Study On Fluid Identification Method Of Carbonate Reservoir

Carbonate oil and gas resources are abundant in Sichuan Basin,but the overall exploration rate is low.Reservoir fluid identification technology is one of the key constraints in the process of exploration and development.How to make full use of the rich amplitude information in prestack seismic data to realize fluid identification in carbonate reservoir is of great significance to improve the success rate of exploration and the production efficiency of oil and gas.The research objects of this paper are porous carbonate reservoirs and fractured carbonate reservoirs.The research method is to construct sensitive fluid factors based on reservoir characteristics under the guidance of rock physics theory,and then estimate fluid factors from seismic data using seismic inversion method,so as to realize reservoir fluid identification.Complete data and mature theory are the prerequisites for reservoir fluid identification.In this paper,we first established petrophysical models applicable to the two types of reservoirs.Based on this model,the shear wave information and anisotropy information on the well were effectively estimated,and then provided data support for reservoir fluid identification.Then,we analyze and summarize the construction ideas of the predecessors’ fluid factors,and provide systematic guidance for the construction of fluid factors.At the same time,the regularization constrained prestack elastic impedance inversion method under the Bayesian framework is developed to provide theoretical support for the estimation of fluid factors.The fluid identification methods of carbonate reservoirs for different pore systems are different and cannot be generalized.Secondly,carbonate reservoir is characterized by high impedance and low porosity,and the change of elastic parameters caused by the change of fluid in the reservoir space is extremely small.Therefore,we need to build more sensitive fluid factors,and highlight fluid information while reducing the influence of solid factors.For porous carbonate reservoirs,we constructed a more sensitive fluid factor on the basis of the Gassmann fluid term based on the theory of porous media,and deduced the AVO approximate formula and the elastic impedance equation including the fluid factor.The fluid factor is obtained by direct inversion,which realizes the fluid identification of the reservoir.For fractured carbonate reservoirs,based on anisotropic theory and considering the influence of fluid on reservoir elastic parameters and fracture parameters,we constructed a more sensitive combined fluid factor,and deduced the AVO approximate formula and elastic impedance equation based on HTI medium hypothesis.The seismic inversion method is used to estimate the fluid factors,so as to realize the reservoir fluid identification.The fluid factors are estimated from seismic data of porous carbonate rock and fractured carbonate rock in Sichuan Basin,and the validity of the fluid identification method is verified by combining the logging interpretation results.