Dongpu Depression is geologically characterized by deeply-buried targets, complex fracture systems and thin beds. In order to accurately depict complex subsurface fracture system, we have conducted prestack migration imaging approach including prestack data regularization, high density automatic velocity picking, anisotropic migration and curved ray migration etc. Based on high density 3D seismic data, this approach improves greatly 3D seismic data imaging, and provides reliable final results for future exploration and development.

东濮凹陷的主要地震、地质特点是目的层埋藏深、断裂体系复杂、储集层单层厚度薄.为了提高勘探、开发效益,精确刻画地下复杂断裂体系,结合东濮高精度三维地震资料的特点,开展了叠前数据规则化、高密度自动速度拾取、各向异性偏移和弯曲射线偏移等技术研究,形成了一套适用于东濮凹陷复杂断块区的高精度三维地震资料叠前偏移关键技术,有效地提高了高精度三维地震资料的品质和成像精度,为勘探、开发提供了可靠的地震成果资料.

Imaging of complicated geological structure is one of the major difficulties in the field of seismic exploration,and the main factor of imaging is migration of the velocity field.Therefore,constructing accurately the migration velocity field is not only the core of high precision imaging,but also the nexus between seismology and geology.In fact,the accuracy of velocity that is picked with the conventional method is rather low under the large offsets,dipping or bend interfaces,pre-salt and deep multilayered medium.As a result,it reduces the accuracy of seismic imaging as well as the reliability of imaging and interpretation.To solve this problem,a new method of PSTM velocity field building is adopted,that is,initial velocity of migration acquiring,bi-spectral high density velocity analysis and anisotropy PSTM.The practical result has proved its good effect and the real accuracy of migration has been increased much.

The structures in Pucheng-Weicheng area of Dongpu sag are complicated and the exploration mainly focuses on the crushing complex fault blocks and lithologic hydrocarbon reservoirs,such as the fault of the narrow space between two adjacent things,and the small fault blocks.The working area features in large-volume seismic data,complex wave field,and interference wave develops.In view of the characteristics of high-precision seismic data of Pucheng-Weicheng area and geological characteristics of the working area,research has been conducted on the fine processing method and high precision seismic imaging technology.High-precision seismic data processing technologies taking high-precision point-to-point velocity analysis,tomographic inversion static correction,prestack time migration,and prestack interference wave suppression as main features are developed.And obvious progress has been made in data processing.

To enhance the imaging precision of complex fault blocks and carry on fine description of small complex fault blocks,the key is to increase the density and precision of velocity analysis.Through actual data processing analysis,2% of the imgration velocity error will exert obvious effect on the intended interval migration imaging results during the application of prestack time migration to imaging of complex fault blocks.Therefore,improving the accuracy of velocity analysis is the key to high-precision seismic imaging.The conventional velocity analysis method is used hyperbolic NMO formula to carry on velocity analysis,and manual pick-up velocity is needed to be used.So the density is restricted,the quality of velocity analysis is also influenced by human factors greatly.In addition,as a result of the anisotropic characteristics underground media,reflecting the travel time is no longer a hyperbola,the application of conventional hyperbolic NMO may lead to uneven correction in the far-offset.In is paper,the high-density anisotropic velocity analysis method is proposed to be used.High-density automatic velocity analysis may be conducted,so non-hyperbolic NMO problems caused by anisotropy could be solved.

The issue of static correction on the complex ground surface comes down to the solution of near-surface layer velocity,so the more complex the ground surface,the more difficult the velocity of near-surface layer to be obtained. According to the peculiarities of ground surface in the desert area such as the abnormally complicated surface condition,low signal-to-noise ratio of source data,and other involved problems,based on the analysis of surface structure,we conducted a study on several static correction methods including the first arrival refraction wave statics,the dune curve statics,and the tomographic inversion statics. According to the relationship between the spread velocity of seismic wave inside the dune and the thickness of the dune,the dune curve statics was improved in this way that in actual calculation,either the quadratic or the cubic polynomial fitting was used for solving the surface velocity,and the mean square error (∑δ2i)~(1/2) and the max|δi|imum deviation were calculated by the deviation between V(hi) and the actual value of vi,and if the calculated results are within the given range of error,it shows that the fitting is effective. Results show that this static correction method by the polynomial fitting is practical and provides a new way for calculating the velocity of ground surface in the desert area.