Pre-stack Seismic Inversion Of Brazilian Subsalt Carbonate Reservoirs And Its Application

Brazil has abundant oil and gas resources in deep-water carbonate reservoirs,which is a hot area of deep-water oil and gas exploration in the world.However,due to the influence of thick rock salt layer on seismic wave shielding effect,the seismic data of target layer have the characteristics of low signal-to-noise ratio and low main frequency,and the carbonate reservoir has strong heterogeneity and fast lateral variation.Therefore,conventional seismic inversion methods can not accurately predict the spatial distribution of reservoirs and fluids in this area,which greatly increases the risk of deep-water exploration in this area.In view of this,this paper combines high-precision post-stack seismic facies-controlled reservoir inversion with pre-stack accurate equation fluid inversion to predict the spatial distribution of carbonate reservoirs and fluids under salt.Firstly,based on the petrophysical statistical analysis of the actual well data in the study area,the sensitive elastic parameters of different lithologies and fluids of carbonate reservoirs are analyzed and determined,which provides a basis for the fine interpretation of seismic inversion results.Secondly,the distribution of carbonate reservoirs under salt is predicted by using seismic facies-controlled non-linear inversion method.Finally,the AVA forward simulation analysis of carbonate reservoirs under salt is carried out,and the precise pre-stack inversion based on Zoeppritz equation achieves fine characterization of favorable reservoirs.The results of post-stack and pre-stack seismic inversion not only have the characteristics of vertical high resolution,but also coincide with the geological background horizontally,which verifies the validity of this method.