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Processing The KTK 3D Seismic Survey For Azimuthal Information: San Joaquin Basin, California


Introduction - Geokinetics acquired the KTK 3D seismic survey in 2013 in conjunction with Aera Energy. The survey took place in the San Joaquin Basin in Kern, Kings and Tulare Counties and was intended to explore the northern extents of the Monterey and Kreyenhagen formations in the Buttonwillow Depocenter which lie between 12,000 and 16,000 ft in depth. With the recent advances in horizontal drilling and fracking in unconventional plays, the Monterey Shale has come under scrutiny as a strong candidate for similar exploitation. Chief among its attributes is not only as an excellent source rock, but an understanding of its natural fracture networks and the local stress regime that it is subjected is important in commercial production. The contribution of seismic data to characterizing the density and direction of fractures, as well as the direction and magnitude of the local stress fields has been well documented. Important to the success of this analysis is the acquisition of sufficient offsets in all directions as well as the careful preservation of this azimuthal information in the data processing. Since land seismic acquisition is by nature irregularly sampled due to a variety of natural and man-made obstacles, sophisticated interpolation schemes and amplitude and azimuth preservative pre-stack migration must be employed to overcome the impact of these effects. Pre-processing and Imaging - A typical amplitude preservative processing sequence was followed. The data were sorted into cubes of offset ranges and azimuth ranges and migrated. However, when subdividing the data into so many domains, a lot of holes in the data are created; thus the necessity of multi-dimensional interpolation. Several methods exist to do this; the one used here is known as the Projection Onto a Convex Set, or POSC. We show several examples of the data holes interpolated using all 5 (x, y, t, offset and azimuth) dimensions. With the 5D interpolation completed, the OVT migration is performed and the data is now ready for analysis for anisotropy, fracture characterization, stress analysis, etc. Conclusions - The KTK survey has been acquired and processed in such a way that a sophisticated azimuthal analysis of the Monterey and Kreyenhagen formations may be performed. The 5D interpolation is a critical step to forming complete OVTs that then may be successfully imaged.