鄂西恩地1井上二叠统大隆组页岩气富集主控因素分析

Analysis on Main Controlling Factors of Shale Gas Enrichment in Upper Permian Dalong Formation in Well Endi 1,Western Hubei

湖北省恩施地区恩地1井在上二叠统大隆组泥页岩中获得较显著的页岩气发现,页岩现场解吸最大含气量达到2.5 m^(3)/t,平均含气量为1.4 m^(3)/t。岩心薄片扫描电镜分析、岩心样品有机碳含量测试、镜质体反射率测试、低温氮气吸附实验表明,大隆组页岩有机碳含量高,为生烃提供了良好的物质基础;有机质演化程度相对适中;页岩中大量的有机质孔隙提供了主要的储集空间;纳米级孔隙的大量发育增加了页岩的比表面积,有利于页岩气的吸附。与此同时,恩地1井所处构造环境相对稳定,受构造改造程度较小,大隆组裂缝发育规模较小;低角度裂缝改善了大隆组页岩储集空间,小规模高角度裂缝可沟通大隆组不同含气层段,改善渗透性,且并未切穿大隆组含气层段造成与其他高渗透性地层沟通,为页岩气保存提供了较理想条件。恩地1井页岩气的发现进一步证实鄂西地区二叠系中浅层页岩气具有良好的勘探前景,为下一步页岩气勘探指明了方向。

There is a significant shale gas discovery in the organic-rich shale of the Upper Permian Dalong Formation in Well Endi 1 in the Enshi area,Hubei Province.The field desorption experiment shows that the maximum gas content is 2.5 m^(3)/t,and the average gas content is 1.4 m^(3)/t.The scanning electron microscope,organic carbon content test of core samples,vitrinite reflectance test and low-temperature nitrogen adsorption experiment show that Dalong Formation shale of Endi 1 well has high organic carbon content,which provides a good material basis for hydrocarbon generation.The evolution degree of organic matter is relatively moderate.A large number of organic pores in shale provide the main reservoir space.And the development of a large number of nanoscale pores increases the specific surface area of shale,which is conducive to the adsorption of shale gas.At the same time,the structural position of Well Endi 1 is relatively stable,the degree of structural transformation is small.Low-angle fractures improve the storage space of shale in Dalong Formation,while small-size high-angle fractures can communicate with different gas-bearing strata in Dalong Formation and improve its permeability.Moreover,they do not cut through the gas-bearing strata in Dalong Formation and communicate with other highly permeable strata,which are ideal conditions for shale gas preservation.The discovery of shale gas in Well Endi 1 further confirmed the exploration prospect of shale gas in Permian in the shallow strata in western Hubei and pointed out the direction for the next step exploration of shale gas.