Synthesis and evaluation of polymer microspheres (P-FLA) synthesized by inverse emulsion polymerization as a filter loss reducer for water-based drilling fluid

Xiaoming Su; Yuan Yuan; Yin Da; Peng Xu; Zhen Zhang; Tao Peng

doi:10.25259/AJC_388_2025

View/Download PDF

Buy Reprints

PDF

Translate this page into:

Original Article

ARTICLE IN PRESS

doi:

10.25259/AJC_388_2025

Synthesis and evaluation of polymer microspheres (P-FLA) synthesized by inverse emulsion polymerization as a filter loss reducer for water-based drilling fluid

Xiaoming Su^a, Yuan Yuan^a, Yin Da^b, Peng Xu^c,*, Zhen Zhang^b, Tao Peng^d,

aLanzhou City College Peili Petroleum Engineering College, Lanzhou, Gansu, China

bChina Petroleum Tarim Oilfield Branch, Korla, Xingjiang, China

cYangtze University, China

dCollege of Petroleum Engineering, Yangtze University, Yangtze University, Wuhan, Hubei, China

* Corresponding author: E-mail address: cdxupeng@yangtzeu.edu.cn (P. Xu)

Received: 2025-04-14, Accepted: 2025-09-23, Epub ahead of print: 2026-03-14,

Licence

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

Abstract

With the continuous advancement of oil exploration and drilling technologies, water-based drilling fluids have become increasingly effective in protecting oil and gas reservoirs. To address the challenge of conventional filter loss reducers losing effectiveness at high temperatures, a novel polymer microsphere-based filter loss reducer was synthesized via inverse emulsion polymerization. The primary monomers used were β-cyclodextrin and soluble starch, with epichlorohydrin serving as the crosslinking agent. Sorbitan monooleate and polyoxyethylene sorbitan monooleate were employed as emulsifiers. The structure of the synthesized polymer microspheres was characterized using various analytical techniques, including scanning electron microscopy (SEM), optical microscopy, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and particle size analysis. The performance of the microspheres was then evaluated in terms of rheology, filtration loss, and sealing ability using a six-speed rotational viscometer, static fluid loss (API) filtration apparatus, and a medium-pressure sand bed apparatus, respectively. Experimental results demonstrated that incorporating the polymer microspheres into water-based drilling fluids had minimal impact on the rheological properties before and after hot rolling aging at 150°C. Furthermore, both filtration loss and sealing performance were significantly improved. These findings indicate that the synthesized polymer microspheres possess excellent high-temperature resistance and sealing capability, making them a promising candidate for use as a filter loss reducer in water-based drilling fluids. Compared to conventional filtration loss reducers such as starch, CaCO₃, and 2-acrylamido-2-methylpropane sulfonic acid (AMPS)-based copolymers, the polymer microspheres (P-FLA) microspheres exhibit superior high-temperature resistance, broader particle size distribution, and enhanced filtration control efficiency, making them more effective under deep well conditions.

Keywords

Filter loss reducer

Inverse emulsion polymerization

Polymer microspheres

Water-based drilling fluid

Show Related Articles from PubMed

1. Introduction

During the exploration and development of oil and gas resources, the drilling depth continues to increase [1], often leading to challenges such as geological instability, wellbore collapse, and wellbore leakage. Moreover, as the development efforts intensify, it can even lead to wellbore abandonment, resulting in significant economic losses [2-4]. Although oil-based drilling fluid has good thermal stability [5], its high cost and poor environmental adaptability limit its application. Therefore, water-based drilling fluid with high temperature stability is preferred as an important protection means [6,7]. Nowadays, increasingly high temperatures and ultra-high temperature wells are encountered when drilling. Improving the fluid loss reduction performance under high temperature and pressure conditions can effectively prevent wellbore instability and other accidents.

Under high temperature conditions, the types of filter loss reducers for water-based drilling fluid are mainly divided into natural polymers and synthetic polymers [8-10]. Natural polymer fluid loss reducer is environmentally friendly but has poor temperature resistance, while synthetic polymer fluid loss reducer has good temperature resistance, but does not biodegrade into its monomer easily, which adversely affects the environment [11,12]. Therefore, to achieve the goal of green exploration and development, the focus should be on studying the relationship between polymer structure and filtration loss performance, developing new monomers, and improving the temperature resistance of polymers [13-16].

In recent years, many scholars have been developing environment-friendly polymer fluid loss reduction agents for water-based drilling fluids. Yang et al [17] synthesized a modified corn starch reducer with good salt and calcium resistance and moderate temperature tolerance (90-130°C), achieving a 46% reduction at 2% dosage. Jie et al [18] developed a sulfonic acid and quaternary ammonium-modified starch (YS) with temperature resistance up to 180°C [19] and reported that increasing concentrations of corn starch improved filtration control between 170-200°F. Prakash et al [20] explored lychee leaf powder (LLP) as a biodegradable additive, which outperformed carboxymethyl cellulose in fluid loss reduction at 100°C. Yanling et al [21] grafted nano-CaCO₃ onto hydroxyethyl cellulose to obtain MND-1, which maintained excellent performance at 180°C with only 6.8 mL filter loss. Chen et al. [10] synthesized starch microspheres via emulsion polymerization, which reduced API fluid loss by up to 70% at 150°C with minimal rheological impact. Zhong et al. [22] constructed lignin-based amphiphilic copolymers for deep-well applications, improving wellbore stability. Yong et al. [23] prepared a biomass-based composite (PLS) achieving only 9.6 mL fluid loss at 180°C. Xin et al. and Zhong et al [24,25] synthesized β-cyclodextrin polymer microspheres using reverse emulsion polymerization, demonstrating excellent filtration control after hot rolling aging at 180-200°C. Li et al [26] presented a silica-reinforced polymer microsphere (M-SiO₂/ZMD) synthesized via reverse suspension polymerization, which demonstrated excellent high-temperature and salt resistance, significantly reducing filtration loss in water-based drilling fluids. Xu et al. [27] developed a high-temperature-resistant nanopolymer microsphere (PSDA), which exhibited excellent thermal stability and plugging performance at 240°C, significantly reducing API filtration and outperforming conventional plugging agents.

However, most starch-based or cyclodextrin-based additives suffer from either limited thermal stability or poor dispersion under high-temperature conditions. Moreover, few studies have combined both β-cyclodextrin and soluble starch into a single microsphere system to enhance filtration control at elevated temperatures. Starch-based materials are widely favored as natural polymers due to their low cost and abundance. Modified soluble starch, including crosslinked or grafted forms, enhances performance for drilling applications [27-29]. β-cyclodextrin, composed of seven D-glucose units in a truncated cone shape, features a hydrophobic cavity and hydrophilic exterior, enabling unique inclusion and interaction properties. Utilizing inverse emulsion polymerization, starch and β-cyclodextrin can be chemically grafted with crosslinking agents to form polymer microspheres with strong adsorption capacity. These microspheres retain the structural advantages of β-cyclodextrin while gaining temperature resistance and environmental compatibility, making them promising filter loss reducers for water-based drilling fluids (Figure 1).

Mechanism of water-based drilling fluid.

In light of the limitations of current polymer-based fluid loss reducers, this study aims to develop a novel, environmentally friendly microsphere-based additive synthesized via inverse emulsion polymerization using β-cyclodextrin and soluble starch as raw materials. This approach leverages the hydrophobic cavity and hydroxyl-rich surface of β-cyclodextrin along with the mechanical reinforcement provided by starch. Unlike conventional additives, the synthesized P-FLA microspheres are expected to exhibit improved thermal stability, dispersibility, and filtration control performance in high-temperature water-based drilling fluids. The study not only evaluates the structural and thermal properties of the microspheres but also investigates their rheological, filtration, and plugging performance under elevated temperature conditions.

2. Materials and Methods

2.1 Monomer selection

Starch is a polymer of high-molecular-weight carbohydrates, appearing as a white powdery substance. It is formed through the covalent polymerization of glucose molecules after dehydration and subsequent linkage by glycosidic bonds. Modified soluble starch, also known as soluble starch, is a starch derivative obtained through treatment with oxidants, acids, glycerol, enzymes, or other methods. Soluble starch finds widespread application in the production of tablets, capsules, and other dosage forms. Compared to cyclodextrin, soluble starch is more stable and exhibits stronger adsorption capabilities, overcoming the drawbacks of high viscosity and difficulty in granulation associated with cyclodextrin and simplifying the manufacturing process [30].

β-cyclodextrin (Figure 2) is a cyclodextrin composed of seven D-glucose units, forming a hollow truncated cone shape. It possesses numerous hydroxyl groups on its surface and inner cavity, exhibiting both hydrophobicity inside the ring and hydrophilicity outside the ring. β-cyclodextrin has the ability for controlled release, catalysis, and recognition. It can form inclusion complexes by encapsulating compounds that are compatible in size with its cavity.

(a) β-cyclodextrin molecular formula (b) β-cyclodextrin 3D structure.

2.2. Experimental materials

Drugs: β-cyclodextrin, anhydrous ethanol, epichlorohydrin, supplied by Shanghai Macklin Biochemical Technology Co., Ltd.; soluble starch, sorbitan oleate (Span80), polyoxyethylene sorbitan monooleate (Tween80), sodium carbonate, calcium carbonate, sodium hydroxide, supplied by Shanghai Aladdin Bio-Chem Technology Co., Ltd.; deionized water, laboratory-made; PF-PLUS (water-based drilling fluid viscosifier), sodium bentonite, supplied by China Jingzhou Jiahua Technology Co., Ltd..

Instruments: Double-digit display, Constant temperature, Magnetic Stirrer (HJ-2B), Changzhou Gaode Instrument Manufacturing Co., LTD. Rotary viscometer, High temperature and high pressure filtration instrument, Qingdao Chuangmeng Instrument Co., LTD. Electronic constant temperature stainless steel water bath, China Shanghai Yulong Instrument Equipment Co., LTD.; Optical microscope, made by Jiangnan Yongxin Optics Co., LTD., Nanjing, China; Scanning Electron Microscope (SEM) (SU8010), Hitachi Corporation, Japan; Laser Particle Size Analyzer, Malvern Mastersizer 2000, UK; Thermogravimetric, TA TGA 550.

Evaluation of the water-based drilling fluid formulation used in the experiment: First, 12.0 g of sodium bentonite was dispersed in 300 mL of water, and the mixing speed was set to 6000 rpm/min to start mixing. During the mixing process, 0.2% NaOH and 0.2% Na₂CO₃ were added to adjust the PH of the base paste. After 30 min of mixing, the base paste was sealed and hydrated for 24 h. Then, 0.5% PF-PLUS was slowly added to the base pulp and stirred evenly at 1000 rpm/min to improve the rheological properties of the base pulp. Finally, different amounts of polymer microspheres were added to the base pulp, and after fully stirring for 20 min; the obtained base pulp was poured into the aging tank. To simulate the high-temperature environment, a fixed temperature (150 °C) of the roller furnace was set for aging treatment.

2.3. Synthetic process

Polymer microsphere-based filter loss reducers are mainly synthesized using the inverse emulsion polymerization method.

(1) Continuous phase preparation: 1.3 g of soluble starch and 14.7 g of β-cyclodextrin were fully dissolved in 40 mL of deionized water. Then, NaOH was added to adjust the pH to approximately 11. During the stirring process, 12.8mL of epichlorohydrin was slowly added. The stirring speed was set at 600rpm/min, and the stirring was continued for 1 h (Figure 3a).

Steps for the synthesis of filter loss reducer (P-FLA microspheres).

(2) Dispersed phase preparation: 160mL of white oil was taken in a beaker, and 3.36 g of Span80 and 1.44 g of Tween80 were added separately. Then, turn on the magnetic stirrer and adjust the speed to 600 rpm/min, and continue stirring for 30 min (Figure 3b).

(3) The three-necked flasks were placed in a water bath, with a stirring rod assembled in the middle neck. The dispersed phase was slowly added, and the stirrer was turned on at a speed of 800rpm/min. The temperature was gradually increased to 60°C. Then, slowly add the continuous phase dropwise into the three-necked flasks. Finally, increase the stirring speed to 1000 rpm/min and wait for 5 h until the reaction is complete (as shown in Figure 3c).

(4) The emulsion synthesized in the three-necked flask was transferred into the beaker, followed by centrifugation and demulsification. It was then sequentially washed with dilute hydrochloric acid, anhydrous ethanol, and distilled water. Afterward, the microspheres were dried in a vacuum dryer at 60°C for 24 h to obtain polymer microspheres as a filter loss reducer, namely P-FLA microspheres (Figure 3d).

2.4. Synthesis mechanism

The inclusion of β-cyclodextrin monomer itself improves bioavailability, and the formation of crosslinking bonds results in the formation of a 3D network of β-cyclodextrins inside the synthesized P-FLA microspheres [31,32]. The addition of a small amount of soluble starch can enhance the mechanical strength of P-FLA microspheres, which not only maintains the inclusion of β-cyclodextrin monomer but also has strong adsorption capacity. P-FLA microspheres were synthesized by inverse emulsion polymerization, in which β-cyclodextrin and soluble starch were the main monomers. β-cyclodextrin and soluble starch were activated in a strong alkaline solution at room temperature and then crosslinked with epichlorohydrin. The main function of the crosslinking agent was to form a 3D spatial network of hydrophobic CH₂-O-(CH₂-CH₂-O)_n-CH₂- structure between β-cyclodextrin monomers. The cross-linking reaction can also occur between soluble starch and β-cyclodextrin monomer, within the soluble starch sugar chain and the crosslinker itself (Figure 4).

Synthesis mechanism of P-FLA microspheres.

2.5. Characterization and evaluation methods

A small number of P-FLA microspheres was taken, and the potassium bromide tablet method was applied according to the Chinese standard GB/T 6040-2002 “Infrared spectrum analysis methods Part 5: Sample preparation method,” using a Fourier transform infrared (FTIR) spectrometer to characterize and analyze them. Then, 10 mL of deionized water was poured into a beaker, a small amount of P-FLA microspheres was added to stir, and their appearance and distribution were observed with an optical microscope. Then, SEM was used to observe the microscopic morphology of P-FLA microspheres, and the Chinese standard “GB/T 36422-2018 SEM Method for the determination of microscopic morphology and diameter” was used as the main operating principle. The P-FLA microsphere sample was installed on double-sided tape and sprayed with a layer of gold before imaging. The thermal stability of the microsphere was measured by using a differential thermogravimetric synchronous analyzer at a temperature of 0-600°C and a heating rate of 10°C/min. The whole microsphere was protected by inert gas. Results: The curve analysis was in accordance with the Chinese standard “NB/SH/T 0859-2013 Determination of thermal stability of chemical substances”. For the analysis of particle size distribution of microspheres, a small amount of sample will be dispersed in deionized water and continuously stirred with a laser particle size analyzer.

(2) In the evaluation experiment, the rheology and filtration loss performance of water-based drilling fluid before and after hot rolling aging were tested. The apparent viscosity (AV), plastic viscosity (PV), and yield point (YP) of the drilling fluid are calculated according to the reading of the six-speed viscometer. The formula is as follows (Eqs. 1-3):

(1)

A V (m P a \cdot s) = \frac{Φ 600}{2}

(2)

P V (m P a \cdot s) = Φ 600 - Φ 300

(3)

Y P (P a) = A V - P V

According to the medium-pressure (API) filtration instrument, standard filter paper is used as the filtration medium, the pressure is set to 0.69MPa, and the test time is 30 min. After the test, the filtration loss is read out, and the mud cake state is observed.

(3) In the evaluation experiment, the plugging performance of P-FLA microspheres was tested with the medium-pressure sand-bed experimental device. P-FLA microspheres of different concentrations were added into the configured water-based drilling fluid, stirred evenly at 6000 rpm/min, and heated rolled at 150°C×16h to obtain the test sample. After a certain amount of quartz sand is washed and dried, it is poured into the tempered glass cylinder of the plugging instrument to the 350 mL scale line, and then the test sample is slowly poured after repeated beating and compacted. Finally, the test sample is pressurized to 0.69 MPa, the valve is opened for timing, and the loss of the sand bed is recorded within 30 min.

3. Results and Discussion

3.1. Structure and characterization

3.1.1. Infrared spectra of P-FLA microspheres

According to the infrared spectrum analysis of P-FLA microspheres synthesized by the inverse emulsion polymerization of starch and β-cyclodextrin (Figure 5), the absorption peak at 3340.18 cm^-1 proves that the -OH in starch and β-cyclodextrin always exists before and after the cross-linking of polymer microspheres. Moreover, the C-H stretching vibration absorption peak (2924.52cm^-1) and bending vibration peak (1380.24cm^-1) of saturated hydrocarbon and the C-O stretching vibration absorption peak at 1156.11cm^-1 are the characteristic absorption peaks of starch and β-cyclodextrin. The -OH bending vibration absorption peak of β-cyclodextrin adsorbed water molecules at 1650.25cm^-1 corresponds to the absorption peak of β-cyclodextrin adsorbed water molecules, and the absorption peak in the range of wave number 850.23-704.35cm^-1 is the absorption peak on the glucose ring of β-cyclodextrin. The polymer microspheres contain the corresponding functional groups designed, which proves that the target product is obtained by inverse emulsion polymerization.

Infrared spectrum analysis of filter loss reducer (P-FLA microspheres).

3.1.2. Optical microscopy of P-FLA microspheres

To observe the overall distribution and appearance of the polymer microspheres, a small amount of P-FLA microspheres was put into deionized water and stirred evenly, a small amount of liquid was sucked into the slide with a rubber head dropper, and then the P-FLA microspheres were observed with an optical microscope adjusted to 20×10 times.

As shown in Figure 6, the polymer microspheres P-FLA were added to water for uniform stirring, and then observed with an optical microscope. It was found that the P-FLA microspheres were uniformly distributed, with a complete spherical shape and uniform particle size, indicating that they could be well dispersed in the water phase. When used in water-based drilling fluid at the same time, it can better coordinate other plugging materials to seal cracks, and has good compatibility.

P-FLA microspheres are 20×10 times larger under an optical microscope.

3.1.3. SEM of P-FLA microspheres

Use conductive tape to stick on the sample table, and then take a small amount of P-FLA microspheres to evenly sprinkle on the conductive adhesive, and then blow off the samples that are not stuck, which can well prevent the samples that are not stuck from polluting the equipment, and finally put them into the SEM for observation (as shown in Figure 7).

The SEM image of the polymer microspheres has been shown in the figure above. The appearance and morphology of P-FLA microspheres observed under an optical microscope are consistent, both displaying a spherical shape. The irregular and fragmented particles on the microsphere’s surface might be attributed to the high stirring rate during the synthesis reaction. From Figure 7, it can be observed that the particle size is in the micrometer range, with an average ranging from 8 to 40 µm.

3.1.4. Particle size analysis of P-FLA microspheres

P-FLA microspheres were dispersed into anhydrous ethanol to obtain samples. After ultrasonic dispersion for 20 min, the particle size distribution was measured by a laser particle size analyzer, and the results have been shown in Figure 8.

Particle size distribution curve of P-FLA microspheres.

The particle size distribution is described using D10, D50, and D90, which represent the particle diameters below which 10%, 50%, and 90% of the sample volume exist, respectively. According to the particle size analysis diagram, the median particle size of P-FLA microspheres is 10.406 µm in D50, 2.480 µm in D10, and 93.939 µm in D90. According to the formula, the span of particle size can be calculated as 8.789, indicating a wide particle size distribution. Part of the particle size in the figure is greater than 100 µm, mainly because some P-FLA microspheres are dispersed in anhydrous ethanol, and the hydroxyl group on the surface will adsorb ethanol molecules, resulting in a certain degree of expansion of P-FLA microspheres.

The superior fluid loss performance of P-FLA microspheres is primarily attributed to their uniform spherical morphology, wide particle size distribution, and the presence of a crosslinked 3D network structure. These microspheres can physically plug pores by bridging and filling microfractures in the filter cake. Furthermore, the hydroxyl-rich surface of β-cyclodextrin facilitates hydrogen bonding with bentonite particles, enhancing the integrity and compactness of the filter cake. Their hydrophilic exterior also ensures good dispersibility in the drilling fluid system, enabling a more homogeneous plugging effect under elevated temperature conditions.

3.1.5. Thermogravimetric analysis of P-FLA microspheres

A small number of P-FLA microspheres were tested and studied with a differential thermogravimetric analyzer. The temperature was set between 0 and 850°C, protected by inert gas, and the heating rate was 10°C/min. The thermal stability of the polymer microspheres was characterized.

As shown in Figure 9, the thermal stability of P-FLA polymer microspheres was evaluated using thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The initial weight loss of approximately 7.13% occurred below 150°C, primarily due to the evaporation of physically adsorbed and crystalline water. A major degradation stage took place between 336.58°C and 438.06°C, corresponding to the breakdown of β-cyclodextrin and starch backbones, involving the cleavage of glycosidic bonds and crosslinked ether structures. The DTG curve shows a peak degradation rate at 394.53°C, indicating the onset of rapid decomposition and confirming the formation of strong ether crosslinks by epichlorohydrin. After 438.06°C, the weight loss slowed significantly, with the residual weight stabilizing at 3.81%, suggesting the formation of a carbonaceous char. These results demonstrate that P-FLA microspheres possess excellent thermal stability and structural integrity under high-temperature conditions, supporting their suitability as filter loss reducers in water-based drilling fluids.

TG-DTG curve analysis of P-FLA microspheres.

3.2. Performance evaluation of P-FLA microspheres

3.2.1. Effects of P-FLA microspheres on rheological properties of water-based drilling fluid

Rheology of drilling fluid refers to the characteristics of fluid flow and deformation under the action of external forces. According to the formula of water-based drilling fluid in the experimental part, the base slurry was prepared, P-FLA microspheres of different concentrations were added, and after being fully mixed and homogenized, the hot rolling aging was carried out at 150°C×16h. Then the rheological properties of the water-based drilling fluid were studied using a six-speed rotating viscometer. The results have been shown in Table 1.

Table 1. Rheological parameters of water-based drilling fluid after adding P-FLA microspheres of different concentrations.

Formula	Before hot rolling aging			After hot rolling aging
Formula	600/300	200/100	6/3	600/300	200/100	6/3
Water-based drilling fluid	70/54	48/37	20/16	60/39	31/20	9/8
Water-based drilling fluid+1wt% P-FLA	70/55	48/37	20/16	61/40	32/22	9/8
Water-based drilling fluid+1.5wt% P-FLA	71/56	49/38	20/17	62/41	32/23	9/8
Water-based drilling fluid+2wt% P-FLA	71/56	49/38	21/18	64/42	33/24	10/9
Water-based drilling fluid+2.5wt% P-FLA	72/57	50/39	22/19	64/42	33/24	11/9
Water-based drilling fluid+3wt% P-FLA	73/58	50/39	22/20	65/43	33/24	11/10
Ageing condition: 150°C×16h

The rheological properties of drilling fluid are usually described using parameters such as apparent viscosity and yield point to ensure safety, quality, and efficiency during drilling. As can be seen from Figure 10, both the apparent viscosity and yield point of water-based drilling fluid tend to rise with the increase of P-FLA microspheres concentration before and after hot rolling aging at 150°C×16h, but the change range is small. The addition of P-FLA microspheres had no significant effect on the rheological properties of water-based drilling fluid. The slight increase in apparent viscosity and yield point after the addition of P-FLA microspheres can be attributed to the uniform dispersion of microspheres in the drilling fluid, which weakly interacts with bentonite particles without significantly altering the flow behavior. The spherical morphology and relatively small size ensure minimal disruption to the fluid’s internal structure, maintaining its pumpability and suspension capacity, which is essential for safe and efficient drilling operations.

Effect of different concentrations of filter loss reducer (P-FLA microspheres) on rheological properties of water-based drilling fluid.

3.2.2. Effects of P-FLA microspheres on the filtration performance of water-based drilling fluid

The filtration performance of drilling fluid mainly refers to the size of the filtration loss of drilling fluid and the quality of the mud cake formed. The base slurry was prepared according to the water-based drilling fluid formula in the experiment. P-FLA microspheres of different concentrations were added, and after being fully stirred and evenly, the fluid loss performance of the water-based drilling fluid was studied at 150°C×16h by using the API filtration tester. The results have been shown in Figure 11.

API filtration loss of water-based drilling fluid with varying P-FLA concentrations after hot rolling at 150°C for 16 h (tested at 0.69 MPa for 30 min).

After hot rolling aging at 150°C for 16 h, the API filtration loss of the water-based drilling fluid decreased significantly with increasing concentrations of P-FLA microspheres. When the dosage reached 2.5 wt% or higher, the filtration volume was reduced from 30.2 mL to 9.8 mL, representing a maximum reduction rate of 67.5%. This marked improvement highlights the strong filtration control capacity and thermal resistance of the microspheres under high-temperature conditions. The enhanced performance is attributed to the embedded distribution of P-FLA microspheres within the mud cake matrix, as confirmed by SEM observations. These microspheres are not only dispersed on the surface but also integrated into the internal structure of the filter cake, where they interact with bentonite particles to form a synergistic plugging network. The resulting mud cake is thinner, denser, and less permeable, effectively minimizing fluid invasion and maintaining wellbore stability.

During the API filtration process, solid particles in the water-based drilling fluid deposit onto the filter paper to form a mud cake. As shown in Figure 12(a), the mud cake formed by the base slurry is thick, loose, and easily collapsible. In contrast, Figure 12(b) shows that after adding 3 wt% P-FLA microspheres, the resulting mud cake is thinner, denser, and more structurally stable. After drying at 40°C for 12 h, the base slurry mud cake (Figure 12c) exhibits significant cracking and delamination, while the modified cake (Figure 12d) maintains its integrity and adheres firmly to the filter paper, indicating enhanced toughness and cohesion. SEM further reveals the internal structure of the dried mud cakes. As seen in Figure 12(e), the base mud cake displays large pores and an irregular clay particle network, resulting from bentonite dehydration and poor compaction, conditions that facilitate fluid invasion. In contrast, Figure 12(f) illustrates that P-FLA microspheres are not only uniformly distributed on the surface but also embedded within the mud cake. These microspheres interact closely with bentonite particles, bridging and filling pore spaces to form a synergistic plugging network. This composite structure effectively blocks filtration channels, reduces permeability, and enhances wellbore stability under high-temperature conditions.

(a) Mud cake of water-based drilling fluid (b) Mud cake of water-based drilling fluid +3wt% P-FLA microspheres (c) Mud cake of water-based drilling fluid after drying at 40°C×12h (d) Mud cake of water-based drilling fluid +3wt% P-FLA microspheres after drying at 40°C×12h (e) Mud cake electron microscopic analysis of water-based drilling fluid after drying at 40°C×12h (f) Mud cake electron microscopic analysis of water-based drilling fluid +3wt% P-FLA microspheres after drying at 40°C×12h.

The observed reduction in filtration loss with increasing P-FLA dosage is mainly attributed to the physical plugging effect of the microspheres and their interaction with the clay matrix. The broad particle size distribution (D10 = 2.5 µm, D90 = 93.9 µm) allows for effective pore bridging across a range of pore sizes, forming a multilayered barrier on the filter cake. Additionally, the hydroxyl-rich surfaces of β-cyclodextrin and starch promote hydrogen bonding and adhesion with bentonite particles, enhancing the compactness and integrity of the filter cake. The 3D crosslinked structure also resists deformation under pressure, preventing filtrate migration even after high-temperature hot rolling aging

Based on the reduction in filtration loss achieved by adding different concentrations of P-FLA microspheres to the water-based drilling fluid, the optimal addition rate of 2.5wt% was chosen for the water-based formulation. This concentration not only effectively reduces filtration loss but also helps in cost-saving during field application. Therefore, using 2.5 wt% of CaCO₃ (300 mesh) and P-FLA microspheres separately added to the drilling fluid, and subjected to hot rolling aging at 150°C for 16 h, the API filtration loss was measured using an API filtration loss tester to observe the change in filtration loss over time, as shown in Figure 13. At 30 min, the API filtration loss of the water-based drilling fluid was 31.6 mL. When 2.5 wt% of CaCO₃ was added to the drilling fluid, the filtration loss reduced to 22.4 mL. However, with the addition of 2.5 wt% of P-FLA microspheres to the drilling fluid, the filtration loss decreased to 12.8 mL, resulting in a high reduction rate of 59.5%. This clearly indicates that P-FLA microspheres exhibit superior high-temperature filtration loss reduction performance compared to CaCO₃.

Different effects of P-FLA microspheres with the same concentration and CaCO3 (300 mesh) on the filtration performance of water-based drilling fluid (API test at 0.69 MPa, 30 min).

3.2.3. Effects of P-FLA microspheres on plugging performance of water-based drilling fluid

The medium-pressure sand bed experimental device, as depicted in Figure 14, was utilized for the experiment. A layer of rapid filter paper was added to the bottom of the device to simulate the well wall. Next, 40-70 mesh quartz sand was washed and dried, and then poured into the device until it reached the designated scale line. Afterward, the prepared 300mL of water-based drilling fluid was hot rolling aging at 150°C for 16 h, and then poured into the device. Once the setup was complete, the equipment was pressurized, and the filtration loss was observed within 30 min. The results have been shown in Figure 15.

Experimental device of medium pressure sand bed.

(a) Variation of filtration loss with time for water-based drilling fluid with different concentrations of P-FLA microspheres for medium-pressure sand bed experiments (b) Variation of filtration loss reduction and reduction rate for water-based drilling fluid with different concentrations of P-FLA microspheres for medium-pressure sand bed experiments.

According to the results shown in Figure 15(a), it is evident that when the water-based drilling fluid was subjected to the middle-pressure sand bed plugging test after hot rolling aging, the filtration loss reached 128 mL within 30 min. However, after adding 1 wt% of P-FLA microspheres, the filtration loss of the water-based drilling fluid reduced to 82 mL, and filtration stopped in about 25 min, indicating a significant plugging effect of P-FLA microspheres. When 2.5 wt% and 3 wt% of P-FLA microspheres were added to the water-based drilling fluid, the filtration rate significantly decreased and stabilized within approximately 15 min, with final filtration volumes of 42 mL and 40 mL, respectively. As shown in Figure 15(b), the corresponding filtration loss reduction rates reached 67.2% and 68.8%. The excellent plugging performance observed in the sand bed tests is a result of both the deformability and the size gradation of the P-FLA microspheres. Under applied pressure, the microspheres migrate into pore channels and deform to form a tight seal. Their chemical composition-hydrophilic surfaces and a stable hydrophobic interior—enables strong interactions with both clay minerals and surrounding fluids. Moreover, the crosslinked polymer network prevents collapse or dissolution of the microspheres under high-temperature conditions, thereby maintaining the integrity of the formed plugging layer over time. These features synergistically contribute to the rapid decrease in filtration rate and early termination of filtrate flow observed in the tests.

3.2.4. Comparative analysis with existing microsphere-based filter loss reducers

In recent years, various microsphere-based filter loss reducers have been developed to improve the high-temperature performance of water-based drilling fluids. These include acrylamide/sulfonated copolymer microspheres, starch-derived microspheres, and β-cyclodextrin-based materials. Each type offers specific advantages but also presents inherent limitations. For example, microspheres based on acrylamide or AMPS monomers demonstrate excellent thermal stability but pose environmental concerns due to poor biodegradability and potential monomer toxicity. Starch-based microspheres are biodegradable and low-cost but often suffer from thermal degradation above 150°C and insufficient mechanical strength. Similarly, β-cyclodextrin microspheres synthesized alone tend to exhibit narrow particle size distributions and limited structural reinforcement. Table 2 provides a comparative analysis of the P-FLA microspheres and several conventional filtration loss reducers, highlighting the superior thermal resistance, lower dosage, and environmental compatibility of the synthesized material.

Table 2. Comparative performance of P-FLA microspheres and conventional filtration loss reducers used in water-based drilling fluids.

Parameter	P-FLA	Starch-based	AMPS-type	CaCO₃
API fluid loss reduction (%)	67.5%	50%	60%	30%
Temperature resistance (°C)	150°C	<120°C	150°C	90°C
Effective dosage (wt%)	2.5-3.0	3.5-5.0	2.0-3.0	5.0
Rheological impact	Minimal	Moderate	Moderate	Slight
Environmental friendliness	Biodegradable	Biodegradable	Low	Neutral

In contrast, the P-FLA microspheres developed in this study combine β-cyclodextrin and soluble starch into a single crosslinked structure via inverse emulsion polymerization. This composite configuration enhances the overall structural integrity, providing a broad particle size distribution that enables multiscale pore bridging and efficient mud cake formation. The TGA shows a primary decomposition temperature near 395°C, significantly higher than typical natural polymer-based systems. Additionally, the environmentally friendly raw materials and the demonstrated superior performance in filtration loss reduction and plugging effectiveness distinguish P-FLA microspheres as a promising alternative to existing microsphere-type additives.

4. Conclusions

In this study, a novel filter loss reducer (P-FLA microspheres) was successfully synthesized via inverse emulsion polymerization using β-cyclodextrin and soluble starch as the primary monomers and epichlorohydrin as the crosslinking agent. Structural characterization confirmed the formation of uniformly dispersed, spherical microspheres with an average particle size of approximately 10 μm. The presence of functional groups and a major thermal degradation event at 394.53°C indicated excellent thermal stability and environmental compatibility of the product. Performance evaluations demonstrated that P-FLA microspheres have minimal impact on the rheological properties of water-based drilling fluids, maintaining stable apparent viscosity and yield point even after high-temperature hot rolling aging at 150°C. In API filtration tests, the addition of 2.5 wt% P-FLA microspheres reduced fluid loss from 30.2 mL to 9.8 mL, achieving a 67.5% reduction, which significantly outperformed the conventional CaCO₃ additive. Moreover, medium-pressure sand bed experiments showed that P-FLA microspheres effectively sealed porous media, reducing filtration loss by over 67% and stopping filtrate flow within 15 min under test conditions. These superior results can be attributed to the microspheres’ wide particle size distribution, thermal resistance, and strong interaction with clay particles, which collectively enhance the formation of a dense and resilient mud cake. The 3D crosslinked network structure contributes to both physical plugging and thermal durability.

In summary, the P-FLA microspheres exhibit excellent fluid loss reduction and plugging performance under high-temperature conditions, making them a promising and environmentally friendly additive for water-based drilling fluids, particularly in deep and ultra-deep well operations where conventional materials may fail.

Acknowledgment

This research is supported by the following:

1.Open Foundation of Cooperative Innovation Center of Unconventional Oil and Gas, Yangtze University (Ministry of Education & Hubei Province), Grant No. UOG2024-05.

2.Hubei Province Science and Technology Plan Project (Key R&D Special Project), China, Grant No. 2023BCB070.

3. Key R&D Program Project in Xinjiang, China, Grant No.2022B01042.

4. Guiding Project of Scientific Research Program of Education Department of Hubei Province, China, Grant No. B2023024.

5. Open Fund of National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), Grant No. PLN2023-03.

6. Gansu Province Natural Science Foundation Youth Science and Technology fund project, Grant No. 25JRRA900

CRediT authorship contribution statement

Xiaoming Su: Writing – original draft, Validation, Investigation, Formal analysis. Yuan Yuan: Formal analysis, Conceptualization. Yin Da: Methodology. Peng Xu: Validation, Writing – review & editing, Zhen Zhang: Investigation. Tao Peng: Investigation. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

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.

Declaration of generative AI and AI-assisted technologies in the writing process

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

References

Wang Y., Liu Zhi., Liu X.. Key technologies of deepwater drilling in the northern basin of the South China Sea. Xinjiang Oil and Gas. 2022;18:12-18.
[Google Scholar]
Jiang G., Dong T., Cui K., He Y., Quan X., Yang L., Fu Y.. Research status and development directions of intelligent drilling fluid technologies. Petroleum Exploration and Development. 2022;49:660-670. https://doi.org/10.1016/s1876-3804(22)60055-7
[Google Scholar]
Perrone D., Jasechko S.. Deeper well drilling an unsustainable stopgap to groundwater depletion. Nature Sustainability. 2019;2:773-782. https://doi.org/10.1038/s41893-019-0325-z
[Google Scholar]
Li Z., Xie R., Wu Y., Yuan J.. Progress and prospect of CNOOC’s oil and gas well drilling and completion technologies. Natural Gas Industry B. 2022;9:209-217. https://doi.org/10.1016/j.ngib.2021.08.020
[Google Scholar]
Deville J.P., Fritz B., Jarrett M.. Development of water-based drilling fluids customized for shale reservoirs. SPE Drilling & Completion. 2011;26:484-491. https://doi.org/10.2118/140868-pa
[Google Scholar]
Bayat A.E., Jalalat Moghanloo P., Piroozian A., Rafati R.. Experimental investigation of rheological and filtration properties of water-based drilling fluids in presence of various nanoparticles. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2018;555:256-263. https://doi.org/10.1016/j.colsurfa.2018.07.001
[Google Scholar]
Galindo K.A., Zha W., Zhou H., Deville J.P.. High temperature, high performance water-based drilling fluid for extreme high temperature wells. SPE International Conference on Oilfield Chemistry. SPE Paper. 2015;D011S001R004:D011S001R004. SPE-173773-MS. https://doi.org/10.2118/173773-MS
[Google Scholar]
Li Z., Wang M.. Research and application evaluation on deep regulation and flooding technology of nano-microspheres in low permeability oilfield. Xinjiang Oil and Gas. 2019;16:61-64. https://doi.org/10.3969/j.issn.1673-2677.2020.01.015
[Google Scholar]
Al-Hameedi A.T.T., Alkinani H.H., Dunn-Norman S., Al-Alwani M.A., Alshammari A.F., Alkhamis M.M., Mutar R.A., Al-Bazzaz W.H.. Experimental investigation of environmentally friendly drilling fluid additives (mandarin peels powder) to substitute the conventional chemicals used in water-based drilling fluid. Journal of Petroleum Exploration and Production Technology. 2020;10:407-417. https://doi.org/10.1007/s13202-019-0725-7
[Google Scholar]
Chang X., Sun J., Xu Z., Lv K., Dai Z., Zhang F., Huang X., Liu J.. Synthesis of a novel environment-friendly filtration reducer and its application in water-based drilling fluids. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2019;568:284-293. https://doi.org/10.1016/j.colsurfa.2019.01.055
[Google Scholar]
Hossain M.E., Wajheeuddin M.. The use of grass as an environmentally friendly additive in water-based drilling fluids. Petroleum Science. 2016;13:292-303. https://doi.org/10.1007/s12182-016-0083-8
[Google Scholar]
Balaga D.K., Kulkarni S.D.. A review of synthetic polymers as filtration control additives for water-based drilling fluids for high-temperature applications. Journal of Petroleum Science and Engineering. 2022;215:110712. https://doi.org/10.1016/j.petrol.2022.110712
[Google Scholar]
Apaleke A.S., Al-Majed A., Hossain M.E.. Drilling fluid: state of the art and future trend. SPE North Africa Technical Conference and Exhibition. SPE Paper 2012:149555. https://doi.org/10.2118/149555-MS
[Google Scholar]
Al-Hameedi A.T.T., Alkinani H.H., Dunn-Norman S., Al-Alwani M.A., Alshammari A.F., Albazzaz H.W., Alkhamis M.M., Alashwak N.F., Mutar R.A.. Insights into the application of new eco-friendly drilling fluid additive to improve the fluid properties in water-based drilling fluid systems. Journal of Petroleum Science and Engineering. 2019;183:106424. https://doi.org/10.1016/j.petrol.2019.106424
[Google Scholar]
Al-Hameedi A.T., Alkinani H.H., Dunn-Norman S., Alashwak N.A., Alshammari A.F., Alkhamis M.M., Ashammarey A.. Evaluation of environmentally friendly drilling fluid additives in water-based drilling mud. SPE Europec featured at EAGE Conference and Exhibition. SPE Paper 2019:D021S003R006. https://doi.org/10.2118/195510-MS
[Google Scholar]
Xinlei W., Lili Y., Lihui W., Fayun W.. Progress in the study of environmentally friendly drilling fluid filtration reducer. Drilling Fluid Completion Fluid. 2018;35:8-16. https://doi.org/10.3969/j.issn.1001-5620.2018.03.002
[Google Scholar]
Yanli Y., Zhongjin L., Zhengfan W., Chunsheng P.. Synthesis of modified corn starch filter loss reducing agents for water-based drilling fluids. Oilfield Chemistry. 2006;03:198-200. https://doi.org/10.19346/j.cnki.1000-4092.2006.03.002
[Google Scholar]
Jie S., Xiwen Z., Chao Y., Zequn Y., Quan W.. Synthesis and performance study of temperature and salt resistant modified starch drilling fluid filter loss reducing agent. Oiffield Chemistry. 2015;32:4. https://doi.org/ 10.19346/j.cnki.1000-4092.2015.04.002
[Google Scholar]
Ghazali N.A., Alias N.H., Mohd T.A.T., Adeib S.I., Noorsuhana M.Y.. Potential of corn starch as fluid loss control agent in drilling mud. Applied Mechanics and Materials. 2015;754-755:682-687. https://doi.org/10.4028/www.scientific.net/amm.754-755.682
[Google Scholar]
Prakash V., Sharma N., Bhattacharya M., Raina A., Gusain M.M., Sharma K.. Evaluation of environment friendly micro-ionized litchi leaves powder (LLP) as a fluid loss control agent in water-based drilling fluid. Journal of Petroleum Exploration and Production Technology. 2021;11:1715-1726. https://doi.org/10.1007/s13202-021-01147-9
[Google Scholar]
Yanling W., Baoyang J., Jincheng L., Lingtao M., Ning X., Qiang L.. The properties of an environmentally friendly high temperature salt resistant micrometer and nanometer filter loss reducer. Drilling Fluid Completion Fluid. 2020;37:737-741. https://doi.org/10.3969/j.issn.1001-5620.2020.06.010
[Google Scholar]
Zhong H., Kong X., Chen S., Grady B.P., Qiu Z.. Preparation, characterization and filtration control properties of crosslinked starch nanospheres in water-based drilling fluids. Journal of Molecular Liquids. 2021;325:115221. https://doi.org/10.1016/j.molliq.2020.115221
[Google Scholar]
Yong S., Luming J., Jun Y., Guancheng J., Guoshuai W., Yinbo H.. Development and application of an environmentally friendly compound filter loss reducer. Drilling Fluid Completion Fluid. 2023;40:35-40. https://doi.org/10.12358/j.issn.1001-5620.2023.01.004
[Google Scholar]
Xin G., Hanyi Z.G., Zhengsong Q., Junbin J., Daqi L., Jia L.. Preparation of microsphere β-cyclodextrin polymer filter loss reducer for drilling fluids. Drilling Fluid Completion Fluid. 2021;38:21-26. https://doi.org/10.3969/j.issn.1001-5620.2021.01.004
[Google Scholar]
Zhong H., Gao X., Qiu Z., Zhao C., Zhang X., Guo B., Li G.. Formulation and evaluation of β-cyclodextrin polymer microspheres for improved HTHP filtration control in water-based drilling fluids. Journal of Molecular Liquids. 2020;313:113549. https://doi.org/10.1016/j.molliq.2020.113549
[Google Scholar]
Li X., Jiang G., He Y., Chen G.. Novel starch composite fluid loss additives and their applications in environmentally friendly water-based drilling fluids. Energy & Fuels. 2021;35:2506-2513. https://doi.org/10.1021/acs.energyfuels.0c03258
[Google Scholar]
Xu Z., Sun J., Liu J., Lv K., Zhang T., Sun Y., Xiu Z., Huang N.. Preparation and evaluation of nanopolymer microsphere plugging agents for ultrahigh-temperature water-based drilling fluids. Energy & Fuels. 2023;37:13093-13103. https://doi.org/10.1021/acs.energyfuels.3c02340
[Google Scholar]
Yaoyuan Z., Shuangzheng M., Jinding C., Wenming L., Huayong L., Guanxiang W.. Preparation and performance of a high temperature modified starch filter loss reducer. Drilling Fluid Completion Fluid. 2019;36:694-699. https://doi.org/10.3969/j.issn.1001-5620.2019.06.006
[Google Scholar]
Li Q., Luo X., Yu X., Han W., Luo Y.. Synthesis and performance evaluation of a micron-size silica-reinforced polymer microsphere as a fluid loss agents. Journal of Industrial and Engineering Chemistry. 2024;130:243-254. https://doi.org/10.1016/j.jiec.2023.09.028
[Google Scholar]
Liu W.. Pharmaceutical Polymer Materials Science (10th ed). Beijing, China: China Traditional Chinese Medicine Publishing House; 2007.
Zhe X., Dong C., Xiqin Y., Yiqun L., Lan L.. Crosslinking synthesis and drug-loading properties of β-cyclodextrin-soluble starch polymer microspheres. Journal of Shenyang Pharmaceutical University. 2009;26:857-862. https://doi.org/ 10.14066/j.cnki.cn21-1349/r.2009.11.016
[Google Scholar]
Yun Z., Xiuxia S.. Adsorption of jasmine flavouring by cross-linked β-cyclodextrin-soluble starch composite microspheres. China Adhesives. 2014;23:23-27. https://doi.org/10.13416/j.ca.2014.10.006
[Google Scholar]

1. Introduction

2. Materials and Methods

2.1 Monomer selection
2.2. Experimental materials
2.3. Synthetic process
2.4. Synthesis mechanism
2.5. Characterization and evaluation methods

3. Results and Discussion

3.1. Structure and characterization
3.2. Performance evaluation of P-FLA microspheres

4. Conclusions

Fulltext Views
310

PDF downloads
1,163

View/Download PDF
Download Citations

BibTeX
RIS

Show Sections

[1] Wang Y., Liu Zhi., Liu X.. Key technologies of deepwater drilling in the northern basin of the South China Sea. Xinjiang Oil and Gas. 2022;18:12-18.
[Google Scholar]

[2] Jiang G., Dong T., Cui K., He Y., Quan X., Yang L., Fu Y.. Research status and development directions of intelligent drilling fluid technologies. Petroleum Exploration and Development. 2022;49:660-670. https://doi.org/10.1016/s1876-3804(22)60055-7
[Google Scholar]

[3] Perrone D., Jasechko S.. Deeper well drilling an unsustainable stopgap to groundwater depletion. Nature Sustainability. 2019;2:773-782. https://doi.org/10.1038/s41893-019-0325-z
[Google Scholar]

[4] Li Z., Xie R., Wu Y., Yuan J.. Progress and prospect of CNOOC’s oil and gas well drilling and completion technologies. Natural Gas Industry B. 2022;9:209-217. https://doi.org/10.1016/j.ngib.2021.08.020
[Google Scholar]

[5] Deville J.P., Fritz B., Jarrett M.. Development of water-based drilling fluids customized for shale reservoirs. SPE Drilling & Completion. 2011;26:484-491. https://doi.org/10.2118/140868-pa
[Google Scholar]

[6] Bayat A.E., Jalalat Moghanloo P., Piroozian A., Rafati R.. Experimental investigation of rheological and filtration properties of water-based drilling fluids in presence of various nanoparticles. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2018;555:256-263. https://doi.org/10.1016/j.colsurfa.2018.07.001
[Google Scholar]

[7] Galindo K.A., Zha W., Zhou H., Deville J.P.. High temperature, high performance water-based drilling fluid for extreme high temperature wells. SPE International Conference on Oilfield Chemistry. SPE Paper. 2015;D011S001R004:D011S001R004. SPE-173773-MS. https://doi.org/10.2118/173773-MS
[Google Scholar]

[8] Li Z., Wang M.. Research and application evaluation on deep regulation and flooding technology of nano-microspheres in low permeability oilfield. Xinjiang Oil and Gas. 2019;16:61-64. https://doi.org/10.3969/j.issn.1673-2677.2020.01.015
[Google Scholar]

[9] Al-Hameedi A.T.T., Alkinani H.H., Dunn-Norman S., Al-Alwani M.A., Alshammari A.F., Alkhamis M.M., Mutar R.A., Al-Bazzaz W.H.. Experimental investigation of environmentally friendly drilling fluid additives (mandarin peels powder) to substitute the conventional chemicals used in water-based drilling fluid. Journal of Petroleum Exploration and Production Technology. 2020;10:407-417. https://doi.org/10.1007/s13202-019-0725-7
[Google Scholar]

[10] Chang X., Sun J., Xu Z., Lv K., Dai Z., Zhang F., Huang X., Liu J.. Synthesis of a novel environment-friendly filtration reducer and its application in water-based drilling fluids. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2019;568:284-293. https://doi.org/10.1016/j.colsurfa.2019.01.055
[Google Scholar]

[11] Hossain M.E., Wajheeuddin M.. The use of grass as an environmentally friendly additive in water-based drilling fluids. Petroleum Science. 2016;13:292-303. https://doi.org/10.1007/s12182-016-0083-8
[Google Scholar]

[12] Balaga D.K., Kulkarni S.D.. A review of synthetic polymers as filtration control additives for water-based drilling fluids for high-temperature applications. Journal of Petroleum Science and Engineering. 2022;215:110712. https://doi.org/10.1016/j.petrol.2022.110712
[Google Scholar]

[13] Apaleke A.S., Al-Majed A., Hossain M.E.. Drilling fluid: state of the art and future trend. SPE North Africa Technical Conference and Exhibition. SPE Paper 2012:149555. https://doi.org/10.2118/149555-MS
[Google Scholar]

[14] Al-Hameedi A.T.T., Alkinani H.H., Dunn-Norman S., Al-Alwani M.A., Alshammari A.F., Albazzaz H.W., Alkhamis M.M., Alashwak N.F., Mutar R.A.. Insights into the application of new eco-friendly drilling fluid additive to improve the fluid properties in water-based drilling fluid systems. Journal of Petroleum Science and Engineering. 2019;183:106424. https://doi.org/10.1016/j.petrol.2019.106424
[Google Scholar]

[15] Al-Hameedi A.T., Alkinani H.H., Dunn-Norman S., Alashwak N.A., Alshammari A.F., Alkhamis M.M., Ashammarey A.. Evaluation of environmentally friendly drilling fluid additives in water-based drilling mud. SPE Europec featured at EAGE Conference and Exhibition. SPE Paper 2019:D021S003R006. https://doi.org/10.2118/195510-MS
[Google Scholar]

[16] Xinlei W., Lili Y., Lihui W., Fayun W.. Progress in the study of environmentally friendly drilling fluid filtration reducer. Drilling Fluid Completion Fluid. 2018;35:8-16. https://doi.org/10.3969/j.issn.1001-5620.2018.03.002
[Google Scholar]

[17] Yanli Y., Zhongjin L., Zhengfan W., Chunsheng P.. Synthesis of modified corn starch filter loss reducing agents for water-based drilling fluids. Oilfield Chemistry. 2006;03:198-200. https://doi.org/10.19346/j.cnki.1000-4092.2006.03.002
[Google Scholar]

[18] Jie S., Xiwen Z., Chao Y., Zequn Y., Quan W.. Synthesis and performance study of temperature and salt resistant modified starch drilling fluid filter loss reducing agent. Oiffield Chemistry. 2015;32:4. https://doi.org/ 10.19346/j.cnki.1000-4092.2015.04.002
[Google Scholar]

[19] Ghazali N.A., Alias N.H., Mohd T.A.T., Adeib S.I., Noorsuhana M.Y.. Potential of corn starch as fluid loss control agent in drilling mud. Applied Mechanics and Materials. 2015;754-755:682-687. https://doi.org/10.4028/www.scientific.net/amm.754-755.682
[Google Scholar]

[20] Prakash V., Sharma N., Bhattacharya M., Raina A., Gusain M.M., Sharma K.. Evaluation of environment friendly micro-ionized litchi leaves powder (LLP) as a fluid loss control agent in water-based drilling fluid. Journal of Petroleum Exploration and Production Technology. 2021;11:1715-1726. https://doi.org/10.1007/s13202-021-01147-9
[Google Scholar]

[21] Yanling W., Baoyang J., Jincheng L., Lingtao M., Ning X., Qiang L.. The properties of an environmentally friendly high temperature salt resistant micrometer and nanometer filter loss reducer. Drilling Fluid Completion Fluid. 2020;37:737-741. https://doi.org/10.3969/j.issn.1001-5620.2020.06.010
[Google Scholar]

[22] Zhong H., Kong X., Chen S., Grady B.P., Qiu Z.. Preparation, characterization and filtration control properties of crosslinked starch nanospheres in water-based drilling fluids. Journal of Molecular Liquids. 2021;325:115221. https://doi.org/10.1016/j.molliq.2020.115221
[Google Scholar]

[23] Yong S., Luming J., Jun Y., Guancheng J., Guoshuai W., Yinbo H.. Development and application of an environmentally friendly compound filter loss reducer. Drilling Fluid Completion Fluid. 2023;40:35-40. https://doi.org/10.12358/j.issn.1001-5620.2023.01.004
[Google Scholar]

[24] Xin G., Hanyi Z.G., Zhengsong Q., Junbin J., Daqi L., Jia L.. Preparation of microsphere β-cyclodextrin polymer filter loss reducer for drilling fluids. Drilling Fluid Completion Fluid. 2021;38:21-26. https://doi.org/10.3969/j.issn.1001-5620.2021.01.004
[Google Scholar]

[25] Zhong H., Gao X., Qiu Z., Zhao C., Zhang X., Guo B., Li G.. Formulation and evaluation of β-cyclodextrin polymer microspheres for improved HTHP filtration control in water-based drilling fluids. Journal of Molecular Liquids. 2020;313:113549. https://doi.org/10.1016/j.molliq.2020.113549
[Google Scholar]

[26] Li X., Jiang G., He Y., Chen G.. Novel starch composite fluid loss additives and their applications in environmentally friendly water-based drilling fluids. Energy & Fuels. 2021;35:2506-2513. https://doi.org/10.1021/acs.energyfuels.0c03258
[Google Scholar]

[27] Xu Z., Sun J., Liu J., Lv K., Zhang T., Sun Y., Xiu Z., Huang N.. Preparation and evaluation of nanopolymer microsphere plugging agents for ultrahigh-temperature water-based drilling fluids. Energy & Fuels. 2023;37:13093-13103. https://doi.org/10.1021/acs.energyfuels.3c02340
[Google Scholar]

[28] Yaoyuan Z., Shuangzheng M., Jinding C., Wenming L., Huayong L., Guanxiang W.. Preparation and performance of a high temperature modified starch filter loss reducer. Drilling Fluid Completion Fluid. 2019;36:694-699. https://doi.org/10.3969/j.issn.1001-5620.2019.06.006
[Google Scholar]

[29] Li Q., Luo X., Yu X., Han W., Luo Y.. Synthesis and performance evaluation of a micron-size silica-reinforced polymer microsphere as a fluid loss agents. Journal of Industrial and Engineering Chemistry. 2024;130:243-254. https://doi.org/10.1016/j.jiec.2023.09.028
[Google Scholar]

[30] Liu W.. Pharmaceutical Polymer Materials Science (10th ed). Beijing, China: China Traditional Chinese Medicine Publishing House; 2007.

[31] Zhe X., Dong C., Xiqin Y., Yiqun L., Lan L.. Crosslinking synthesis and drug-loading properties of β-cyclodextrin-soluble starch polymer microspheres. Journal of Shenyang Pharmaceutical University. 2009;26:857-862. https://doi.org/ 10.14066/j.cnki.cn21-1349/r.2009.11.016
[Google Scholar]

[32] Yun Z., Xiuxia S.. Adsorption of jasmine flavouring by cross-linked β-cyclodextrin-soluble starch composite microspheres. China Adhesives. 2014;23:23-27. https://doi.org/10.13416/j.ca.2014.10.006
[Google Scholar]

Synthesis and evaluation of polymer microspheres (P-FLA) synthesized by inverse emulsion polymerization as a filter loss reducer for water-based drilling fluid

Abstract

Keywords

Filter loss reducer

Inverse emulsion polymerization

Polymer microspheres

Water-based drilling fluid

1. Introduction

2. Materials and Methods

2.1 Monomer selection

2.2. Experimental materials

2.3. Synthetic process

2.4. Synthesis mechanism

2.5. Characterization and evaluation methods

3. Results and Discussion

3.1. Structure and characterization

3.1.1. Infrared spectra of P-FLA microspheres

3.1.2. Optical microscopy of P-FLA microspheres

3.1.3. SEM of P-FLA microspheres

3.1.4. Particle size analysis of P-FLA microspheres

3.1.5. Thermogravimetric analysis of P-FLA microspheres

3.2. Performance evaluation of P-FLA microspheres

3.2.1. Effects of P-FLA microspheres on rheological properties of water-based drilling fluid

3.2.2. Effects of P-FLA microspheres on the filtration performance of water-based drilling fluid

3.2.3. Effects of P-FLA microspheres on plugging performance of water-based drilling fluid

3.2.4. Comparative analysis with existing microsphere-based filter loss reducers

4. Conclusions

Acknowledgment

CRediT authorship contribution statement

Declaration of competing interest

Declaration of generative AI and AI-assisted technologies in the writing process

References

Suggested read for related articles: