摘要:
检测煤岩的矿物组分,研究煤岩的损害机理,结合敏感性实验提出保护型钻、完井液体系。结果表明该钻井液体系具有较强的抑制性,可防止黏土矿物水化膨胀,保证井壁稳定;滤失量低,室内实验后30 min滤失量为12.6 mL;黏度适中动塑比为0.45 Pa/(mPa·s),能够有效携岩,清洁井底,级配的超细碳酸钙能够有效封堵煤层裂隙减少储层伤害。完井液体系中表面活性剂降低水锁效应;生物酶对纤维素进行降解;盐酸对超细碳酸钙进行溶蚀,消除井壁泥皮,对煤岩中碳酸岩盐进行溶蚀,生成的CO2吸附于煤岩裂隙表面,同时可作为动力源推动完井液进一步深入作用且增加煤储层能量起到助排作用;铁离子稳定剂能够有效防止氢氧化铁沉淀;完井液的替入能够有效改善煤储层的渗透性。
Abstract:
Through the detection of mineral composition of coal and rock and the study of damage mechanism of coal, we propose the protected drilling and completion fluid system combining with sensitivity experiments. The results show that the drilling fluid system has a strong inhibitory effect to prevent the expansion of clay mineral hydration and to ensure the stability of the well, and has a low filtration loss（12.6 mL/30 min）, has a moderate viscosity （0.45 Pa/（mPa·s）） which can effectively carry rock and clean the bottom hole. The graded ultrafine calcium carbonate can effectively block coal seam fractures and reduce reservoir damage. Well completion fluid system: the water lock effect is reduced by surfactant, the cellulose is degraded by enzymes, the superfine calcium carbonate is dissolved by hydrochloric acid to remove the wall-mud and the carbonate in coal are dissolved by hydrochloric acid too. CO2 generated by dissolution is adsorbed by fissure surface of the coal and can act as a power source to push completion fluid to carry out further action and increase coal reservoir energy for drainage. The precipitation of iron hydroxide is prevented by iron ion stabilizer. Finally the completion fluid can effectively improve the permeability of coal reservoirs.
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