Design and performance evaluation of a novel integrated surfactant for ultra-high-temperature oil-based drilling fluids
摘要
In response to the extreme high-temperature and high-pressure conditions encountered in drilling operations in complex formations such as deep and ultra-deep wells, this paper describes the synthesis of a novel integrated surfactant that combines a dual-chain hydrophobic backbone with polyfunctional polar hydrophilic groups. Its structure was characterized using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and elemental analysis, and its interfacial properties, emulsifying performance, biological toxicity, and application effectiveness in oil-based drilling fluids were systematically evaluated. The results indicate that at a concentration of 3.0 wt%, this surfactant can reduce the oil-water interfacial tension to 1.98 mN·m− 1 and maintain a high emulsification rate under various oil-to-water ratios. Notably, the 85:15 oil-to-water ratio system still exhibited good emulsification stability and uniform droplet distribution after high-temperature aging. Acute ecotoxicity tests (96 h LC50: crustaceans 4.03 × 104 mg·L− 1; fish 5.16 × 104 mg·L− 1) met the biotoxicity admission requirements for offshore oil exploration. The oil-based drilling fluid system formulated with this surfactant exhibited optimal comprehensive performance at a concentration of 3.0 wt% concentration, exhibiting optimal comprehensive performance. After aging at 232 °C for 16 h, the demulsification voltage remained at approximately 1000 V and the dynamic shear stress at approximately 6 Pa, with high-temperature, high-pressure (HTHP) filtrate loss controlled at 6.6 mL, and stability maintained within a density range of 1.5–2.4 g·cm− 3. High-temperature rheological analysis confirmed that the viscosity retention rate of this system at 232 °C was approximately 6.5%, demonstrating good high-temperature rheological stability. The results indicate that this novel surfactant possesses good emulsification stability, high-temperature resistance, and low biotoxicity, providing a reference for the design and application of ultra-high-temperature deep-well oil-based drilling fluid systems.