The Review Of The Wave Field Separation Method About Reflection And Diffraction Based On The Kirchhoff Integral

With the development of precision exploration and further exploitation over structure and lithology reservoirs, as a precondition of more precise seismic interpretation, the high-resolution imaging of sub-surface media (especially the heterogeneity geological bodies) is playing an increasingly important role in oil and gas field prospecting. At the present stage, seismic interpretation mainly focuses on the object of faults, channels, salt-bodies and carbonate reservoirs being rich in karsts and cracks. It is the reason why people focus on this point that these kinds of objects hold the characteristic of sharp lateral and vertical velocity variation, relative small scale, strong anisotropy and irregular shape, whose response is shown as complex diffraction on seismic record. However, traditional seismic data processing based on the reflection wave always treat diffraction wave as noisy, which is different from continuous reflection events. Even though diffraction are focused properly, its low energy will also hardly be recognized in the imaging result with reflection of strong stack amplitude, which leads to a poor imaging resolution of anisotropy geological bodies.In this paper, we promote diffraction imaging as a supplement to the conventional reflection imaging to be used in mainstream processing and imaging. We propose an imaging algorithm that is intentionally diffraction biased, instead of reflection biased. The crucial point here is to find a domain where the diffracted and reflected waves are well separated from each other. Our approach is based on focusing reflected waves to their imaginary source points and then muting them from the full wavefield. Reflection focusing can be achieved by the so-called reflection-stack type of migration. Because of different moveout properties (or integration curves), diffraction and reflection focusing are fundamentally different. Whereas the first is a standard tool in migration to stack energy along elementary diffractions at their respective elementary sources, together making up a reflecting surface, the second stacks energy along real reflection events and trans-ports it to mirrored points on the opposite side of the reflector. Therefore, the reflection-stacked energy is typically concentrated twice as deep as the diffraction-stacked energy, and we have, in principle, obtained a separation. Based on this idea, the outline of our algorithm is (1) apply the reflection stack to the full-wave shot gather,(2) mute areas with strongly focused energy,(3) reconstruct the shot gather, now with mostly diffracted energy, and (4) apply the diffraction stack to this diffracted shot gather. This basically eliminates the normal reflected wave energy, leaving the diffracted wave energy, highlighting the diffracted wave; validation after model instance, to illustrate the effectiveness of these methods, summed up the advantages and disadvantages of the method are given some suggestions for improvement.