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3D Geomodeling of Grand Valley, Parachute, and Rulison Fields, Piceance Basin, Colorado

Cumella, Stephen1, Jack Wiener2
(1) Williams Production, Evergreen, CO (2) Halliburton Energy Services, Denver, CO

Grand Valley, Parachute, and Rulison fields are part of a giant basin-centered gas accumulation in the Williams Fork Formation of the Mesa Verde Group that is currently being actively developed at 10-acre density. Gas is produced from highly lenticular fluvial sandstones contained within a continuously gas-saturated interval of 1,800-2,400 feet. Over 700 Williams Fork wells have been drilled, and an extensive data base of digital well logs, 3D-seismic data, completion and production data, and formation pressure data has been compiled. Extensive data quality control and normalization of the wireline logs has been conducted to ensure and accuracy from the geostatistics. Outcrop and subsurface studies have documented that the lateral extent of the fluvial sandstones are typically 500-1,000 ft. Because 10-acre density is the equivalent of 660 ft between wells, many of the productive sandstones do not correlate between wells. 3D geomodeling is a very effective tool for visualizing these complex reservoirs. Many important aspects of field development, such as identifying depleted zones that should be avoided during completion, are greatly enhanced with 3D geomodeling. Petrophysical calculation have been integrated into the model to identify areas of better reservoir characteristics and to differentiate gas versus water-bearing sandstones.