The Columbia Basin of Eastern Washington: A Review of Arguments for Basin-Centered Gas Accumulation

Montgomery, Scott
Consultant, Seattle, WA

The Columbia Basin of eastern Washington state is a large, structurally complex, Cretaceous-Early Tertiary depression with excellent potential for a basin-centered gas accumulation. Sporadically explored and sparsely drilled during the past several decades, the basin has remained resistant to detailed subsurface characterization by geophysical methods, due to the presence of a thick (3,000-5,000 ft), capping sequence of Miocene known as the Columbia River Basalts. During the late 1990s, U.S.G.S. scientists performed a review of geochemical and test data from six wells penetrating beneath the volcanic cover and concluded that there is strong potential for the existence of a gas-related overpressure cell beginning at depths ranging from 8,300-12,700 ft. Some of the strongest supporting evidence for this conclusion comes from a deep well drilled by Shell Oil in 1983, the 1-9 Burlington Northern, which reached total depth at 17,518 ft. This well reported a flow of gas from Early Tertiary sandstones at a tested rate of 5-6 million cu. ft per day, but was abandoned. High drilling costs ($18 million, in the case of the 1-9 Burlington N.) and the lack of infrastructure have been disincentives to further exploration. However, new interest in the area has occurred in recent years, due to the basin-centered gas accumulation hypothesis—such accumulations having become the focus of much successful drilling in Rocky Mountain basins. Will the Columbia Basin again be the target of deep drilling and strong hopes? The future of this enigmatic province has yet to be written.