Research On Fliud Migration And Transformation Of Dolomite Reservoirs In Shizhu Synclinore Zone

Fluid is the bridge and link between preservation conditions and tectonic deformation.Poly-cycle Tectonic deformation resulted in the release of multi-stage fluid.Identifying the fluid characteristics of a research area can contribute to evaluating the preservation conditions and storage conditions. Shizhu synclinore zone is a NE–trending tectonic unit of central Yangtze.In this thesis , have searched a way which how to trace the origin and migration trajectory of fluid by the 87Sr/86Sr,δ18O andδ13C geochemical method.The method is that collecting the fillings in vugs and fissures and their host rocks to analyse their isotopes geochemistry features and then compare the 87Sr/86Sr of fillings in vugs and fissures with the 87Sr/86Sr of their host rocks and Contemporaneous seawater and combine withδ18O andδ13C analysis to determine these fluids were from host rocks( endogenous fluid) or from other stratas (allogenetic fluid).Combining the 87Sr/86Sr,δ18O andδ13C geochemical method with fluid inclusion studies, traced the origin and migration trajectory of fluid in every single well and sections . Established fluid migration model of every single well and sections .At the basis of studying the fluid origin of very single well and sections ,Established fluid migration model of marine carbonates strata in Shizhu synclinore zone,The study shows that there are two fluids system in the synclinore zone.They are lower and upper fluid system. lower fluid system developed in the lower Sinian - Ordovician stratas , upper fluid system developed in the Silurian - Middle Triassic stratas.There is a isolated interval between the upper and lower fluid system.The lower fluid system was blocked under the isolated interval within the Sinian - - Ordovician strata in the Northeast to the central of synclinore zone.There are multiple fluid compartments in the overlying Permian, Triassic and Carboniferous stratas , the fluid inside flow in the compartments and not exchange with the fluid outside .Close to the southeast of synclinore zone, faults destroyed the fluid compartments , lower fluid transported to the overlying Ordovician, Permian and Triassic stratas through the channel provided by the fault.In the southeast of synclinore zone,the lower fluid was sealed by the isolated interval. Local fluid compartments exist in the Silurian - Middle Triassic stratas.By researching the sequence of asphalt and hydrothermal alteration dolomite of core,ascertained that hydrothermal alteration dolomite is before the filling of large-scale reservoir.Hydrothermal fluid 87Sr/86Sr ratio between 0.7097 and 0.7092 had obviously effect on improving hydrocarbon pore volume of dolomite. Hydrothermal fluid transformation dolomite and without hydrothermal fluid transformation dolomite owned the same major composition like MgO, CaO, FeO, MnO and so on. Furthermore, hydrothermal fliud transformation dolomite had good comparison with abroad typical pattern of structural hydrothermal dolomite, it showed obviously negativeδ18O andδ13C and obvious positive 87Sr/86Sr.