煤岩孔隙结构特征及其对储层损害的影响

煤岩特殊的孔隙结构及甲烷赋存和产出方式决定了其损害机理与常规储层存在明显差异。在此以六盘水地区亦资孔盆地二叠系煤岩气藏为对象,应用压汞和扫描电镜等手段,研究煤岩储层孔隙类型和孔隙结构特征,结合煤岩学、敏感性及工作液损害评价实验,探讨了煤岩气层损害机理。研究表明,煤岩中常见植物组织孔和气孔,裂缝发育,属双重孔隙介质,表现出很强的应力敏感性。工作液易通过天然裂缝系统侵入煤层中,导致裂缝内的固相沉积、水相圈闭和高分子处理剂吸附滞留损害。

CHARACTERISTICS OF PORE STRUCTURE AND ITS IM-PACT ON RESERVOIR DAMAGE MECHANISMS OF COAL BEDS

There are great differences in damage mechanism between coal-beds and conventional reservoirs owing to the unique char-acteristics of pore structure, gas storage and production process-es in coal-beds. Coal-beds at the national test site for coal-bed methane development in Liupanshui are selected. Mercury in-jection and SEM are applied to analyze pore types, size and dis-tribution of pore throats of coal-beds. The parameters of pore structure of coal-bed are computed. On this basis of anthropo-logical features, pore structure, sensitivity and damage evalua-tion test from working fluids, damage mechanisms of coal seams have been analyzed. Results indicate that microprobes occurred in plant tissues, pores resulted from gas generation, and frac-tures are well developed in coal seams, so the reservoirs belongto dual-porous medium. Therefore coal-beds can easily be invad-ed and damaged by working fluids. The study shows that solid invasion, stress sensitivity, aqueous trapping and adsorption of high molecular polymers are major damage factors.