四川盆地中国石化探区三叠系须家河组深层致密砂岩气勘探进展与潜力OA

To understand the enrichment patterns and exploration potential of deep tight sandstone gas in the Upper Triassic Xujiahe Formation in the Sichuan Basin,systematic researches were conducted based on latest drilling and seismic data acquired in the exploration area of China Petrochemical Corporation(Sinopec)in the basin.An isochronous stratigraphic framework was established and the tectono-paleogeography was reconstructed.Essential hydrocarbon accumulation elements such as source rock and reservoir,as well as their spatiotemporal matching relationships,were analyzed.Then,the dynamic evolution process of tight sandstone gas accumulation in this formation was investigated.Finally,the main factors controlling the differential gas enrichment were identified,and the favorable exploration zones were evaluated.The following results are obtained.(i)The Xujiahe Formation in the study area experienced three tectonic movements(Indosinian,Yanshanian,and Himalayan),resulting in three sets of source rocks(Xu 1 Member,Xu 3 Member,and Xu 5 Member)and three sets of reservoirs(Xu 2 Member,Xu 4 Member,and Xu 6 Member),forming a favorable"three-source,three-reservoir"configuration.(ii)The gas enrichment is constrained by three"controls":the control of structures on zones in the early stage,that is,paleo-structures laid the foundation of gas enrichment zones;the control of differential densification on reservoirs in the middle stage,that is,the differential densification process created relatively good reservoirs;and the control of reworking-induced fractures on productivity,that is,the fracture network formed by tectonism governed the distribution of productive"sweet spots"in the late stage.(iii)Key support technologies are developed,including log-based evaluation of deep tight clastic rocks,quantitative matrix reservoir prediction and fracture-developed zone depiction and inversion based on classified lithofacies,and comprehensive fracturability index evaluation,which have supported the discovery and production of large gas fields such as Hexingchang and Tongnanba.The Xu 2 Member in the Fenggu area,western Sichuan Basin,and the Xu 2 and Xu 4 Members in the Bazhong-Tongjiang area,northeastern Sichuan Basin,are identified as core targets for subsequent tight sandstone gas exploration.Moreover,it is proposed that future research priorities will focus on geologic theory,logging prediction,seismic prediction,and reservoir stimulation.Once breakthroughs are achieved,they are expected to facilitate subsequent exploration of tight sandstone gas in the Xujiahe Formation of the Sichuan Basin.