Organization
SINOPEC Exploration Company, Chengdu, Sichuan 610041, China
摘要
四川盆地复兴地区侏罗系发育多套富有机质页岩，多口井试获高产工业油气流。明确不同页岩岩相沉积储层特征及富集主控因素对勘探部署具有重要意义。基于岩心精细描述、实验分析及钻井勘探实践，开展了陆相地层细粒沉积岩岩相划分与对比、储层精细表征、油气藏类型及富集高产主控因素解剖，形成了以下几点认识：(1)复兴地区侏罗系发育自流井组东岳庙段一亚段、凉高山组二段下亚段两套半深湖相优质页岩，具有多层叠置、中等有机碳含量、纹层发育、源储一体及高气油比特征；两套目的层页岩岩性复杂，为此，建立了基于“颜色—有机碳含量—沉积结构—矿物成分”四元岩相划分方案，明确了灰黑色高碳粉砂纹层型黏土页岩为凉二段下亚段有利岩相，灰黑色高碳介屑纹层、粉砂介屑纹层型黏土页岩为东一亚段有利岩相，3种有利岩相在研究区横向分布稳定。(2)灰黑色高碳粉砂纹层、介屑纹层、粉砂介屑纹层型黏土页岩具有“多孔共生、大孔大喉、孔缝一体”的储集特征，储集物性好、渗透率高，利于页岩油气在孔—缝储集体系中高效储集流动。(3)东一亚段为凝析气藏，凉二段下亚段为挥发性油藏。(4)明确了陆相页岩油气富集主控因素：中高生烃潜力、强滞留率为纹层型页岩油气富集提供物质基础；良好的成烃—成岩—成储—成藏配置关系利于油气聚集成藏；微裂缝发育及合适的热演化程度利于烃类富集及流动；大型宽缓向斜及高压—超压条件利于烃类持续保存。
Abstract
The Fuxing area of the Sichuan Basin is known for its multiple sets of organic-rich shale in the Jurassic period, with several wells yielding significant amounts of industrial oil and gas. Understanding the characteristics and factors influencing the enrichment of different shale facies sedimentary reservoirs is crucial for effective exploration. Through detailed rock core descriptions, experimental analysis, and drilling exploration, the author has classified and compared fine-grained sedimentary rock facies in terrestrial strata, characterized reservoirs, identified types of oil and gas reservoirs, and analyzed the main factors influencing enrichment and productivity. The study reveals that the Jurassic strata in the Fuxing area contain two sets of high-quality shale with semi-deep lacustrine facies: the first sub-section of the Dongyuemiao section of the Ziliujing Formation and the lower sub-section of the second section of the Lianggaoshan Formation. These shale layers exhibit multi-layer stacking, moderate TOC content, well-developed bedding, integrated source storage, and high gas/oil ratio characteristics. The lithology of these target shale layers is complex, leading to the establishment of a four-element lithofacies classification scheme based on “color-TOC-sedimentary structure-mineral composition”. This scheme identifies the gray-black high carbon sand-laminated clay shale as the favorable lithofacies for the lower sub-section of the second section of the Lianggaoshan Formation, and the gray-black high carbon medium debris-laminated and fine sand medium debris-laminated clay shale as the favorable lithofacies for the eastern sub-section. The three lithofacies in the study area are horizontally distributed in a stable manner. The gray-black high carbon fine sand layer, medium debris layer, and fine sand-medium debris layer type clay shale exhibit reservoir characteristics of “porous coexistence, large pores and throats, and integrated pores and fractures”. These reservoir properties, including good permeability, facilitate the efficient storage and flow of shale oil and gas in the pore-fracture storage system. The first sub-section of the Dongyuemiao section is a condensate gas reservoir, while the lower sub-section of the Lianggaoshan Formation’s second section is a volatile oil reservoir. Key factors contributing to the enrichment of continental shale oil and gas have been identified, including medium to high hydrocarbon generation potential and strong retention rates supporting the accumulation of laminated shale oil and gas. A favorable hydrocarbon-diagenesis-reservoir formation configuration promotes oil and gas accumulation. Additionally, the development of micro cracks and suitable thermal evolution aids in hydrocarbon enrichment and flow, while large, wide, gentle synclines and high-pressure overpressure conditions support the sustained preservation of hydrocarbons.
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