摘要
本文根据天山南缘地区三维叠前深度偏移结果,建立了亚肯北地区的二维地震地质模型,模型设计中考虑了亚肯北浅层第四系西域组沿横向速度变化的高速砾岩层和深层上第三系吉迪克组构造形态变化较大的低速膏泥岩层。按照该区野外观测系统模拟计算出炮集记录,进而获得常规叠加速度及叠偏剖面,并与该模型的实际均方根速度值及地震地质模型进行了对比分析。分析结果表明:目的层上方速度沿横向渐变,叠加速度低于均方根速度;而浅部砾岩层的存在,使目的层上方的叠加速度高于均方根速度,上述两者综合影响使得叠加速度比均方根速度增大8%;浅部高速砾岩层对下伏地层的时间成像影响较小,但使得砾岩层两端的较深部位的叠加速度偏高,导致深度剖面产生凹陷假象,也使得凹陷附近的构造变化幅度增加。因此定量分析亚肯北地区的浅部高速砾岩层及低速膏泥岩层两大速度异常区的速度异常对常规速度分析产生的误差及其变化规律,对于指导常规速度分析误差校正具有重要意义。
Based on the 3-D prestack depth migration results in Tianshan southern margin, the paper built up 2-D seismic-geologic model of Yakenbei area. In the design of model, we considered the gravel layer with high velocity that rapidly changes in lateral direction in Quaternary Xiyu Formation of shallow layer in Yakenbei area and the low-velocity gypsum mudstone layer that significantly changes in structural feature in Tertiary Jidike Formation of deep layer. The shot gather records were computed by simulation of field geometry in the area, then the common stack velocity and stack-migration sections were further yielded, with which the practical mean-square-root (msr) velocity values of the model and seismic-geologic models ware correlated. It is shown by analyzed results that the velocities gradually changing laterally above the target makes the stack velocities be lower than msr velocities; existence of shallow gravel layer makes the stack velocities be higher than msr velocities above the target. Abovementioned both integrative influences make the stack velocities increasing by 8% in comparison with msr velocity. The influence of shallow high-velocity gravel layer on time imaging of underburden is lower, but makes the stack velocities higher in deeper parts on both sides of high-velocity gravel layer, leading depth section to produce false sag image, and also to increase the structural variation amplitude near sag. Therefore, there is important meaning for guiding the error correction of common velocity analysis that quantitatively analyzing the errors of ordinary velocity analysis produced by velocity anomaly of two anomalous velocity zones: shallow high-velocity gravel layer and low-velocity gypsum mudstone layer in Yakenbei area and variation law.
出处
《石油地球物理勘探》
EI
CSCD
北大核心
2007年第4期407-412,共6页
Oil Geophysical Prospecting
关键词
正演模拟
速度精度
影响因素
定量分析
forward simulation, velocity precision, influence factor, quantitative analysis
