基于叠前深度偏移的三相融合速度分析与复杂圈闭落实

克深三维地震区位于库车坳陷克拉苏构造带东部,其地表地形高陡,起伏剧烈,地下构造复杂,地震资料信噪比较低,叠前时间偏移处理后误差很大。为提高目的层成像质量,使断片接触关系更清楚,运用了叠前深度偏移处理。但受叠前深度偏移速度模型精度限制,利用叠前深度偏移确定的构造形态与实际存在一定差异。为了提高构造成图精度,提出了利用叠前深度偏移速度模型,将叠前深度偏移数据转换到时间域,即深时转换,同时开展岩相、地震相和应力相三相融合的速度分析,最终利用变速成图落实复杂圈闭。该方法继承了深度偏移资料归位较准确、三相融合速度场精度较高和变速成图技术成熟的优点,提高了圈闭落实精度。利用该成果部署的一批井位与实钻吻合程度显著提高,为克拉苏构造带山地三维地震区油气发现及整体评价勘探奠定了基础。

Three-Facies Fusion Velocity Analysis and Complex Trap Identification on the Basis of Prestack Depth Migration

Keshen 3D seismic area is located in the eastern Kelasu tectonic belt of Kuqa depression,whose surface topography is high and steep with intense fluctuation and complex underground structure,leading to the low signal?to?noise ratio of seismic data and large errors in prestack time migration processing.In order to improve the image quality of target zone and make contact relationship more clear,prestack depth migration is performed.But limited by the precision of the prestack depth migration model,the structural configuration obtained from prestack depth migration processing is different from the actual one.A velocity model of prestack depth migration is proposed to improve the accuracy of structure mapping,which can be used to convert the prestack depth migration data to time domain.Meanwhile,3?facies fu?sion velocity analysis of lithofacies,seismic facies and stress facies is carried out.Finally,variable velocity mapping is used to identify com?plex traps.This method have some advantages such as accurate depth migration data homing,high accuracy of 3?facies fusion velocity field and mature variable velocity mapping technique etc.,which can improve the precision of trap identification.The actual drilling data has proved the identified traps in the Keshen 3D area.The study lays a foundation for oil and gas discovery and exploration in the mountain ar?eas of the Kelasu tectonic belt.