Study On Seismic Response And Anisotropy Of Fluid-saturated Media

Seismic prospecting has been widely used as a vital tool for oil and gas reservoir research and prediction in energy industry for many years.To meet the global energy demand,more and more academics all around the world take their eye to the deeper and anisotropic seismic exploration and reservoir prediction based on modeling and inversion.As we all know,the fluid saturated and flow in the formation can lead to remarkable influence on seismic propagation.Anisotropy theory has been developing for decades with more focus on complex reservoir by geophysicists.How to make connection between anisotropy and fluid influence through seismic simulation has become a popular topic.Therefore,this paper presents seismic response and anisotropy study by seismic wave equation simulation and we hope to be theoretically helpful to the further exploration and development of complex reservoir like shale gas and dense oil.Seismic wave equation modeling technology takes reasonable and effective extrapolation to simulate the seismic wave propagation based on scalar or elastic wave equation.Traditional frequency wave-number domain wave equation simulation technology includes Phase Shift,Phase Shift Plus Interpolation and Split-step Fourier method,while Finite Difference method is the most popular one in time domain.Phase shift method helps us analyze the seismic response of fluid-saturated media,which reflected the seismic energy attenuation lead by the viscosity of fluid.And finite difference method helps us get the seismic propagation law with anisotropy.Two dimension three components elastic wave equation simulation presents shear wave splitting phenomenon and describe the vibration of particle in seismic wave field.With the help of rock physics model,the simulation could be more practical.We can obtain the seismic response of different physical properties from multiple directions,which intuitively reflects the seismic response and anisotropy of fluid saturated media.This paper first introduce the sphere patchy saturated model and dynamic bulk modulus theory,then describe the rock physics characteristics of classic gas saturated sandstone reservoir and analyze what permeability and gas saturation can do to frequency-dependent seismic phase velocity and inverse quality factor.Further,simulation can be taken place for the seismic response characteristics of gas sandstone reservoir based on PS two dimension vis in F-K domain scalar wave equation.So we can presents the influence of permeability and gas saturation on vertical incident seismic reflection.We believe that gas saturation can make great difference on seismic response based on the results of simulation and different physical properties have different influence on the response of fluid saturated media.Then,in order to analyze the anisotropy,this paper introduces the two dimension three components visco-elastic TTI media wave equation based on general standard linear solid and anisotropic theory proposed by Carcione.After simulating the seismic filed information,we summarize the different elastic components which control the corresponding seismic wave front and finally describe the compressed wave and shear wave attenuation caused by visco-elastic characteristics of media.In order to make connection between anisotropy and fluid,we present the relationship between seismic velocity,quality factor and extra compliances with frequency,permeability and effective pressure based on dual-porosity media.After introducing the attenuation anisotropy theory,we propose a matrix that can reflect different attenuation magnitude and anisotropic quality factor.Derivating visco-elastic TTI two dimension three components wave equation based on attenuation anisotropy theory,we make simulation of seismic wave field of dual porosity based on staggered grid based on some kind of hypothesis.Then,we discuss the influence of different fluid and fracture density on seismic propagation and attenuation.The anisotropic characteristics of fluid saturated media can be summarized finally.