The shallow-middle formation of Songliao Basin belongs to the terrestrial delta sand-shale thin interbed deposit with small vertical dimension of single sand body and quick horizontal change, and the faults of different sizes make the lithologic identification more complex. Therefore, accurate imaging and amplitude fidelity of seismic data have become the technical keys for lithological exploration. Due to the reason that the conventional Kirchhoff integral prestack migration technique can not satisfy the demands of fine study, the 3D prestack time migration method which considers the medium anisotropy under the large offset-depth ratio is investigated, and the algorithm is realized under the CPU system. In the travel time calculation, the fourth and sixth order terms are introduced to solve time difference caused by large offset, and meanwhile the travel time difference caused by the medium anisotropy is considered. In the integrated weighting function, the influence of azimuth of ray and strata dip on amplitude is considered. The actual seismic data processing effect proves that this method is superior to the conventional migration method in the aspect of fractured surface imaging and amplitude fidelity.%松辽盆地中浅层属于陆相三角洲砂泥岩薄互层沉积,储层单砂体垂向厚度小、横向变化快,不同规模的断层使岩性识别问题复杂化,因此地震资料的准确成像和振幅保真成为岩性勘探的技术关键.由于常规克希霍夫积分法叠前偏移技术难以满足精细研究需求,研究了在大偏移距—深度比条件下考虑介质各向异性的三维叠前时间偏移方法,并在GPU系统下实现算法.在走时计算中,引入4次项和6次项解决大偏移距引起的时差,同时考虑介质的各向异性引起的走时差异；在积分加权函数中,考虑了射线方位角和地层倾角对振幅的影响.实际资料的处理效果证实,该方法在断面成像和振幅保真方面优于常规偏移方法.
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