盐下碳酸盐岩储层叠前深度偏移成像分析

研究区内盐丘众多,盐丘厚度大、形状各异,从而改变了盐下反射能量的分布,进而导致盐下目的层构造不能正确成像。本文在比较叠前时间偏移和深度偏移效果的基础上,确信只有应用叠前深度偏移技术才是解决研究区内盐下构造正确成像的惟一途径。理论模型试算结果及实际资料应用效果表明:叠前深度偏移可以使复杂盐丘下目的层准确成像,消除高速盐丘对下伏地层的上拉效应。钻井标定结果也证实叠前深度偏移结果解释的盐下构造真实可靠,提高了钻探成功率,降低了勘探风险。

Analysis of pre-stack depth migration for complex sub-salt structures

There is a variety of salt domes with complex shapes and large thickness in the working area,which cause serious seismic ray distortion and pull-up of underlying strata,and impact sub-salt seismic reflections and accurate structure imaging.The comparison between post-stack time migration and pre-stack depth migration results indicates that 3D pre-stack depth migration can successfully image the sub-salt carbonate rocks and restore the true shape of the underlying structures.This paper analyzes pre-stack depth migration with theoretical model and real data applications,and demonstrates that 3D pre-stack depth migration can eliminate the pull-up impact from salt domes on the underlying strata and achieve accurate images of sub-salt targets.The drilling results confirm that sub-salt structures from pre-stack depth migration are reliable,the success rate of drilling is improved,and the exploration risk is reduced.