Characteristics of Sequencebased Lithofacies and Paleogeography,and Reservoir Prediction of the Jialingjiang Formation in Sichuan Basin

Key words: 
• Sichuan Basin /
• Jialingjiang Formation /
• sequence stratigraphy /
• lithofacies paleogeography /
• reservoir prediction

Abstract: The Jialingjiang Formation of Lower Triassic in Sichuan basin is composed of carbonate platform sedimentary system and carbonateterrigenous clastic sedimentary system, and including four major sedimentary facies such as carbonateterrigenous clastic tidal, restricted platform, open platform and evaporite platform. In the end of Feixianguan stage of Early Triassic, there was a largescale regression and regional exposure and erosion in the Upper Yangtze maritime space, and until early Jialingjiang stage the Upper Yangtze maritime space undergoed extensive transgression and accepted the deposition again. Therefore, at the bottom of Jialingjiang Formation of Lower Triassic developed partial exposure unconformity surface and inner of the Jialingjiang Formation mainly developed lithologylithofacies transformational sequence interface. According to the tracing and recognition of sequence interface and through the sequence stratigraphy division of typical singlewell and the sequence stratigraphy comparison of well tie, the Jialingjiang Formation of Lower Triassic in Sichuan basin can be devided into 3 thirdorder sequences. The sequence 1 which is located in the lower part of Jialingjiang Formation belongs to the type Ⅰ sequence, the sequence 2 and 3 in the middle and supreme part belongs to the type Ⅱ sequence. Based on the sequence stratigraphy division and sedimentary facies analysis, we first systematic compiled the sequencelithofacies paleographic map of each system tract with the system tract as unit and analysed the characteristic of sequencelithofacies paleographic of Jialingjiang Formation in the study area. It shows that from west to east in Sichuan Basin with a clear differentiation in the plane , in the vertical facies belt with a clear evolution. Open platform facies are dominated and oolitic shoal reservoirs are the most developed ones in the east and middle part of Sichuan basin during the trassgrassive system tracts, restricted and evaporite platform facies are dominated and dolomite reservoirs are the most developed ones in the north and northeast part of Sichuan basin during the highstand system tracts. It can be divided into three types oil prospect zone in Sichuan basin Primarily based on reservoir distribution, united of generating rock, reservoircapping rock composition and forming conditions. The most favorable oil prospect zone is located in northeast Sichuan basin,because granule shoal reservoirs and dolomite reservoirs are the most favorable developed and it is also the karst slope distributed area. The more favorable oil prospect zone is from Hechuan in central of Sichuan to Gaoxun in south of Sichuan. This district developed the granule shoal reservoirs and dolomite reservoirs and we have found several accumulation of gas in Jialingjiang Formation, so it's the more favorable oil and gas prospect zone in Sichuan Basin.