Low-relief structural imaging with model-based tomographic velocity inversion
Guan Wensheng1,2, Duan Wensheng2, Zha Ming1, Sun Qi2, Song Xiaoping3, Su Zhou2
1. School of Geosciences, China University of Petroleum(East China), Qingdao, Shandong 266580, China;
2. Research Institute of Exploration and Development, Tarim Oilfield Company, PetroChina, Korla, Xinjiang 841000, China;
3. Paradigm Technology(Beijing) Co. Ltd., Beijing 100083, China
Abstract：Horizon-based tomographic inversion performs velocity inversion by calculating ray path and residual delay time in multiple velocity interfaces of simple layered model,and it needs structural model for interpretation to be input.It is quite difficult to carry out horizon interpretation on low SNR seismic data based on this inversion,and the model accuracy cannot be guaranteed when classifying velocity interfaces.Grid-based tomographic inversion carries out velocity inversion by obtaining globally ray path and residual delay time,which can describe details of interval velocity in layered model.However sometimes velocity model cannot be appropriately converged,and the model does not have the constraints of geological significance,and the inversion results do not conform to geological rule.Therefore,model-based tomographic inversion method takes the advantage of horizon constraint and global inversion to build a model based on geological horizons,which updates horizontally parameters along geologic horizon grid,and updates interval grid scale with the geologic horizon of the model in the vertical direction.It solves the problem of velocity model building for thin layer and obtains precise high-frequency and low-frequency velocity components,and anisotropic parameters.Furthermore,model-based tomographic inversions takes the depth of geological horizon in the model as a variable into the tomographic inversion data space,and the velocity structure and reflection point position (or the reflector depth) can be simultaneously obtained by inversion.Thereby model-based tomographic inversion has higher accuracy of inversion.The proposed model-based tomographic inversion method is applied to the real data in the area YM,and the accuracy of velocity model is improved by anisotropic prestack depth migration,and low-relief structures in the area are correctly imaged.
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