Seismic Wave Fields Simulation In Fracture-induced Two-phase HTI Medium By Staggered Grid Pseudo-spectral Method

Naturally fractured reservoirs has caused more and more attention as a kind ofimportant oil and gas resources type. The related techniques developed based on thetheory of seismic anisotropy are a class of important means to be used to fracturedreservoir recognition and prediction, and the relation of seismic anisotropy andfractured reservoirs parameters is established through the equivalent medium theorymodel. Equivalent medium models play a very important role in the exploration offractured reservoirs indirectly. The closer the model get to the actual reservoirmedium, it can descripe the features of seismic wave propagation in reservoir morefinely, the seismic response characteristics of fractured reservoir is the more clearunderstanding, thus the techniques used to fractured reservoir prediction and fluididentification developed based on it is more effective. Traditional equivalent mediumtheory is established based on the theory of single-phase medium theory, withoutconsidering the porosity and permeability of reservoir rock, but in fact, fracturedreservoir rock is a kind of fractured porous media containing both cracks and poresusually. And, with the deepening of the research, people gradually realize thedirectional fracture in fractured reservoirs caused by anisotropy and bipolar or causedby the existence of the pore fluid heterogeneity has a great influence on the spread ofseismic wave. Therefore, to establish a more accurate description of fracturedreservoir medium equivalent medium theory model for fractured reservoir explorationis particularly important. To this end, this paper carried out the cracks induced bipolarHTI media issues related to research, mainly includes the model establishment, thewave equation is derived and the characteristics of seismic wave field numericalsimulation and analysis. The Biot theory and Gurevich combined fracture anisotropy theory, based oncertain assumptions, the establishment of a crack induced with horizontal axis ofsymmetry (HTI) two-phase medium model, the use of constitutive equation andkinematics equation, dynamic darcy’s law was deduced crack induced bipolar HTImedium wave equation, and the equation of the rigid problems and solving methodare analyzedUsing the time splitting method and fault pseudo-spectral method to solve the first-order rate-in the form of stress wave propagation equation, the crack induced bipolarHTI medium seismic wave field numerical simulation and characteristics analysis.Studied the characteristics of seismic wave field propagation in the medium andreflection and transmission on the medium interface, and the background of pore,fracture parameters and fluid types of the influence of the wave field are analyzed.The results show that the time splitting method and anacoluthon pseudo-spectralmethod for wave field numerical simulation, can get high precision of the simulationresults; Cracks induced bipolar HTI medium with anisotropic medium and the seismicwave propagation characteristics of two phase medium, dominant dielectricanisotropy, fracture system and fluid two-phase matrix pore system of main; Wavefield by the background porosity, fracture parameters and fluid types, the influence ofbackground porosity not only affect the velocity, also affect the degree of anisotropy,mainly due to fracture and pore fluid exchange between the fracture parametersmainly affect the rate of all kinds of wave anisotropic characteristics, fluid typemainly affect the magnitude of velocity. In addition, the double medium model theresults of numerical simulation, the identification and analysis of many kinds of wave,use of multiwave seismic data is helpful to fractured reservoir is more in-depth studyand explore.