Research Of Multiple Attenuation Method Based On Wave Equation

In terms of the problems of multiple in seismic exploration especially in sea exploration, improve the precision of seismic data processing and the quality of seismic imaging, make the seismic interpretation work carry on smoothly, lower the risk of oil-gas exploration, based on the achievement of predecessor, this paper researches the characteristics of multiple, the basic principle and its advantage and disadvantage of varies multiple attenuation methods and then key researches the principle of multiple attenuation based on inverse scattering of wave equation, analyses the essence of surface related multiple in detail. Starting with the WRW model of primary production, by defining surface related operator, simplifying seismic source function and surface related reflection coefficient, infers a formula which adapted arbitrary order surface related multiple attenuation, and using it attenuated surface related multiple. Through the examination of theory model calculates and actual data processing, testified the correctness and validity of this method, has a wide application prospect. The main achievements of research include four aspects as follow:1) This paper depicts the characteristics and types of multiple, and then expound the principle and advantage and disadvantage of some comparatively typical multiple attenuation methods thoroughly and profoundly. take for the position of multiple downlink with basic point, multiple can be divided into two kinds: surface related multiple and layer multiple. The attenuate method of multiple can be divided into two kinds: one is using the differences of primary and multiple, which called filtering method; the other one is predicting the multiple and subtract it based on wave equation, which called wave equation method. This method predicts multiple by using wave equation simulates wave field or inverses seismic data, and then subtract it from original seismic data.2) Derivates the forward formula for arbitrary order multiple. Analyses the characteristics of seismic data and the nature of surface related multiple. On the base of the nature of surface related multiple, this paper gives mathematic model and forward method of the surface related multiple. Starting with the WRW model of primary production, by defining surface related operator, infers a series formula of surface related multiple, in order to adapt the case of strong surface related multiple, derivates the iterative forward formula for arbitrary order multiple.3) Derivates formula of surface related arbitrary order multiple. On the basis of mentioned above, by simplifying seismic source function and surface related reflection coefficient, this paper infers iterative formula of surface related arbitrary order multiple attenuation based on wave equation, through trial calculation and analysis to three typical theory models, obtains ideal results. Secondly, this paper briefly expound the method progresses of layer multiple attenuation. In order to subtract multiple more effectively under the precondition of unimpair primary, using adaptive filtering to obtained filtering factor, then make the actual multiple and multiple subtracted matched. This method need not prior information underground completely, it can attenuate all of surface related multiple theoretically. But it should be satisfies some precondition: Seismic data must be continuous, shot to receiver distance should be as nearly as possible, using stable source, eliminates the impact of source wavelet, all of above are key points to determine the success or failure of the method. Through the examination of theory model calculates and actual data processing, testified the correctness and validity of this method, has a wide application prospect.4) Actual data processing. In order to verificate the validity and efficiency of the method this paper proposed, It using the method this paper proposed and software system to process actual data comprehensively, which achieved good effect. This method is proved to be effective. It is guiding significant for actual production.It is a challenging subject to research the method of multiple attenuation. With the increasement of energy demand and the improvement of technology, multiple attenuation method will be continue to develop,evolution and mature. Filtering method based on kinematics, and wave field prediction based on wave equation will solve more complex problem of geological condition, it will be the development trend of multiple attenuate method.