Full Wave Equation Depth Migration Based On The Dual Sensor Seismic Acquisition System

This paper firstly analyzes the existing problem of the conventional depth migration algorithms,which is that the boundary conditions provided by the current seismic data acquisition system can not accurately be used to solve the second-order partial derivative acoustic wave equation in the depth domain.In order to solve this contradiction,the land dual sensor seismic data acquisition system is adopted in this paper.In the dual sensor seismic data acquisition system,the secondary receivers are set under the conventional seismic receivers at a certain depth;these two receivers provide the enough initial conditions for solving the second-order partial derivative wave equation.Based on dual sensor seismic data acquisition system,three depth migration algorithms are proposed.In the first set of dual sensor depth migration methods,we use the wavefields recorded at the surface and its partial derivative to depth as two initial conditions to solve the first-order wave equations at the depth domain.In order to eliminate the influence of the evanescent wave on the stability of the migration algorithm,the spectral projection algorithm is used based on the previous researches.The comparative analysis of the reflection coefficients calculated by reverse time migration,the conventional Kirchhoff depth migration algorithm and our first set of dual sensor depth migration methods for complex models prove that our first set of dual sensor depth migration methods has better true amplitude calculation performances than others.Finally,this paper studies the influence of the distance change between dual sensors on the true amplitude calculations,which lay a foundation for practical application.In the second set of dual sensor migration algorithms,this paper combines the research achievements of reverse time migration algorithm,and puts forward the dual sensor reverse time migration algorithm.In the dual sensor reverse time migration algorithm,we use the wavefields recorded at the surface and its partial derivative to depth as two initial conditions to solve the first-order wave equation in the time direction,which makes the numerical solution more accurately.By comparing amplitudes calculated by the conventional reverse time migration and dual sensor reverse time migration methods for the multiple-layers model and Marmosusi model prove that our dual our dual sensor migration method can obtain more reliable and accurate amplitude estimation than that of the conventional reverse time migration.In the third set of dual sensor migration algorithms,we use the wavefields recorded by the upper and lower dual sensors as the initial condition to deduce a two-way wave depth migration algorithm based on one-way wave propagator.The algorithm fully absorbs the development of one-way wave equation migration algorithm.The study of impulse responses shows that our proposed two-way wave migration algorithm overcomes the limited imaging angles of the conventional one-way wave equation migration algorithm.By comparing the imaging results of salt model achieved by our proposed two-way wave equation migration,reverse time migration and the conventional one-way wave equation migration methods,we can see that compared with the conventional one-way wave migration algorithm,our proposed two wave migration algorithm is able to provide more accurate wavefield descriptions in the strong lateral velocity variation medium.Moreover,compared with reverse time migration algorithm,our proposed two-way wave migration algorithm has the advantages of imaging results with a better imaging resolution,less low-frequency artifacts and weaker multiples imaging events.