Research On Correction Method Of Non-stretching Distortion For Long Offset Seismic Data

In conventional seismic exploration,due to the limitation of the incident angle of the seismic wave,the thickness of the target layer is generally not lower than the maximum offset,so the conventional hyperbolic NMO can be used.However,with the oil and gas exploration gradually developing towards the deeper layer,conventional seismic exploration can no longer meet the requirements,and large-scale wide-angle reflection seismic exploration can solve such problems.it is difficult to level the event at a large offset using the conventional hyperbolic correction formula.Conventional data processing methods cut off the event of larger errors,thus losing the information of deep reflections.In order to take advantage of deep reflection information,a more precise T-D curve equation is needed to describe the travel time.In order to adapt to the non-hyperbolic characteristics of remote offset,Firstly,the conventional T-D curve equation(Dix formula)and Taylor series expansion fourth-order and sixth-order non-hyperbolic T-D curve equation are introduced,and constant coefficients are optimized.Then,the advantages and disadvantages of higher-order truncation of Chebyshev polynomials and Taylor series expansion equation are discussed,and case studies are carried out.In the optimized Chebyshev polynomial truncation equation,the coefficients of each layer are calculated.In order to ensure that the error of higher order truncation reaches the allowable range,constant coefficients are optimized by simulated annealing algorithm to improve the overall accuracy and stability of NMO correction equation.Dynamic calibration stretching often occurs in actual seismic data.In this paper,an improved matching pursuit algorithm is selected for NMO calculation.Using the advantage of matching pursuit in signal decomposition and reconstruction,starting from the optimized Chebyshev non-hyperbolic equation,the relatively accurate arrival time is calculated.The pre-stack CMP gather data are decomposed into different seismic wavelets and corrected.Finally,the corrected wavelets are used to reconstruct new seismic data.The application of model test and simulated physical model data shows that the CMP gathers corrected by the optimized matching pursuit algorithm are more isotropic and the dislocation phenomenon has been eliminated to a certain extent.Fromthe comparison of stacked sections,it can be seen that the wide-angle reflection wave and some formation information under the high-speed shield layer can be enhanced.