Acrylamide-based polymers have been widely applied in drilling fluids due to their excellent water solubility, structural tunability, and adaptability to various fluid systems. However, under high-temperature downhole conditions, these polymers are prone to molecular chain degradation, conformational collapse, and reduced adsorption capacity, resulting in a significant decline in rheological control and filtration loss performance. These limitations severely restrict their application in high-temperature wells. Enhancing the structural stability and functional durability of polymers under elevated temperatures has become a critical challenge in the development of high-performance drilling fluid materials. Isoprenol polyoxyethylene ether (TPEG) has been demonstrated to improve the thermal resistance of acrylamide-based polymers. Nevertheless, incorporating TPEG into polymer chains contradicts the conventional design paradigm that seeks to eliminate thermally labile structures in high-temperature-resistant polymers. Therefore, elucidating the microscopic mechanisms by which TPEG modulates polymer chain evolution, conformational behavior, thermal degradation pathways, and adsorption characteristics at elevated temperatures is essential to understanding its synergistic effect. In this study, isoprenol polyoxyethylene ether (the most commonly used type with a molecular weight of 2400 was chosen, TPEG-2400) was introduced into a DMAA/AMPS acrylamide-based copolymer system and systematically compared with conventional DMAA/AMPS binary copolymers. The incorporation of TPEG-2400 significantly enhanced the thermal conformational stability and clay adsorption capacity of the polymer, enabling the drilling fluid to retain favorable rheological and filtration properties even after aging at 220 ℃. The mechanism of action was elucidated by correlating changes in the physicochemical properties of the polymer with the analysis of its thermal degradation products. The highly flexible polyether structure was found to hinder interchain entanglement and coiling, while the strongly hydrophilic polyether segments formed a robust hydration layer, increasing electrostatic repulsion between clay particles. Moreover, the polyether chains may exhibit a “self-sacrificing” behavior under high-temperature conditions, preferentially decomposing to protect key functional groups such as amide moieties from thermal damage. This cooperative effect, from both conformational and thermodynamic perspectives, contributes to delaying polymer failure. It is concluded that the functional behavior of the segment structure plays a more significant role than its intrinsic thermal stability in enhancing the effective operating temperature of acrylamide-based polymers in drilling fluids. This counterintuitive yet strategically effective approach—introducing structurally specific but thermally less stable segments to achieve performance enhancement—offers a novel design perspective for future development of high-temperature-resistant polymer additives in drilling fluids.

As the global exploration and development of oil and gas resources advances into deep formations, the harsh conditions of high temperature and high salinity present significant challenges for drilling fluids. In order to address the technical difficulties associated with the failure of filtrate loss reducers under high-temperature and high-salinity conditions. In this study, a hydrophobic zwitterionic filtrate loss reducer (PDA) was synthesized based on N,N-dimethylacrylamide (DMAA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), diallyl dimethyl ammonium chloride (DMDAAC), styrene (ST) and a specialty vinyl monomer (A₁). When the concentration of PDA was 3%, the FL_API of PDA-WBDF was 9.8 mL and the FL_HTHP (180 °C, 3.5 MPa) was 37.8 mL after aging at 240 °C for 16 h. In the saturated NaCl environment, the FL_API of PDA-SWBDF was 4.0 mL and the FL_HTHP (180 °C, 3.5 MPa) was 32.0 mL after aging at 220 °C for 16 h. Under high-temperature and high-salinity conditions, the combined effect of anti-polyelectrolyte and hydrophobic association allowed PDA to adsorb on the bentonite surface tightly. The sulfonic acid groups of PDA increased the negative electronegativity and the hydration film thickness on bentonite surface, which enhanced the colloidal stability, maintained the flattened lamellar structure of bentonite and formed an appropriate particle size distribution, resulting in the formation of dense mud cakes and reducing the filtration loss effectively.

Antarctica contains numerous scientific mysteries, and the Antarctic ice sheet and its underlying bedrock contain important information about the geological structure of Antarctica and the evolutionary history of the ice sheet. In order to obtain the focus of these scientific explorations, the Antarctic drilling engineering is constantly developing. The drilling fluid performance directly determines the success or failure of drilling engineering. In order to enhance the poor performance for drilling fluids due to poor dispersion stability and easy settling of organoclay at ultra-low temperatures, the small-molecule wetting agent (HSR) for drilling fluid suitable for Antarctica was prepared by oleic acid, diethanolamine and benzoic acid as raw materials. Its chemical structure, properties and action mechanism were investigated by various experimental methods. The experimental results showed that 2% HSR could improve the colloidal rate for drilling fluid from 6.4% to 84.8%, and the increase rate of yield point was up to 167%. Meanwhile, it also made the drilling fluid excellent in shear dilution and thixotropy. In addition, 2% HSR could increase the density from 0.872 to 0.884 g/cm³ at −55 °C. And the drilling fluid with 2% HSR had a good thermal conductivity of 0.1458 W/(m·K) at −55 °C. This study gives a new direction for the research of drilling fluid treatment agents suitable for the Antarctic region, which will provide strong support for the scientific exploration of the Antarctic region.

As drilling wells continue to move into deep ultra-deep layers, the requirements for temperature resistance of drilling fluid treatments are getting higher and higher. Among them, blocking agent, as one of the key treatment agents, has also become a hot spot of research. In this study, a high temperature resistant strong adsorption rigid blocking agent (QW-1) was prepared using KH570 modified silica, acrylamide (AM) and allyltrimethylammonium chloride (TMAAC). QW-1 has good thermal stability, average particle size of 1.46 μm, water contact angle of 10.5°, has a strong hydrophilicity, can be well dispersed in water. The experimental results showed that when 2 wt% QW-1 was added to recipe A (4 wt% bentonite slurry+0.5 wt% DSP-1 (filtration loss depressant)), the API filtration loss decreased from 7.8 to 6.4 mL. After aging at 240 ℃, the API loss of filtration was reduced from 21 to 14 mL, which has certain performance of high temperature loss of filtration. At the same time, it is effective in sealing 80–100 mesh and 100–120 mesh sand beds as well as 3 and 5 μm ceramic sand discs. Under the same conditions, the blocking performance was superior to silica (5 μm) and calcium carbonate (2.6 μm). In addition, the mechanism of action of QW-1 was further investigated. The results show that QW-1 with amide and quaternary ammonium groups on the molecular chain can be adsorbed onto the surface of clay particles through hydrogen bonding and electrostatic interaction to form a dense blocking layer, thus preventing further intrusion of drilling fluid into the formation.

With the exploration and development of deep and ultra-deep oil and gas, high torque and high friction during the drilling of deep and ultra-deep wells become one of the key issues affecting drilling safety and drilling speed. Meanwhile, the high temperature and high salt problem in deep formations is prominent, which poses a major challenge to the lubricity of drilling fluids under high temperature and high salt. This paper reports an organic borate ester SOP as an environmentally friendly drilling fluid lubricant. The performance evaluation results show that when 1% lubricant SOP is added to the fresh water-based mud, the lubrication coefficient decreases from 0.631 to 0.046, and the reduction rate of lubrication coefficient is 92.7%. Under the conditions of 210 ℃ and 30% NaCl, the reduction rate of lubricating coefficient of the base slurry with 1% SOP was still remain 81.5%. After adding 1% SOP, the wear volume decreased by 94.11% compared with the base slurry. The contact resistance experiment during the friction process shows that SOP can form a thick adsorption film on the friction surface under high temperature and high salt conditions, thus effectively reducing the friction resistance. Molecular dynamics simulation shows that lubricant SOP can be physically adsorbed on the surface of drilling tool and borehole wall through hydrogen bond and van der Waals force. XPS analysis further shows that SOP adsorbs on the friction surface and reacts with metal atoms on the friction surface to form a chemically reactive film. Therefore, under high temperature and high salt conditions, the synergistic effect of physical adsorption film and chemical reaction film effectively reduces the frictional resistance and wear of the friction surface. In addition, SOP is non-toxic and easy to degrade. Therefore, SOP is a highly effective and environmentally friendly lubricant in high temperature and high salt drilling fluid.