Study Of Influence Of Overlying Stratum On Imaging Amplitude Of Target Stratum Based On 3D Staggered Grid Forward Modeling Using GPU

In oil and gas exploration, with the constant improvement of the accuracy of seismic exploration, the requirements of seismic imaging method is not only to get underground structure imaging, but also to get the amplitude information of the underground lithologic body. It is thought that imaging amplitude of the reflect interface obtained by migration imaging method can reflect the lithologic variation of reflect interface, and then the underground reservoir space distribution can be depicted through seismic amplitude slice. But because of the influence of overlying complex geological structure, the amplitude of target horizon information from migration section cannot correctly reflect lithology changes. Amplitude preserving migration eliminates the influence of overlying strata from the Angle of inversion. But the relationships between purpose layer and the overlying strata are still few studied.In order to solve this problem, from the perspective of forward modeling, with the help of GPU parallel technology, using high order staggered grid finite difference method to forward modeling different velocity model, the relationships between purpose layer and the overlying strata are studied, and this will provide theoretical help to lithologic identification in the process of practical seismic data processing.In the derivation process of staggered grid finite difference formulas, PML attenuation coefficients are integrated to the differential formulas, the core computing area and PML boundary absorption area are unified, and finally staggered grid finite difference formulas contained PML attenuation coefficients are established.According to the characteristics of the staggered grid and the GPU, this paper makes full use of high speed share memory of GPU chip, establishes the staggered grid finite difference GPU forward modeling method, and improves computing efficiency of staggered grid forward modeling and achieved satisfactory results.Through the forward modeling carried out on the different model, the law of imaging amplitude changing with interface dip angle is studied. This paper studied the influence of overlaying velocity anomaly body on amplitude of objective layer,respectively established the connection between amplitude of objective layer and different interfaces such as titled, horizontal, anticline and syncline ones,preliminarily summarized the relationship between the reflection coefficient of overlying interface and amplitude of purpose layer. From different perspective of the depth, the radian and the velocity of overlying interface, the influence of interface of horizontal, anticline and syncline on imaging amplitude of purpose layer is studied.The relationship between velocity and radius of lithology anomalous body and imaging amplitude of purpose layer is analyzed. Based on the series results of forward modeling, the quantitative relation between change of overlying strata and imaging amplitude of purpose layer is analyzed, and this has theoretical significance and practical value for amplitude preservation of migration imaging.