SEISMIC MODELS OF OUTCROPS IN THE BRUSHY CANYON FORMATION OF WEST TEXAS: IMPLICATIONS FOR RESERVOIR CONNECTIVITY DETECTION

Connectivity within and between channels and channel complexes is a significant issue affecting the performance of deep-water reservoirs. Seismic data is a critical tool to identify potential compartment boundaries. To refine the use of seismic data in identifying stratigraphic connections, we constructed a series of 2-D seismic models of outcropping deepwater channels and channel complexes in the Brushy Canyon Formation of West Texas. The deepwater deposits of the Brushy Canyon Formation are ideally suited for this type of modeling as they are well exposed and the Brushy displays a range of deepwater channel architecture from confined slope channels to larger aspect ratio distributary channels.

Three channel complexes, a low aspect ratio slope channel complex, an amalgamated toe-of-slope channel complex and a high aspect ratio distributary channel complex, were modeled. These channel complexes were chosen to illustrate a range of channel-fill geometries. For each of these channel complexes stratigraphic sections were measured about every 30 m (comparable to 3D seismic trace spacing). Facies and stratigraphic surfaces were interpreted and correlated between measured sections using photo pans. Rock properties characteristic of Tertiary deepwater reservoirs were assigned to each facies. The seismic response of these outcrop was simulated at a range of frequencies from 10 – 60 Hertz. From this modeling exercise, we discovered that it is often difficult, especially with lower (<30 Hz) frequency data and channel-fill deposits that lack coarse grained traction deposits, to detect the depth and extent of erosion at the base of deepwater channels that controls vertical connectivity. Inversion techniques used to bring out the low-frequency component of the seismic spectrum can help improve detection of these features. However, in many cases they will remain below seismic detection and vertical connectivity may be underestimated.