湘中坳陷二叠系海陆过渡相页岩气地质条件  

Geological conditions of Permian sea-land transitional facies shale gas in the Xiangzhong depression

作　　者：顾志翔[1,2] 彭勇民[2] 何幼斌[1] 胡宗全[2] 翟羽佳[2,3] 

机构地区：[1]长江大学地球科学学院,湖北武汉430100 [2]中国石油化工股份有限公司石油勘探开发研究院,北京100083 [3]中国地质大学(北京)海洋学院,北京100083

出　　处：《中国地质》2015年第1期288-299,共12页Geology in China

基　　金：国家科技重大专项项目(2011ZX05004-001-004)资助

摘　　要：根据湘中坳陷二叠系黑色页岩的露头及岩心观测、含气量、地化和物性资料,以及等温吸附、氩离子抛光＋扫描电镜等方法所获数据,探讨了页岩气地质条件。研究认为二叠系龙潭组、大隆组海陆过渡相页岩具备良好的页岩气地质条件。有机碳含量在2%以上;成熟度分布于1.2%-1.6%;储集类型主要为残留粒间孔、粒内孔、溶蚀孔等矿物质孔和少量有机质孔,孔隙度在0.54%-5.15%,等温吸附实验测试平均含气能力在5.488-6.905 m3/t。热演化史分析表明二叠系页岩在沉积之后经历了两次抬升剥蚀,第二次沉降没有达到第一次的最大埋深且没有二次生烃,这可能是导致研究区页岩总体含气量低的原因之一。构造分析表明,印支期和燕山期改造作用,对油气破坏明显,恶化了保存条件增加勘探风险。运用叠合法预测页岩气有利区为湘中涟源—娄底—双峰区、邵阳—邵东区,采用体积法计算页岩气总资源量为（127-425）×10^8m3（中值254×10^8m3）,显示一定的页岩气资源潜力。综合分析认为保存条件是该区页岩气成藏的关键因素,也是勘探成功与否的首要因素。Based on such analytical methods as outcrop core observation, gas content, geochemical and physical property data and isothermal adsorption as well as argon ion polishing plus scanning electron microscopy of Permian black shale in the center of Hunan depression, the authors investigated the geological conditions of shale gas. The results show that the geological conditions of shale in Permian Longtan Formation and Dalong Formation of sea-land transitional facies are beneficial to gas accumulation. Theorganic carbon content is high than 2%, the grade of maturity distribution is between 1.2% and 1.6%, the main reservoir types are mineral holes with minor organic holes such as residual intergranular pores, intragranular pores and corrosion holes. The porosity is between 0.54% and 5.15%, the average gas content capacity of isothermal adsorption test is between 5.488 and 6.905 m3/t. The thermal evolution analysis shows that Permian shale experienced two times of uplift and denudation, and the second denudation didn＇ t reach the maximum depth of the first time and there was no secondary hydrocarbon. This might have been the reason which led to the low gas content in the study area. Structural analysis shows that the modification effect of Indo- Chinese epoch and Yanshanian period resulted in the poor preservation conditions that damaged the oil gas obviously and increased the risk of exploration. Using the method of superposition to predict the areas, the authors reveal that Lianyuan- Loudi- Shuangfeng area and Shaoyang- Shaodong area are favorable shale gas areas. The volume method was used to calculate the total quantity of shale gas resource, which yielded （127 - 425 ） ×10^8 m3, （the medium value being 254×10^8 m3）, suggesting a certain potential of shale gas resources. The comprehensive analysis shows that the preservation condition is the key factor for shale gas accumulation in this area, and is also the principal factor for successful exploration.

关 键 词：湘中坳陷 二叠系 页岩气 保存条件 

分 类 号：P618.13[天文地球—矿床学]