In the process of oil extraction, the drilling fluid, as a critical operational fluid, directly impacts the drilling efficiency and safety. However, under high-temperature and high-pressure conditions, the drilling fluid tends to experience fluid loss, which not only causes environmental pollution but also increases the drilling costs and challenges. To address this issue, this study aimed to develop a novel high-temperature-resistant and environmentally friendly polymer fluid loss additive—EnSipoly-FL—designed to enhance the thermal stability and environmental performance of drilling fluids. The copolymerization of acrylamide (AM), N-vinylpyrrolidone (NVP), acrylic acid (AA), and vinyltrimethoxysilane (A-171) was selected to ensure the thermal and chemical stability of the fluid loss additive. The synthesis conditions, including the initiators, emulsifiers, reaction temperature, and time, were optimized in the experiments. The structure of the target product was confirmed by infrared spectroscopy and nuclear magnetic resonance analysis. Thermogravimetric analysis and particle size analysis demonstrated that the polymer possessed excellent thermal stability and appropriate physical dimensions. Environmental impact assessments indicated that EnSipoly-FL exhibited good biodegradability and low toxicity, meeting environmental protection standards. Comprehensive performance tests showed that the polymer microspheres exhibited exceptional fluid loss reduction capabilities and environmental friendliness in high-temperature and high-pressure drilling fluid applications. This makes it a promising candidate for widespread use in the oil drilling industry, advancing the green development of drilling fluid technology.

The Tarim Basin, as the core strategic replacement area for oil and gas resources in western China, holds immense deep oil and gas development potential. However, this region features extensive deserts, fragile saline–alkali ecosystems, and extreme geological conditions—160°C high temperatures, high-salt/high-alkali formation fluids, and well-developed microfractures—that impose stringent dual requirements on drilling fluids for both engineering performance and environmental compatibility. Traditional drilling fluids suffer severe performance deterioration under high-temperature/high-salt coupling, and their poorly biodegradable, toxic additives exacerbate ecological pollution upon disposal, failing to meet green development demands. To address these issues, this study prepared four eco-friendly, temperature- and salt-resistant drilling fluid additives via chemical modification of natural degradable materials, and constructed a 160°C-resistant eco-friendly water-based drilling fluid system using orthogonal experiments. Furthermore, an innovative “waste-to-resource” strategy was proposed to repurpose spent drilling fluid for saline–alkali land restoration, investigating its improvement effects and environmental safety. The results show that the system withstands 160 °C and 15% NaCl, with excellent engineering performance (HTHP filtration loss ≤ 9.0 mL at 160 °C, friction coefficient ≤ 0.18) and compliance with national environmental standards (EC₅₀ = 36,000 mg/L, BOD₅/COD = 6.8%). Applied at an optimal 10–15% dosage, the spent fluid significantly improves saline–alkali soil properties, promotes Haloxylon ammodendron growth, and achieves >90% pollutant degradation within 3 months without secondary pollution. This integrated technology synergizes drilling engineering and ecological protection, providing technical support for green oil and gas development and saline–alkali land restoration in the Tarim Basin.

Aiming at the industrial problems of traditional sulfonated drilling fluids in high-temperature drilling of deep oil and gas reservoirs at 180°C, including high-temperature degradation, poor environmental protection, and severe reservoir damage, this paper adopts a function-oriented research idea to construct a set of non-sulfonated water-based drilling fluid systems with excellent comprehensive performance and temperature resistance up to 180 °C. Strict screening criteria for single agents were established, and six core non-sulfonated treatment agents were selected from 18 candidate agents in four categories: viscosifiers, fluid loss reducers, inhibitors, and high-temperature stabilizers. The compounding synergistic effects of cross-category treatment agents were studied, and four core action mechanisms were revealed. The optimal formula was obtained through optimization. Tests show that after hot rolling at 180 °C for 16 h, the system has an apparent viscosity retention rate of ≥81%, a yield point retention rate of ≥76%, and a high-temperature and high-pressure filtration loss of ≤12.8 mL. It can resist 15% salt, 1.0% calcium, and 15% drill cuttings, and maintains stable performance under composite pollution. At 180 °C, the shale linear expansion rate is only 8.6%, and the cuttings rolling recovery rate reaches 92.4%. The core permeability recovery value is ≥90.2%, the biotoxicity EC₅₀ value is 42,600 mg/L, and the 28-day biodegradation rate is 68.3%. This system can replace traditional sulfonated drilling fluids and provide a green and feasible technical solution for safe and efficient drilling in deep high-temperature formations.