| Prestack reverse-time migration based on the double wave theory,has the velocity field of underground complex to carry out the ability of imaging,not only to the dramatic change of velocity field has a good adaptability,but also to complex terrain and steep dip Angle imaging of complex geological target medium(especially large dip Angle area)exploration and has a significant effect.Currently used in seismic exploration reverse-time migration imaging operator is mostly in the assumption of the ideal elastic isotropic medium is derived under the condition of,however,the seismic exploration in the face of a common actually actual underground medium viscosity,seismic waves through the underground strata,the underground medium is not completely elastic medium,even if the transmission loss and compensation for the geometric diffusion attenuation caused by factors such as,the seismic profiles in the inside,the deep energy is still weak in shallow.Found in the path of seismic wave in the actual transmission through the energy loss,make the seismic wave amplitude attenuation,phase distortion,makes the signal-to-noise ratio of seismic data is low,deep get blurred.Therefore,it is necessary to study based on the viscous medium two-way wave equation theory,the development of viscous medium reverse-time depth migration method,the correction of space-variant wavelet features,to compensate the amplitude attenuation,to adapt to the actual demand of strata seismic exploration.Seismic wave imaging is the key of seismology intermediate link,it is closely related with the field seismic data acquisition,in front of the back of post-stack impedance inversion and prestack AVO/AVA inversion data provide a solid foundation,the seismic processing and imaging of the requirements,not only is to put the record on the earth's surface reflected wave homing to the correct position of theunderground,in depth domain imaging,the goal is to make the reflection coefficient directly place to the right depth and position of it.Also calls for the amplitude of wave"and partial reflection point to the size of the reflection coefficient was positively related to relationship;And then the physical parameters to estimate the underground rock medium,main parameters,velocity and density is ultimately describe the oil and gas reservoir.Conventional reverse-time migration imaging,however,tend to have low frequency noise,and the lack of compensation of seismic wave transmission in the process of transmission and reflection energy loss,and often irregular observation system,seismic data are limited frequency band,this is to restrict the true amplitude migration imaging.In order to improve imaging effect,implementation of migration imaging,the development of imaging medium parameters according to need,in the inversion under the theoretical framework of the objective function of the least-square deviation and iterative inversion algorithm is derived with the help of adjoint state method,using the local optimization operator,build a least-squares iterative inversion method of reverse-time migration will effectively improve the imaging accuracy of complex medium above conditions on the plastid,reasonable to eliminate such as stratigraphic absorption,transmission and geometric diffusion effect of amplitude,frequency and phase effect,improve the imaging resolution,improve amplitude attribute,realize the painting,fidelity,high resolution imaging section.Based on the above,on the basis of theoretical analysis,this article is based on the standard linear viscoelastic solid mechanism model of viscous medium theory,the realization of viscous medium reverse-time depth migration,and will be sticky reverse-time migration acoustic medium combined with least square thought,developed with amplitude compensation of viscous medium least-square LSRTM.Model data trial results are good,stick to verify the acoustic medium reverse-time migration and least-square deviation can compensation acoustic medium to the earthquake. |
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