泥页岩地层微纳米封堵水基钻井液技术研究

Research on micro-nano plugging water-based drilling fluid technology in shale formations

泥页岩地层钻井过程中容易发生井壁失稳问题,钻井液滤液侵入后,泥页岩水化膨胀产生的膨胀压加剧了裂缝的扩展,降低了岩石强度;钻井液的压力传递作用会减少液柱与井壁岩石的压差,降低了钻井液液柱对井壁的支撑作用。本文优选了纳米封堵剂GW-NBA、亚微米封堵剂GW-MPA、超细钙、磺化沥青作为钻井液的封堵剂,将刚性封堵剂与柔性封堵剂相结合,并且其粒径范围与一般的泥页岩微孔隙、微裂缝相近,在此基础上构建一套适用于泥页岩地层的水基钻井液体系。结果表明,该水基钻井液体系具有较好的封堵性能以及承压能力,具有较好的流变性、滤失性、抑制性、封堵性,适用于泥页岩地层钻井。

Borehole instability easily occurs during drilling in mud shale formations.This paper studied themechanism of wellbore instability in mud shale formations.The strength of the rock was reduced after the inva-sion of drilling fluid filtrate the swelling pressure caused by the hydration expansion of shale accelerated thefracture expansion.The pressure transfer effect of the drilling fluid reduced the pressure difference between theliquid column and the wellbore rock,and reduce the supporting effect of the drilling fluid column on the well-bore wall.In this paper,nanometer plugging agent GW-NBA,submicron plugging agent GW-MPA,ultrinecalcium,and sulfonated asphalt were selected as plugging agents for drilling fluid,and the rigid pluggingagent was combined with the flexible plugging agent.The particle size range was similar to that of general mudshale micr-ores and micr-ractures.On this basis,a set of water-based drilling fluid system suitable for mudshale formations was constructed.The research results showed that the system had good plugging performanceand pressure bearing capacity,and had good rheology,fluid loss,inhibition,plugging and other properties,and was suitable for drilling in shale formations.shaleborehole instabilityplugging agentwater-based drilling fluidhydrations.