辽河大民屯凹陷页岩油储层强封堵恒流变油基钻井液技术

Technology of Strong Plugging Constant Rheology Oil-Based Drilling Fluid for Shale Oil Reservoir in Damintun Sag of Liaohe Basin

针对辽河油田页岩油储层开发过程中油基钻井液封堵性能不足导致复杂事故频发,低温敏感性强导致循环处理时间长和转运难度大等技术难题,研制了油基交联封堵剂和低温流变性改进剂,形成了一套强封堵恒流变油基钻井液体系,并对该钻井液体系进行了性能评价和实际应用。研究表明:强封堵恒流变油基钻井液密度为1.80~2.40 g/cm^(3),耐低温达到-25℃,耐高温达到220℃以上;钻井液具有良好的流变性和沉降稳定性,页岩一次回收率为100.0%,二次回收率为97.5%,对页岩的封堵率达到了60%,可有效减缓压力在页岩内部的传递。现场应用表明:强封堵恒流变油基钻井液体系流变性稳定且易调整,井壁稳定效果好,机械钻速高。该技术可为页岩等复杂地层深井、超深井的高效钻井提供技术参考。

In response to the technical problems such as frequent occurrence of complicated accidents due to insufficient plugging performance of oil-based drilling fluid and long cycle processing time and difficulty in transfer due to strong sensitivity to low temperature in the development of shale oil reservoir in Liaohe Oilfield,an oil-based cross-linked plugging agent and low temperature rheology improving agent were developed to form a set of strong plugging and constant rheology oil-based drilling fluid system,and the performance evaluation and practical application of this drilling fluid system were carried out.The study shows that:The density of strong plugging constant rheology oil-based drilling fluid is 1.80-2.40 g/cm^(3),and the low temperature resistance reaches-25℃and high temperature resistance reaches over 220℃;the drilling fluid has good rheology and settlement stability,the primary recovery rate of shale is 100.0%,the secondary recovery rate is 97.5%,and the plugging rate for shale reaches 60%,which can efficiently slow down the pressure transfer inside the shale.The field application shows that,Strong plugging constant rheology oil-based drilling fluid system has stable rheology and is easy to adjust,with good wellbore stability and high rate of penetrate.This technology can provide a technical reference for efficient drilling of deep and ultra-deep wells in shale and other complex formations.