陆上盐丘区叠前深度偏移建模技术

Pre-stack depth migration modeling technique on onshore salt dome area.

针对陆上复杂盐丘区的地震、地质特点,将叠前深度偏移的速度建模分为盐上沉积层建模、盐间沉积层建模、盐顶建模、盐底建模、盐下沉积层建模五步,形成了一系列针对性很强的配套处理技术,主要包括:①面向叠前深度偏移的叠前道集配套处理;②时间域速度谱上异常时空调查;③借助于叠前时间偏移提高盐丘两翼的刻画精度;④叠前深度偏移迭代中CIP道集对盐丘顶、底刻画的约束;⑤地质、测井、钻井等信息对深度—速度模型迭代的约束。利用针对不同目标体的分步建模技术,建立了陆上A区盐丘区的符合实际地质构造的速度模型,实现了对盐丘侧翼的准确偏移归位,较好地消除了盐丘对下伏地层的影响,实现了盐下目的层合理、准确的成像。

For the seismic and geological characteristics in complex onshore salt dome area, pre-stack depth migration velocity modeling includes the following 5 steps: sediment on salt-bed modeling, inter salt modeling, salt top modeling, salt bottom modeling and sub-salt sediment modeling, while building the velocity modeling, several corresponding and matching seismic data processing workflows were developed, the workflows are as the follow: (1)Pre-stack depth migration oriented pre-stack gather matching processing. (2)Anomaly time and space investigation on velocity spectrum in time domain. (3)Making use of pre-stack depth migration to better image the two flanks of the salt domes. (4)In pre-stack depth migration iteration, applying CIP (common imaging point ) gathers to constrain the delineation of salt top and salt bottom; (5)Using information of geology, seismic and drilling to constrain depth-velocity model iteration. The step to step modeling technique during building different geological objects was used to define a velocity model which is in consistent with geological structures in onshore A block in salt dome area, the technique is also used to better image the two flanks of the salt domes and to remove the salt dome's effects over underlie layers, as a result the accurate and reasonable imaging for sub-salt geological bodies was realized.