A deep seismic profile from noise records

Abstract

Active-source surveys are widely used for the delineation of hydrocarbon accumulations. Most source and receiver configurations are designed to illuminate the first 5 km of the earth. For a deep understanding of the evolution of the crust, much larger depths need to be illuminated. The use of large-scale active surveys is feasible, but rather costly. As an alternative, we use passive acquisition configurations, aiming at detecting body-wave responses from noise sources, in combination with seismic interferometry (SI). SI refers to the principle of generating new seismic responses by combining seismic observations at different receiver locations. We studied 40 hours of continuous data, recorded with an array in the Abu Gharadig basin, Egypt. We split up the record in many small time-windows and bandpass filtered the record between 0.4 and 1.0 Hz. It turned out that body waves dominated many noise intervals recorded on the vertical component. By selectively applying seismic interferometry to those noise windows with a favorable illumination, we retrieved P-wave reflection responses. The retrieved shotgathers could straightforwardly be processed into an image. However, we had to add a correction term to account for the angle between the dominant illumination and the array orientation.