Numerical Simulation Of The Seismoelectric Effect And Attenuation Parameter Estimation In Complex Porous Media

China has vast oil and gas resources,but low rates of resource exploration and support contradict the every-increasing demand.The seismoelectric detection method has the advantages of both seismic and electromagnetic(EM)exploration.It can ensure exploration resolution while also identifying differences in fluid electrical impedance waves,assisting seismic exploration to obtain more reservoir information,and having enormous potential and application prospects in oil and gas exploration.The seismoelectric effect refers to the coupling phenomenon between seismic and EM waves that occurs due to the existence of the double electric layer at the interface between the solid skeleton and pore fluid in a biphasic porous medium.In other words,seismic waves can generate EM waves during the propagation process in a porous medium,and vice versa.Numerical simulation of the seismo-electric effect is an effective method to understand the characteristics of seismoelectric wave fields,and can provide a solid theoretical basis for seismoelectric exploration.Traditional numerical simulation algorithms for solving seismoelectric wave fields typically use the EM static approximation,which results in the inability to calculate the accompanying transverse electric field and produces significant numerical errors in interface responses.Therefore,it is urgent to develop a high-precision numerical method based on Maxwell’s time-varying EM field.In addition,traditional theoretical models are based on simple isotropy and cannot accurately characterize the propagation characteristics of seismoelectric wave fields in complex porous media.It is therefore necessary to further construct a seismo-electric model that includes anisotropy,viscoelastic properties,and low-frequency polarization effects.Finally,the seismoelectric wave field is affected by the viscoelastic properties of complex porous media,resulting in a decrease in frequency bandwidth and phase distortion,which seriously reduces data resolution.Accurate estimation of near-surface attenuation parameters is a key step in achieving attenuation compensation and improving the resolution of measured data.Based on the above-identified issues,this thesis focuses on the seismoelectric effect and attenuation parameter estimation in complex porous media,and the main research outcomes are summarized as follows:(1)Developing a numerical simulation method based on the Maxwell time-varying field for the seismoelectric effect.Based on the Pride seismoelectric decoupling equation,the staggered grid time-domain finite-difference(FDTD)method is used to derive a differential format based on the time-domain high-order staggered grid.Using an adaptive time step method,a numerical simulation algorithm based on the Maxwell time-varying field for the seismoelectric effect is established.Under different mineralization conditions,the simulation results of this method are consistent with those of analytical methods,indicating the effectiveness of this method in simulating seismoelectric responses in porous media.(2)Constructing a numerical model for the seismoelectric effect in complex porous media.The generalized standard linear solid(GSLS)model and Cole-Cole model are introduced into the Pride equations to characterize the viscoelastic properties and frequency dependence of conductivity of subsurface media.The model is extended to anisotropic media.By using memory variables to replace convolution terms,the corresponding timedomain control equation is derived to simulate the seismic-electric effect in complex porous media.(3)The time-domain simulation and analysis of the seismoelectric coupling wave field in complex porous media are implemented.Based on the numerical simulation algorithm and seismoelectric model for complex porous media proposed above,the effectiveness of the algorithm for simulating the seismoelectric effect is verified in isotropic elastic media and complex porous media,using a homogeous model,a two-layered model,an anomalous body model,and a 3D model.The propagation characteristics and features of the seismoelectric wave field are analyzed.The results show that the numerical simulation based on the Maxwell time-varying field can effectively capture the reflection and transmission phenomena of seismic and EM wave fields at interfaces,and the TI anisotropy,fluid viscosity,and tilt angle all have a significant impact on the propagation of the seismicelectric wave field.The viscoelastic model and Cole-Cole model can effectively characterize the attenuation and dispersion of the wave field.(4)Conducting the estimation of attenuation parameters in complex porous media.The classic centroid frequency shift,weighted exponent function,and adaptive asymmetric wavelet centroid frequency shift methods are introduced,and the accuracy of estimating Gaussian,FWE,and Ricker sub-waves is compared and analyzed to construct an effective attenuation parameter estimation method.The Q value of the attenuation parameter is estimated for theoretical data,and the accuracy of the method is verified by comparison.The method is applied to the measured data in the loess hilly area to estimate the Q value of the attenuation parameter.The research outcome obtained in this thesis can effectively enable the numerical simulation of seismoelectric effects and the estimation of near-surface attenuation parameters Q in complex porous media,providing new insights and methodologies for highprecision numerical simulation of seismoelectric effects and near-surface attenuation parameter Q estimation of field data.It provides useful tools for studying the signal characteristics in more complex oil and gas reservoirs and is of great significance to the understanding of actual observed data and the promotion of seismic-electric exploration services for resource exploration.