湘西北下志留统龙马溪组页岩气成藏条件及勘探潜力分析

Accumulation conditions and exploration potential of shale gas in Lower Silurian Longmaxi Formation,Northwestern Hunan

对湘西北地区下志留统龙马溪组进行野外地质勘查和样品采集,并进行相关实验分析。研究认为：龙马溪组黑色页岩厚度大,最厚可达150 m;有机碳含量高,平均1.02%;Ro值处于1.06%-4.28%之间,热演化程度高;页岩中微孔隙和微裂缝较发育,为页岩气提供了足够的储集空间。等温吸附实验也表明,龙马溪组页岩具有较强的气体吸附能力,平均1.58 m3/t。因此,湘西北地区下志留统龙马溪组具有形成页岩气藏的良好潜力。根据研究区页岩厚度、有机碳含量、成熟度分布特征以及储层物性等方面的综合分析,认为桑植东北部、龙山—永顺一带为页岩气勘探有利区。

Based on the data of shale outcrops,sampling and laboratory analysis,the reservoir forming conditions and exploration potential of shale gas in Lower Silurian Longmaxi Formation in Northwestern Hunan are investigated. It is shown that Longmaxi Formation black shale is of great thickness,maximum thickness is 150 m,high organic carbon content,the average value is 1. 02%,and high thermal evolution degree,Ro is 1. 06% ~ 4. 28%. There developed micropores and microfractures in shale matrix,which provide enough storage space and migration pathways for shale gas. Besides,isothermal adsorption experiments show that Longmaxi Formation black shale is of strong adsorption ability to gas,the average adsorption capacity is 1. 58 m3/ t. Therefore Longmaxi Formation black shale has a good potential forming shale gas reservoirs. According to the comprehensive analysis of shale thickness,organic carbon content,maturity distribution and reservoir physical properties in the research area,it is held that there are two shale gas exploration potential areas: northeast Sangzhi and Longshan-Yongshun zone.