湖南保靖地区震旦系陡山沱组页岩气成藏地质条件分析

The shale gas accumulation in the Sinian Doushantuo Formation in the Baojing region,Hunan

关键词:  页岩气  陡山沱组  成藏条件  沉积环境  储集空间  湖南保靖

Key words:  shale gas  Doushantuo Formation  accumulation  sedimentary environment  reservoir space  Baojing in Hunan

摘要:

为评价湖南保靖地区震旦系陡山沱组页岩气勘探潜力，利用野外地质调查及页岩气井勘探成果资料，结合钻井岩心样品测试结果，研究了湖南保靖地区陡山沱组页岩储层发育的特征及其分布规律。湖南保靖震旦系陡山沱组发育被动大陆边缘浅水陆棚斜坡相灰色白云质灰岩、黑色碳质泥岩、黑色硅质岩、黑色硅质岩、深灰色泥晶灰岩、深灰色含钙碳质泥岩等。该页岩层分布稳定，厚度巨大（150～200m）；有机碳含量较高（4.07%～10.25%），热演化程度较高（3.78%～4.97%），达到过成熟阶段；页岩孔隙度中等（0.19%～2.355%），渗透率极低（0.0005257～0.5910081 mD）；脆性矿物含量较高（55.9%～84.5%），主要以石英、方解石、黄铁矿、斜长石为主；黏土矿物含量较低（16.5%～44.1%），以伊利石和伊蒙混层为主，经历了晚成岩作用阶段；储集空间主要有矿物溶蚀孔、有机质溶蚀孔、黄铁矿晶间孔、黏土矿物晶间孔、成岩解理缝及构造微裂缝等。综合研究分析认为，湖南保靖地区陡山沱组具有较好的页岩气成藏条件，可继续加大勘探力度。

Abstract:

The development and distribution of the shale reservoirs in the Sinian Doushantuo Formation in the Baojing region, Hunan are examined on the basis of field geological investigation and analytical results of core samples so as to evaluate the exploration potential of the shale gas in the Doushantuo Formation, where there developed grey dolomitic limestone, black carbonaceous mudstone, black siliceous rocks, dark grey micritic limestone and dark grey calcium-bearing carbonaceous mudstone of the passive continental margin shallow shelf-slope facies. These shale reservoirs have tremendous thickness (150-200 m), higher organic carbon contents (4.07%-10.25%), and higher maturity (3.78%-4.97%), moderate porosity (0.19%-2.355%) and extremely low permeability (0.0005257-0.5910081 mD). The contents of the brittle minerals in the shale reservoirs are relatively higher, varying from 55.9% to 84.5%, and consist dominantly of quartz, calcite, pyrite and plagioclase, while the contents of the clay minerals are relatively lower, ranging from 16.5% to 44.1%, and mainly composed of illite, chlorite, mixed illite-montmorillonite beds and chlorite-montmorillonite beds, suggesting that the Sinian Doushantuo Formation went through the late diagenetic stages. The reservoir spaces include solution openings, organic matter solution openings, intercrystalline pores in pyrite and clay minerals, diagenetic cleavage cracks and structural microfractures. It is concluded from the results of research cited above that the Doushantuo Formation in the Baojing region is of favourable geological conditions for the shale gas accumulation, and thus may have the potential for further exploration in this region.