3D Reservoir Characterization and Geostatistical Modeling of Amalgamated Fluvial Channels: Grand Valley Field, Piceance Basin, Colorado

By

Jack Wiener

Halliburton Energy Services, Denver, CO

Steve Cumella

Williams Production RMT Company, Denver, CO

Grand Valley Field is a basin centered gas accumulation producing from a 1,800 ft. gross interval. These reservoirs are comprised of stacked lenticular, fluvial sand bodies of the Cretaceous Williams Fork Formation. As this field becomes developed at 20 acre and greater densities, reservoir correlation and continuity play an important role in determining new well locations and field economics. Also, because of the nature of these tight reservoirs, natural fractures and fracture stimulation are equally important in understanding well performance.

The sandstones of the Williams Fork are point bar deposits that can be extremely difficult to correlate from well to well. 3D earth modeling and geostatistical techniques are now being employed in order to better: 1) visualize these complex reservoirs in true 3D space, 2) reliably correlate and interpolate these fluvial deposits, and 3) distribute reservoir properties for volumetric calculations and reserve estimates. Extensive data QC and normalization of the wireline logs have taken place to ensure the highest quality and accuracy from the geostatistics. Other inputs into our model are field geologic studies, production data, pore pressure and pressure gradient information, and stimulation results with the intention of producing a data consistent interpretation of Grand Valley Field.

The result of this modeling are being used for accurate well placements and infill drilling programs, identification and correlation of reduced-pressure zones for frac staging, and optimizing completion design. The particulars of the model construction, spatial data analysis, and fluvial simulation design will be discussed.

AAPG Search and Discovery Article #90004©2002 AAPG Rocky Mountain Section, Laramie, Wyoming