for the source rocks from the Lower Silurian Longmaxi Formation in northern Guizhou. Sediment. Geol. Tethyan Geol.. 2014;34(2):79-85.
[Google Scholar]
Liu S.G., Yang Y., Deng B., Zhong Y., Wen L., Sun W., Li Z.W., Jansa L., Li J.X., Song J.M., . Tectonic evolution of the sichuan basin, southwest China. Earth Sci. Rev.. 2021;213:103470
[Google Scholar]
Liu A., Yang J.H., Cheng L., Ren J.T., . Climate-controlled coastal deposition of the early permian liangshan formation in Western South China. Front. Earth Sci.. 2022;10:888012
[Google Scholar]
Long S.X., Lu T., Li Q.W., Yang G.J., Li D.H., . Discussion on China's shale gas development ideas an goals during the 14^th Five-Year Plan. Nat. Gas Ind.. 2021;41(10):1-10.
[Google Scholar]
Lou Y., Su Y.L., Gao W., Wang W.D., Xiong W., Chen J., Xia P., . Pore characteristics and fractal characterization variability of typical middle-and high-rank coal reserves: a case study of middle-and high-rank coal samples in western Guizhou. Front. Energy Res.. 2022;10:981530
[Google Scholar]
Loucks R.G., Reed R.M., Ruppel S.C., Hammes U., . Spectrum of pore types and networks in mudrocks and a descriptive classification for matrix-related mudrock pores. AAPG Bull.. 2012;96(6):1071-1098.
[Google Scholar]
Lu S.F., . Study on Shale Gas A ccumulation Rules and Exp loration Area of Dawuba Formation of Carboniferous in Guizhou Province. Guiyang: Guizhou University; 2019.
Lu S.F., Luo X.J., Du S.J., He B., Fu H.B., Liu K.Y., . Discovery and analysis of shale gas in a carboniferous reservoir and its enrichment characteristics in the Northern Nanpanjiang Depression, Guizhou Province China. Acta Geologica Sinica-English Edition. 2019;93(3):561-572.
[Google Scholar]
Lu S.F., Chen Y., Luo X.J., He B., Fu H.B., . Sedimentary characteristics and distribution of the carboniferous black shale in Guizhou Province. Journal of Sedimentology. 2021;39(3):672-685.
[Google Scholar]
Ma X., . Fine characterzation of shale reservoir of Longtan Formation in western Guizhou. Beijing: China University of Geosciences; 2017. Master Thesis
Ning S.T., Xia P., Hao F., Tian J.Q., Zhong Y., Zou N.N., Fu Y., . Shale facies and its relationship with sedimentary environment and organic matter of Niutitang black shale Guizhou Province. Natural Gas Geoscience. 2021;32(9):1297-1307.
[Google Scholar]
Ning S.T., Xia P., Zou N.N., Zhong Y., Yu Y., Mou Y.L., Wang K., . Organic matter pore characteristics of over-mature marine black shale: a comparison of organic fractions with different densities. Frontiers of Earth Science. 2023;17(1):310-321.
[Google Scholar]
Niu J.L., Zhang J.C., Tang X., Yuan K., Lin T., Liu Y., Niu Y.J., Li P., Li X.Q., Liang Y.T., . Main Controlling factors and models of organic matter accumulation in lower carboniferous dawuba formation shale in Southern Guizhou China. ACS Omega. 2021;6(48):32441-32459.
[Google Scholar]
Qin Y., Gao D., Wu C.F., . Prediction and evaluation of coalbed methane resource potential in Guizhou Province. Xuzhou: China University of Mining and Technology Press; 2012.
Shao, L., XU, X., Wang, S., Wang, D., Gao, D., Wang, X. and Lu, J., 2021. Research progress of palaeogeography and palaeoenvironmental evolution of coal-bearing series in China. Journal of Palaeogeography, 23(1): 19–38.
Shi S.Y., Wang Y.P., Sun Y., Guo H.J., . The volume and geochemical characteristics of desorption gases from wufeng-longmaxi (O₃w–S₁l) shale in the Xishui Area, North Guizhou China. Frontiers in Earth Science. 2022;10:879959
[Google Scholar]
Su H., . Analysis on the sedim entary environm ent and hy drocarb on source rock characteristics of black shale in dawub a forr ation of early carb oniferous in Huishui, Guizhou. Guiyang: Guizhou University; 2018.
Sun Q.H., . Forming Condition and Distribution Prediction of Shale Gas of Longtan Formation in Northwest Guizhou. Beijing: China University of Geosciences; 2014.
Sun J., Xiao X.M., Cheng P., . Influence of water on shale pore heterogeneity and the implications for shale gas-bearing property-a case study of marine Longmaxi Formation shale in northern Guizhou. Mar. Pet. Geol.. 2021;134:105379
[Google Scholar]
Sun M.D., Yu B.S., Hu Q.H., Zhang Y.F., Li B., Yang R., Melnichenko Y.B., Cheng G., . Pore characteristics of Longmaxi shale gas reservoir in the Northwest of Guizhou, China: investigations using small-angle neutron scattering (SANS), helium pycnometry, and gas sorption isotherm. Int. J. Coal Geol.. 2017;171:61-68.
[Google Scholar]
Sun W.J.B., Zuo Y.J., Wu Z.H., Liu H., Xi S.J., Shui Y., Wang J., Liu R.B., Lin J.Y., . Fractal analysis of pores and the pore structure of the Lower Cambrian Niutitang shale in northern Guizhou province: investigations using NMR, SEM and image analyses. Mar. Pet. Geol.. 2019;99:416-428.
[Google Scholar]
Sun W.J.B., Zuo Y.J., Wu Z.H., Liu H., Zheng L.J., Shui Y., Xi S.J., Lou Y.L., Luo X., . The distribution characteristics of brittle minerals in the Lower Cambrian Niutitang Formation in northern Guizhou. J. Nat. Gas Sci. Eng.. 2021;86:103752
[Google Scholar]
Tan J.Q., Wang Z.H., Wang W.H., Hilton J., Guo J.H., Wang X.K., . Depositional environment and hydrothermal controls on organic matter enrichment in the lower Cambrian Niutitang shale, southern China. AAPG Bull.. 2021;105(7):1329-1356.
[Google Scholar]
Tilley B., McLellan S., Hiebert S., Quartero B., Veilleux B., Muehlenbachs K., . Gas isotope reversals in fractured gas reservoirs of the western Canadian Foothills: mature shale gases in disguise. AAPG Bull.. 2011;95(8):1399-1422.
[Google Scholar]
Usui A., Someya M., . Distribution and composition of marine hydrogenetic and hydrothermal manganese deposits in the northwest Pacific. Geol. Soc. Lond. Spec. Publ.. 1997;119(1):177-198.
[Google Scholar]
Valetich M., Zivak D., Spandler C., Degeling H., Grigorescu M., . REE enrichment of phosphorites: an example of the Cambrian Georgina Basin of Australia. Chem. Geol.. 2022;588:120654
[Google Scholar]
Wang Y., Gui H.R., Su S.G., Zhou Q.M., . Sedimentary environment and paleoclimate geochemical characteristics of shale in the wufeng and longmaxi formations Northern Yunan-Guizhou Area. Acta Sedimentologica Sinica. 2022;40(3):653-666.
[Google Scholar]
Wang E., Guo T.L., Li M.W., Xiong L., Dong X.X., Zhang N.X., Wang T., . Depositional environment variation and organic matter accumulation mechanism of marine-continental transitional shale in the upper permian longtan formation, Sichuan Basin, SW China. ACS Earth Space Chem.. 2022;6(9):2199-2214.
[Google Scholar]
Wang P.F., Jiang Z.X., Yin L.S., Chen L., Li Z., Zhang C., Li T.W., Huang P., . Lithofacies classification and its effect on pore structure of the Cambrian marine shale in the Upper Yangtze Platform, South China: evidence from FE-SEM and gas adsorption analysis. J. Pet. Sci. Eng.. 2017;156:307-321.
[Google Scholar]
Wang X.T., Shao L.Y., Eriksson K.A., Yan Z.M., Wang J.M., Li H., Zhou R.X., Lu J., . Evolution of a plume-influenced source-to-sink system: an example from the coupled central Emeishan large igneous province and adjacent western Yangtze cratonic basin in the Late Permian SW China. Earth-Science Reviews. 2020;207:103224
[Google Scholar]
Wang Y.M., Wang S.F., Dong D.Z., Li X.J., Huang J.L., Zhang C.C., Guan Q.Z., . Litheofacies characterization of Longmaxi Formation of the Lower Silurian, southern Sichuan. Eareh Science Frontiers. 2016;23(1):119-133.
[Google Scholar]
Wang P.F., Zhang C., Li X., Zhang K., Yuan Y., Zang X.P., Cui W.J., Liu S.Y., Jiang Z.X., . Organic matter pores structure and evolution in shales based on the he ion microscopy (HIM): a case study from the Triassic Yanchang, Lower Silurian Longmaxi and Lower Cambrian Niutitang shales in China. J. Nat. Gas Sci. Eng.. 2020;84:103682
[Google Scholar]
Wei H.R., Yang R.D., Gao J.B., Chen J.Y., Liu K., Cheng W., . New evidence for hydrothermal sedimentary genesis of the Ni-Mo deposits in black rock series of the basal cambrian, guizhou province: discovery of coarse-grained limestones and its geochemical characteristics. Acta Geologica Sinica-English Edition. 2012;86(3):579-589.
[Google Scholar]
Wu Y., Qin Y., Yi T.S., . Enrichment of rare earth elements in high sulfur coal of liangshan formation from kaili guizhou china and geological origin. Acta Geol. Sin.. 2010;84(2):280-285.
[Google Scholar]
Wu C.J., Tuo J.C., Zhang L.F., Zhang M.F., Li J., Liu Y., Qian Y., . Pore characteristics differences between clay-rich and clay-poor shales of the Lower Cambrian Niutitang Formation in the Northern Guizhou area, and insights into shale gas storage mechanisms. Int. J. Coal Geol.. 2017;178:13-25.
[Google Scholar]
Xia P., Wang G.L., Zeng F.G., Mou Y.L., Zhang T.H., Liu J.G., . The characteristics and mechanism of high over matured nitrogen-rich shale gas of Niutitang Formation, northern Guizhou a area. Nat. Gas Geosci.. 2018;29(9):1345-1355.
[Google Scholar]
Xia P., Fu Y., Yang Z., Guo C., Huang J.Q., Huang M.Y., . The relationship between sedimentary environment and organic matter accumulation in the Niutitang black shale in Zhenyuan, northern Guizhou. Acta Geol. Sin.. 2020;94(3):947-956.
[Google Scholar]
Xia P., Fu Y., Guo C., Yang Z., Huang J.Q., Mou Y.L., . Shale gas reservoir evaluation by geophysical measurements: a case study of the upper ordovician-lower silurian in the fenggang block, Northern Guizhou Province. Acta Geologica Sinica-English Edition. 2021;95(4):1310-1321.
[Google Scholar]
Xia P., Li H.N., Fu Y., Qiao W.L., Guo C., Yang Z., Huang J.Q., Mou Y.L., . Effect of lithofacies on pore structure of the Cambrian organic-rich shale in northern Guizhou. China. Geological Journal. 2021;56(2):1130-1142.
[Google Scholar]
Xia P., Hao F., Tian J.Q., Zhou W.X., Fu Y., Guo C., Yang Z., Li K.J., Wang K., . Depositional environment and organic matter enrichment of early cambrian niutitang black shales in the upper Yangtze Region. China. Energies. 2022;15(13):4551.
[Google Scholar]
Xia P., Hao F., Tian J.Q., Fu Y., Mou Y.L., Guo C., Yang Z., Wang K., . Organic matter occurrence and its effects on pore structure and methane adsorption capacity capacity: A case study of the Niutitang black shale in Guizhou, China. J. Earth Sci. 2023
[CrossRef] [Google Scholar]
Xiao J.F., Li Y.T., Yang H.Y., Xu J.B., Huang M.L., . Geochemistry of the Yudong bauxite deposit, south-eastern Guizhou, China: implications for conditions of formation and parental affinity. J. Geochem. Explor.. 2021;220:106676
[Google Scholar]
Xu Q., . Study on permian liangshan formation shale gas exploration potential in Southwestern Guizhou Area. Coal Geology of China. 2017;29(5):20-26.
[Google Scholar]
Xu S., Gou Q.Y., Hao F., Zhang B.Q., Shu Z.G., Lu Y.B., Wang Y.X., . Shale pore structure characteristics of the high and low productivity wells, Jiaoshiba shale gas field, Sichuan Basin, China: Dominated by lithofacies or preservation condition? Mar. Pet. Geol.. 2020;114:104211
[Google Scholar]
Yang Z.B., . Geological evaluation technology for the development of multi-layer joint mining of coalbed methane. Xuzhou: China University of Mining and Technology Press; 2020.
Yang Z., Wu P., Fu Y., Qiao W.L., Qin Y., Li C., Xia P., Guo C., Long X.L., Wu L., . Coupling of the redox history and enrichment of Ni-Mo in black shale during the early Cambrian: constraints from S-Fe isotopes and trace elements of pyrite South China. Ore Geol. Rev.. 2022;143:104749
[Google Scholar]
Yeasmin R., Chen D.Z., Fu Y., Wang J.G., Guo Z.H., Guo C., . Climatic-oceanic forcing on the organic accumulation across the shelf during the Early Cambrian (Age 2 through 3) in the mid-upper Yangtze Block, NE Guizhou, South China. J. Asian Earth Sci.. 2017;134:365-386.
[Google Scholar]
Yi T.S., Zhao X., . Characteristics and distribution patterns of the Lower Cambrian Niutitang Shale reservoirs in Guizhou China. Gas Industry. 2014;34(8):8-14.
[Google Scholar]
Yu Y., Xia P., Wang Y.B., Ning S.T., Zhong Y., Mou Y.L., Li K.J., . Organic matter occurrence status and characteristics of over-mature marine shale: a case study of shale in the Lower Cambrian Niuhoitang Formation in Guizhou. Journal of Northeast Petroleum University. 2022;46(4):48-61.
[Google Scholar]
Zeng P., Guo T.L., . Enrichment of shale gas in different strata in sichuan basin and its periphery-the examples of the cambrian qiongzhusi formation and the Silurian Longmaxi formation. Energy Explor. Exploit.. 2015;33(3):277-298.
[Google Scholar]
Zhang D., . China issued the “shale gas development plan (2011–2015)”. Fault-Block Oil and Gas Fields. 2012;19(4):429.
[Google Scholar]
Zhang H.J., Fan H.F., Wen H.J., Han T., Zhou T., Xia Y., . Controls of REY enrichment in the early Cambrian phosphorites. Geochim. Cosmochim. Acta. 2022;324:117-139.
[Google Scholar]
Zhang D.M., He L.L., Zeng G.Q., Yang K.G., Dai C.G., Zhang H., . Superimposed deformation and its controlling effect on Pb-Zn deposits of guanziyao region in West Guizhou. Guizhou Geology. 2014;31(4):241-251.
[Google Scholar]
Zhang W.T., Hu W.X., Borjigin T., Zhu F., . Pore characteristics of different organic matter in black shale: a case study of the Wufeng-Longmaxi Formation in the Southeast Sichuan Basin, China. Mar. Pet. Geol.. 2020;111:33-43.
[Google Scholar]
Zhang Q.M., Jiang X.S., Qin J.H., Cui X.Z., Liu C.Z., . Lithofacies palaeogeography of the early Middle Permian Liangshan Formation in northern Guizhou-southern Chongqing area and its bauxite ore-forming effect. Geol. Bull. China. 2012;31(4):558-568.
[Google Scholar]
Zhang G.T., Peng Z.Q., Wang C.S., Li Z.H., . Geochemical characteristics of the Lower Permian Liangshan Formation in Dushan area of Guizhou Province and their implications for the paleoenvironment. Geol. China. 2016;43(4):1291-1303.
[Google Scholar]
Zhang J.C., Shi M., Wang D.S., Tong Z.Z., Hou X.D., Niu J.L., Li X.Q., Li Z.M., Zhang P., Huang Y.Q., . Fields and directions for shale gas exploration in China. Nat. Gas Ind.. 2021;41(8):69-80.
[Google Scholar]
Zhang B., Tang S.H., Xi Z.D., Lin D.L., Ye Y.P., . Sequence stratigraphic characteristics and organic matter enrichment of wufeng-longmaxi formation in Northwestern Huna: a case study of well XY-3*. Adv. Earth Science. 2021;36(10):1026-1038.
[Google Scholar]
Zhao, L.Y., Zhou, P.M., Lou, Y., Zhao, Y.Z., Liu, W., Liao, Z.W. and Xia, P., 2021. Geochemical Characteristics and Sedimentary Environment of the Upper Permian Longtan Coal Series Shale in Western Guizhou Province, South China. Geofluids, DOI: 10.1155/2021/9755861.
Zhao F.P., Sun Z., Sang S.X., Zhou X.Z., Han Z.Q., Zhao L.Y., Wu Z.L., . Progress of coalbed methane exploration and development in Guizhou and the 14th Five-Year Plan development strategy. Nat. Gas Ind.. 2022;42(6):65-75.
[Google Scholar]
Zheng F.Z., Tang X., Yuan K., Lin T., You M.X., Niu J.L., Zi Y.Y., Liang Y.T., . Sedimentation models and development mechanisms of organic-rich shales of the lower carboniferous dawuba formation: a case study in the Yaziluo Rift Trough, South of Guizhou Province Southern China. ACS Omega. 2022;7(33):29054-29071.
[Google Scholar]
Zhong Y., Yang Y.M., Wen L., Luo B., Xiao D., Tan X.C., Zhao L.K., Li M.L., . Sedimentary environments controlled by tectonics and induced differential subsidence: a perspective in the Permian Liangshan and Qixia Formations, northwestern Sichuan Basin China. Journal of Central South University. 2020;27(11):3398-3416.
[Google Scholar]
Zhong Y., Xia P., Ning S.T., Fu Y., Li Q.G., Yu Y., . Geochemical characteristics and its geological application of over-mature Longmaxi shale gas in the northern Guizhou area China. Arabian Journal of Geosciences. 2021;14(18):1-9.
[Google Scholar]
Zou C.N., Yang Z., Pan S.Q., Chen Y.Y., Lin S.H., Huang J.L., Wu S.T., Dong D.Z., Wang S.F., Liang F., . Shale gas formation and occurrence in China: An overview of the current status and future potential. Acta Geologica Sinica-English Edition. 2016;90(4):1249-2183.
[Google Scholar]
Zhu L.J., Zhang D.W., Zhang J.C., Chen Y., Wang G.L., Yang T.B., Chen H.G., . Paleozoic passive continental margin shale gas in eastern Shangyangzi Geological theory, technology and practice. Beijing: Science Press; 2019.
Zou C.N., Dong D.Z., Wei Y.J., . Marine Shale Gas. Beijing: Science Press; 2021.
Zou C.N., Yang Z., Dong D.Z., Zhao Q., Chen Z.H., Feng Y.L., Li J.R., Wang X.N., . Formation, Distribution and Prospect of Unconventional Hydrocarbons in Source Rock Strata in China. Earth Sci.. 2022;47(5):1517-1533.
[Google Scholar]

Introduction

Organic-rich shales in Guizhou Province

Distribution of the organic-rich shales

Sedimentary environment of organic-rich shales in different strata

Sedimentary environment of the Niutitang organic-rich shale
Sedimentary environment of the Wufeng-Longmaxi organic-rich shale
Sedimentary environment of the Dawuba organic-rich shale
Sedimentary environment of the Liangshan organic-rich shale
Sedimentary environment of the Longtan organic-rich shale

Composition of the different shales

Geochemical characteristics of the organic-rich shales
Shale lithofacies
Pore characteristics

Prospect of shale gas in Guizhou Province

Gas resources and origin
Brittle index and compressibility
Prospect for exploration and development
“Sweet spot” of shale gas

Conclusions

Fulltext Views
6

PDF downloads
0

View/Download PDF
Download Citations

BibTeX
RIS

Show Sections

[1] Cao T.T., Liu G.X., Gao Q.G., Deng M., . Influence of maceral composition on organic pore development in shale: a case study of transitional Longtan Formation shale in eastern Sichuan Basin. Oil Gas Geol.. 2018;39(1):40-53.
[Google Scholar]

[2] Cao T.T., Liu H., Pan A.Y., Deng M., Cao Q.G., Yu Y., Huang Y.R., Xiao Z.H., . Marine shale gas occurrence and its influencing factors: a case study from the wufeng-longmaxi formation, northwestern guizhou China. Geofluids. 2022;2022:203651
[Google Scholar]

[3] Cao T., Xu H., Liu G., Deng M., Cao Q., Yu Y., . Factors influencing microstructure and porosity in shales of the Wufeng-Longmaxi formations in northwestern Guizhou, China. J. Pet. Sci. Eng.. 2020;191:107181
[Google Scholar]

[4] Cavelan A., Boussafir M., Rozenbaum O., Laggoun-Defarge F., . Organic petrography and pore structure characterization of low-mature and gas-mature marine organic-rich mudstones: Insights into porosity controls in gas shale systems. Mar. Pet. Geol.. 2019;103:331-350.
[Google Scholar]

[5] Chen, L., 2006. Sedimentology and geochemistry of the Early Cambrian black rock series in the Hunan-Guizhou area, China. Doctor Thesis, Institute of Geochemistry, Chinese Academy of Sciences,Guiyang, Guizhou province, China.

[6] Dai C.G., Zheng Q.Q., Chen J., Wang M., Zhang H., . The metallogenic geological background of the Xuefeng-Caledonian tectonic cycle in Guizhou. China.. 2013;20(6):219-225.
[Google Scholar]

[7] Dai J.X., Zou C.N., Liao S.M., Dong D.Z., Ni Y.Y., Huang J.L., Wu W., Gong D.Y., Huang S.P., Hu G.Y., . Geochemistry of the extremely high thermal maturity Longmaxi shale gas, southern Sichuan Basin. Org Geochem.. 2014;74:3-12.
[Google Scholar]

[8] Ding J.H., Zhang J.C., Shi G., Shen B.J., Tang X., Yang Z.H., Li X.Q., Li C.X., . Sedimentary environment and organic matter accumulation for the longtan formation shale in xuancheng area. Acta Sedimentol. Sin.. 2021;39(2):324-340.
[Google Scholar]

[9] Fan D.L., Zhang X., Ye J., . China’s Black Rock System and Its Related Deposits. Beijing: Science Press; 2004.

[10] Feng Z.Q., Hao F., Zhou S.W., Tian J.Q., Wu W., Xie C., Cai Y.W., . Pore systems of the different lithofacies of the Longmaxi formation at depths exceeding 3500 m in the Zigong area Sichuan Basin. Energy & Fuels. 2020;34(5):5733-5752.
[Google Scholar]

[11] Fu Y., Dong L., Li C., Qu W.J., Pei H.X., Qiao W.L., Shen B., . New Re-Os isotopic constrains on the formation of the metalliferous deposits of the Lower Cambrian Niutitang formation. J. Earth Sci.. 2016;27(2):271-281.
[Google Scholar]

[12] Fu Y., Xia P., Long Z., Zhang G.J., Qiao W.L., Guo C., Yang Z., . Continental weathering of Yangtze area during Edicaran (Sinian)—Cambrian transition stage: advances and prospects. Geological Review. 2021;67(4):1077-1094.
[Google Scholar]

[13] Geng M., Chen H., Chen Y.P., Zeng L.J., Chen S.S., Jiang X.C., . Methods and results of the fourth round national CBM resources evaluation. Coal Science and Technology. 2018;46(6):64-68.
[Google Scholar]

[14] Gentzis T., . A review of the thermal maturity and hydrocarbon potential of the Mancos and Lewis shales in parts of New Mexico, USA. Int. J. Coal Geol.. 2013;113:64-75.
[Google Scholar]

[15] Goldberg T., Strauss H., Guo Q., Liu C., . Reconstructing marine redox conditions for the Early Cambrian Yangtze Platform: evidence from biogenic sulphur and organic carbon isotopes. Palaeogeogr. Palaeoclimatol. Palaeoecol.. 2007;254(1–2):175-193.
[Google Scholar]

[16] Guo T.L., Zeng P., . The structural and preservation conditions for shale gas enrichment and high productivity in the Wufeng-Longmaxi Formation, Southeastern Sichuan Basin. Energy Explor. Exploit.. 2015;33(3):259-276.
[Google Scholar]

[17] Guo X., Zhao Y.Q., Shen B.J., Wei X.F., Lu L.F., Pan A.Y., Li Y.P., . Marine shale gas exploration theory in southern China: review and prospects. Acta Geol. Sin.. 2022;96(1):172-182.
[Google Scholar]

[18] Han S.B., Wan J.B., Sun M.D., Dang W., Lang Y., . Formation and Evaluation of High-Over Matured Shale Gas. Beijing: Science Press; 2021.

[19] Hao F., Zou H.Y., Lu Y.C., . Mechanisms of shale gas storage: Implications for shale gas exploration in China. AAPG Bull.. 2013;97(8):1325-1346.
[Google Scholar]

[20] He B., . The research of sedimentary environment of Dawuba Formation (lower carboniferous) in ZiYun, Guizhou aera. Guiyang: Guizhou University; 2019.

[21] Horsfield B., Zou C.N., Li J., Yang S.Y., Mahlstedt N., Misch D., Gross D., Wei M., Wang Y.F., Tan J.Q., . Prediction of the gas-generating characteristics of the Qiongzhusi and Longmaxi Formations, Yangtze Platform, southern China, using analogues. AAPG Bull.. 2021;105(5):945-985.
[Google Scholar]

[22] Hu T., Pang X.Q., Jiang F.J., Zhang C.X., . Dynamic continuous hydrocarbon accumulation (DCHA): existing theories and a new unified accumulation model. Earth Sci. Rev.. 2022;232:104109
[Google Scholar]

[23] Huang Z., Gao G., . Comprehensive research methods of petroleum geology. Beijing: Petroleum Industry Press; 2017.

[24] Guizhou Geological Survey Institute., 2017. Geological records of Guizhou Province. Beijing: Geology Press.

[25] Jarvie D.M., Hill R.J., Ruble T.E., . Unconventional shale-gas systems: the Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment. AAPG Bull.. 2007;91(4):475-499.
[Google Scholar]

[26] Jia Z., Hou D., Sun D., Jiang Y., Zhang H., Han X., Zhang Z., Hong M., Chang Z., . The intensity evaluation of the hydrothermal sedimentation and the relationship with the formation of organic-rich source rocks in the Lower Cambrian Niutitang Formation in Guizhou Province, China. Energy Sources Part A. 2018;40(12):1442-1451.
[Google Scholar]

[27] Jiang Y.L., Cha M., . Oil and gas geology and exploration. Beijing: Petroleum Industry Press; 2006.

[28] Jin W.Z., Tang L.J., Yang K.M., Wan G.M., Lu Z.Z., Yu Y.X., . Tectonic evolution of the middle frontal area of the Longmen Mountain thrust belt, western Sichuan basin China. Acta Geologica Sinica-English Edition. 2009;83(1):92-102.
[Google Scholar]

[29] Lan, B.F., Zhao, F.P., Li, S.P., Jiang, H., Liu, S. and Zhang, Z.Y., 2022. Investigation of the enrichment and accumulation of normal pressure shale gas in Anchang syncline outside of Sichuan Basin. Advances in the Exploration and Development of Unconventional Oil and Gas: From the Integration of Geology and Engineering. Frontiers in Earth Science, 9: 802142.

[30] Lehmann B., Frei R., Xu L.G., Mao J.W., . Early Cambrian black shale-hosted Mo-Ni and V mineralization on the rifted margin of the Yangtze Platform, China: reconnaissance chromium isotope data and a refined metallogenic model. Econ. Geol.. 2016;111(1):89-103.
[Google Scholar]

[31] Li H., . Sedimentary Env ironment characteristics and Evolutionary Analysis of the late Permian-early Triassic in Dejiang area, Guizhou Province. Chengdu: Chengdu University of Technology; 2019.

[32] Li X.J., . Guizhou Qianbei shale gas generation mechanism. Beijing: Science Press; 2020.

[33] Li J.Z., Li D.H., Dong D.Z., Wang S.J., . Comparison and enlightenment on formation condition and distribution characteristics of shale gas between China and US. Strategic Study of CAE. 2012;14(6):56-63.
[Google Scholar]

[34] Li Y., Pan S.Q., Ning S.Z., Shao L.Y., Jing Z.H., Wang Z.S., . Coal measure metallogeny: metallogenic system and implication for resource and environment. Sci. China Earth Sci.. 2022;65(7):1-18.
[Google Scholar]

[35] Li C., Zhang Z.H., Jin C.S., Cheng M., Wang H.Y., Huang J.H., Algeo T.J., . Spatiotemporal evolution and causes of marine euxinia in the early Cambrian Nanhua Basin (South China) Palaeogeogr. Palaeoclimatol. Palaeoecol.. 2020;546:109676
[Google Scholar]

[36] Liang C., Jiang Z.X., Cao Y.C., Zhang J.C., Guo L., . Sedimentary characteristics and paleoenvironment of shale in the Wufeng-Longmaxi Formation, North Guizhou Province, and its shale gas potential. J. Earth Sci.. 2017;28(6):1020-1031.
[Google Scholar]

[37] Lin J.S., Liu J.Q., Feng W.M., Jing X.Y., . Organic geochemical signatures and palaeo-environmental implications for the source rocks from the Lower Silurian Longmaxi Formation in northern Guizhou. Sediment. Geol. Tethyan Geol.. 2014;34(2):79-85.
[Google Scholar]

[38] Liu S.G., Yang Y., Deng B., Zhong Y., Wen L., Sun W., Li Z.W., Jansa L., Li J.X., Song J.M., . Tectonic evolution of the sichuan basin, southwest China. Earth Sci. Rev.. 2021;213:103470
[Google Scholar]

[39] Liu A., Yang J.H., Cheng L., Ren J.T., . Climate-controlled coastal deposition of the early permian liangshan formation in Western South China. Front. Earth Sci.. 2022;10:888012
[Google Scholar]

[40] Long S.X., Lu T., Li Q.W., Yang G.J., Li D.H., . Discussion on China's shale gas development ideas an goals during the 14^th Five-Year Plan. Nat. Gas Ind.. 2021;41(10):1-10.
[Google Scholar]

[41] Lou Y., Su Y.L., Gao W., Wang W.D., Xiong W., Chen J., Xia P., . Pore characteristics and fractal characterization variability of typical middle-and high-rank coal reserves: a case study of middle-and high-rank coal samples in western Guizhou. Front. Energy Res.. 2022;10:981530
[Google Scholar]

[42] Loucks R.G., Reed R.M., Ruppel S.C., Hammes U., . Spectrum of pore types and networks in mudrocks and a descriptive classification for matrix-related mudrock pores. AAPG Bull.. 2012;96(6):1071-1098.
[Google Scholar]

[43] Lu S.F., . Study on Shale Gas A ccumulation Rules and Exp loration Area of Dawuba Formation of Carboniferous in Guizhou Province. Guiyang: Guizhou University; 2019.

[44] Lu S.F., Luo X.J., Du S.J., He B., Fu H.B., Liu K.Y., . Discovery and analysis of shale gas in a carboniferous reservoir and its enrichment characteristics in the Northern Nanpanjiang Depression, Guizhou Province China. Acta Geologica Sinica-English Edition. 2019;93(3):561-572.
[Google Scholar]

[45] Lu S.F., Chen Y., Luo X.J., He B., Fu H.B., . Sedimentary characteristics and distribution of the carboniferous black shale in Guizhou Province. Journal of Sedimentology. 2021;39(3):672-685.
[Google Scholar]

[46] Ma X., . Fine characterzation of shale reservoir of Longtan Formation in western Guizhou. Beijing: China University of Geosciences; 2017. Master Thesis

[47] Ning S.T., Xia P., Hao F., Tian J.Q., Zhong Y., Zou N.N., Fu Y., . Shale facies and its relationship with sedimentary environment and organic matter of Niutitang black shale Guizhou Province. Natural Gas Geoscience. 2021;32(9):1297-1307.
[Google Scholar]

[48] Ning S.T., Xia P., Zou N.N., Zhong Y., Yu Y., Mou Y.L., Wang K., . Organic matter pore characteristics of over-mature marine black shale: a comparison of organic fractions with different densities. Frontiers of Earth Science. 2023;17(1):310-321.
[Google Scholar]

[49] Niu J.L., Zhang J.C., Tang X., Yuan K., Lin T., Liu Y., Niu Y.J., Li P., Li X.Q., Liang Y.T., . Main Controlling factors and models of organic matter accumulation in lower carboniferous dawuba formation shale in Southern Guizhou China. ACS Omega. 2021;6(48):32441-32459.
[Google Scholar]

[50] Qin Y., Gao D., Wu C.F., . Prediction and evaluation of coalbed methane resource potential in Guizhou Province. Xuzhou: China University of Mining and Technology Press; 2012.

[51] Shao, L., XU, X., Wang, S., Wang, D., Gao, D., Wang, X. and Lu, J., 2021. Research progress of palaeogeography and palaeoenvironmental evolution of coal-bearing series in China. Journal of Palaeogeography, 23(1): 19–38.

[52] Shi S.Y., Wang Y.P., Sun Y., Guo H.J., . The volume and geochemical characteristics of desorption gases from wufeng-longmaxi (O₃w–S₁l) shale in the Xishui Area, North Guizhou China. Frontiers in Earth Science. 2022;10:879959
[Google Scholar]

[53] Su H., . Analysis on the sedim entary environm ent and hy drocarb on source rock characteristics of black shale in dawub a forr ation of early carb oniferous in Huishui, Guizhou. Guiyang: Guizhou University; 2018.

[54] Sun Q.H., . Forming Condition and Distribution Prediction of Shale Gas of Longtan Formation in Northwest Guizhou. Beijing: China University of Geosciences; 2014.

[55] Sun J., Xiao X.M., Cheng P., . Influence of water on shale pore heterogeneity and the implications for shale gas-bearing property-a case study of marine Longmaxi Formation shale in northern Guizhou. Mar. Pet. Geol.. 2021;134:105379
[Google Scholar]

[56] Sun M.D., Yu B.S., Hu Q.H., Zhang Y.F., Li B., Yang R., Melnichenko Y.B., Cheng G., . Pore characteristics of Longmaxi shale gas reservoir in the Northwest of Guizhou, China: investigations using small-angle neutron scattering (SANS), helium pycnometry, and gas sorption isotherm. Int. J. Coal Geol.. 2017;171:61-68.
[Google Scholar]

[57] Sun W.J.B., Zuo Y.J., Wu Z.H., Liu H., Xi S.J., Shui Y., Wang J., Liu R.B., Lin J.Y., . Fractal analysis of pores and the pore structure of the Lower Cambrian Niutitang shale in northern Guizhou province: investigations using NMR, SEM and image analyses. Mar. Pet. Geol.. 2019;99:416-428.
[Google Scholar]

[58] Sun W.J.B., Zuo Y.J., Wu Z.H., Liu H., Zheng L.J., Shui Y., Xi S.J., Lou Y.L., Luo X., . The distribution characteristics of brittle minerals in the Lower Cambrian Niutitang Formation in northern Guizhou. J. Nat. Gas Sci. Eng.. 2021;86:103752
[Google Scholar]

[59] Tan J.Q., Wang Z.H., Wang W.H., Hilton J., Guo J.H., Wang X.K., . Depositional environment and hydrothermal controls on organic matter enrichment in the lower Cambrian Niutitang shale, southern China. AAPG Bull.. 2021;105(7):1329-1356.
[Google Scholar]

[60] Tilley B., McLellan S., Hiebert S., Quartero B., Veilleux B., Muehlenbachs K., . Gas isotope reversals in fractured gas reservoirs of the western Canadian Foothills: mature shale gases in disguise. AAPG Bull.. 2011;95(8):1399-1422.
[Google Scholar]

[61] Usui A., Someya M., . Distribution and composition of marine hydrogenetic and hydrothermal manganese deposits in the northwest Pacific. Geol. Soc. Lond. Spec. Publ.. 1997;119(1):177-198.
[Google Scholar]

[62] Valetich M., Zivak D., Spandler C., Degeling H., Grigorescu M., . REE enrichment of phosphorites: an example of the Cambrian Georgina Basin of Australia. Chem. Geol.. 2022;588:120654
[Google Scholar]

[63] Wang Y., Gui H.R., Su S.G., Zhou Q.M., . Sedimentary environment and paleoclimate geochemical characteristics of shale in the wufeng and longmaxi formations Northern Yunan-Guizhou Area. Acta Sedimentologica Sinica. 2022;40(3):653-666.
[Google Scholar]

[64] Wang E., Guo T.L., Li M.W., Xiong L., Dong X.X., Zhang N.X., Wang T., . Depositional environment variation and organic matter accumulation mechanism of marine-continental transitional shale in the upper permian longtan formation, Sichuan Basin, SW China. ACS Earth Space Chem.. 2022;6(9):2199-2214.
[Google Scholar]

[65] Wang P.F., Jiang Z.X., Yin L.S., Chen L., Li Z., Zhang C., Li T.W., Huang P., . Lithofacies classification and its effect on pore structure of the Cambrian marine shale in the Upper Yangtze Platform, South China: evidence from FE-SEM and gas adsorption analysis. J. Pet. Sci. Eng.. 2017;156:307-321.
[Google Scholar]

[66] Wang X.T., Shao L.Y., Eriksson K.A., Yan Z.M., Wang J.M., Li H., Zhou R.X., Lu J., . Evolution of a plume-influenced source-to-sink system: an example from the coupled central Emeishan large igneous province and adjacent western Yangtze cratonic basin in the Late Permian SW China. Earth-Science Reviews. 2020;207:103224
[Google Scholar]

[67] Wang Y.M., Wang S.F., Dong D.Z., Li X.J., Huang J.L., Zhang C.C., Guan Q.Z., . Litheofacies characterization of Longmaxi Formation of the Lower Silurian, southern Sichuan. Eareh Science Frontiers. 2016;23(1):119-133.
[Google Scholar]

[68] Wang P.F., Zhang C., Li X., Zhang K., Yuan Y., Zang X.P., Cui W.J., Liu S.Y., Jiang Z.X., . Organic matter pores structure and evolution in shales based on the he ion microscopy (HIM): a case study from the Triassic Yanchang, Lower Silurian Longmaxi and Lower Cambrian Niutitang shales in China. J. Nat. Gas Sci. Eng.. 2020;84:103682
[Google Scholar]

[69] Wei H.R., Yang R.D., Gao J.B., Chen J.Y., Liu K., Cheng W., . New evidence for hydrothermal sedimentary genesis of the Ni-Mo deposits in black rock series of the basal cambrian, guizhou province: discovery of coarse-grained limestones and its geochemical characteristics. Acta Geologica Sinica-English Edition. 2012;86(3):579-589.
[Google Scholar]

[70] Wu Y., Qin Y., Yi T.S., . Enrichment of rare earth elements in high sulfur coal of liangshan formation from kaili guizhou china and geological origin. Acta Geol. Sin.. 2010;84(2):280-285.
[Google Scholar]

[71] Wu C.J., Tuo J.C., Zhang L.F., Zhang M.F., Li J., Liu Y., Qian Y., . Pore characteristics differences between clay-rich and clay-poor shales of the Lower Cambrian Niutitang Formation in the Northern Guizhou area, and insights into shale gas storage mechanisms. Int. J. Coal Geol.. 2017;178:13-25.
[Google Scholar]

[72] Xia P., Wang G.L., Zeng F.G., Mou Y.L., Zhang T.H., Liu J.G., . The characteristics and mechanism of high over matured nitrogen-rich shale gas of Niutitang Formation, northern Guizhou a area. Nat. Gas Geosci.. 2018;29(9):1345-1355.
[Google Scholar]

[73] Xia P., Fu Y., Yang Z., Guo C., Huang J.Q., Huang M.Y., . The relationship between sedimentary environment and organic matter accumulation in the Niutitang black shale in Zhenyuan, northern Guizhou. Acta Geol. Sin.. 2020;94(3):947-956.
[Google Scholar]

[74] Xia P., Fu Y., Guo C., Yang Z., Huang J.Q., Mou Y.L., . Shale gas reservoir evaluation by geophysical measurements: a case study of the upper ordovician-lower silurian in the fenggang block, Northern Guizhou Province. Acta Geologica Sinica-English Edition. 2021;95(4):1310-1321.
[Google Scholar]

[75] Xia P., Li H.N., Fu Y., Qiao W.L., Guo C., Yang Z., Huang J.Q., Mou Y.L., . Effect of lithofacies on pore structure of the Cambrian organic-rich shale in northern Guizhou. China. Geological Journal. 2021;56(2):1130-1142.
[Google Scholar]

[76] Xia P., Hao F., Tian J.Q., Zhou W.X., Fu Y., Guo C., Yang Z., Li K.J., Wang K., . Depositional environment and organic matter enrichment of early cambrian niutitang black shales in the upper Yangtze Region. China. Energies. 2022;15(13):4551.
[Google Scholar]

[77] Xia P., Hao F., Tian J.Q., Fu Y., Mou Y.L., Guo C., Yang Z., Wang K., . Organic matter occurrence and its effects on pore structure and methane adsorption capacity capacity: A case study of the Niutitang black shale in Guizhou, China. J. Earth Sci. 2023
[CrossRef] [Google Scholar]

[78] Xiao J.F., Li Y.T., Yang H.Y., Xu J.B., Huang M.L., . Geochemistry of the Yudong bauxite deposit, south-eastern Guizhou, China: implications for conditions of formation and parental affinity. J. Geochem. Explor.. 2021;220:106676
[Google Scholar]

[79] Xu Q., . Study on permian liangshan formation shale gas exploration potential in Southwestern Guizhou Area. Coal Geology of China. 2017;29(5):20-26.
[Google Scholar]

[80] Xu S., Gou Q.Y., Hao F., Zhang B.Q., Shu Z.G., Lu Y.B., Wang Y.X., . Shale pore structure characteristics of the high and low productivity wells, Jiaoshiba shale gas field, Sichuan Basin, China: Dominated by lithofacies or preservation condition? Mar. Pet. Geol.. 2020;114:104211
[Google Scholar]

[81] Yang Z.B., . Geological evaluation technology for the development of multi-layer joint mining of coalbed methane. Xuzhou: China University of Mining and Technology Press; 2020.

[82] Yang Z., Wu P., Fu Y., Qiao W.L., Qin Y., Li C., Xia P., Guo C., Long X.L., Wu L., . Coupling of the redox history and enrichment of Ni-Mo in black shale during the early Cambrian: constraints from S-Fe isotopes and trace elements of pyrite South China. Ore Geol. Rev.. 2022;143:104749
[Google Scholar]

[83] Yeasmin R., Chen D.Z., Fu Y., Wang J.G., Guo Z.H., Guo C., . Climatic-oceanic forcing on the organic accumulation across the shelf during the Early Cambrian (Age 2 through 3) in the mid-upper Yangtze Block, NE Guizhou, South China. J. Asian Earth Sci.. 2017;134:365-386.
[Google Scholar]

[84] Yi T.S., Zhao X., . Characteristics and distribution patterns of the Lower Cambrian Niutitang Shale reservoirs in Guizhou China. Gas Industry. 2014;34(8):8-14.
[Google Scholar]

[85] Yu Y., Xia P., Wang Y.B., Ning S.T., Zhong Y., Mou Y.L., Li K.J., . Organic matter occurrence status and characteristics of over-mature marine shale: a case study of shale in the Lower Cambrian Niuhoitang Formation in Guizhou. Journal of Northeast Petroleum University. 2022;46(4):48-61.
[Google Scholar]

[86] Zeng P., Guo T.L., . Enrichment of shale gas in different strata in sichuan basin and its periphery-the examples of the cambrian qiongzhusi formation and the Silurian Longmaxi formation. Energy Explor. Exploit.. 2015;33(3):277-298.
[Google Scholar]

[87] Zhang D., . China issued the “shale gas development plan (2011–2015)”. Fault-Block Oil and Gas Fields. 2012;19(4):429.
[Google Scholar]

[88] Zhang H.J., Fan H.F., Wen H.J., Han T., Zhou T., Xia Y., . Controls of REY enrichment in the early Cambrian phosphorites. Geochim. Cosmochim. Acta. 2022;324:117-139.
[Google Scholar]

[89] Zhang D.M., He L.L., Zeng G.Q., Yang K.G., Dai C.G., Zhang H., . Superimposed deformation and its controlling effect on Pb-Zn deposits of guanziyao region in West Guizhou. Guizhou Geology. 2014;31(4):241-251.
[Google Scholar]

[90] Zhang W.T., Hu W.X., Borjigin T., Zhu F., . Pore characteristics of different organic matter in black shale: a case study of the Wufeng-Longmaxi Formation in the Southeast Sichuan Basin, China. Mar. Pet. Geol.. 2020;111:33-43.
[Google Scholar]

[91] Zhang Q.M., Jiang X.S., Qin J.H., Cui X.Z., Liu C.Z., . Lithofacies palaeogeography of the early Middle Permian Liangshan Formation in northern Guizhou-southern Chongqing area and its bauxite ore-forming effect. Geol. Bull. China. 2012;31(4):558-568.
[Google Scholar]

[92] Zhang G.T., Peng Z.Q., Wang C.S., Li Z.H., . Geochemical characteristics of the Lower Permian Liangshan Formation in Dushan area of Guizhou Province and their implications for the paleoenvironment. Geol. China. 2016;43(4):1291-1303.
[Google Scholar]

[93] Zhang J.C., Shi M., Wang D.S., Tong Z.Z., Hou X.D., Niu J.L., Li X.Q., Li Z.M., Zhang P., Huang Y.Q., . Fields and directions for shale gas exploration in China. Nat. Gas Ind.. 2021;41(8):69-80.
[Google Scholar]

[94] Zhang B., Tang S.H., Xi Z.D., Lin D.L., Ye Y.P., . Sequence stratigraphic characteristics and organic matter enrichment of wufeng-longmaxi formation in Northwestern Huna: a case study of well XY-3*. Adv. Earth Science. 2021;36(10):1026-1038.
[Google Scholar]

[95] Zhao, L.Y., Zhou, P.M., Lou, Y., Zhao, Y.Z., Liu, W., Liao, Z.W. and Xia, P., 2021. Geochemical Characteristics and Sedimentary Environment of the Upper Permian Longtan Coal Series Shale in Western Guizhou Province, South China. Geofluids, DOI: 10.1155/2021/9755861.

[96] Zhao F.P., Sun Z., Sang S.X., Zhou X.Z., Han Z.Q., Zhao L.Y., Wu Z.L., . Progress of coalbed methane exploration and development in Guizhou and the 14th Five-Year Plan development strategy. Nat. Gas Ind.. 2022;42(6):65-75.
[Google Scholar]

[97] Zheng F.Z., Tang X., Yuan K., Lin T., You M.X., Niu J.L., Zi Y.Y., Liang Y.T., . Sedimentation models and development mechanisms of organic-rich shales of the lower carboniferous dawuba formation: a case study in the Yaziluo Rift Trough, South of Guizhou Province Southern China. ACS Omega. 2022;7(33):29054-29071.
[Google Scholar]

[98] Zhong Y., Yang Y.M., Wen L., Luo B., Xiao D., Tan X.C., Zhao L.K., Li M.L., . Sedimentary environments controlled by tectonics and induced differential subsidence: a perspective in the Permian Liangshan and Qixia Formations, northwestern Sichuan Basin China. Journal of Central South University. 2020;27(11):3398-3416.
[Google Scholar]

[99] Zhong Y., Xia P., Ning S.T., Fu Y., Li Q.G., Yu Y., . Geochemical characteristics and its geological application of over-mature Longmaxi shale gas in the northern Guizhou area China. Arabian Journal of Geosciences. 2021;14(18):1-9.
[Google Scholar]

[100] Zou C.N., Yang Z., Pan S.Q., Chen Y.Y., Lin S.H., Huang J.L., Wu S.T., Dong D.Z., Wang S.F., Liang F., . Shale gas formation and occurrence in China: An overview of the current status and future potential. Acta Geologica Sinica-English Edition. 2016;90(4):1249-2183.
[Google Scholar]

[101] Zhu L.J., Zhang D.W., Zhang J.C., Chen Y., Wang G.L., Yang T.B., Chen H.G., . Paleozoic passive continental margin shale gas in eastern Shangyangzi Geological theory, technology and practice. Beijing: Science Press; 2019.

[102] Zou C.N., Dong D.Z., Wei Y.J., . Marine Shale Gas. Beijing: Science Press; 2021.

[103] Zou C.N., Yang Z., Dong D.Z., Zhao Q., Chen Z.H., Feng Y.L., Li J.R., Wang X.N., . Formation, Distribution and Prospect of Unconventional Hydrocarbons in Source Rock Strata in China. Earth Sci.. 2022;47(5):1517-1533.
[Google Scholar]

Geochemical characteristics of the shale gas reservoirs in Guizhou Province, South China

Abstract

Abstract

Keywords

Shale gas

Organic-rich shale

Organic matter

Marine shale

Marine-continental transitional shale

South China

1 Introduction

2 Organic-rich shales in Guizhou Province

3 Distribution of the organic-rich shales

4 Sedimentary environment of organic-rich shales in different strata

4.1 Sedimentary environment of the Niutitang organic-rich shale

4.2 Sedimentary environment of the Wufeng-Longmaxi organic-rich shale

4.3 Sedimentary environment of the Dawuba organic-rich shale

4.4 Sedimentary environment of the Liangshan organic-rich shale

4.5 Sedimentary environment of the Longtan organic-rich shale

5 Composition of the different shales

5.1 Geochemical characteristics of the organic-rich shales

5.1.1 Organic matter abundance

5.1.2 Organic matter type

5.1.3 Organic matter maturity

5.2 Shale lithofacies

5.2.1 Mineralogical characteristics

5.2.2 Lithofacies classification and features

5.3 Pore characteristics

5.3.1 Porosity and permeability

5.3.2 Pore types

5.3.3 Pore structure

6 Prospect of shale gas in Guizhou Province

6.1 Gas resources and origin

6.2 Brittle index and compressibility

6.3 Prospect for exploration and development

6.4 “Sweet spot” of shale gas

7 Conclusions

Acknowledgements

Declaration of competing interest

References

Suggested read for related articles: