Fault Constructions In The Chengdao Buried Hill And Reservoir Alteration By Fluid Flowing

Chengdao Buried Hill is located in the southern sea area of Bohai Sea.It is an interior reservoir composed of limestone and dolomite.It is an interior-type reservoir composed of limestone and dolomite.Its storage space has always been considered as a crack.However,combined with the practice of crude oil development for many years,the original crack-based and actual There are differences in geological laws.Combined with sampling and thin section analysis,four reservoirs are divided: early(Mesozoic fault-induced)breccia,late(Mesozoic fault-induced)breccia,cataclastic rock and fracture.Influenced by tectonic stress and lithology,five kinds of spatial combination models are formed between fault plane and fracture section,fault cataclastic rock and fault breccia.Combining core description with well logging curve,the sensitive parameters are selected to establish the discriminant model(M)of the four reservoirs.When M > 0.18 is late breccia section,0.075 < M < 0.18 is early breccia section,0.025 < M < 0.075 is fractured section,0.01 < M < 0.025 is fractured section.Through the combination of well and earthquake,the seismic reflection characteristics of reservoir space are defined,and their distribution in buried hill interior is predicted with fault interpretation.Based on the analysis of carbon,oxygen and strontium isotopes of surrounding rocks and fissure fillings,it is determined that surface freshwater and hydrothermal fluid can transform fault breccia and cataclastic rocks through fault-fissure: the surface freshwater dissolution is very obvious,and the degree of limestone breccia dissolution is greater than that of dolomite limestone and dolomite breccia;hydrothermal fluid mainly shows chemical filling in fault breccia and fissures.As a result,the decrease of temperature and flow rate is beneficial to the precipitation of calcite.The filling degree of dolomite limestone is greater than that of limestone and dolomite,and the dissolution phenomenon of hydrothermal solution is rarely observed in samples.The homogenization temperature of inclusions indicates that fluid activity is approximately equal to oil and gas filling.Therefore,the formation of Chengdao buried hill reservoir is affected by fault activity,surface freshwater and hydrothermal transformation.Through the study on the origin and distribution of reservoir space in the study area,it can guide the subsequent development of Chengdao buried hill reservoir and provide new ideas for the study of buried hill carbonate reservoir.