Sedimentary Configuration And Sequence Filling Configuration Of Changxing-Feixianguan Formations In Northeastern Sichuan Basin

Along with breakthrough of Puguang, Yuanba, Longgang areas in northeastern Sichuan basin, distribution and character of hydrocarbon resources development are more and more regarded. People have great controversy in sedimentary configuration of Changxing-Feixianguan stage in northeastern Sichuan basin.This dissertation was primarily focused on the upper Permian Changxing formation and lower Triassic Feixianguan formation in northeastern Sichuan basin. Based on lots of outcrops, combining some drilling and seismic data, this dissertation studied rock association, palaeontologic assemblages, deposition fabric, section, Mechanism of deposition with multiple methods. The principle of Sedimentology, Sequence Stratigraphy, Geochemistry, Paleontology, Geophysics and Tectonics and some other traditional geology theories were used as the instructions of this dissertation. Two sedimentary system has been recognized , that is carbonate platform system and inter-platform basin system. Carbonate platform system was composed by evaporate platform, restrctied platform, open platform, reef-bank on the edge of the platform and marginal slope. Carbonate platform system was the primary Sedimentary environment, inter-platform basin system was developed form Kaijiang to Liangping, Guangyuan and from Chengkou to Enshi. Based on analysis sedimentary system in detail and make a reference from predecessors, this dissertation found northeastern Sichuan basin in Changxing-Feixianguan stage was extension background. The sedimentary configuration of platform-basin and in carbonate platform was caused by synsedimentary fault developed in the most dramatic extensional period of south Qinling ocean during Changxing-Feier stage. Because of synsedimentary faulting from weaken to sease, sedimentary configuration had gone through evolution as follow: from late Feiyi to Feier stage, Kaijiang to Liangping platform-basin filled to closed rapidly, Guangwan and Chengkou to Eixi platform-basin became narrows, sedimentary environments became to carbonate platform and was shoal alternating with depression as a whole, from Feisi stage, eastern border of carbonate platform expend eastward as sea level became to fall, the whole northeastern Sichuan basin had became evaporated tidal environment.Based on analysis of three apparent types and three genetic types of sequence bottom boundary surface. Base on these, upper Permian Changxing formation and lower Triassic Feixianguan formation were divided into 4 third-order sequences in the study area, and different characters in different facies was discussed and correlated regionally in detail. Based on analysis of sequence stratigraphy, this dissertation have discussed matter component of system tracts, combination of different matter, contrast of bed thickness of system tracts on the control of tectogenesis, changes of globe sea level, deposition. We obtained the findings that sedimentary configuration and water energy change of sedimentary environment were controlled by fossil fracturte and relative sea-level change, and then interacted on characteristic and diversity of carbonate sequence filling configuration. In the end, we concluded that in the peculiar sedimentary configuration from Changxing Stage of late Permian to Feixianguan Stage of early Triassic reservoir in study areas, accumulation factors developed in sequence filling configuration composed the integrated source-reservoir-cap assemblages of ree??d shoal gas reservoirs in northeast Sichuan basin.