无毒环保型高性能水基钻井液室内研究

由于油基钻井液存在使用成本高、环保处理难度大等弊端，使用水基钻井液替代油基钻井液已成为大势所趋。针对页岩地层对钻井液性能的要求，以无氯、无重金属离子、无黑色材料等环保指标为基本原则，优选了胺基聚醇和乳液大分子作为环保型高性能水基钻井液的包被抑制主剂，配合甲酸钾进一步提高体系的抑制性，并通过高效封堵剂提高体系对页岩地层纳微米孔缝的封堵能力，构建了无毒环保型高性能水基钻井液体系。性能评价结果表明，该钻井液在密度为1.22~2.18 g/cm3范围内均具有优良的流变性及滤失造壁性能，该体系静置24 h后上下密度差为0.03~0.06 g/cm3，沉降指数低于0.508，悬浮稳定性好，触变性高，钻井液样品API泥饼黏滞系数最低达到0.026 2，润滑性能好，并兼具较强的抑制性和抗岩屑污染性能，5.0%及8.0%英国评价土或古巴VDW**井岩屑污染前后的塑性黏度、动切力、静切力的变化率均控制在25%左右，能够满足不同压力系统页岩地层钻井的需要。 

Laboratory Study of an Environmentally Friendly Non-toxic High Performance Water Base Drilling Fluid

Oil base drilling fluids, because of its high operation cost and pollution to the environment, are more and more replaced by water base drilling fluids. Based on the requirements for the performance of drilling fluids imposed by shale drilling, drilling fluid additives have been optimized to formulate an environmentally friendly non-toxic high performance water base drilling fluid. In selecting the additives, the environmental rules of "chloride-free, heavy metal ion-free and no black material" were followed. Amine based polyalcohol and polymers synthesized through emulsion polymerization were selected as the main shale encapsulators, whose inhibitive capacity was enhanced with potassium formate. A highly effective plugging agent was selected to improve the ability of the drilling fluid to plug the nanometer and millimeter micro-fractures. Laboratory evaluation indicated that in a density range of 1.22-2.18 g/cm3, the drilling fluid had excellent rheology and filtration property. After standing for 24 hours, the density difference between the top and the bottom of the mud sample was 0.03-0.06 g/cm3, and the settling index was less than 0.508, indicating good suspending stability and high thixotropy. The friction coefficient of the mud cakes formed by the sample drilling fluid on an API filter press was as low as 0.0262, meaning that the drilling fluid had very good lubricity. Laboratory experiments also showed that this drilling fluid had strong inhibitive capacity and tolerance to drilled cutting contamination. After contamination with 5.0% and 8.0% British evaluation clay or drilled cuttings from the well VDW** (Cuba), changes in PV, YP and gel strengths of the drilling fluid were controlled within about 25%. The evaluation results also proved that this drilling fluid satisfied the needs for drilling shales of varied formation pressures.