无土相油基钻井液关键处理剂研制及体系性能评价

Development of key additives for organoclay-free oil-based drilling mud and system performance evaluation

针对传统油基钻井液固相含量较高、不利于提高机械钻速和保护储集层的问题,研制了一种无土相油基钻井液体系,阐述了关键处理剂的合成方法、作用机理,并进行了体系性能评价。利用二聚脂肪酸与二乙醇胺反应,制备了提切剂;利用脂肪酸的氧化和加合反应,制备了主乳化剂;对脂肪酸进行酰胺化改性,制备了辅乳化剂;将丙烯酸单体引入到苯乙烯、丙烯酸丁酯聚合反应中,合成了水性丙烯酸树脂降滤失剂。提切剂通过分子间的氢键作用增强乳液中液滴、颗粒之间的相互作用力,在乳液中形成三维网架结构,从而起到提切的作用。室内性能评价实验表明:无土相油基钻井液可抗220℃高温,高温高压滤失量小于5 mL;与传统油基钻井液相比,无土相油基钻井液具有较低的黏度以及较高的切力、动塑比和渗透率恢复值,有利于提高钻速、清洁井眼和保护储集层。

Traditional oil-based drilling muds （OBMs） have a relatively high solid content, which is detrimental to penetration rate increase and reservoir protection. Aimed at solving this problem, an organoclay-free OBM system was studied, the synthesis methods and functioning mechanism of key additives were introduced, and performance evaluation of the system was performed. The rheology modifier was prepared by reacting a dimer fatty acid with diethanolamine, the primary emulsifier was made by oxidation and addition reaction of fatty acids, the secondary emulsifier was made by amidation of a fatty acid, and finally the fluid loss additive of water-soluble acrylic resin was synthesized by introducing acrylic acid into styrene/butyl acrylate polymerization. The rheology modifier could enhance the attraction between droplets, particles in the emulsion via intermolecular hydrogen bonding and improve the shear stress by forming a three-dimensional network structure in the emulsion. Lab experimental results show that the organoclay-free OBM could tolerate temperatures up to 220 ℃ and HTHP filtration is less than 5 mL. Compared with the traditional OBMs, the organoclay-free OBM has low plastic viscosity, high shear stress, high ratio of yield point to plastic viscosity and high permeability recovery, which are beneficial to penetration rate increase, hole cleaning and reservoir protection.