Fine Characterization Of Cault-Controlled Carst Carbonate Ceservoir Cased On Five-Dimensional Data In OVT Domain

The large heterogeneous oil and gas reservoirs developed in the Ordovician carbonate rocks in the Tazhong area of Tarim Basin have become the main oil exploration and accumulation areas in the Tarim oilfield.However,the dunes in Tazhong’s large desert area have profound absorption of single beat energy.It is difficult to describe the fault solution accurately and even more challenging to identify fractures and small cracks.The reasons are as follows.Firstly,the signal-to-noise ratio of the target layer of the original earthquake data is low.Secondly,the gun path density of the conventional 3D earthquake is low and narrow.Thirdly,the reflection of carbonate rocks and the development of multiple interlayer waves are weak.Therefore,the scale of the fault-solution hydrocarbon unit and effective evaluation unit cannot be accurately divided and determined.Conventional fracture prediction methods can not accurately predict fractures’ distribution direction and development intensity,restricting the capacity of fault-solution reservoirs exploration.Through years of technical research,the interpretation of deep-buried fracture-vuggy carbonate reservoirs has developed from narrow azimuth to omnidirectional,also from low coverage and low density to high range and high density.In addition,from three-dimensional structure to four-dimensional track set(such as CRP)and then to five-dimensional track set(such as OVT),characterized by applying five-dimensional track set to massive terabyte data.Five-dimensional seismic data have azimuth information and offset information.The anisotropy information is implied in the data,which is more conducive to describing fault solution characteristics and fracture prediction.The data can effectively support geology-driven explanatory target processing,fault solution characterization,and anisotropic fracture prediction,but the methods and techniques still need to be solved.The offset and azimuth of OVT domain track set data are relatively constant,which is beneficial to regularization and offset processing.The offset data can better preserve the azimuth information of seismic data.It is beneficial for azimuth anisotropy analysis.Eliminating the influence of azimuth-anisotropy and improving the imaging quality facilitates high-precision prestack reservoir and fracture prediction research.By optimizing the azimuth and offset information of the OVT track set to ensure that the data have uniform coverage times and true amplitude energy,it is ensured that the amplitude difference at different directions is mainly due to the anisotropy of the formation.Based on azimuth and offset superposition data,rich discontinuous attribute information(coherence,curvature,ant-tracking attribute,AFE)was extracted to characterize the fracture characteristics of different scales.Then,the seismic facies of carbonate rocks are divided into stratified stratigraphic facies and fractured zone facies.At the same time,seismic facies constraint modeling and pre-stack inversion are carried out to solve the quantitative prediction problem of carbonate fracture-cave assemblage.At the same time,based on two methods of pre-stack anisotropy inversion and elliptic fitting,semi-quantitative characterization of fractured reservoir characteristics is carried out.Finally,comprehensive the above results,the prestack inversion to predict reservoir contour as broken solution the boundary,outside the prestack fracture prediction of lateral reservoir contour as fractured zone boundaries,combined with the characteristics of fracture distribution,coupled with the drilling results of dynamic division favorable fractured seam area and hole unit,support for the study of the carbonate drill site.