准噶尔盆地侏罗纪低成熟度煤系致密砂岩气储层形成机制

The Junggar Basin develops lots of piedmont deep depressions, lake basins and slope zones from the Jurassic, which is the favorable zone to look for tight sandstone gas with the basic geological conditions. The tight sandstone reservoir in the study area belongs to the typical continental low maturity coal reservoir, with low porosity permeability, strong non uniformity and complex digenetic evolution. In order to fully reveal the reservoir formation mechanism of the continental low maturity tight sandstone gas, with the guidance of sedimentology, reservoir and well logging geology, through field geological survey, core description, logging interpretation, seismic interpretation, slice observation and analysis, this project is applied to further study the reservoir sedimentary environment, reservoir property, the impact of diagenesis on porosity evolution and the configuration relationship of reservoir “four histories”, analyze the difference between continental coal measure and marine/excessive in the land and sea phase tight sandstone reservoir, build the reservoir classification evaluation standard, reveal the reservoir forming mechanism and main controlling factors of low maturity tight sandstone gas from the coal measure, and lay the theoretical and technical basis for the exploration and development of tight sandstone gas resource in this area.

准噶尔盆地侏罗纪发育多个山前断陷和凹陷湖盆以及斜坡地带，具备形成致密砂岩储层的基础地质条件，是寻找致密砂岩气的有利区带。研究区致密砂岩储层属于典型的陆相低成熟度煤系储层，具有低孔低渗、非匀质性强、成岩演化复杂的特点。为了全面揭示陆相低成熟度致密砂岩气储层形成机制，拟申请项目通过野外地质调查、岩心观察描述、测井解释、地震解释、薄片观察和分析测试等技术手段，以沉积学、储层地质学和测井地质学等理论为指导，深入研究储层发育的沉积环境、储层特性、成岩作用对孔隙演化的影响以及储层“四史”配置关系等，分析陆相煤系致密砂岩储层与海相/海陆过渡相致密砂岩储层之间的差异性，构建储层分类评价标准，揭示陆相低成熟度煤系致密砂岩气储层形成机制及主控因素，为该地区致密砂岩气资源的勘探开发奠定理论和技术基础。

准噶尔盆地东部发育侏罗系陆相低成熟度煤系储层，具备形成致密砂岩储层的基础地质条件。因此，选取了五彩湾凹陷和白家海凸起侏罗系八道湾组和西山窑组为主要目的层位。在整理分析前人研究成果的基础上，收集了岩心、地震、测井、录井等资料，选取大量的取心样及剖面资料进行送样分析，得出以下成果。致密砂岩气储层沉积相为河流-泛滥平原相，发育滩坝、河道、三角洲平原分支河道、水下分流河道、河口沙坝、远砂坝等沉积微相。储层岩石类型主要以岩屑中细砂岩、细粒岩屑砂岩及粉砂岩等为主，粒度较细，成分和结构成熟度较低。储层以粒间溶蚀孔隙、粒内溶蚀孔隙为主，以粒间溶孔、晶间孔隙、微裂缝为辅，粒间溶孔以剩余粒间孔隙为主，晶间孔隙以伊利石晶间微孔和高岭石晶间微孔为主；整体为低孔、低渗储层。储层经历了早成岩A期至中成岩B期等成岩演化阶段，强压实作用、胶结作用等成岩作用是储层致密化的主要原因。综合分析影响储层储集性各类因素，将研究区内储层分为四类储层，阐明了储层形成机制，并建立了一套致密砂岩储层评价体系。预测河道、分支河道、河口沙坝、远砂坝为有利目标勘探区。