海相深水—浅水陆棚环境下页岩气地质条件差异性研究:以雪峰隆起西北缘五峰组—龙马溪组为例OA

This study investigates the differences in geological conditions for shale gas between deep and shallow marine shelf sedimentary environments,by taking the Wufeng-Longmaxi Formation in Well Xiandi-2 and Well Laidi-1 in the Jianshan-Laifeng area,located on the northwest margin of the Xuefeng Uplift,as the research objects.On the basis of core observation,samples were systematically collected for mineralogical,organic geochemical,and physical property analyses.Combined with the analytical data of gas-bearing properties,the effect of sedimentary facies belt and structure controls on shale gas enrichment and reservoir development was revealed.The results show that:(1)The Wufeng-Longmaxi Formation in the study area takes the Xuefeng Uplift in the east as the main provenance area,with deposition thickening westward toward the sedimentary center.The sedimentary environment transitions from the shallow-water shelf to the deep-water shelf,forming the distribution and thickness characteristics of organic-rich shale;(2)Compared with the shallow-water shelf environment,deep-water shelf environment hosts more organic-rich shale with a higher content of brittle minerals such as quartz,carbonate,and feldspar;(3)Organic matter types and TOC values reflect a stronger potential of organic matter enrichment in the deep-water shelf environment,and high maturity is not a limiting factor for shale gas formation in this area;(4)The weak correlation between porosity and permeability suggests that pore connectivity is not the primary controlling factor for shale gas enrichment,instead,the gas content is still directly determined by organic matter content;(5)The sedimentary environment influences the burial depth of the formation,and the burial depth and structural stability are key constraint factors on shale gas preservation.Research shows that the Wufeng-Longmaxi Formation in the deep-water shelf environment in this area has a good prospect for shale gas accumulation,and the northwest side is a favorable area for future shale gas exploration.