湘中涟源凹陷石炭系测水组页岩气富集主控因素与成藏模式  

Main controlling factors of enrichment and accumulation pattern of Carboniferous Ceshui Formation shale gas in Lianyuan sag,Central Hunan

作　　者：苗凤彬 张国涛 张保民 罗胜元 王强 田巍 陈林 MIAO Fengbin;ZHANG Guotao;ZHANG Baomin;LUO Shengyuan;WANG Qiang;TIAN Wei;CHEN Lin(Wuhan Center of China Geological Survey(Central South China Innovation Center for Geosciences),Wuhan 430205,Hubei,China)

机构地区：[1]中国地质调查局武汉地质调查中心(中南地质科技创新中心),湖北武汉430205

出　　处：《地质通报》2024年第10期1689-1704,共16页Geological Bulletin of China

基　　金：中国地质调查局项目《洞庭盆地及周缘页岩油气调查评价》(编号:DD20243464);《洞庭−沅麻盆地页岩气战略性矿产调查评价》(编号:DD20230323)。

摘　　要：湘中坳陷是是四川盆地外围页岩气勘探的重要区域,石炭系测水组是页岩气重点产出层位。以区内次级构造涟源凹陷为研究对象,基于野外剖面和钻井资料、分析测试及现场实测含气性数据,开展测水组页岩气地质条件与差异分布特征研究,并探讨页岩气富集主控因素与成藏模式。结果表明:①潟湖沉积相区测水组发育暗色泥页岩,厚度为30~80 m,有机质以Ⅱ型为主,总有机碳含量(TOC)大于1.5%,2.0%<R_(o)<3.0%,具备良好的生烃基础;②测水组主要为高脆性矿物的硅质页岩,储集空间包括有机质孔、无机质孔与裂缝,具特低孔特低渗特征;③测水组气藏的形成主要经历早期原地聚集—中期调整改造—晚期逸散-残留3个演化阶段,主成藏改造期为中侏罗世—早白垩世;④潟湖相还原环境发育的富有机质页岩是测水组气藏形成的物质基础,热演化程度是富集成藏的重要影响因素,保存条件是成藏的关键,层内滑脱是气体富集程度的控制条件。通过综合分析,建立了测水组“沉积环境控区、构造-滑脱双重控保定富”的页岩气成藏模式,潟湖相区的向斜构造为有利富集区,翼部封闭性逆断层下盘为有利富集部位。The central Hunan depression is an important area for shale gas exploration in the periphery of the Sichuan Basin,and theCarboniferous Ceshui Formation is the key shale gas layer in this area.Taking the secondary structure Lianyuan sag in the area as theobject,based on the field stratigraphic section and drilling data,experimental analysis and field gas−bearing monitoring data,thegeological conditions and differential distribution characteristics of shale gas accumulation of the Ceshui Formation were studied.Themain controlling factors of enrichment and accumulation pattern of shale gas were discussed above.The results show that:①Dark shaleare mainly developed in the lagoon sedimentary facies area.The shale with a thickness of 30~80 m.The organic matter is mainly typeII,total organic carbon content(TOC)greater than 1.5%,2.0%<R_(o)<3.0%,and has a good foundation for hydrocarbongeneration.②The Ceshui Formation is mainly a type of siliceous shale with high brittleness minerals.The shale reservoir space includesorganic pores,inorganic pores and fractures,and has the physical characteristics of ultra−low porosity and ultra−lowpermeability.③The formation of shale gas reservoirs in Ceshui Formation mainly experienced three stages of forming and evolution:early in−situ accumulation,medium−term adjustment and transformation,and late dissipation−residue.The main reservoir formationand transformation period was from the Middle Jurassic to the Early Cretaceous.④Organic−rich shale formed in the reductionenvironment of the lagoon facies is the material basis for the formation of gas reservoirs in Ceshui Formation.The thermal evolutiondegree is an important factor affecting the enrichment and accumulation.Preservation conditions are the key to enrichment andaccumulation.The Intraformational detachment structure controls the enrichment degree of gas.Based on the comprehensive analysis,the shale gas accumulation pattern of Ceshui Formation‘sedimentary environment controlling favorable area and tectonic−d

关 键 词：富集主控因素 成藏模式 页岩气 石炭系 测水组 涟源凹陷 湘中坳陷 

分 类 号：P534.45[天文地球—古生物学与地层学] P618[天文地球—地质学]