CO2 foam flooding effectively suppresses gas channeling and plugs high-permeability pathways through its high apparent viscosity, significantly enhancing oil recovery while enabling geological storage. However, the stability of CO2 foam in high-salinity reservoirs remains a critical challenge. The results demonstrated that under the conditions of 323.15 K, 20 MPa, and near-saturation concentrations, sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium hydroxide (DTAOH) reduced the CO2-water interfacial tension to 5.28 mN/m and 8.25 mN/m, respectively. Further analysis indicated that the DTAOH monolayer exhibited lower porosity and greater interfacial thickness: the lower porosity could reduce the contact probability between CO2 molecules and water molecules, thereby delaying the foam decay process; while the greater interfacial thickness could enhance the anti-interference capability of the interfacial film and improve its structural stability. In terms of salt tolerance in high-salinity environments, DTAOH showed significantly superior performance compared to SDS. Specifically, the single anionic head group of SDS molecules was prone to strong electrostatic adsorption with cations in the system, which further induced molecular aggregation and precipitation, and ultimately led to the loss of its interfacial activity. In contrast, DTAOH could mitigate the interference of ions on its interfacial adsorption behavior through a charge compensation effect, effectively maintaining its own interfacial activity and ensuring the stability of CO2 foam under complex reservoir conditions.

The Xujiahe Formation in western Sichuan Basin has abundant resources and is the main battlefield for increasing reserves and production,but the degree of reserve utilization is low.In this gas reservoir with complex geological conditions,horizontal well drilling faces several challenges such as low build-up efficiency of large-sized wellbore,low rate of penetration(ROP),difficult prevention of collision and interwell interference in long vertical well section,wellbore stability,lost circulation and wellbore cleaning.Through researches on key technologies including anti-inclination,anti-collision and anti-collision while fast drilling of large-sized wellbore in easily inclined formations based on pre-bending dynamics,ROP improvement in difficult-to-drill formations,real-time optimization of drilling parameters based on ROP sensitivity analysis,geology-engineering integrated precise control of wellbore trajectory,drilling fluid and lost circulation control,and wellbore cleaning based on the evaluation of friction during actual drilling,a ROP improving technology for horizontal well drilling in tight sandstones was formed.This technology was successfully applied in two horizontal wells,with the drilling cycle reduced by 65.7%,the average ROP improved by 194%,and a horizontal length up to 1 021 m.The research results provide technical support for the exploration and development of tight gas resources,and also provide reference for efficient and fast drilling of horizontal wells in tight sandstones in China.

Water-based drilling fluids (WBDFs) are gaining popularity as they exhibit comparable inhibitory properties to oil-based drilling fluids, making them an ideal choice for drilling horizontal shale gas wells. This study focuses on understanding the intercalation inhibition mechanism of various inhibitors, namely 1,6-hexane diamine (HDA), N,N '-dimethyl-1,6-hexane diamine (DHDA), N,N,N ',N '-tetramethyl-1,6-hexane diamine (THDA), and hexamethyl diammonium chloride (HDC), each possessing different functional groups. The interaction and performance of these inhibitors on the swelling of montmorillonite (Mt) were investigated through a combination of experi-mental techniques containing X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and density functional theory simulation. Re-sults reveal that at a low dosage of 0.7 CEC (cation exchange capacity), the wet Mt-HAD, Mt-DHDA, Mt-THDA, and Mt-HDC compounds exhibit basal spacing of 1.30 nm, 1.33 nm, 1.34 nm, and 1.42 nm, respectively. The basal spacing remains unchanged when a higher dosage of 3.0 CEC is added. Comparatively, the basal spacing of dry Mt-inhibitor compounds is slightly reduced. This suggests that the addition of a smaller amount of inhibitor also demonstrates excellent inhibitory performance. Thermogravimetric and differential thermogravimetric analysis of Mt-inhibitor hybrid structure indicate that Mt-HDA compounds exhibit both low and high -temperature peaks, while Mt-DHDA, Mt-THDA, and Mt-HDC compounds only show a low-temperature peak. This indicates that while HDA partially inhibits surface hydration of Mt, DHDA, THDA, and HDC effectively inhibits surface hydration of Mt. Additionally, the microscopic mechanism of inhibitor adsorption on the Mt was explored using density functional theory simulation. HDC adsorption energy on Mt significantly increased relative to DHDA, THDA, and HDA. This indicates that inhibitors featuring quaternary ammonium functional groups exhibited superior inhibitory performance. As a result, inhibitors with quaternary ammonium functional groups hold promise as potential shale inhibitors for WBDFs.

In deep-formation drilling, effective filter loss control in ultrahigh-temperature conditions and high-salt conditions faces challenges. Comb polymer/LDH composites (P-LDH) with partially intercalated and partially exfoliated structures were prepared by in-situ polymerization as fluid loss materials. A series of characterization results showed that the P-LDH composites were successfully synthesized. P-LDH had partially intercalated and partially exfoliated structures and excellent thermal stability. In addition, the rheological evaluation results showed that P-LDH had a low viscosity effect while maintaining the rheological properties of the drilling fluid. PLDH can significantly reduce the filtrate loss of drilling fluids at ultrahigh temperatures and high salt concentrations. At 240 degrees C and 15 wt% NaCl, the filtration loss was only 6.3 mL, and the high-temperature and highpressure filtration loss was only 29.6 mL. Through the analysis of drilling fluid particle size and filter cake microstructure, based on hydrogen, ionic bonds, and intercalation effects, P-LDH acted closely with bentonite to promote stable dispersion, improve the drilling fluid's stability, and form a dense filter cake to reduce the filtration loss. Therefore, P-LDH has broad application prospects in ultrahigh-temperature and high-salinity formation drilling.

Currently, the trade-off between mechanical stability and electrical conductivity has become one of the challenges in developing high-performance anion exchange membranes. Here, we propose a fluorinated crosslinking strategy to improve the mechanical properties of the membrane while achieving high conductivity. The introduction of hydrophobic fluorination units provides a further driving force for the aggregation of hydrophilic ion clusters within the membrane, forming continuous ion transfer channels within the membrane. The results show that the crosslinked membranes maintain a low swelling rate as well as a high OH- conductivity at 80 degrees C. Among them, the FPTBP-TMA-7 membrane showed the most comprehensive performance, with a OH- conductivity of 116.9 mS cm-1 and a swelling rate of only 14.1% at 80 degrees C. The chemical structure of the membranes maintained high stability after immersion in highly concentrated alkaline solutions (2 M NaOH at 80 degrees C for 720 h), with a conductivity retention rate of over 91.8%. In addition, the FPTBP-TMA-7 based fuel cell achieves a peak power density of 264.2 mA cm-2 at 80 degrees C, showing an attractive application prospect in alkaline fuel cells.

Nano-/submicron-scale plugging is critical for wellbore stability during shale gas exploitation but typically fails under high-temperature and extreme-salinity conditions due to colloidal instability. Herein, polyampholyte polymers (ZP) were grafted from the surface of silicon dioxide (SiO2) nanoparticles through surface-triggered free radical polymerization to generate nanoplugging additives (SiO2-g-ZP). SiO2-g-ZP exhibited excellent colloidal dispersion stability with a nano/submicron size distribution in 35 w/v% sodium chloride (NaCl) and 11 w/v% calcium chloride (CaCl2) brines at 160 degrees C for a long time and over a wide pH range, and efficiently plugged 220 nm and similar to 20 mu m pores and 5 mu m fractures at 160 degrees C and 3.5-5.5 MPa. Three critical aspects of observation and analysis obtained through microstructure analysis and molecular dynamics (MD) simulations helped elucidate the mechanisms that control the SiO2-g-ZP's performances: an increase in SiO2-g-ZP's hydration capability with salinity due to the antipolyelectrolyte behaviours of ZP coatings with zwitterionic nature, an efficient mitigation of Na-bent agglomeration even at harsh conditons due to the preferential adsorption of SiO2-g-ZP rather than Na+, Ca2+ and Cl- on Na-bent, and the presence of a nanosilica core and rigid groups and massive hydratable groups. The first two aspects caused a perfect matching of particles in muds to pores and fractures in formation and the third aspect helped enhance the SiO2-g-ZP's thermal resistance and residence in the pores and fractures. This work provides a novel approach that can be broadly generalized to address the thermal- and salt-tolerance challenges of colloidal systems used in the exploration and development of deep and complex shale formations.

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As a backbone with ether-free for anion exchange membranes (AEMs) with good alkali stability, poly(aryl-co-aryl piperidine) (c-PAP) has received much attention in the development of polyelectrolytes. More importantly, the trade-off between high conductivity and stability has been a thorny issue for researchers in the study of AEMs. Typically, non-cationic crosslinked membranes have lower water absorption and swelling rates compared to multi-cationic crosslinked membranes, resulting in better dimensional stability of the membrane. Here, we designed a non-cationic crosslinked AEMs based on poly(p-terphenyl-co-1,2-diphenylethane piperidinium) (PDTP). The experimental results show that the combination of hydrophobic crosslinking and side chain in-duction results in excellent conductivity and alkali resistance of the membranes. The crosslinked membranes reached an OH- conductivity of 104.61 mS cm-1 and a swelling rate of less than 15 % at 80 degrees C. In addition, the length of the hydrophobic crosslinker was varied to explore its effect on the membrane properties. The PDTP-BMP-6 C membrane (C=6 in crosslinker) shows the most excellent overall performance among them. The conductivity was retained at 86.5 % after immersion in 2 M NaOH at 80 degrees C for 720 h, and the peak power density reached 214 mW cm- 2.

In the oil and gas industry, the selection of tubing and casing materials is required to follow international standard ISO 15156. However, it does not provide guidance on selecting stainless steel materials for H2S-containing wells above 232 degrees C, which raises uncertainty about the suitability of 13Cr steel. This work focuses on investigating the mechanical degradation and failure mechanisms of 13Cr stainless steel exposed to high-temperature conditions and proposed a creep constitutive model. Then, the corrosion and cracking mechanisms of 13Cr stainless steel at temperatures ranging from 150 degrees C to 350 degrees C were elucidated. Results show that 13Cr stainless steel meets the current material selection criteria (GB/T34907-2017) for mechanical properties and creep resistance. In the range of 150-250 degrees C, the localized corrosion is dominant, and stress-oriented hydrogen-induced cracking occurs at 150 degrees C. As the temperature increases from 250 degrees C to 350 degrees C, although the maximum value of uniform corrosion rate is as high as 0.2960 mm/a, the cracking does not happen. Therefore, with the implementation of suitable protective measures, 13Cr stainless steel can be utilized in wells that the temperatures ranging from 250 degrees C to 350 degrees C and H2S partial pressures up to 0.17 MPa. This aligns with the global carbon-neutral agenda.

The preparation of true shale cores is limited by the characteristics of shale formations, such as the development of bedding and micro-fractures, poor cementation, and fragility. Artificial cores cannot meet the requirements of shale at the nanometer scale and are not representative. Existing plugging evaluation methods have problems such as cumbersome steps, long time consumption, and low evaluation accuracy. Therefore, this paper proposes a shale plugging evaluation method based on the simulation of “thick mud cakes”. This method analyzes the effects of factors such as bentonite dosage, type and dosage of treatment agent, barite content and particle size distribution on mud cake parameters through approximation experiments, establishes a standard slurry formula for “thick mud cakes”, and prepares a standard “thick mud cake” with a thickness of 10.03 mm and a permeability of 4.79·10 -4 mD to evaluate the plugging effect by the reduction rate of permeability. Based on this method, four plugging agents were selected and combined to obtain the best compound plugging agent. The drilling fluid system plugging evaluation was carried out on both the standard “thick mud cake” and thin mud cake, and the microscopic plugging mechanism of shale was analyzed. The results show that this method is simple to operate, has good reproducibility and high accuracy in plugging evaluation results, and has strong application potential.

During the drilling of deep/ultradeepwells, water-based drillingfluids (WBDFs) often experience harsh conditions of ultrahigh temperatureand high salt. Ultrahigh temperatures and high salts cause rheologicalinstability in drilling fluid, reducing its suspension and cutting-carryingcapacity. In this study, a comb polymer, P-TPEG with isopentenol polyoxyethyleneether (TPEG) as the side chain, was prepared via free radical polymerizationin an aqueous solution and then compounded with nanolaponite (LAP)to obtain a composite rheological modifier (LAP/P-TPEG). In situ Fouriertransform infrared spectroscopy and thermogravimetric analysis showedthat LAP/P-TPEG had an excellent thermal stability. The LAP/P-TPEGsolution test showed a shear thinning behavior. The results demonstratethat LAP/P-TPEG can improve the rheology of WBDFs before and afteraging at 240 & DEG;C and can resist 15 wt % NaCl. LAP/P-TPEG formeda strong adsorption with bentonite through hydrogen bonds and electrostaticinteractions. LAP, P-TPEG, and bentonite formed a "reversible""dual" spatial network structure in WBDFs, improvingthe rheology and the suspension, cutting-carrying, and wellbore-cleaningabilities of the drilling fluid under ultrahigh temperature and highsalt.

Shale reservoirs are characterized by the presence of nano-micron pores in abundance, easy breakage due to bedding development, and difficulty in preparing true core samples. Therefore, 3D reconstruction of digital cores has become an important means of studying the microstructure features of shale. Currently, for shale matrix of dense reservoirs, existing deep learning-based reconstruction methods suffer from high costs and low accuracy, mainly due to the insufficient extraction capability of the networks for nano-micron pore features and low core resolution during reconstruction. To accurately predict the nano-micron scale pore structure of shale, we propose a shale 3D reconstruction method based on context-aware generative adversarial networks and high-resolution optical flow estimation (COFRnet-3DWGAN). This method optimizes the 3DWGAN(Wasserstein GAN) and high-resolution optical flow estimation networks by incorporating context-awareness, enhances the feature extraction capability of the networks to improve the learning degree of core nano-micron pores, and optimizes the core resolution by increasing the resolution of optical flow between core sequence images, thereby improving the accuracy of core reconstruction. The results show that, compared with WGAN, the proposed method is closer to the true core in terms of porous media morphological functions, porosity and permeability distribution, and pore structure parameters, indicating that this method has certain advantages in improving the accuracy of shale reconstruction.

The hydration of clay minerals in shale is one of the main causes of borewall instability. Efficient shale hydration inhibitors require strong interactions between the inhibitor and the mineral surface, such as van der Waals forces, static electricity, hydrogen bonds, and even the formation of chemical bonds, which can significantly reduce the crystal layer spacing of clay minerals. The selection of main functional group of inhibitor plays a decisive role in the performance of inhibitor. The density functional theory method based on quantum mechanics can simulate and calculate the interaction between inhibitor and montmorillonite (001) plane, and study its electronic structure and properties at the atomic level. The adsorption of C 2 H 5 –NH 2 , C 2 H 5 –OH, C 2 H 5 –OCH 3 , C 2 H 5 –CHO and C 2 H 5 –COCH 3 on Montmorillonite (001) was calculated by density functional simulation. The adsorption of inhibitor functional groups on montmorillonite (001) layer was studied comprehensively from the aspects of adsorption configuration, adsorption energy, charge population, frontier orbit and differential electron density distribution. According to this study, the primary amine group is suitable as the main functional group of hydration inhibitor. Meanwhile, this paper provides theoretical support for the development of efficient surface hydration inhibitors..

针对超低孔超低渗页岩地层的井壁失稳问题,以延长组长7段页岩为参考对象,采用X射线衍射、渗透率、孔隙度、比表面积、平均孔径测定和扫描电子显微镜等手段,分析了矿物组分、岩性特征,提出了页岩井壁维稳思路.借助模拟"标准厚泥饼"封堵评价方法,对ZD-1、JB53、EP-2和ZD-3等封堵剂最佳加量及其复配的封堵效果进行评价,优选得到了高效封堵的复配封堵剂SPA-1.在延长页岩用水基甲酸钾钻井液体系中加入4.0％SPA-1后,其流变性易于控制且渗透率降低率高达94.20％,作用前后的模拟岩芯电镜图像进一步验证了其封堵效果,并分析了封堵剂封堵作用机理.结果表明,SPA-1集合理的粒度级配和刚柔性粒子协同作用可以实现有效封堵,有利于延长组长7段页岩井壁稳定.

A novel sulfur-modulated metal–organic framework photocatalyst, MIL-101(Fe), with CQDs anchored on its surface has been successfully synthesized to efficiently separate photo-induced carriers for the degradation of Rhodamine B and Cr 6+ removal.

A g-C3N4/NH2-MIL-88B(Fe)/CD@GO membrane (M2) was prepared by a simple vacuum filtration method.

In the process of deep oil and gas drilling, high temperature and high amounts of salt will greatly deteriorate the rheological properties of water-based drilling fluids (WBDFs), increase the fluid loss of drilling fluids, and seriously threaten the safety of operations. It is urgent to develop new high-temperature and salt-resistant drilling fluid additives. In this study, a novel organic-inorganic polymer nanocomposite (P-RD') was synthesized by combining laponite and polymer, and its chemical structure and properties were characterized and evaluated by various experimental methods. The results show that P-RD' forms a spatial network structure in aqueous solu-tion, and has good clay adsorption capacity and pore and crack sealing ability. At 180 degrees C and 15 wt% NaCl, it has good rheological stability to WBDFs, the American Petroleum Institute (API) filtration loss is only 7.1 mL, and the high temperature and high pressure (HTHP) filtration loss is controlled at 29.2 mL. P-RD' has dual functions, which can effectively strengthen the temperature and salt resistance of WBDFs, and is expected to be used as a rheology modifier and filtration loss reducer in high-temperature deep well drilling.

The development of shale gas reservoirs with water-based drilling fluids is complicated by the problem of clay mineral hydration. The method of molecular simulation is widely used in many research fields, in both humanitarian and material sciences. In this paper, based on the previously published studies, the authors propose a comprehensive review of molecular simulation of inhibiting the surface hydration swelling of clay minerals. Swelling characteristics and the adsorption properties of clay minerals are reviewed and discussed. The results can be useful for future development of the MD (molecular dynamics) simulation method and its application in studies of inhibition of the surface hydration swelling in clay minerals.

Nowadays, oily wastewater is a severe threat to the living environment of humankind. In recent years, MOF materials have shown great application potential in membrane separation and treatment of oily wastewater. In this paper, the mixed cellulose ester membrane (MCEM) was modified by polydopamine, and the NH2-MIL-125 (Ti)/Sep(sepiolite)/PDA composite membrane was prepared by simple vacuum filtration. The composite membrane had super-hydrophilic performance and underwater super-oleophobic performance, and could effectively separate oil-water emulsion separation performance. Also, the composite membrane showed good repeatability. After 10 cycles, the retention rate of petroleum ether-in-water emulsion was still more than 99%, and the flux was more than 2000 L·m−2·h−1. Since strong adhesion ability of PDA and the covalent interaction between NH2-MIL-125(Ti) and Sep, the chemically stable NH2-MIL-125(Ti)/Sep/PDA composite membrane was exposed to the strong acid (pH=1), alkali (pH=11), and salt (5% saturated NaCl) solutions showed excellent chemically stable. These outstanding properties made the composite membrane have great potential in the removal of oily wastewater.

目的 在油田压裂返排液中,由于含有大量成分复杂且稳定的有机物,传统方法处理有限,采用光催化环保技术进行处理的研究.方法 以BiOBr和BiOI为单体,采用原位合成法分别制备BiOI/BiOBr和U-BiOI/BiOBr复合体,并通过XRD、AFM、SEM、TEM、DRS和BET等手段表征其结构、组成、厚度、形貌和孔径大小.以压裂返排液中羟丙基胍胶为光催化降解反应模型,考察了光催化剂活性,测定了光催化剂加量、羟丙基胍胶含量等因素对降解羟丙基胍胶效果的影响.结果 在羟丙基胍胶溶液为100 mL、质量浓度为200 mg/L的情况下,BiOI/BiOBr和U-BiOI/BiOBr的投加量均为120 mg,反应时间为60 min对羟丙基胍胶污染物降解率分别为73.0％和77.2％,U-BiOI/BiOBr降解羟丙基胍胶的效果优于BiOI/BiOBr.结论 通过采用光催化氧化技术降解羟丙基胍胶,为油气田压裂返排液中大量有机污染物的环保处理提供了新思路和理论支撑.