崎岖海底和海洋深水区速度的复杂性导致沉积层构造畸变、深度预测难度大,严重制约了深水区的油气勘探.利用测井速度、VSP速度对白云凹陷速度结构特征和影响因素进行了分析,结果表明,地层速度与海水深度不存在必然的联系,沉积环境的差别是陆架、陆坡深水区速度异常的根本原因,陆架坡折带是界定地层速度异常的关键.理论模型正演方法研究表明,叠前相干速度反演的精度高、可操作性强,是解决速度异常的有效方法.利用测井速度、叠前相干反演速度及地震叠加速度的优势互补,建立了白云凹陷时深转换速度场,较好地解决了深水区崎岖海底造成的构造畸变问题.利用建立的时深转换速度场转换得到B19井和B20井的深度,与实际钻井深度相比,T50反射层深度误差分别为6和7m,大幅提高了海洋深水区深度预测的精度.%he complexity of velocity structure in deepwater area leads to distortion of the sedimentary layer structure and the difficulty of depth forecast, and seriously hampered oil and gas exploration of the deepwater area. We analyze characteristics and influencing factors of velocity structure in the Baiyun sag, using AL velocity, VSP velocity, and recognize that there is no necessary relationship between formation velocity and the water depth, and the sedimentary environment essential difference between continental shelf, continental slope deep water area is the fundamental cause of the abnormal rate. Then, we buildup the depth conversion method suitable for the deepwater area of Baiyun sag, by use of the mutual restraint of drilling speed, velocity of coherent inversion and seismic stacking speed. This method resolves tectonic distortion due to rough subsea preferably, and improves depth-prediction accuracy considerably.
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