Petroleum Potential of Central Columbia Basin

William S. Lingley, Jr., Timothy J. Walsh

Ten deep wildcat wells have been drilled in the 75,000 mi² Columbia basin. These wells penetrated Miocene Columbia River Basalt up to 11,000 ft thick and Paleogene nonmarine siltstones, claystones, shales, coals, sandstones, and volcanogenic rocks exceeding 11,000 ft in aggregate thickness. Lithic and arkosic sandstones range from several inches to more than 60 ft in thickness, average 26 ft thick, and are variedly argillaceous. Mean log-derived sandstone porosity ranges from 18% at 6,000 ft to 8% at 14,000 ft drilled-depth. Mean vitrinite reflectance ranges from 0.4 to 1.3 within the siliciclastic section. Numerous wet-gas shows were logged in three wells including a 3.1 MMCFGD flow on a 10/64-in. choke with 3,965 psi FTP recorded during a test of Shell's 1-9 urlington Northern. The Rattlesnake Hills gas field, in the southcentral Columbia basin, produced 1.3 bcf of methane from Columbia River Basalt before depletion in 1941. The east-central basin comprises a plain and the west-central basin includes the hilly Yakima foldbelt where topography mimics structure. The foldbelt includes several northwest and southwest-trending anticlines, most of which are asymmetric, verge to the north, range from 3 to 6 mi across strike, and are longer than 60 mi along trend. These anticlines have numerous faulted surface culminations. Assuming the Paleogene section is conformable with surficial structure, the estimated range of possible in-place gas under these culminations is 40 bcf to 1 tcf. Most of these culminations have not been tested. The potential of t e east-central Columbia basin remains unknown.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.