Forward Modeling,Analysis And Comparison Of Seismic Wave Field Of Multi Type Sources In Sanhu Lake,Qinghai Province

Nine component elastic wave exploration represented by shear wave source acquisition is a new technology developed rapidly in oil and gas exploration industry at home and abroad in recent years.Although the acquisition and processing technology of shear wave source has achieved remarkable results,the understanding of the propagation mechanism of pure shear wave and the difference between pure shear wave and longitudinal wave needs to be further improved.This subject mainly carries out the forward simulation and comparative analysis of multi type source seismic wave field for the two-dimensional nine component test site in Sanhu area,Qinghai Province.Firstly,the numerical simulation of explosion source,torsional shear wave source and vertical and horizontal concentrated force source is realized.Secondly,for isotropic media and different types of anisotropic media,the elastic wave field loaded with different types of sources is simulated and analyzed,with emphasis on the factors affecting shear wave splitting in HTI media.Finally,aiming at the shear wave splitting phenomenon in Sanhu area,the actual stratigraphic model is established by using the logging curve and velocity profile of the area,and the elastic wave field of the model is numerically simulated by using five types of sources(explosion source,torsional shear wave source,vertical and two horizontal concentrated force sources).Through comparative analysis,it is found that the type of elastic wave excited in isotropic and anisotropic media is related to the source type,and the shear wave splitting phenomenon of excited shear wave in HTI media is related to the source type,observation orientation and fracture density,and has little relationship with pore fluid.The numerical simulation results of surface wave show that the surface wave energy of different components is related to the source type.The numerical simulation of horizontal layered and two-dimensional actual strata shows that the shear wave generated by five types of sources has shear wave splitting in HTI medium stratum,which is mainly reflected in the horizontal component.