非对称走时叠前时间偏移在青东4东地区的应用

Application of asymmetric traveltime prestack time migration in QD4D,Shengli Oilfield

胜利青东4东地区滩海三维横跨潍北凸起、青东凹陷、郯庐断裂带,地下地质情况复杂,构造变化大,第三系地层发育大量的低序级断层,中生界古潜山特征复杂。为了做好该区复杂构造的成像工作,地震资料处理中采用了非对称走时叠前时间偏移方法。该方法走时计算公式中含有水平源像距的多次项以及关于速度的横向导数,能够有效提高走时计算精度,改善复杂条件下的地震波聚焦效果。抽取一条南北向的测线测试了非对称走时方法的有效性;用该方法进行实际资料处理有效改善了中生界古潜山的成像效果,较准确、精细地刻画了层间信息的细节及断层的边界。

3-D seismic data from Qingdong 4 East offshore area of Shengli oilfield are structurally athwart Weibei uplift,Qingdong sag,and Tanlu fault zone.The subsurface is complex and changes drastically.There develops a lot of low level faults in the Tertiary layer.To image the complex structures,asymmetrical traveltime prestack time migration was applied in data processing.The equation for calculating asymmetrical travel time contains polynomial items of horizontal source image distance and horizontal derivatives of velocity,which can improve the accuracy of travel time calculation and focusing of seismic waves.Accurate travel time ensures the accuracy of spherical spreading weighting coefficient,which guarantees the preservation of amplitude.In addition,asymmetrical traveltime prestack time migration adopts GPU/CPU co-processing parallel computation scheme,which is highly effective in calculation.The feasibility of the proposed method was tested on an S-N line.Processing of real seismic data indicates that the proposed method improves the imaging of the Mesozoic buried hill,and the definition of interbedding features and fault boundaries.