Reduce Fluid Loss Research Articles

New Zwitterionic Polymer as a Highly Effective Salt- and Calcium-Resistant Fluid Loss Reducer in Water-Based Drilling Fluids.

To control the filtration loss of drilling fluids in salt-gypsum formations, a novel type of zwitterionic polymer gel (DNDAP) was synthesized by free radical polymerization, which was used as a salt- and calcium-resistant fluid loss reducer for water-based drilling fluids (WBDF). DNDAP was prepared with N, N-dimethylacrylamide (DMAA), N-vinylpyrrolidone (NVP), Diallyl dimethyl ammonium chloride (DMDAAC), 2-acrylamide-2-methylpropaneonic acid (AMPS), and isopentenol polyether (TPEG) as raw materials. Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H-NMR) were used to characterize the composition and structure of the DNDAP copolymer. The thermal stability of DNDAP was evaluated by the use of thermogravimetric analysis (TGA). WBDF with DNDAP was analyzed for zeta potential and particle size and the corresponding filter cake underwent energy dispersive spectrum (EDS) analysis and scanning electron microscope (SEM) analysis. The results showed that the thermal decomposition of DNDAP mainly occurred above 303 °C. DNDAP exhibits excellent rheological and filtration properties in water-based drilling fluids, even under high-temperature aging (up to 200 °C) and high salinity (20 wt% NaCl or 5 wt% CaCl2) environments. The strong adsorption effect of DNDAP makes the particle size of bentonite reasonably distributed to form a dense mud cake that reduces filtration losses.

Preparation and properties of fluid loss reducer for anti-CO32- pollution in ultra-high temperature and high salt drilling fluids

Aiming at the problems of poor system stability and large-filtration loss after CO2 pollution in oil and gas drilling at ultra-high temperatures deep wells, an ultra-high temperatures anti-CO32- pollution strong adsorption-drilling fluid defiltration loss agent (PMSC) was prepared using acrylamide (AM), sodium p-styrene sulfonate (SSS), N-vinylpyrrolidone (NVP) and dimethyldiallylamlammonium chloride (DMDAAC) as raw materials. The structure and morphology of PMSC were characterized by Fourier infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis. The performance test shows that PMSC has the ability to resist saturated saline (36 % NaCl) and composite saline. In addition, it has better anti-CO32- (5000 ppm) pollution and filtration reduction performance than the same product at ultra-high temperature (210 ℃), and FLAPI is only 6.8 mL. The mechanism of PMSC anti-CO32- pollution and filter loss reduction was analyzed by particle size distribution, SEM, and UV–visible spectrophotometer. PMSC forms crosslinked network structures in drilling fluid. Amphoteric polymer increases the competitive adsorption capacity with CO32-, firmly adsorbs on the surface of clay particles, and forms a thick hydration film. This suppresses the coalescence effect of CO32- contaminated drilling fluid caused by high temperature and promotes reasonable particle size distribution. Finally, a compact filter cake is formed to reduce filtration loss. Due to the good filtration loss performance of PMSC under ultra-high temperatures and CO32- pollution, PMSC is expected to become a promising drilling fluid filtration loss agent used in formations with high CO2 salinity at ultra-high temperatures.

Nano-Modified Polymer Gels as Temperature- and Salt-Resistant Fluid-Loss Additive for Water-Based Drilling Fluids.

With the continuous exploration and development of oil and gas resources to deep formations, the key treatment agents of water-based drilling fluids face severe challenges from high temperatures and salinity, and the development of high temperature and salt resistance filtration reducers has always been the focus of research in the field of oilfield chemistry. In this study, a nano-silica-modified co-polymer (NS-ANAD) gel was synthesized by using acrylamide, isopropylacrylamide, 2-acrylamide-2-methyl propane sulfonic acid, diallyl dimethyl ammonium chloride, and double-bond-modified inorganic silica particles (KH570-SiO2) through free radical co-polymerization. The introduction of nanotechnology enhances the polymer’s resistance to high temperature degradation, making it useful as a high-temperature-resistant fluid loss reducer. Moreover, the anions (sulfonates) and cations (quaternary ammonium) enhance the extension of the polymer and the adsorption on the surface of bentonite particles in a saline environment, which in turn improves the salt resistance of the polymer. The drilling fluids containing 2.0 wt% NS-ANAD co-polymer gels still show excellent rheological and filtration performance, even after aging in high temperature (200 °C) and high salinity (saturated salt) environments, showing great potential for application in deep and ultra-deep drilling engineering.

Effect of poly(AMPS/DMAA/IA/SSS) intercalated Mg/Al layered double hydroxides on reducing fluid loss at 240 °C and improving early strength of oil well cement

Fluid loss agent (FLA) was adopted to reduce the fluid loss of cement paste to ensure the safety of cementing construction. With the increase of exploration depth, FLA applied at high temperatures has been urgently required. To meet the cementing requirements at 240 °C, the FLA with organic/inorganic intercalated microstructure was prepared. Anionic polymer FLA (ADIS) was comprised of 2-acrylamido-2-methylpropane sulfonic Acid (AMPS), N, N-dimethylacrylamide (DMAA), Itaconic acid (IA) and Sodium p-styrene sulfonate (SSS). The organic-inorganic hybrid FLA (MgAl-ADIS-LDH) was prepared via intercalating ADIS into Mg/Al hydrotalcite (MgAl-NO3-LDH) interlayers. The intercalated microstructure was observed by SEM, TG results exhibited that the intercalation of polymer ADIS in MgAl-NO3-LDH enhanced the thermal stability of overall FLA. When applied in cement, the cement with MgAl-ADIS-LDH showed a small water loss of 36 mL at 240 °C. Moreover, the structure avoided the decrease in the compressive strength of hardened cement resulted from traditional polymer FLA. Compared with the cement contains 1.6% bwoc ADIS, the compressive strength of specimen with MgAl-ADIS-LDH increased by 20.5% after cured for 3 days.

Application of Psyllium Husk as a Friendly Filtrate Reducer for High-Temperature Water-Based Drilling Fluids.

Aiming at the challenge that environmental protection and high-temperature fluid loss reduction performance of the traditional water-based drilling fluid treatment agent are difficult to balance, our studies added psyllium husk as a high-temperature-resistant and environmentally friendly filtrate reducer to a water-based drilling fluid. The composition, physical and chemical properties, and microstructure of psyllium husk are characterized. Then, the effects of psyllium husk after hot rolling at different temperatures on the rheological properties and fluid loss properties of bentonite-based slurry are evaluated. The results show that the psyllium husk added to the bentonite-based slurry can effectively improve the rheological properties and fluid loss properties of the bentonite-based slurry, and the temperature resistance can reach 160 °C. After hot rolling at 160 °C, adding 1 w/v % psyllium husk can reduce the API fluid loss and high-temperature and high-pressure fluid loss of the bentonite-based slurry by 76.04 and 56.91%, respectively, showing excellent fluid loss reduction performance at high temperatures. The branched structure and uronic acid of psyllium husk can inhibit the degradation of its own molecular structure to a certain extent, which is the fundamental reason why psyllium husk still has excellent fluid loss reduction performance at high temperatures. Psyllium husk is expected to replace some traditional synthetic polymers and be used in environmentally friendly high-temperature-resistant water-based drilling fluids.

Invasion of CaCO3 particles and polymers into porous formations in presence of fibres

Formation damage can occur through migration of drilling fluid particles and polymers into porous formations. A methodology for assessing formation damage was applied to measure invasion of CaCO3 and polymers into porous formations, where the CaCO3 particles size had been selected using established particle size selection methods. Tests were conducted with and without the presence of a cellulose-based additive, to study if the fibres could reduce the fluid loss and limit the formation damage.Input factors such as applied differential pressures, ranging from 6.9 to 34.9 MPa (1000-5000psi), and median pore-throat openings of discs were also varied to investigate which parameters affected the significance of the formation damage.The results showed invasion of CaCO3/ground marble into the formation and that particle size selection methods used to reduce fluid loss also led to formation damage. Further it was discovered that the presence of fibres limited the invasion of both CaCO3 and polymers into the porous formations when the D90 of the fibres were ≥3/2 times the pore-throat size, and that higher applied pressures led to larger formation damage. The fluid loss tests also showed both lower total fluid losses and lower fluid loss rates over time with the fibres added to the fluids, indicating that the filter-cake permeability was reduced with the addition of the fibre particles.

Investigation and analysis of cement slurries

Laboratory studies of grouting slurries and cement compositions corresponding to specific mining and geological conditions are an important link in the design and construction of wells. In this work, a study of the rheological and physical-mechanical properties of cement grouting mixture and grouting cements was carried out. In the research for laboratory tests, samples of ground-bed mortars “GranTSEM - 7 BG” and “CemFrost”, “CemFrost Lite - 5” were used. For the qualitative process of cementing, the analysis of grouting slurries was carried out with the study of changes in the consistencies of grouting slurries over time. Thus, the acceleration of the process of drilling observation and production wells depends on the correct selected cement slurry. As a result, of the studies carried out, it was revealed that the introduction of additives into the cement slurry that bind the barrier water and the drilling fluid helps to reduce fluid loss and increases the specific surface area, which speeds up the drilling process.

An Inverse Emulsion Polymer as a Highly Effective Salt- and Calcium-Resistant Fluid Loss Reducer in Water-Based Drilling Fluids.

To control the fluid loss of water-based drilling fluids (WBDFs) in salt-gypsum formations, a nano-SiO2 graft copolymer was prepared by inverse emulsion polymerization. The polymer (EAANS) was prepared with acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, N-vinylpyrrolidone, and KH570-modified nano-silica (M-SiO2) as raw materials. The molecular structure and morphology of EAANS were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, transmission electron microscopy (TEM), and other methods. In the temperature range of 150 °C, 2 wt % EAANS can reduce the API filtration volume of the base slurry to within 20 mL and the HP-HT filtration volume at 150 °C to 21.8 mL. More importantly, 2 wt % EAANS can maintain the API filtration volume less than 10 mL even when the concentration of NaCl or CaCl2 was as high as 36 or 30 wt %, and as the salt/calcium content increased, the amount of filtration continued to decrease. The results of TEM, X-ray diffraction, particle size distribution, and scanning electron microscopy showed that the fluid loss control mechanism of EAANS was that EAANS can form a crosslinked network structure in the solution and adsorb on the clay surface, so as to reduce the particle size of clay particles, increase the proportion of fine particles in drilling fluids, and finally form a dense filter cake to reduce the filtration volume. Because of the excellent filtration performance of EAANS at high Na+/Ca2+ concentration, EAANS can become a promising WBDF fluid loss reducer in salt-gypsum formations.

Development of novel inhibitive water-based drilling muds for oil and gas field applications

The aim of this study is to develop inhibitive drilling fluid systems generated from waste materials that can contribute to the reduction of potential well instability problems caused by drilling fluid based on rheological and filtration properties. In this study, a comprehensive experimental work was carried out to assess suitability of fly ash and rice husk ash, which are quite a large amount of waste, in inhibitive water based-drilling fluids at ambient temperature. To this end, inhibitive drilling fluids systems were formulated with various concentrations (0, 1, 3, 5, 7, 9, 12.5, 15 (wt%)) of fly ash and rice husk ash with 0, 2, 4, 7, 9, 12.5, 15 (wt%) concentrations in the two type of inhibitive drilling fluid systems and combined use of fly ash and rice husk ash with their optimum concentrations determined was analyzed in the inhibitive drilling fluid in order to determine the drilling fluid with the most favorable characteristics based on rheological and filtration properties including apparent viscosity (AV), plastic viscosity (PV), yield point (YP), gel strength, fluid loss and mud cake thickness. In addition, grinding impact of fly ash particles in the inhibitive drilling fluid system was determined in the development of the drilling fluid by employing mechanically ground fly ash for 30, 60 and 120 min in a tumbling ball mill. Finally, fly ash and rice husk ash were characterized based on X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Experimental results show that developed drilling fluids with fly ash and rice husk ash not only enhanced rheological properties but also improved the filtration properties by increasing the rheological parameters and decreasing fluid loss and mud cake thickness. With the developed drilling fluids, AV, YP and PV increased by 35%, 32%, 28%, respectively with fly ash for the 12.5 wt% concentration while the parameters increased by 19%, 27%, 14%, respectively with the 4 wt% rice husk ash. Gel strengths of the fluids slightly increased compared to reference fluid and were in acceptable range. On the other hand, developed drilling fluid resulted in a 10% and 12% reduction in fluid loss for fly ash and rice husk ash at 12.5 wt% and 4 wt% concentrations, respectively, as well as a 54% and 63% reduction in mud cake thickness. In addition, the results reveal that developed drilling fluid with sieved fly ash yielded superior flow behavior compared to drilling fluid formulated with ground forms of fly ash. Consequently, based on the study, non-damaging and inhibitive drilling fluid systems were developed by using waste material fly ash and rice husk ash, and hence enhancing performance of drilling operation as well as reducing the risk of amount of wastes disposed to the environment and the potential of issues such as formation damage, wellbore instability caused by drilling fluid and associated challenges. • Inhibitive drilling fluid systems were formulated with various concentrations of fly ash and rice husk ash. • Effect of ground fly ash in the inhibitive drilling fluid system was determined at various grinding times. • Fly ash and rice husk ash were characterized. • Non-damaging and inhibitive drilling fluid systems were developed by using fly ash and rice husk ash.

Biopolymeric formulations for filtrate control applications in water-based drilling muds: A review

The forthcoming future of environmental protection mandates the utilization of naturally abundant, biodegradable, sustainable and ecofriendly materials for a wide variety of applications. Fluid loss behavior is considered the most severe problem in oil and gas well drilling operations. Because several other issues are associated with it. As a working way out, viscosifiers and fluid loss additives are introduced to the mud for rheology and filtration characteristics improvements, respectively. Polymers and starches are commonly added to base fluid to increase viscosity and reduce fluid loss of a mud. In this paper, the utilization of biopolymers used in the drilling fluid industry for filtrate reduction has been addressed. This review further emphasizes on the recent developments in native and modified starches utilization in drilling fluids extracted from various sources and the present research gaps for future developments. The utilization of biopolymers as potential additive in nondamaging water-based muds have been addressed to reduce the impacts of mud filtrate in the exposed formations. Moreover, various factors that influence the effectiveness of biopolymers and the utilization of such polymers in different muds are also discussed. The filtration characteristics in terms of filtrate volume and filtercake thickness generally showed improvements by using biopolymers. Filtercakes generated from starch-containing muds have been found to be thinner and more compact, resulting in reduced formation damage due to lower mud particle penetration.

Experimental investigation of mechanical behavior and microstructural analysis of bagasse fiber-reinforced polypropylene (BFRP) composites to control lost circulation in water-based drilling mud

During the drilling operation in high-permeability, natural and artificial fractured formations, the lost circulation of drilling mud is a common problem. Various methods have been applied to control lost circulation and among these methods, using Lost Circulation Materials (LCM) is the most common method that blocks the fluid loss channels in the formation by creating structures. In this project, the aim is to develop and use natural fiber-reinforced composites as LCM can be an innovative and technical solution. Natural fiber-reinforced composites have excellent properties such as high specific strength, non-abrasive, eco-friendly, and biodegradability. It seems to be possible that manufacturing composite can provide more desirable properties by changing its formulation. In this work, the Bagasse Fiber Reinforced Polymer (BFRP) composites were prepared with a twin-screw extruder and tested in Bridging Material Tester (BMT) with a slotted disk based on API standard. Finally, the obtained results were compared with those obtained using some conventional LCM's. In addition, the effect of the fiber content on the mechanical properties has also been evaluated. At 30% Bagasse fiber loadings, BFRP composite shows better mechanical properties compared to those of 40% fiber content BFRP composite. Also, fractured surface and Fiber-PP interaction have been studied by Scanning Electron Microscopy (SEM). The results show that the BFRP composite creates a suitable and persistent bridge inside the fractures and was able to seal slotted disks up to 0.12-in. Moreover, a reasonable combination of BFRP composite and Bagasse fiber increase plug breaking pressure contributing to reduce fluid loss can cause less fluid invasion upon the establishment of an effective seal. Optimal selection of size distribution leads to building a network for opening of fractured formations by Bagasse fiber. Also, BFRP granular particles can fill the empty space as well as reducing the amount of leakage. This study proposes new insights into the design of engineered loss control material with more effective loss formation control ability.

Assessment of Lost Circulation Material Particle-Size Distribution on Fracture Sealing: A Numerical Study

Summary Lost circulation materials (LCMs) are essential to combat fluid loss while drilling and may put the whole operation at risk if a proper LCM design is not used. The focus of this research is understanding the function of LCMs in sealing fractures to reduce fluid loss. One important consideration in the success of fracture sealing is the particle-size distribution (PSD) of LCMs. Various studies have suggested different guidelines for obtaining the best size distribution of LCMs for effective fracture sealing based on limited laboratory experiments or field observations. Hence, there is a need for sophisticated numerical methods to improve the LCM design by providing some predictive capabilities. In this study, computational fluid dynamics (CFD) and discrete element methods (DEM) numerical simulations are coupled to investigate the influence of PSD of granular LCMs on fracture sealing. Dimensionless variables were introduced to compare cases with different PSDs. We validated the CFD-DEM model in reproducing specific laboratory observations of fracture-sealing experiments within the model boundary parameters. Our simulations suggested that a bimodally distributed blend would be the most effective design in comparison to other PSDs tested here.

Modified Corn Starch as an Environmentally Friendly Rheology Enhancer and Fluid Loss Reducer for Water-Based Drilling Mud

SummaryDrilling fluid rheology and fluid loss property are fundamental parameters that dictate the effectiveness and easiness of a drilling operation. Maintaining these parameters under high temperatures is technically challenging and has been an exciting research area for the drilling industry. Nonetheless, the use of drilling mud additives, particularly synthetic polymers, threaten ecological environments. Herein, modified corn starch (MCS) was synthesized, characterized, and investigated as an environmentally friendly rheology enhancer and filtration loss controlling agent for water-based mud (WBM) at high temperatures. The experimental results indicated that MCS exhibits better performance in improving rheological properties and fluid loss controlling ability for WBM than the commonly used mud additives. With the addition of an optimal concentration (0.3 wt%), MCS improved the rheology and fluid loss behavior of WBM formulation at harsh aging temperature (220°C) by practically 4 times and 1.7 times, respectively. The MCS was revealed to perform superbly over polyanionic cellulose (PAC) addition at all investigated temperatures. The better performance of the MCS was ascribed to the improved entanglements in the mud system owing to the additional hydroxyl (OH) groups. Besides, the Herschel-Bulkley model was found to be a constitutive model that described the rheological properties of the investigated muds satisfactorily. Moreover, the MCS was found to exhibit acceptable biodegradability properties.

Development of a high temperature resistant nano-plugging agent and the plugging performance of multi-scale micropores

Nano-plugging agents (NPAs) are very important to stabilize the wellbore by reducing pressure transmission and drilling fluid invasion during drilling engineering. A functionalized polystyrene latex (FPL) was synthesized by micellar polymerization as a NPA for drilling fluids. The particle size and thermal stability of FPL were characterized by particle size analysis and thermogravimetric analysis (TGA). The experimental results showed that the initial thermal decomposition temperature of FPL was 310.6 ℃. The medium value of particle size distribution (D50) of FPL decreased from to 371–235 nm after aging at 220 ℃, indicating that FPL had good temperature resistance property. The plugging method and plugging performance of FPL for four filter media with pore sizes from 0.01 µm to 10 µm were introduced. FPL itself was difficult to plug the filter papers and ceramic filter disks, but FPL could reduce fluid loss of bentonite suspensions. SEM observation indicates that FPL could improve the quality of mud cakes and plug the small pores of ceramic filter disks. For microporous membranes and artificial mud cakes with low permeability, FPL aqueous suspensions had a good plugging performance. The plugging experimental results conformed well to the 2/3 bridging rule. This paper provides a good reference for the development of high temperature NPAs and the establishment of evaluation methods of NPAs.

An experimental analysis on nanoparticles role in drilling fluids

The study around nanotechnology has increased in the last decade or so, with rise in applications in many industries. There are now many nanotechnology-based products available like in healthcare, defense, coating industries etc. It has seen rise in usage in oil and gas industry as well. Application of nano particles in water based muds results in reduction of fluid loss and hence increases the wellbore stability and drilling efficiency. In this study, we have examined the fluid loss on water-based mud by adding graphene nanoparticles as additive and estimated the optimum value of nanoparticle composition for having less fluid loss. The results of experimental analysis for filtration loss from water-based mud with addition of graphite nanoparticles was studied and effect of friction factor was analyzed. The nanoparticles concentration added in fluid ranges from 1 to 5 lb/bbl and the size of the particles was observed to be 30–80 nm. Variation of fluid loss volume and friction coefficient under different nanoparticle composition was established.

Synthesis of a copolymerization and the anti-high temperature property in oil well cement slurry fluid

Four monomers including AMPS, acrylic acid (AA), N,N-dimethylacrylamide (DMAA), and sodium allylsulfonate (AS) were used to synthesize quaternary fluid loss reducer (FRW) through copolymerization. The optimal reaction conditions were optimized by orthogonal experiment method, and the water loss reduction performance of FRW was evaluated. The results show that the optimal synthesis conditions for FRW are that the molar ratio of AMPS:AA:DMAA:AS is 4.2:1.8:3.5:0.5, the amount of initiator added is 0.3% of the total monomer mass, the monomer mass percentage is 40%, The reaction temperature was 50°C, and the pH was 7. The performance evaluation results show that FRW has good fluid loss control ability. Under the condition of adding 2%, the fluid loss is 141mL when the temperature is 220°C, which has no negative impact on the comprehensive performance of cement slurry and has strong practicability.

Sealing Mechanism Based on Force Chain and Experimental Investigation of Sealing Fractures

Abstract Lost circulation often occurs in fractured formations, which was a main technological problem during drilling. Conventional lost circulation material (LCM) was often used to form a plugging zone to prevent fluid loss during drilling. The formed seal was a granular material system composed of LCMs. This paper presented the physical mechanism of the force chain within the plugging zone. The seal performance is related to the properties of LCMs. A device for testing seal performance of LCMs with long fracture was developed. The effects of LCM performance on seal integrity were investigated using a plugging device with long fracture. The results showed that the wide particle size distribution (PSD) of LCMs tended to form a strong force chain network structure within the sealing zone. Increasing the stiffness and roughness of LCMs resulted in higher breaking pressure. The addition of fiber with high length-diameter ratio could improve the shear strength of the sealing zone and form a strong force chain network structure, and it can reduce fluid loss.

Evaluating sealability of blended smart polymer and fiber additive for geothermal drilling with the effect of fracture opening size

Geothermal formations often contain extensive fracture networks. These fracture networks contribute to the significant loss of drilling fluids during geothermal drilling. Multiple loss circulation materials (LCM) such as fiber, granules, and pills have been proposed to tackle this problem but with only limited success. Recent advances in materials science have led to the development of thermoset shape memory polymers (SMP) to address the lost circulation problem. In this paper, we evaluate a thermoset SMP performance in sealing near wellbore fractures of different sizes in geothermal wells. The SMP performance was assessed using granite disks and cylindrical granite cores having fracture sizes of 1000 μm and 3000 μm. A static filtration test was performed using cedar fiber, CaCO3, and SMP. Results showed cedar fiber performed better than the CaCO3., reducing fluid loss by 89% and improving sealing pressure by 200 psi. A novel dynamic testing unit that allows for high-temperature testing under flowing conditions was used in this study. The analysis showed that 3% by weight SMP and fiber blends could bridge and plug the 1000 μm fracture. For a larger fracture of 3000 μm width, there was a need to increase the weight concentration of the SMP to 6% to plug the fracture opening effectively. We showed the influence of key parameters such as the type of LCM, concentration, and particle size distribution in optimizing the performance of drilling fluid loss treatment.

Synthesis of a Novel Filtrate Reducer and Its Application in Water-Based Drilling Fluid for Ultra-High-Temperature Reservoirs

The high-temperature stability and filtration property controlling of ultra-high-temperature water-based drilling fluids is a worldwide problem. To resolve this problem, a high-temperature-resistant quaternary copolymer (HTRTP) was synthesized based on molecular structure optimization design and monomer optimization. The physical and chemical properties were characterized by infrared spectroscopy, thermal weight, and spectrophotometry, and their temperature and salt resistance was evaluated in different drilling fluids, combined with adsorption, particle size analysis, and stability test. The results show that the thermal stability of HTRTP is very strong, and the initial temperature of thermal decomposition is above 320°C. The salt resistance of HTRTP is more than 162 g/L, and the calcium resistance is more than 5000 mg/L, which is equivalent to the foreign temperature-resistant polymer DCL-a, and is superior to the domestic metal ion viscosity increasing fluid loss agent PMHA-II for drilling fluids. It has excellent high-temperature resistance (245°C) and fluid loss reduction effect in fresh water base mud, fresh water weighted base mud, saturated brine base mud, and composite salt water base mud, which is better than foreign DCL-a (245°C) and domestic PMHA (220°C). The adsorption capacity of HTRTP on clay particles is large and firm, and the adsorption capacity changes little under the change of chemical environment and temperature. Both before and after HTRTP aging (245°C/16 h), the permeability of filter cake can be significantly reduced and its compressibility can be improved. By optimizing the particle size gradation of the drilling fluid and enhancing the colloid stability of the system, HTRTP can improve the filtration building capacity of the drilling fluid and reduce the filtration volume. The development of antithermal polymer provides a key treatment agent for the study of anti-high-temperature-resistant saline-based drilling fluid.

Influence of different oil types on the stability and oil displacement performance of gel foams

Foam stability drives its mobility control ability and displacement effects. In addition to the chemical composition of the foam system, the oil types are also a key element that affects the stability of the foam. Three kinds of crude oil with different components were used to explore the stability and oil displacement ability of the gel foam system. And then, the foam performance, coarsening behavior, emulsifying properties, plugging ability, and oil recovery enhancement of oil-bearing gel foam were examined. Experimentally, our results demonstrate that the more polar heavy components (asphaltene and resin) in crude oil, the gel foam exhibits higher foam stability performance when the oil saturation is 0–20%. Owing to the stable crude oil emulsion reduces fluid loss and hinders the movement of oil droplets within the lamella, a highly stable pseudo-emulsion liquid film is formed, which reduces the rupture of the oil-bearing gel foam. The results of oil displacement experiments show that LD-2 crude oil with the highest concentration of heavy oil components produced the most stable oil-containing gel foam, with a plugging rate of 95.33% and an enhanced recovery rate of 23.1%. In addition, different sampling points are set for the sandpack model to observe the stable state and migration of the oil-bearing gel foam in the porous medium. This study revealed the stability of oil-bearing gel foams under different crude oil types and provides a theoretical basis for applying gel foam in enhanced oil recovery of different types of crude oil reservoirs.