The Study Of The Sequence Straigraphy And Diagenesis Of The Fei Xianguan Formation In Yuanba Area Of The Northeastern Sichuan

The paper focused on the problems of petrological characteristics, sedimentary facies, sequence stratigraphy, diagenesis and reservoir of Fei Xianguan Formation In Yuanba area which is in Northeast of Sichuan basin,.Guided by the Theory of carbonate sedimentology, sequence stratigraphy and diagenesis, making full use of core, well logging, log,seismic, and test results. It studies about the sequence stratigraphy, sedimentary facies and reservoir diagenesis in the Fei Xianguan Formation.This thesis is not only important to improve exploration of hydrocarbon, but is also benefit to develop the theory of carbonate.The rock types have been grouped on the basis of observed core and analysis of rock slice of6wells in Fei Xianguan Formation in the study area. Through The origin of deposition the rock types can been divided into3groups those are land sources sedimentary rock, authigenic clastic rock and diamict. Again the rock can be classified into38types based on the color, component and composition of rock. Based On the characteristics of the rock and fossil-types, with the data of well logging and seismic, the sedimentary facies are identified. And it is identified about the characteristics of sedimentary facies.That is platform pattern, and deep water continental shelf developed in well4and well5. And the sedimentary facies is identified with restricted platform, open platform, platform edge, platform front slope and continental shelf.On the basis of sedimentary researches and logging features analysis,2third order sequence Ⅲ type sequence boundaries and4inner system tract boundaries are confirmed in Fei Xianguan formation of Yuanba area. And Fei Xianguan formation is divided into2third sequences, Sequence2and Sequence3, in the study area. Sequence2-Sequence3includes1.5Ma, and every thied order sequence about0.75Ma. SQ2equals to section1and section2of Fei Xianguan formation, SQ3equals to section3and4of Fei Xianguan formation. Through logging-seismic combination of the composite recording the2length-breadth sections chosen in this paper, the third sequence stratigraphy equitime frame of Fei Xianguan formation is built in the study area. SQ2compose of low system tract, transgressive system tract and high system tract, while SQ3compose of transgressive system tract and high system tract and lack low system tract. Sea level fluctuation, tectonic events and palaeo-climate are the main factors of the third sequence formation and development of Fei Xianguan formation.The research of diagenesis and diagenetic stages are proceeded, combine with the study of sedimentary facies, sequence stratigraphy and other test data, illustrating that the main diagenesis of Fei Xianguan formation are compaction-pressolution, cementation, rejuvenation of crystals, metasomasis(silication, celestition, pyritization, dolomitization etc.), denudation and packing action etc. Of the diagenesis above, the destructive diagenesis for the reservoir formation of Fei Xianguan formation in the study area are compaction-pressolution, cementation, celestition, silication and packing action, the beneficial diagenesis are denudation and dolomitization.Integrated the sedimentary facies, sequence stratigraphy and diagenesis of Fei Xianguan formation in the study area, it is suggested that the third order sequence controlled the sedimentary facies, syngenesis setting and diagenesis types, and determined the early reservoir distribution, it is also suggested that the main reservoir of carbonate develop in section2of Fei Xianguan formation, the lithologic character is oolitic limestone, and after deposition it going through sea-floor cementation, atmosphere fresh water denudation and shallow-deep burial. According to the study, the destructive diagenesis for the reservoir formation of section2of Fei Xianguan formation are cementation, compaction-pressolution, rejuvenation of crystals and packing action, the beneficial diagenesis are dolomitization, denudation and cataclasis. Through the comparison of the two diagenesis, it is learned that destructive diagenesis is stronger than beneficial diagenesis, and the pore space of oolitic limestone dose not develop. Through the stratic view, it is suggested that the reservoir of Fei Xianguan formation only develop in SQ2high system tract, low system tract and transgressive system tract did not develop reservoir, either nor SQ3transgressive system tract and high system tract.