黔西北五峰-龙马溪组页岩气成藏条件综合评价

Comprehensive evaluation of shale gas reservoir conditions of Wufeng-Longmaxi formation in Northwest Guizhou

通过黔西北五峰-龙马溪组页岩岩心样品地球化学、岩石矿物学、储层孔隙和含气量等成藏条件分析发现,五峰-龙马溪组有机质产率高,还原环境强,有机碳含量4.15%～8.46%,古生物以甲藻等水生生物占优势,有机质类型以I型为主,有机质成熟度2.34%～3.96%,处于成熟-高成熟阶段。页岩矿物成分以黏土矿物和石英为主,平均含量分别为42.6%和27.9%,具有良好的脆性。页岩孔隙类型主要为粒间孔、粒内孔、有机质孔和微裂缝,孔隙表面粗糙程度中等,吸附能力中等,孔隙结构复杂。现场解析实验数据测得五峰-龙马溪组的含气量为0.04～2.81m3/t,气体主要成分为CH4。黔西北五峰-龙马溪组虽然具有良好的页岩气成藏条件,但不同地区页岩含气性差异较大,后期保存条件是影响页岩气能否富集的关键因素。

The shale reservoir conditions such as the geochemical, mineralogical porous and gas content conditions were analyzed based on the study of shale core samples of Wufeng-Longmaxi formation in Northwest Guizhou. It is found that with an organic content of 4.15%-8.46%, the Wufeng-Longmaxi formation is of high yield of organic matter and strong reduction environment. Aquatic organisms such as dinoflagellates are the dominant ancient creature. With type I as its main form and a maturity of 2.34%-3.96%, the organic matter is in its high-mature stage. Mainly composed of clay minerals and quartz, whose average contents are 42.6% and 27.9% respectively, the shale has good brittleness. With intergranular pore, intragranular hole, organic pore and micro crack as the main types, the shale pores have medium roughness pore surface, medium adsorption capacity, and complex pore structures. The data obtained from field experiments shows that the gas content of Wufeng-Longmaxi formation is 0.04- 2.81 m^3/t and the main composition of gas is CH 4 . Although the shale reservoir conditions of Wufeng-Longmaxi formation in Northwest Guizhou are good, the preservation conditions are the key factors to determine the shale enrichment due to the different gas contents in different regions.