Study On Multi-parameter Full Waveform Inversion Method In Time Domain

With the deepening of oil and gas exploration and development,how to improve the accuracy of reservoir prediction gradually become the focus on the research of experts and scholars.So it is especially important to find a suitable inversion method for complex medium.Full waveform inversion(FWI)takes advantage of the kinematic and dynamic information in the pre-stack seismic wave field to obtain the rock physical characteristics of the underground which can explain the details of the structure under complex geological background.FWI is based on wave equation forward modelling.The goal of FWI is to find the most accurate rock physics parameters by minimizing the misfit between the observed and the simulated seismic data at the receivers.In this paper,the finite difference forward modeling of acoustic wave and elastic wave in time domain is derived which lays the foundation for full waveform inversion.Then,the gradient formula of full waveform inversion is derived,and the model inversion is taken.Then we compare the accuracy and efficiency of the steepest descent method,conjugate gradient method,L-BFGS method and pre-treated L-BFGS method and form FWI process.Density is one of the most important information in seismic exploration,but the strong nonlinear of multi-parameter inversion has been a big problem in FWI.In this paper,we derive formula of multi-parameter FWI of acoustic media in time domain.We discuss the influence of density and velocity on inversion and obtain the appropriate density inversion strategy.The strategy is applicated to actual data which get good result.Next,the formulas of multi-parameters elastic media inversion are derived.