A Study On The Seismic Wave Forward Simulation Of Low-level Sequence Faults

Low-level sequence faults are important research contents on the exploration and development of complex fault block's reservoirs.Actually,geophysical workers often consider the following technical problems in the interpretation and detailed description of the low-level sequence faults:(1)What is the relationship between low-level sequence faults' drop,the main frequency,buried depth,and signal-tonoise ratio?(2)What are the effects of formation inclination and fault inclination on the wavefield characteristics of low-level sequence faults' imaging?(3)What are the characteristics of small faults derived from the edges of large faults,and how to identify effectively?(4)What are the typical combinations of complex fault zones? How to identify correctly and so on.Based on the above problems,this paper mainly studies the seismic wavefield characteristics of low-level sequence faults below the fourth level,and hopes to have a preliminary quantitative understanding,in order to help the interpretation of the actual low-level sequence faults.Numerical simulation of seismic forward modeling based on wave equation has become an important part of seismic exploration.With the continuous improvement of seismic exploration technology and the development of complex geologic petroleum exploration,the study of seismic wave propagation medium has becoming more and more complicated.This paper discusses isotropic and anisotropic media,and analyzes the propagation and imaging characteristics of seismic wavefield on these two media.We derived the elastic wave equations of different propagation media,introduced the high-order finite difference method to discuss the forward precision and added PML(perfect matching method)into the attenuation coefficient to absorb the artificial boundary.Then deviate the Pre-stack Reverse Time Migration(PRTM)to image and process the low-frequency noise caused by correlation filtering.Finally,analyze the migration profiles of each low-level sequence fault models.Established the velocity models according to various seismic and geological parameters when we discuss the wavefield characteristics of the migration profile of the low-level sequence fault.Then,systematically analyzed the specific laws of various seismic and geological factors.Next,quantitatively analyzed the seismic profile established according to the actual data and the minimum longitudinal and lateral distances of the low-level sequence faults distinguished by high-precision imaging parameters.Finally,established simple 3D the low-level sequence fault models according to the plane and the distribution law of the profile,and analyzed wavefield characteristics.According to the analysis,in the general data through high-precision processing,the theoretically identifiable fault minimum break is about 7m,and the minimum may reach 5m.However,it is theoretically possible to identify faults with a break of 5m or less for high-density and wide-azimuth data with high-precision seismic data processing and interpretation.In conclusion,the larger the fault dip angle,the smaller the dip angle of the layer,the suitably higher the dominant frequency of the wavelet,the denser the shots and the detection points during data acquisition,the smaller the track spacing,the suitably higher the migration aperture,and the horizontal or vertical of multiple faults.The larger the interval,the larger the fault drop,the more accurately the fault point can be located and the fault location determined.