湖南保靖龙马溪组页岩气富集主控因素分析

Analysis of main controlling factors of shale gas accumulation of Longmaxi formation in Baojing block of Hunan province

为了查明湖南保靖区块龙马溪组页岩气富集的主控因素,基于研究区龙马溪组页岩样品测试成果,采用数理统计以及对比分析方法,分析了龙马溪组页岩气富集的地质条件以及富集影响因素。结果表明:龙马溪组底部岩层主要为黑色碳质泥岩,且含有大量笔石,优质页岩段厚8~16 m,总有机碳(TOC)含量普遍接近2%,干酪根类型以I型为主,Ro平均值大于2%,达到高热演化程度;龙马溪组岩层主要发育粒间孔和有机质孔,微裂隙相对发育,孔隙以微孔和中孔为主,为页岩气富集提供了足够的空间;孔隙度及渗透率较差,但脆性矿物质量分数较高(≥43%),为后期的压裂改造提供了有利条件;龙马溪组TOC、构造保存条件、底部泥质深水陆棚微相和硅质深水陆棚微相,以及发育的孔裂隙系统为页岩气富集的主控因素。

Abstract： In order to determine the controlling factors of shale gas accumulation of Longmaxi formation in Bao- jing block, the shale gas geological conditions and enrichment factors of Longmaxi formation were analyzed based on shale gas test. The mathematical statistics and comparative analysis methods were used for data analy- sis. The results show that the bottom lithology of Longmaxi formation is mainly composed by black carbonaceous mudstone and contains a large number of graptolites. The thickness of high quality shale section ranges 8 16 m and TOC generally is close to 2%. The kerogen type is I and the average of R~ is more than 2% ,which has reached high maturity. The main pores are intergranular pores and organic pores with many microcracks. The pores are dominated by micropores and mesopore,which provide sufficient space for shale gas enrichment. The porosity and permeability are low. However, the brittle mineral content is high （more than 43% ） , which provides favorable conditions for later fracturing reconstruction. The key factors of shale gas enrichment are TOC, storage conditions, bottom of mud deep shelf facies, siliceous deep shelf facies and pore fracture system.