The Tectonic Evolution In The Southeast Chongqing And Its Controlling Effect To Shale Gas Accumulation

Southeast Chongqing has experienced complex tectonic movement,but previous studies in this area were more concentrated in shale gas reservoir,with little regard for effect of the tectonic evolution to shale gas accumulation.So this article will focus on the structural characteristics and tectonic evolution' controlling effects to the shale gas accumulation and enrichment.According to 19 shale gas exploration blocks and 23 geological cross-sections in the Southeast Chongqing province,the main structure type which in the study area is divided into 7 kinds,and combined with modern exploration and practice,it shows that the favorable structural type' characteristic is that shale buried deep in 1500-3500 m,fault not active or closed relatively well,and away from the outcrop.In the region of southeastern Chongqing we suggest that box faulted anticline,lateral wide gentle syncline and symmetric gentle syncline most conducive to the accumulation of shale gas.The strata exposed in the study area show that: the Caledonian,Hercynian—Indosinian,Yanshan and Himalayan.Late Ordovician—Early Silurian deposited the black shale in Deep Sea continental shelf face,Hercynian—Indosinian occurred sedimentation interruption,Yanshanian J3-K1 period occurred tectonic deformation with the trend of a progressive change from the southeast to the Northwest,Himalayan strengthen the tectonic deformation.In the region of southeastern formed There are a series of Fold Belt with the trend of Northeast to Southwest,and in the southeastern region of Chongqing occurs uplift widely,maximum erosion volume reached6000—7000 meters,which resulting the cease of hydrocarbon generation and effect the shale gas preservation conditions.According to geochemical data and drilling data and using the basin model software to make six wells' single well burial history and hydrocarbon generation andexpulsion intensity history to analysis the control effect of tectonic evolution to shale gas accumulation in the research area.