The Evolution Of Tectonic Sequence-based Lithofacies-paleogeography And Its Significance Of Accumulation Of Superimposed Basins

Because of the polycyclic tectonic movements, there are polycyclic oil and gassuperimposed basins in south China. The research thought, methods, and technologyfor superimposed basins formation, evolution, source-reservoir-cap rockcombinations in the course of tectonic evolution, and latter preservation conditionsare developing.The middle-upper Yangtze superimposed basin which has the characters ofpolycyclic, multi-layered, various, multi-stage of hydrocarbon accumulation wasselected for research area in this thesis. It rounded the thought that the tectonicscontrols basin, basin controls facies, and based on lots of outcrops, combining somedrilling and seismic data, with the director of tectonic geology, sedimentation, sequence stratigraphy and basin analysis, taking the main line of tectonics evolution, sedimentary evolution, sequence evolution and basin evolution, and it emphasized theresearch of entirety, epoch, degree of order, difference and synthesis. Based on whatare writhen above all, a systematic study has been made on the depositional system ofmiddle-upper Yangtze region form Sinian to middle Triassic, and divided into threetypes of depositional system groups and some depositional system, facies, sub-faciesand micro-facies. Further, it discussed the characters of all kinds of depositionalsystem, and set up depositional mdels, and also held the point that the developmentand the evolution of depositional system was the synthetical effect of serious ofgeological factors. Based on the study of mechanics of platform-uplifts andinter-platform basin sedimentary framework of Changxing Formation of upperPermian to Feixianguan Formation of lower Triassic in northern Sichuan Basin, itpointed out that the sedimentary framework of platform-uplifts and inter-platformbasin interphase which was caused by the palaeo-faults can correlated well in the middle-upper Massif, meanwhile, accumulation was obviously controlled bysedimentary facies of this framework. Further more, systematic study has been madeon 10 kinds of sequence boundary surface and their origin types, based on it, thethesis divided 13 super-sequences (second-order) and 82 third-order sequences, anddifferent character in different facies was discussed in details, and made correlation inthis region, in general, every super-sequence which was controlled by the tectonicmovements, global sea level change, sediments supply and climate could becorrelated, but the feather wasn't alike in term of different facies. Regardingsuper-sequence (second-order) systems tract as study unit, twenty-sevensequence-based lithofacies-paleogeography maps were worked out which were morescientifically, more isochronously, more continuously, more practically, and so on, and it disclosed the distribution and the evolution of source-reservoir-cap rocks.Further, using sequence stratigraphy theory, vertically, fore source-reservoir-capcombinations occur in the marine carbonates in milddle-upper and they can bedivided into five types, including boundary type, lowstand type, transgressive type, highstand type and composite type. Each type of source-reservoir-cap combinationhas different features of reservoiring geology. On the basis of systemic studying ofsedimentation and sequences, colligating with the data of plate tectonic framework, regional tectonic activity, basin evolution and source-reservoir-cap combination, itdivided overlay relationship of basins into the covered type (continuous covered type, discontinuous covered type) and uncovered type(upper assemblage holding type, lower assemblage holding type). The superimposed relationship between Mesozic andCaniozoic continental basin and pro-Mesozoic and Caniozoic marine basin effect theformation, evolution, migration, conservation and destruction of the hydrocarbon.The types and relationship of multiple superimposing and rebuilding were discussedduring the polycyclic tectonic movements. Finally, it analyzed the effect andcontrolling of the evolution and difference of sequence-basedlithofacies-paleogeography and basins superimposing and rebuilding, and theprospect of different overlay relationship of basins as a whole.