延长组页岩气水平井水基钻井液体系研制与应用

Development and application of the water-based drilling fluid system in Yanchang-Formation shale-gas horizontal well

为了解决页岩气井水平段发生井漏、井塌及油基钻井液使用过程中的环境污染问题,开展了可替代油基钻井液的高性能抑制防塌水基钻井液体系研究。通过大量室内实验,评价筛选出最佳的抑制剂、封堵剂类型和添加量,优化处理剂的协同及配伍性关系,最终研制出膨润土-甲酸钾水基钻井液体系,并室内实验评价了该钻井液体系的抑制性、封堵性、润滑性、抗污染能力和热稳定性。实验结果表明,膨润土-甲酸钾水基钻井液的渗透率降低率达91%,岩屑回收率达97%,具有较好的抗盐、抗钙能力,可抗温120℃。现场应用表明,页岩气井造斜段和水平段钻进过程中,该水基钻井液的密度、黏度和失水等指标均在设计范围之内,体系性能始终保持稳定,能够满足延长页岩气钻井的需要。

In order to solve the well leakage & collapse in the horizontal section of shale gas well and reduce the environmental pollution of the oil-based drilling fluid, the study on the high-performance inhibiting anti-collapse water-based drilling fluid system was conducted to replace the oil-based drilling fluid. By means of the large amount of the indoor experiments, the maximal inhibitor, plugging agent type and added amount were evaluated and screened, the synergistic and compatible relationships between the treating agents were optimized, finally the bentonite-potassium formate water-based drilling fluid system was developed, and moreover the inhibiting, plugging and lubricating performances and furthermore the properties such as pollution resistance and thermal stability were evaluated as well in the indoor experiments. The experimental results show that the permeability reduction rate of the new water-based drilling fluid is over 91%, the recovery rate of the cuttings is 97%, and moreover it possesses much better salt and calcium resistances, the temperature resistance can reach 120 ℃. The field application shows that in the drilling process of the deflecting and horizontal sections for the shale gas well, the density, viscosity and water loss of the new water-based drilling are all in the ranges of the design, the system performances can keep the stability all the time, so it can meet the requirements of lasting the shale gas drilling.