CAJ | 학술논문

针对煤层气钻井过程中钻井液的侵入可能给煤岩储层造成的损害，选用宁武盆地9号煤和现场用钻井液为研究对象，开展了煤样钻井液动–静态损害评价、毛细管自吸、应力敏感性评价等实验。钻井液动–静态损害评价表明，钻井液滤液损害是造成煤层渗透率下降的主要原因；与地层水相比，煤样对钻井液的自吸能力强且吸附滞留严重，导致液相返排率偏低；钻井液作用后弱化煤样力学性质强化了煤样应力敏感性。结合水敏、碱敏、润湿性评价和扫描电镜分析结果，指出钻井液作用后煤岩裂隙堵塞、润湿性差异和钻井液吸附是钻井液造成煤层损害的主要因素。
침대매층기찬정과정중찬정액적침입가능급매암저층조성적손해，선용저무분지9호매화현장용찬정액위연구대상，개전료매양찬정액동–정태손해평개、모세관자흡、응력민감성평개등실험。찬정액동–정태손해평개표명，찬정액려액손해시조성매층삼투솔하강적주요원인；여지층수상비，매양대찬정액적자흡능력강차흡부체류엄중，도치액상반배솔편저；찬정액작용후약화매양역학성질강화료매양응력민감성。결합수민、감민、윤습성평개화소묘전경분석결과，지출찬정액작용후매암렬극도새、윤습성차이화찬정액흡부시찬정액조성매층손해적주요인소。
Aiming at reservoir damage caused by drilling fluid invasion during CBM drilling, the paper, by selecting seam No.9 in Ningwu basin and drilling fluid used in site as research object, conducted evaluation of dynamic- static damage of coal samples caused by drilling fluid, capillary imbibition and stress sensitivity. Dynamic-static damage evaluation shows that filtrate damage of drilling fluid is the main cause for reduction of permeability in coal seam, coal imbibitions ability is strong and adsorption retention is serious for drilling fluid when compared with formation water, which lead to the low liquid phase flow-back, after being reacted with the drilling fluid, coal samples has weakened mechanical properties and strengthened stress sensitivity. In combination with the analysis results of water sensitivity, alkali sensitivity, wettability evaluation and scanning electron microscopy (SEM), it is pointed out that fracture blocking, wettability difference and drilling fluid adsorption of coal are the main factors of seam damage caused by drilling fluid.