Full-waveform Inversion Of Variable-density Acoustic Waves For Reservoirs

Full-waveform inversion has great potential for high-precision reservoir information prediction because it fully includes the kinematics and dynamics information of the seismic wave field.Many scholars' research on full waveform inversion has focused on its speed modeling ability.With the continuous refinement of oil and gas exploration targets,the difficulty of oil and gas exploration is increasing.More and more researchers are gathering their eyes to full waveform inversion research in lithology identification and reservoir prediction.The investigation has become more and more concerned.The full-waveform inversion of variable-density acoustic waves is the inheritance and development of the general waveform inversion of ordinary acoustic waves.It is an application for applying full waveform inversion to reservoir practice.To get good inversion results,we must have good forward modeling.In this paper,we use the staggered grid finite difference forward operator and we cooperate with the split perfect matching layer(SPML)to eliminate the influence of computer boundary reflection on the simulation results.In the process of inversion,this paper focuses on the establishment process of the forward and reverse wave fields of two parameters,the gradient and the basic implementation process.The in-depth research and analysis of the two-parameter magnitude balance,gradient illumination preprocessing and iterative algorithm are carried out,and the mixed nonlinear conjugate gradient based on the gradient preprocessing of the forward and reverse wavefield is finally selected.We apply it to the model for testing to prove its validity.In the reservoir-oriented study,the experiment proved the mutual leakage phenomenon caused by the coupling crosstalk between the two parameters and the sensitivity of the velocity density was analyzed.In the specific inversion process of two parameters,combined with the previous research,a two-parameter continuous decoupling inversion strategy is developed to achieve the purpose of eliminating the coupling to meet the actual demand accuracy.Applying this scheme to the model test with reservoir significance,it finally achieved a good inversion effect.At the end of the paper,the content and key technical issues are summarized and forecasted.