A Velocity Model Building Method in the Igneous Rock Based on Facies-controlled Inversion

In the regions with igneous rocks, it is very difficult to conduct velocity modelling and velocity imaging because of large buried depth, low signal-to-noise ratio of seismic data, large change of lithologies, drastic change of lateral velocity and complex seismic wave field. In this paper, an igneous rock velocity modelling method based on facies-controlled inversion is proposed and applied to migration imaging. Firstly, based on the analysis of lithofacies in this method, the active periods and lithofacies of volcanic rocks are determined, and the initial velocity model is established by using facies-controlled velocity inversion. Secondly, a high-precision velocity model is constructed by multi-information constrained target inversion method. This method has been successfully applied in many prospect areas in western China. Through the comparative analysis of imaging sections and comprehensive attributes, it shows that this method can eliminate the inherited pseudo structures and pseudo faults in the underlying strata of igneous rocks to the maximum extent, and restore the real underground structures, which provides a reference for the velocity-depth modelling and imaging of similar special geologic bodies.