论文详情
速度模型的精度决定了碳酸盐岩缝洞型储层“串珠”成像的效果。利用风化壳模型对比分析了不同速度误差下缝洞成像剖面和成像道集的特征,发现剖面中“串珠”成像的收敛情况对速度变化非常敏感,而道集的剩余时差对速度误差不敏感。利用层析反演速度建模技术难以获得使“串珠”成像完全收敛的精细速度模型。基于此,提出了一种基于目标区速度扫描的单程波波动方程叠前深度偏移成像方法。该方法假设目标区以上的速度模型精度较高,首先利用分步傅里叶单程波波场延拓算子,将震源波场和记录波场延拓到目标区上方,再利用不同百分比的速度模型对目标区进行偏移成像,进而得到一系列不同速度下的目标区成像结果,改善了原来收敛效果不佳的“串珠”成像效果。塔河某实际资料应用结果表明,该方法可在常规偏移成像的基础上,整体调整目标区速度,使原本收敛效果较差或未收敛的“串珠”成像更好地收敛,较大程度地提高了“串珠”识别能力。
The imaging performance of carbonate fractured-vuggy reservoirs is mainly controlled by the accuracy of the velocity model.The convergence of beads is generally influenced by velocity variations rather than by residual time differences.This can be demonstrated by analyzing the imaging results of a weathering crust model with different velocity errors.A background velocity model that is sufficiently accurate at achieving convergent ‘string beads’ is hardly obtainable using current tomographic inversion techniques.Therefore,a pre-stack depth migration method based on a one-way wave equation was proposed in this study on the basis of the velocity scanning of a target area.The method was implemented under the assumption that the velocity model was sufficiently accurate.Based on the split-step Fourier operator,the source and recorded wavefields were extended to the top surface of the target area,and a series of velocity imaging results were obtained using different velocity scan ratio sequences.A practical application in the Tahe area showed that the proposed method can remarkably improve the imaging quality and recognition of some beads that exhibit weak or no constringed effects by adjusting the velocity model based on a conventional migration process.
国家科技重大专项“塔里木盆地碳酸盐岩油气田提高采收率关键技术示范工程”(2016ZX05053)资助。