基于井壁稳定的大位移井水基钻井液体系研究

Research on Water-based Drilling Fluid System for Extended Reach Wells based on Wellbore Stability

针对南海东部区块大位移井低承压地层易井壁失稳、安全密度窗口窄易漏失等问题,设计开发了一种提高井壁稳定性的大位移井水基钻井液体系。该体系通过高效抑制剂HIB-3实现对地层泥页岩水化分散的有效抑制;利用化学固壁剂HXGB-1与岩石反应,在井壁表面形成具有较强内聚力和黏附性的凝胶,提高低承压地层的抗压强度;使用复合封堵剂FHSEAL-4进行有效物理封堵裂缝,降低漏失风险和漏失影响程度,提高井壁稳定性。实验评价表明,该体系的流变性能、润滑性能、封堵滤失性能和造壁性能等满足钻井要求,抑制性能和封堵防塌能力强,泥页岩岩屑在该钻井液中的热滚回收率达92.6%,砂岩岩心在该钻井液中浸泡2天后,单轴抗压强度提高20.2%。

A water-based drilling fluid system for extended reach wells is designed and developed to improve the stability of the well wall, aiming at the problems that the low pressure bearing formation of extended reach wells in the eastern block of South China Sea is prone to wellbore instability and the narrow safety density window is prone to leakage. This system can effectively inhibit the hydration and dispersion of formation shale through the highly effective inhibitor HIB-3. The chemical wall fixing agent HXGB-1 reacts with the rock to form a gel with strong cohesion and adhesiveness on the surface of the borehole wall,improving the compressive strength of the low pressure bearing formation. The composite plugging agent FHSEAL-4 is used to effectively physically plug the fractures, reduce the leakage risk and impact degree, and improve the wellbore stability. The experimental evaluation shows that the rheological property, lubricating property, plugging and filtration performance and wall building performance of the system meet the drilling requirements, and the inhibition performance and plugging and anti sloughing ability are strong. The hot roll recovery rate of shale cuttings in the drilling fluid is 92.6%, and the uniaxial compressive strength of sandstone cores increases by 20.2% after soaking in the drilling fluid for 2 days.