ABSTRACT In deep reservoir environments, the effectiveness of polymer gel systems for enhanced oil recovery (EOR) is often compromised by extreme conditions of high temperature, high salinity, and elevated pressure. As the most extensively used polymer gel, polyacrylamide‐based gel particles have shown great promise but suffer from limited thermal and chemical stability under harsh conditions. The multiscale degradation mechanisms governing their breakdown remain poorly understood. In this study, we systematically investigate the degradation behavior of polyacrylamide nanospheres, a model system with controlled particle size under representative reservoir conditions (150°C, 5 MPa, up to 100 g/L salinity). Through a combination of thermal analysis, structural and surface characterization, gas‐phase product profiling, in situ high‐pressure IR spectroscopy, and density functional theory (DFT) calculations, we map out the key degradation pathways and their molecular origins. Results show that salinity promotes hydrolysis of amide groups, particularly at MBA crosslinking sites, while high‐pressure oxygen accelerates deamination and chain scission. In situ IR confirms the evolution of functional groups into carboxylic acids, and DFT results reveal that carboxyl‐rich environments significantly reduce the activation energy for bond cleavage, initiating autocatalytic degradation. Importantly, oxidative degradation under air proves more damaging than ionic effects alone. This comprehensive, multiscale approach not only clarifies the intertwined roles of heat, salt, and oxygen in destabilizing polymer gels but also provides a mechanistic foundation for developing salt‐tolerant, oxidation‐resistant gel formulations for high‐temperature reservoir applications.

Polymer hydrogel is widely used to enhance oil recovery in oilfields. However, it is facing great challenges under high temperature and salinity conditions due to its degradation. Distilled spent grain (DSG) with rice husk is a typical organic waste from Chinese baijiu, which has attracted increasing attention. Polyacrylamide (PAM) based hydrogel with high-temperature and high-salinity resistance performance was developed using aminated distilled spent grain (ADSG), which was prepared using DSG reaction with NH3 & sdot;H2O. ADSG can realize crosslinking with PAM via transamination reaction to improve cross-linking density and enhance the stability of gel under harsh conditions. Hence, it is designed as a cross-linking agent. Hemicellulose in ADSG reacted with NH3 & sdot;H2O to draft -NH2. Non-cross-linked PAM was found in PAM-ADSG. PAM-ADSG exhibited excellent performance for 25 days under 150 degrees C and 200,000 mg/L salinity. The plugging rate was 99.98%, and the breakthrough pressure was 2.69 MPa, indicating that PAM-ADSG had a high plugging capacity in high-permeability fractures. The transamination reaction for ADSG improves the stability of gel under harsh conditions. It paves a new pathway to treat organic waste for Chinese baijiu and it proposes a new method to improve polymer gel's stability under ultrahigh-temperature and high-salinity conditions.

Water management in high-temperature and high-salinity reservoirs remains a critical challenge for oilfield operations, with conventional polymer gel systems exhibiting insufficient thermal stability and salt tolerance under extreme conditions. Here, we establish an integrated computational-experimental platform combining density functional theory (DFT) and molecular dynamics (MD) simulations to rationally design a novel AM/AMPS/AMB (Acrylamide/2-acrylamido-2-methylpropanesulfonic acid/sodium 3-acrylamido-3-methylbutanoate) terpolymer gel plugging agent tailored for the Tahe Oilfield (140 °C, Ca2+/Mg2+ 10,000 mg L-1). Density functional theory (DFT) calculations of fourteen functional monomers identified AMB as the optimal candidate, achieving further hydrogen bond interactions that stabilize the crosslinked architecture under extreme conditions. This computational pre-screening reduced experimental iterations by over 60% and significantly shortened development cycles compared to conventional trial-and-error approaches. Experimentally, the optimized terpolymer exhibited a 40% increase in storage modulus (150 Pa) relative to AM/AMPS binary systems, 25% improvement in thermal stability (residual carbon at 300 °C), and plugging efficiency exceeding 92% in core flooding tests.

The extra-heavy oil in the Tahe Oilfield of China has extremely high viscosity, as it is rich in the heavy components asphaltene and resin, creating significant difficulties in its exploitation and transportation. Therefore, it is important to effectively reduce the viscosity and improve the fluidity of this extra-heavy oil. The traditional viscosity reduction method suffers from a high blending ratio and a shortage of light crude oil resources for extra-heavy oil blending. In this study, coal tar and washing oil—widely available low-cost by-products of the coal chemical industry—are used for extra-heavy oil blending and viscosity reduction. Washing oil—containing light components distilled from coal tar—was highly effective in reducing the viscosity of extra-heavy oil. When the dilution ratio of washing oil is 0.25, the viscosity of extra-heavy oil is reduced to 1214 mPa·s, and the viscosity reduction rate is 99.8%, indicating that washing oil is an efficient viscosity-reducing agent in extra-heavy oil blending. GC-MS showed that the washing oil contained abundant aromatic hydrocarbons and aromatic heterocyclic rings. A multi-component viscosity reduction system using washing oil coupled with toluene, xylene, and surfactant achieved an even better viscosity reduction effect. In conclusion, we designed a low-cost, high-efficiency, multi-component, and multi-functional synergistic system for extra-heavy oil viscosity reduction in the Tahe Oilfield. In the proposed working mechanism, aromatic hydrocarbons and aromatic heterocyclic rings in washing oil can intercalate into the layered structure of dense asphaltene aggregates, thereby dispersing and dissociating them.

Many efforts have been made to realize the sewage sludge (SS) valorization. Due to the low duration of polyacrylamide (PAM) under high temperatures and high salinity conditions in oilfields, a new organic cross-linking agent, SS extract (SE), has been developed to enhance the PAM cross-linking strength. PAM-SE exhibits excellent temperature and salinity resistance. Due to the disruption of the alpha-helix structure of proteins in SE, the released -OH and -NH2 could react with acrylamide to enhance hydrogen bonding and covalent bonding (transamidation and dehydration), resulting in increasing thermal stability of PAM-SE. The PAM-SE exhibits high plugging capacity (93.93 %) in high-permeability fractures. The breakthrough pressure is 2.73 MPa. The pressure gradient is 27.3 MPa/m. CaCl2 plays a key role in PAM-SE, leading to excellent salt resistance and high thermal stability due to cross-linking network formation. The key reason for the high-temperature and high-salt resistance of PAM-SE is that: i) SE is a cross-linking agent that can react with AM during polymerization to enhance cross-linking; ii) Ca2 + in formation water could cross-link SE and carboxylic acid in polymer to form a stable gel due to the presence of proteins in SE. The unique properties of PAM-SE provide a new approach to increasing hydrogel stability under high-salinity conditions and at high temperatures. It paves a new way for resource utilization of SS.

Based on rich proteins and polysaccharides, how to utilize sewage sludge (SS) becomes a hot topic. Traditional polyacrylamide (PAM)-based gels for petroleum recovery face significant challenges for long-term utilization because the gel is easily broken under high temperature and salinity conditions. In this study, a new method to prepare green hydrogels with excellent temperature and salinity resistance is developed. Biodegradable low-temperature hydrochar (LTH) from SS is prepared and added to hydrogels. Non-cross-linked polyacrylamide is detected in the PAM-LTH. LTH can react with acrylamide (AM) to enhance hydrogen bonding and covalent bonding owing to the presence of active functional groups (-OH and-NH2) on its surface. The presence of more small pores on PAM-LTH indicates that it is not a filler but a cross-linking agent. The plugging rate, breakthrough pressure, and pressure gradient are 94.96 % and 2.71 MPa, and 27.1 MPa/m, respectively. This paves the way for the utilization of SS and the development of ultrahigh-temperature and high-salt resistant hydrogels for petroleum recovery, which are conducive to environmental protection.

To address the challenges of insufficient compatibility between crosslinking agents and main agents, as well as the shear failure of polymer gels under extreme conditions such as high-temperature (130°C) and high-salinity (20×104 mg·L-1), molecular dynamics simulations were employed to study the crosslinking effects of three agents ethyleneimine (EI), phenolic formaldehyde resin (PF), and N,N'-methylenebisacrylamide (MBA) on Acrylamide (AM) monomer and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) copolymer systems. The stability of these systems under high temperature and salt conditions was also examined. By quantitatively evaluating electrostatic energy, van der Waals force energy, total potential energy, and total kinetic energy in each cross-linked network, it was found that PF-crosslinked gels exhibit superior stability. These gels demonstrated not only excellent thermal stability and salt resistance, but also remarkable resilience against adverse external conditions. To further enhance the material's potential, a dynamic crosslinking network based on carboxymethyl cellulose (CMC) and magnetic iron oxide (Fe3O4) nanoparticles was introduced. This was combined with a polymer formed by PF crosslinking PAA@PF, leading to the creation of a double-network gel system that significantly improved the self-healing capability. The results indicate that the developed composite plugging agent not only rapidly restores its physical and chemical properties after damage but also maintains high mechanical strength and toughness. This research provides new insights for developing a next-generation high-performance self-healing plugging agent and offers significant implications for expanding the applications of self-healing materials.

Applying polymer gel systems is critical to enhancing oil recovery in oilfields. However, traditional gel applications face challenges such as high temperature and salinity. Herein, a method for the design of hydrogels that exhibited excellent temperature and salinity resistance performance was developed. Lignin-containing nanocellulose (LCN) was prepared as a crosslinker to enhance the polyacrylamide (PAM) cross-link network. Noncross-linked PAM in PAM-LCN was observed, indicating that LCN had a relatively low activity at room temperature, but strong interactions between LCN and PAM occurred at high temperature. PAM-LCN exhibited excellent performance within 65 days under ultrahigh-temperature (150 degrees C) and high-salt (200000 mg/L) conditions. The storage module and viscosity results demonstrated that the incremental -OH in cellulose linked to PAM enhanced the network in the range of 90-130 degrees C. The key role of LCN promoted crosslink point formation in PAM-LCN. The plugging rate was 96.77 %, and the breakthrough pressure was 3.16 MPa. It paves a new way to improve polymer gel's ultrahigh-temperature and high-salt resistance performance.

Formaldehyde emission is a critical threat from conventional adhesives. Herein, bio-adhesives have been developed using oxidized lignin-containing cellulose nano fiber (OLCNF) as a cross-linking agent to enhance the performance of sewage sludge hydrochar-based wood bio-adhesives. Abundant active functional groups can be found on the surface of sewage sludge (SS) due to presence of proteins and polysaccharides that can react with OLCNF to form macromolecular via Schiff base reaction. The key reason is OLCNF can improve molecular weight of macromolecular in bio-adhesives due to low molecular weight of proteins and polysaccharides in SS. Consequently, the wet shear strength of the SS-derived bio-adhesives, denoted as BD-SS-OLCNF, was elevated to a peak of 1.54 MPa, exceeding the minimum standard set by the Chinese national standard GB/T 9846-2015(>= 0.7 MPa). In contrast with untreated SS, hydrothermal carbonization (HTC) treatment facilitated the creation of reactive functional groups while concurrently diminishing the molecular weight and the wet shear strength of the bio-adhesives. The formation of covalent bonds was identified as a decisive factor in enhancing the wet shear strength. Subsequent mechanistic studies have elucidated that the presence of reactive functional groups and the formation of covalent bonds are pivotal elements for the efficacy of bio-adhesives. This study concurrently elucidates the role of HTC treatment of SS and the addition of OLCNF in developing high-performance bio-adhesives from wastes, favoring high-value utilization of SS and the development of sustainable bio-adhesives.

Barite blockage formed by drilling fluid filter cake with barite weighting agent as the main component is one of the main factors causing oil and gas reservoir damage and affecting oil and gas production. Conventional acidification measures are difficult to dissolve the barite blockage, and the development of a cost-effective non-acid chelating removal agents and the formulation of a scientific blocking removal construction process are effective engineering means to solve the barite blockage. Amino carboxylic acid chelating agent forms strong chelate with barium ions on the surface of barite, promotes the rapid dissolution of barite, and helps to relieve the blockage of barite filter cake. However, key technologies such as the commercial selection of chelating removal agents, the material chemical design of chelating removal agents, the evaluation method of chelating removal agents, and the construction technology of chelating removal agents, seriously affect the engineering application value of barite blocking removal. In this paper, the structural characteristics of the special chelating agent for barite blocking removal are summarized, the main factors affecting the blocking removal effect of the chelating removal agents are reviewed, the guiding principles for designing the product formulation of the chelating removal agents, the product performance evaluation method and the potential industrial by-product raw materials that can be used for the preparation of the chelating removal agents are proposed, and the construction process design method and control essentials of on-site blocking removal are analyzed. Finally, through the analysis of two typical application cases in sandstone and carbonate reservoirs, it provides readers with new ideas for the chemical design of chelating removal agents for barite filtrate cake and field-removing techniques.

To address the charge layer structure in dispersed heavy oil droplets and its correlation with oil–water interfacial properties, this study investigates the influence of asphaltenes on the oil–water interfacial characteristics and emulsion stability of heavy oils. Techniques such as dynamic light scattering, and interfacial tension measurement were employed to conduct this research. It highlighted how the molecular structure and dispersibility of asphaltenes influence the interfacial tension and stability of oil emulsions. The research demonstrated that the interfacial activity and size of asphaltenes affect their aggregation and adsorption at the oil–water interface. Furthermore, it examined how aromatics enhance the dispersibility of asphaltenes and reduce the average droplet size in oil emulsions, thereby improving the stability of heavy oil systems. These findings enhance understanding of the complex interactions at the oil–water interface, especially involving asphaltenes in extra-heavy oils.

We report a method for the of coal-based fluorescent carbon dots (CDs) at room temperature using a mixture of hydrogen peroxide (H2O2) and formic acid (HCOOH) as the oxidant instead of concentrated HNO3 or H2SO4. The CDs have an excitation dependent behavior with a high quantum yield (QY) of approximately 7.2%. The CDs are water soluble and have excellent photo-stability, good resistance to salt solutions, and are insensitive to pH in a range of 2.0-12.0. The CDs were used as a very sensitive probe for the turn-off sensing of Fe3+ ion with a detection limit as low as 600 nmol/L and a detection range from 2 to 100 μmol/L. This work provides a way for the high value-added utilization of coal.

随着起泡剂的深入研究,泡沫在孔隙介质中生存的状态可以在纳米颗粒的作用下更加稳定.综述了孔隙介质中泡沫的生成机制和纳米颗粒对泡沫液膜性质的影响,并对比了表面活性剂和纳米颗粒在孔隙介质中生成泡沫的能力.在此基础上,提出了双面神纳米粒子作为孔隙介质中起泡剂这一有潜力的研究方向.

采用扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等方法检测分析了塔河油田轻烃站部分设备内表面的腐蚀产物,并且通过现场取样试验对单质硫的来源进行了分析.结果表明:该轻烃站内设备及管线的腐蚀产物中含有大量单质硫,单质硫腐蚀是该轻烃站腐蚀的重要原因之一;该轻烃站内的单质硫主要来源于原料气;该轻烃站单质硫腐蚀的主要机理为水解机理即单质硫水解生成硫酸、硫化氢等腐蚀性物质.

Some oil wells in the Tahe oilfield have been reported to produce extremely heavy oil due to asphaltene deposition. To enhance the flow of crude oil through the wellbore, engineers adopted the use of light oil from nearby wells to dissolve the heavy crude in the wells’ sections to maximize recovery from the Tahe oilfield. However, this mixing has led to the problem of accelerated asphaltene deposition, which often blocks the wellbore in the process. In this research, the factors that influence the stability of diluted heavy oil, temperature, and mixing ratio on asphaltene deposition characteristics under high pressure are studied using a high-temperature and high-pressure crude oil flow property experimental device based on the differential pressure method. The results under high pressure show that the initial deposition pressure of asphaltene decreases as the experimental temperature increases. With an increase in the mixing light oil ratio, the initial deposition pressure of diluted heavy oil increases, and the deposition trend of asphaltene strengthens. The asphaltene accumulation and deposition will be aggravated by filling quartz sand and pipe diameter changes. The research here is helpful to understand the deposition characteristics of asphaltene during the production of diluted heavy oil. It offers significant guidance in the prevention and control of asphaltene precipitation in heavy oil wells.

As a common heat exchanger in the field of petroleum industry, the structure of reboiler is extremely complex, in which U-tube bundle is the key part. The N-Methyldiethanolamine medium contains hydrogen sulfide, carbon dioxide and other acidic gases, which is highly corrosive. In addition, due to the contact with a variety of materials, there is the risk of galvanic corrosion. Firstly, the galvanic corrosion behavior of reboiler materials in solution was studied by numerical simulation, and it was found that the corrosion of U-tube bundle was serious. Then, the combined protection design of coating and sacrificial anode is used to protect the reboiler U-tube bundle from corrosion. The numerical simulation results show that the combined protection of coating and sacrificial anode has a good effect. This numerical simulation method also provides an effective idea and method for the corrosion research of super complex structures such as reboiler.

针对边底水薄层特稠油油藏热采高轮次后注汽易窜,封堵困难,含水大幅上升导致开发效益下降的问题,以丙烯酰胺(AM)、丙烯酸钠(AA)、4-苯基-1-丁烯(PB)、丙烯酰胺-2-甲基丙磺酸(AMPS)为原料、四甲基乙二胺为催化剂制备了水溶性活性分子共聚物(AAPA).研究了油剂比、AAPA加量、pH值、Ca2+、Mg2+、温度对降黏效果的影响,分析了AAPA的降黏机理,并以多浓度多段塞式注入的方法,进行了化学降黏冷采矿场试验.结果表明,1 g/L的AAPA与原油以质量比1:1混合后的降黏效果最佳,可使黏度(50℃)<50 Pa·s的脱气脱水稠油的静置降黏率>90％.AAPA具有耐高矿化度、易于破乳以及降黏温度范围宽的特点.其有效降黏温度范围为50～180℃;耐Ca2+质量浓度≤10 g/L,耐Mg2+质量浓度<3 g/L;pH<4时降黏乳化后的稠油可快速破乳,pH>10时可进一步提高AAPA的降黏活性.现场应用4井次,提液增油效果明显.通过多浓度多段塞的方式将AAPA注入储层可有效降低原油黏度,明显提高边底水薄层特稠油油藏冷采开发效益.图7表1参15

针对塔河油田站内容器设备在高矿化度环境中的腐蚀情况,采用失重法和电化学测试方法,研究了3种C1-浓度下Q245R钢在塔河油田模拟水中的腐蚀行为.结果 表明:在H2S/CO2环境中,随着C1-浓度的增加,Q245R钢的腐蚀速率先减小后急剧增大;高C1-浓度下,腐蚀产物膜中S元素的原子分数有所增加,而O元素的原子分数先增加后急剧减少,此时腐蚀产物不具有保护性;在3种Cl-浓度条件下,均匀腐蚀速率均大于0.25 mm/a,评级为极严重腐蚀.由此可见,Q245R钢在高含C1-的塔河模拟水中不具备抗腐蚀能力.

为有效利用棉浆黑液、减少环境污染,以碱法棉浆黑液、苯酚、甲醛和聚丙烯酰胺为原料,通过水热法制备了黑液-酚醛复合凝胶,通过红外光谱、热重分析和扫描电镜对凝胶结构进行了表征,研究了苯酚加量对凝胶的影响,评价了凝胶的耐盐性、耐酸碱腐蚀性和封堵效果.结果表明,黑液-酚醛复合凝胶网络致密紧凑,热分解温度为200℃.苯酚加量为2％～4％的凝胶的成胶时间为24～14 h,含水率为72％～75％,吸水倍数为3.60％～3.92％.该凝胶具有黏度低、易泵入的优点,且具有良好的耐盐、耐酸碱性能.凝胶的封堵效果良好,对人工模拟岩心的封堵率大于99％.利用棉短绒黑液制备油田堵剂,不仅可以改善黑液污染,还可降低稠油开采成本.