Elastic Wave Field To The Beginning Of The Numerical Simulation Of Crosswell Seismic Travel Time Tomography

The paper includes two aspects.One is the forward modeling of cross-hole elastic wave field.and another is the cross-hole seismic traveltime tomography.The first one is an important means of understanding the rules of seismic wave propagation,and is a tool for us to identify the cross-hole seismic wave field.lt also is the basic of the wave tomography.Seismic wave simulation techniques are used in almost every aspects of seismic data collection,processing,interpretation and oil exploitation engineering.To do further research about seismic wave modeling is the urgent needs to meet the high request of exploration precision and more and more complicated exploration task.lt may help us to get more knowledge about seismic wave propagation in complicated exploration target,and to solve the difficult problem in oil and gas exploration and exploitation.With the developments of cross-hole seismic equipments and techniques,the cross-hole seismic techniques are more and more used in actual production.lt is hopeful to solve the issues,such as fine structrure etc.,which are difficult to solve in 2-D or 3-D surface seismic exploration,so that to increase the exploitation rate of oil and gas ,and to meet the the urgent needs in our country.Cross-hole tomography is an important part of cross-hole seismic techniques.To do further research about cross-hole tomography,especially cross-hole anisotropic tomography, may help to solve the problems, such as structure accurate imaging and reservoir characterization and monitoring.In this paper, after analyzing the basic principle of pseudo-spectrum(PS) method of solving wave equation, the algorithm is improved to increase the calculation speed. Then through introducing pure P-wave variables and pure S-wave variables into elastic wave equation, we get equivalent equations wich can be used to simulate the decomposition of elastic wave into pure P-wave and pure S-wave and preserve the amplitude and conversion information of P-wave and S-wave completely .By using pseudo-spectral method.we realized the elastic wave decomposition.This may help us to realize the elastic wave propagation. After analyzing the basic principle and implement approach of finite element(FE) method we develop a hybid method which couples the finite element method with pseudo-spectrum method to model near boundary wave field and inner wave field respectively , in order to use the advantages of the two methods and to increase the numerical accuracy and computation efficiency. Numerical examples have demonstrated the validity and the advantages of...