基于小波束偏移算子的井间地震成像

Beamlet prestack depth migration on crosswell data

应用地面地震叠前深度偏移能够较好地对复杂构造成像,但对于薄层的成像其分辨率不够。而井间地震受地面的干扰较少,并且信号主频较高,成像具有较高的分辨率。基于单程波方程的波动方程偏移方法可以适应速度场的强横向变化,但不能够直接应用到井间地震成像。本文基于起伏地表直接向下延拓法成像的思想,应用波场逐步累加的方法,实现井间地震的叠前深度偏移。在此基础上,将小波束偏移算子引入到井间地震成像中,由于其局部化的参考速度,减小了局部速度扰动,提高了计算精度。通过复杂的井间地震模型试算验证了该方法的正确性和有效性,与分步傅里叶偏移方法相比,断层成像更清晰,偏移噪声得到了较好的压制。

We can get better complex structure image from prestack depth migration of surface seismic data,but it lacks of resolution when imaging in some area with thin layers.Cross-well acquisition system has little effect from the surface and has higher frequency information,which can get higher resolution image.Prestack depth migration based on one way wave equation can adapt to area with strong velocity variation.However,this conventional migration method cannot be directly used for corsswell data.In this paper,we perform the crosswell prestack depth migration with the thought of wave field accumulation gradually based on the directly downward continuation.The beamlet migration operator was introduced which has localized reference velocity.The localized reference velocity reduces the perturbation velocity and improves the calculation accuracy.The test of complex crosswell model migration has proved the validity and effectiveness of our method.The faults are clearer and migration noise was better suppressed.