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传统的炮集偏移采用Claerbout提出的互相关型成像条件,然而互相关型成像条件不能保持反射振幅。反褶积型成像条件可以改善成像振幅和照明补偿,但存在不稳定问题。最小平方成像条件计算所有炮集上、下行波场的互相关,求和后再与下行波场的照明总能量相除,因此比传统的成像条件稳定,然而在照明很弱且照明不均衡的区域,其成像效果不理想。针对成像条件稳定性和照明均衡问题,在最小平方成像条件的基础上,本文提出了一种地层构造约束的稳定最小平方成像条件。在反问题正则化理论框架下,采用平面波重建算子约束的偏移成像结果沿构造同相轴方向光滑,提高了成像条件计算的稳定行,均衡了成像振幅。水平层状模型和Sigsbee2A模型的算例均表明了本方法的有效性,与阻尼最小平方成像条件相比,构造约束的稳定最小平方成像条件提高了偏移成像的稳定性和成像振幅的均衡性,成像结果同相轴更加连续,改善了照明不足和照明不均衡,压制了假象和噪声,有利于深层构造的保幅成像。
Conventional shot-set migration uses the cross-correlation imaging conditions proposed by Claerbout, whereas cross-correlation imaging conditions do not preserve the reflection amplitude. Deconvolution imaging conditions can improve imaging amplitude and illumination compensation, but have instability problems. The minimum square imaging condition calculates the cross-correlation of all the up and down wavefields of the shots, and then divides the total illumination energy of the down-going wavefields by summing them, so it is more stable than the traditional imaging conditions. However, when the illumination is weak and the illumination is not balanced Region, the imaging effect is not ideal. Aiming at the problem of imaging condition stability and illumination equalization, based on the least square imaging condition, a stable least square imaging condition of formation constraint is proposed in this paper. Under the framework of inverse regularization theory, the migration imaging results using plane wave reconstruction operator constraint are smooth along the tectonic events, which improves the stability of imaging conditions and balances the imaging amplitude. Both the horizontal layered model and the Sigsbee2A model show the effectiveness of the proposed method. Compared with the least squares imaging, the constrained stable least squares imaging condition improves the stability of the migration imaging and the balance of the imaging amplitude , The imaging results are more continuous with the phase axis, improving the lack of lighting and lighting imbalance, suppressing the illusion and noise, which is beneficial to the deep-tectonic amplitude preserving imaging.