Research on Environmentally Friendly Drilling Fluid System and Exploration of Waste Utilization in Desert Saline–Alkali Lands

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.