Migration of crosswell seismic data

Lewei Mo

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ABSTRACT

Crosswell seismic survey has proven to be an effective, high-resolution method of reservoir characterization. However, its application has been mainly confined to transmission traveltime tomography, even though extensions have recently been made to reflection imaging. This paper describes the application of reverse-time wavefield extrapolation coupled with the excitation-time imaging condition to the migration of crosswell seismic common-shot profiles. I have applied fourth-order-in-time, tenth-order-in-space finite differencing to perform the crosswell seismic modeling of the two-way acoustic wave equation. During the migration wavefield backpropagation, I gradually drop the order of finite differencing to the second-order near the recording boundary for the derivative perpendicular to the recording boundary, so that the numerical computation conforms to physical wave phenomena. Modeling and migration are based on the geometry of a true field survey. This method successfully models high frequency crosswell seismic wavefields. Migration of one common-shot profile gives a very clear reflectivity image. Vertical resolution up to a half wavelength and horizontal resolution as governed by the first Fresnel zone width have been realized. At the end, the paper presents some suggestions to facilitate field data migration, which include removal of tube waves and wavefield separation.