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The state of Washington is one of the few potential oil and gas provinces in the United States in which no commercial production has been developed. Market demand for oil and gas in the Northwest would make any discovery very attractive economically.
This paper deals with that portion of Washington situated west of the Cascade Mountains, approximately the western one-fourth of the state. An aggregate of over 50,000 feet of marine. Tertiary sediments of Pliocene, Miocene, Oligocene, and Eocene age are present. The stratigraphy varies greatly from one sedimentary basin to another, and up to 20,000 feet of sediments have been found in some of the basins. Volcanics varying greatly in thickness, according to their distance from their source vents, are common in the middle and lower Eocene. A few hundred feet of Miocene lavas extend part way across southwestern Washington.
Structural conditions of the area are typical of coast-range structure, except for the Olympic Peninsula area. The sediments of the western Olympic Peninsula have been folded, faulted, and crushed into one of the most complex structural conditions found anywhere in the world.
Most geologists who have worked in the area believe that commercial oil and gas discoveries will be made. Oil and gas seeps are present and in several areas sub-commercial production has been found. Source beds are abundant and permeable sands are present in all formations. Contrary to popular opinion, the lack of successful discoveries to date can be attributed more to poor structural locations of the wells drilled, rather than to lack of reservoir rocks.
Exploration is difficult, not only because of the complex structural and stratigraphic conditions, but surface exposures are limited by extensive glacial deposits and thick growth of forests and underbrush. Subsurface data are needed for intelligent exploration.
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