ABSTRACT: Petroleum Potential of Oregon and Washington
The states of Oregon and Washington border the Pacific Ocean within an area of diverse topography, climate, and vegetation with
altitudes ranging from sea level to more than 8000 ft. The Mesozoic and Paleozoic rocks are quasi-eugeosynclinal but badly indurated and/or metamorphosed, implying that almost all the pre-Tertiary rocks were unfavorable for oil and gas except some 700 mi2 of outcropping Mesozoic rocks exposed through windows in the overlying volcanics along the SW extension of the Blue and the Klamath mountains, accordingly. A profound angular and erosional unconformity separates the Tertiary sediments and volcanics from the older rocks. During Late Mesozoic and Tertiary time, uplift accompanied by erosion caused the removal of large areas of metamorphosed sediments and the development of pre-Miocene surface of large relief. Crustal movements of Late Miocene age produced NW-SE folds in Wash ngton, and NS folds in the Coast range of Oregon. Some of the exploration methods (excluding wildcat drilling) were inconvenient. Seismic and gravity methods are impeded, the first by glacial till, basalt flows, sills, and dikes, and the second by laccoliths. Although the region is not the best place for hustling, drilling activity for development of potential oil and gas ushered 78% success rate in Oregon, and Shell and Exxon earned significant bonus bids in Washington.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990