一次波和层间多次波联合成像方法

Joint imaging method of primaries and internal multiples

地下强反射界面产生的层间多次波传播路径复杂,压制难度大而且成本高,一直以来都是困扰油气勘探的棘手难题。考虑到层间多次波也是来自地下界面的真实反射,同时逆时偏移可以实现多次波的正确归位,因此,从节省计算成本和提高成像精度的角度出发,开展了一次波和层间多次波联合成像方法研究。首先,通过分析联合成像过程,引入了基于上、下行波场分离的成像条件以提高成像精度;然后,重点针对联合成像过程中引入的串扰假象,分析了其产生机制,提出了基于缺失边界匹配补偿的解决策略,通过将震源正向延拓上边界与实际地震资料进行匹配求取匹配因子,并将其作用于缺失边界的正演数据,从而实现保真逆时延拓,有效避免串扰假象的产生;最后,应用数值试算验证了方法的可行性、有效性和适用性。

The internal multiples generated by strong reflection interfaces have bothered the oil and gas exploration for a long time because of their complicated propagation paths and high costs in difficult suppression.Since internal multiples are also real reflections from the underground interfaces and reverse time migration can realize the imaging of multiples,ajoint imaging method of primaries and internal multiples is studied to reduce calculation cost and improve imaging accuracy.First,the imaging conditions based on the separation of up-going and down-going wavefields are introduced by analyzing the joint imaging process to improve imaging accuracy.Then,the generation mechanism of crosstalk artifacts that are introduced in the joint imaging process is analyzed,and the corresponding solution based on missing boundary matching and compensation is put forward.The matching factor is obtained by matching the upper boundary of forward-extrapolation with the real seismic data and then employed to the forward-extrapolation boundaries to compensate for the missing boundaries.As a result,the fidelity of reverse time extrapolation is realized,which can effectively avoid the crosstalk artifacts.Finally,the feasibility,effectiveness,and applicability of the method are verified by numerical tests.