扬子区二叠系孤峰组(段)页岩气储层特征及勘探潜力OA

The Permian Guofeng Formation(Member)in the Yangtze Region is a set of marine organic-rich black shale series exhibiting distinct diachronous characteristics,serving as a key replacement stratigraphic unit for shale gas exploration.This paper systematically analyzes and summarizes the spatiotemporal differentiation patterns,hydrocarbon generation characteristics,reservoir characteristics,and preservation conditions of the Permian Gufeng Formation(Member)in the Yangtze Region.From west to east,the Gufeng Formation(Member)exhibits a pattern of"east-west differentiation and multi-center sedimentation"with its distribution controlled by the synergistic effects of paleo-tectonics,sea-level fluctuations,and sedimentary environments.The reservoir lithologies are dominated by siliceous and carbonaceous shales,exhibiting a mineral combination characterized by"high silica,rich calcium,and low clay content".The content of brittle minerals is high(averaging 85%),indicating excellent fracturability.Reservoir space types are diverse,dominated by organic pores and dissolution pores,with mesopores constituting the main pore size distribution.Pore development and gas content exhibit significant regional differentiation,characterized by"better in the west,poorer in the east".In the Upper Yangtze Region,the hydrocarbon generation quality is excellent(TOC 3%-10%,Type Ⅰ-Ⅱ₁kerogen),reservoir physical properties are good(average porosity 4.46%),gas content is high(average＞4 m³/t),and preservation conditions are favorable,making it the core area for shale gas enrichment.In the Middle Yangtze Region,shallow burial depth(＜2 000 m)and moderate thermal evolution provide engineering cost advantages,but reservoir heterogeneity is strong.In the Lower Yangtze Region,burial depth is moderate,but reservoir physical properties(average porosity 1.99%),gas content,and preservation conditions are generally poor,limiting exploration potential.Comprehensive evaluation indicates that the Upper Yangtze Region(Guangyuan-Bazhong-Dazhou,Fengjie-Enshi)is the most favorable Class Ⅰ exploration area,though deep engineering challenges must be overcome;the Middle Yangtze Region(Jingshan-Wuhan)is a Class Ⅱ favorable exploration area where geological-engineering"sweet spots"should be targeted;the Lower Yangtze Region(Wuwei-Xuancheng)is a Class Ⅲ potential risk zone.