VSP逆时偏移技术及其成像效果

为提高VSP地震成像精度,从构建16阶有限差分精度的VSP逆时偏移算子出发,采用脉冲响应,进行VSP关键环节算法精度和炮检点可互换性分析,验证了三维VSP逆时偏移算子的精度;基于国际标准岩丘理论模型,对比了归一化VSP逆时成像和常规互相关逆时成像的效果,前者对地质体边界与地层界面刻画更加清晰和准确,消除了覆盖次数不均的影响,能量分布更加均匀,且不存在井痕迹。将高精度的三维VSP逆时偏移技术应用于松辽盆地L井walkaway VSP资料,实现了井旁地层和小断裂的准确精细成像,进一步验证了VSP逆时偏移技术的准确性,为提高井周复杂储集层成像精度的有效技术手段。

VSP Reverse Time Migration Technology and Its Imaging Effect

In order to improve the precision of VSP seismic imaging, a VSP reverse time migration (RTM) operator with 16-order finite difference accuracy was constructed, and then the algorithm accuracy of VSP key links and the interchangeability of shot and receiver points were analyzed by using impulse responses to verify the accuracy of the 3D VSP RTM operator. Based on the standard theoretical model of lava dome, the imaging effects of normalized VSP RTM and conventional cross-correlation RTM were compared. It is found that VSP RTM can describe the geological body boundary and formation interface more clearly and more accurately, and can eliminate the uneven influence of folds to make energy distribution more uniform, with no well trace. The high-precision 3D VSP RTM technology was applied to the walkaway VSP data of Well L in the Songliao basin, and accurate and fine imaging of near-wellbore formations and small faults was achieved, which further verified the accuracy of the technology. The proposed VSP RTM technology can help improve the imaging accuracy of complex reservoirs around the wellbore.