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    针对拖缆数据逆时偏移的炮域规则化方法

    A shot-domain regularization method for streamer data reverse time migration

    • 摘要: 拖缆数据无固定检波点,无法在炮点−检波点域进行规则化,为避免“偏移画弧”现象,实际生产中将拖缆数据在CMP域进行四维规则化,使覆盖次数更加均匀,再进行克希霍夫偏移,但CMP域四维规则化后的数据无法直接分选到炮域并进行逆时偏移成像,因此,为使拖缆数据在避免“偏移画弧”前提下进行逆时偏移成像,本文提出了一种拖缆数据逆时偏移的炮域规则化方法,首先,对拖缆数据进行极坐标下的CMP域四维规则化,使全工区覆盖次数更加均匀;其次,设置合理的炮点网格尺寸,对CMP域四维规则化后的数据进行炮点网格化;然后,将同一网格内的杂乱炮点坐标统一位移至炮点网格中心点,并同时反向位移检波点坐标,保证该地震道的CMP点坐标不变,在对炮检点位移之前,对地震道做动校正处理,并且在位移结束后做反动校处理,动校正和反动校正处理可以保证地震反射信号样点的旅行时和偏移距在炮检点位移前后均符合反射波时距曲线方程;最后,将地震数据分选到炮域进行逆时偏移成像。该方法在实际拖缆资料中成像效果较好,突破了拖缆资料在实际工程生产中无法进行逆时偏移成像的局限,在油气勘探高精度成像中有重要意义。

       

      Abstract: Since streamer seismic data have no fixed receiver positions, regularization in the source–receiver domain is not feasible. To avoid migration smiles, 4D regularization in the CMP domain is conventionally applied to streamer data in practical production, which renders the fold more uniform, prior to Kirchhoff migration. However, data processed using this method cannot be directly sorted back into the shot domain for reverse time migration (RTM). Therefore, to enable streamer data RTM while avoiding migration smiles, this paper proposes a shot-domain regularization method. First, 4D regularization of the streamer data is performed in the CMP domain in polar coordinates, so that the fold over the entire survey area becomes more uniform. Second, an appropriate shot-point grid size is set, and the 4D-regularized data in the CMP domain are binned onto this shot grid. Third, the scattered shot coordinates within each grid cell are uniformly shifted to the center of the shot grid cell, while the receiver coordinates are simultaneously displaced in the opposite direction, thereby keeping the CMP coordinates of each seismic trace unchanged. Prior to the source–receiver displacement, normal moveout (NMO) correction is applied to the seismic traces, and inverse NMO is applied after the displacement is completed. These NMO and inverse NMO corrections ensure that the travel times and offsets of the reflected seismic samples both before and after the source–receiver displacement remain consistent with the reflection time–offset (hyperbolic moveout) equation. Finally, the seismic data are sorted into the shot domain for RTM. The proposed method yields good imaging results on field streamer data, overcoming the limitation of applying RTM to streamer data in actual production, and is therefore of great significance for high-precision imaging in hydrocarbon exploration.

       

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