Summary

Due to the differences in acquisition methods, parameters and time periods among different 3D seismic datasets, it is difficult to conduct joint 3D seismic data reprocessing. One of the key issues for joint 3D data reprocessing is the statics correction problem. Since last decade, BGP has performed many projects of joint 3D data reprocessing, each one is composed of at least 2-3 blocks, and a large project may consist of more than 10 blocks of 3D seismic data. The acquisition parameters such as azimuth, bin size, group interval, receive line interval, shot interval, shot line interval, minimum offset and maximum fold differ among those 3D seismic datasets, which bring more difficulties to near-surface model building and the calculation of statics corrections, especially when computing statics correction based on first break, the technical difficulty is severe.On the base of analysis of the feature of statics problems, this paper discusses the solutions for real problems and provides a good example to solve the statics problem in joint 3D data reprocessing.

Introduction

In recent years, the multi-block joint 3D seismic data reprocessing has become more and more popular. One of the major problems in reprocessing multi-block joint 3D data is the calculation of statics corrections. It is much different between the single block 3D data and multi-block joint ones. For a single block 3D data, the acquisition method and the parameter are basically the same. Because the 3D acquisition block is small, the near-surface model building is relatively simple, and the factors influencing model accuracy are relatively less. But for multi-block joint 3D data reprocessing, the azimuth, receiving interval, minimum offset and the fold bring many problems to model building and calculation of statics corrections, especially when extracting the statics correction on the base on the first break of refraction, there will be more problems to be considered.

Problems and Solutions

For the 3D seismic data acquired in different time periods, the acquisition parameters are much different, which creates difficulties for near-surface model building and calculation of statics corrections. The key issue for calculating statics corrections in multi-block joint 3D data reprocessing is to build a reasonable near-surface model and select the datum and the replace velocity to ensure the good connection among different time sections. For the interpolation on the base of the near-surface investigation data, the difficulty is relatively small and the only requirement is that the near-surface investigation points should be dense enough and well-distributed. The difference, compared with a single block 3D data processing, mainly exists in azimuth and density of shotreceiver points in different 3D blocks. These differences will cause the near-surface model to be less accurate, which can degrade the effect of statics corrections. A better solution is first to mesh the un-uniformed near-surface elevation data and then to make the grid to be as squarely as possible (the size of grid can be determined according to the situation of near-surface undulation). In principle, the tougher the near-surface undulation is, the denser the grid should be.

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