碳酸盐岩缝洞型储层三种不同地震成像效果对比

Comparison of Three Seismic Imaging Effects in Fractured-cavity Carbonate Reservoir

碳酸盐岩缝洞型储层具有埋深大、非均质性强、尺度变化大等特点,溶蚀洞体的地震识别特征——串珠状反射的成像精度是制约这类储层成功勘探和开发的控制因素之一。尤其对于小规模溶蚀洞体,如何选取更好的地震成像方法是目前缝洞单元预测的关键。以在塔河某油田采集的全方位三维地震为例,在地震偏移成像前的预处理流程相同的基础上,分别利用PSTM(pre-stack time migration)、RTM(reverse time migration)及OVT(offset vector tile)三种不同的成像方法对资料进行了处理。处理效果对比和叠后属性分析表明:OVT处理获得的三维地震数据对溶洞成像聚焦性较好,边界清晰,RTM对中小尺度的洞体成像能力更强,归位精度最高;而从保幅性和P波各向异性分析的角度,OVT成像效果则更有利于方位信息的使用。因此,针对不同尺度的溶蚀洞体成像要求出发,RTM与OVT表现了明显好于PSTM的优点,针对不同的地质任务应分别选择使用不同的成像方法。

The fractured-cavity reservoirs of carbonate have the characteristics of deep burial,strong heterogeneity and large scale change,imaging precision of caves is one of the main factors restricting the exploration an development,especially for the small scale caves.How to select a better seismic imaging method is the key to the prediction of the fractured-cavity units.A oilfield located in Tahe is took for example,on the basis of the same pre-processing flow,PSTM,RTM and OVT migration imaging methods were used for processing.Comparison results show that OVT data has a better imaging focusing and cave boundary depiction,RTM data shows better imaging capability for small caves,and higher precision of homing.While from the aspect of amplitude preserving and anisotropy,OVT method has a better use of azimuthal anisotropy.Therefor,for the imaging of caves,RTM and OVT are better than PSTM,different imaging methods should be used for different geological tasks.