Research And Application Of Fast And Slow Shear Wave Imaging And Fluid Prediction

The importance of seismic anisotropy has been recognized by the oil industry since it was first observed in oil and gas reservoirs in 1986,and since then,the application of seismic anisotropy in solving geophysical problems has attracted much attention.However,many problems remain,which limit the application of this technology.At present,more and more 3d multi-component seismic data have wide azimuth.These provide more opportunities for the study of seismic anisotropy.The research in this paper focuses on using shear wave splitting to characterize underground fractures in threedimensional multi-component seismic data,improving the imaging quality of converted wave,detecting the fluid type of fractured reservoirs,and comprehensively using VSP and ground seismic data to interpret fractured reservoirs,which is of great significance for exploration and monitoring of fractured reservoirs.In order to characterize the underground fracture system by using shear wave splitting,the principle of transformation shear wave splitting is analyzed first,and the mathematical interpretation of shear wave splitting is given.This paper studies the algorithm of shear wave splitting analysis and compensation,and compares the analysis criteria of several shear wave splitting attributes(direction of fast shear wave polarization and time delay).After that,the multi-layer fracture system is designed,and the wave field response of fracture stratum is simulated numerically by using the finite difference method.Then the converted wave data of sanhu fractured reservoir are analyzed,and the compensation results improve the "binocular phenomenon" indicating shear wave splitting.In order to accurately image the multi-group fracture strata in xinchang.Firstly,the algorithm of shear-wave splitting layer splitting is studied,and the model data verifies the feasibility of layer splitting.The actual data are divided into shallow layer,target layer and deep layer for splitting analysis and compensation.The maximum coherence criterion of Alford and the minimum residual energy criterion of triangulation T component are used to scan the fracture orientation and delay respectively,and the advantages of Alford rotation method are analyzed.Finally,the polarization azimuth and delay of fast transverse wave in each layer are calculated.It is in good agreement with actual work area geostress field.Monitoring fluid distribution is an important task in reservoir production.Comprehensive study based on multi-scale rock physical model shows that it is feasible to derive viscosity information in HTI medium by seismic anisotropy,and the influence of fluid viscosity on the elastic properties and seismic reflectivity of medium,as well as the possibility of identifying oil and water saturation by using them.The analysis of actual data shows that it is difficult to distinguish oil and water saturation by longitudinal wave.However,the characteristic shear wave splitting caused by the change of pore water pressure shows the potential of identifying oil or water content in fractured reservoirs.For Paris basin Villeperdue oilfield p-waves characterization reservoir properties do not have much diverse solution as well as the limitations of the problem,using integrated VSP and surface seismic data processing and interpretation,through the analysis of the shear wave splitting of vector wave field,the shear wave splitting the relevant properties of wave field,and anisotropy of target reservoir modeling,the results show that shear wave splitting related attributes reveals the internal structure of reservoir in more detail,and the horizontal and vertical changes are not reflected on the longitudinal data.The advantages of comprehensive utilization of VSP and ground data for reservoir characterization are illustrated.