The Research Of Dolostone Reservoir Characteristics Of The Feixianguan Formation Of Lower Triassic In The NE Sichuan Basin

The dolostone reservoir characteristics of the Feixianguan Formation of Lower Tower Triassic in the NE Sichuan Basin are discussed as the object on the paper. Guided by the theories of carbonate reservoir geology and sequence stratigraphic, and based on analysis of the rock structure, combining with analysis of order degree of dolomite and trace element and strontium isotopes and microelement strontium, the authors widly study the characteristics of sedimentary facies and petrologic and diagenetic and geochemical on the origin of dolomite reservoir in Lower Triassic Feixianguan Formation in the NE Sichuan Basin.By sequence stratigraphic research, and on the basis of analysis of the rock structure, the Feixianguan Formation sequences consist of two third-order sequences, eight system tracts, of which the sedimentary facies and palaeogeography of the third-order sequence cycles are accentuated in this paper.On the basis of analysis of the rock structure, combining with analysis of strontium isotopes and microelement strontium, the authors study on the origin of dolomite reservoir in Lower Triassic Feixianguan Formation in the NE Sichuan Basin and recoglize two kinds of origin types: penecontemporaneous dolostone and the burial dolostone. The burial dolostone which is multiperiodic metasomatic origin is only of reservoir signification, including two main structure types of oolitic dolostones and Crystalline dolostone. Intigrativly analyzing two kinds of dolostone's rock structure and the geochemical characheristics of strontium isotopes and microelement strontium, the authors divide the diagenesis process of the burial dolomitization into early diagenesis,meso diagenesis and late diagenesis. In every diagenesis stage, though the rock structure of reservoir dolostones has notable differences, the geochemical characteristics of strontium isotopes and microelement strontium has notable comparability and homogeny, which not only shows that the burial dolostone diagenetic fluids have the characteristics of sea source formation water which has much strong composition characteristics of strontium isotope in Triassic seawater, but also reflects that the diagenesis process of multiperiodic burial dolomitization happens in the system of succession developed evolving and sealing off relatively.