The virtual‐source method applied to Mars field OBC data for time‐lapse monitoring

Abstract

The virtual source method has recently been proposed to image and monitor below a complex and time-varying overburden. The method requires surface shooting recorded by subsurface receivers placed below the distorting or changing part of the overburden. Redatuming the recorded response to the receiver locations allows the reconstruction of a complete downhole survey as if the sources were also buried at the receiver locations. The ability to redatum the data independent of the knowledge of time-varying overburden velocities makes the virtual source method a valuable tool for time-lapse monitoring. We apply the virtual source method to the Mars field OBC data acquired in the deepwater Gulf of Mexico with 120 multi-component sensors permanently placed on the seafloor. Applying to the virtual source method, a combination of up-down wavefield separation and deconvolution of the correlation gather by the source power spectrum suppresses the influences of changes in the overburden (sea water), thus strengthening the virtual source method for time-lapse monitoring.