Deep Seismic Reflection Studies in the Pacific Northwest U.S. Open File Report 92-714

From its inception in May of 1982, the U.S. Department of Energy Deep Source Gas project has investigated the possibility that significant quantities of hydrocarbons, natural gas in particular, may be generated during and following convergent plate tectonic sediment subduction. Sediment subduction is believed to have been an important process during the past 180 million years along the western margin of North America. Several years of regional geological, and limited geochemical investigations led to the theory that some portion of these subducted sedimentary units may have been left in place in the upper crust of the continental plate margin of this region. The potential for these, in part, deeply buried rocks to generate petroleum, and to contain important quantities of natural gas at drillable depths, was at the heart of this effort. Along with Gas Hydrates, the Deep Source Gas program of the Morgantown Energy Technology Center was structured under the heading of Speculative Gas Resources being investigated in frontier areas of the U.S.

Following an initial reconnaissance geophysical effort in the Pacific Northwest and Alaska, which included the use of magnetotellurics (MT), gravity, and magnetics information, an important high conductivity MT anomaly was identified in southwest Washington. This feature later identified as the Southern Washington Cascades Conductor, or SWCC, was of sufficient areal extent to warrant further study for its potential as a deeply buried subduction system with significant sedimentary section. Approximately 238 kilometers of 1024 channel deep seismic reflection data were collected in 1988, 1989 and 1990 across the SWCC anomaly in six seismic lines. At this time approximately half of the data has been analyzed and released in the following publications: U.S. Geological Survey, Open File Report 91-119 entitled "Are Hydrocarbon Source Rocks Hidden Beneath the Volcanic Flows in the Southern Washington Cascades?" by W. D. Stanley, W. J. Gwilliam, G. V. Latham, and J.

K. Westhusing, 41 p., 12 figs.; American Association of Petroleum Geologists 1990 Annual Convention, San Francisco, abstract entitled "Deep Seismic Surveys of a Dormant Subduction Zone in the Pacific Northwest United States", by W. J. Gwilliam, W. D. Stanley, G. V. Latham and J. K. Westhusing; U.S. Department of Energy, Morgantown Energy Technology Center Proceedings of the 1990 Natural Gas Research and Development Contractors Review Meeting, entitled "Exploration For Deep Source Hydrocarbons in Subduction Terrain of the Pacific Northwest" by Keith Westhusing and Steve Krehbiel, 22 p. 18 figs., available through the National Technical Information Service (NTIS) Publication No.DE9100203035; U.S. Department of Energy Morgantown Energy Technology Center Proceedings of the 1992 Natural Gas Research and Development Contractors Review Meeting, abstract, entitled "Deep Source Gas Seismic Survey - Washington State" by Steven C. Krehbiel, Mary Rafalowski-Guide and Mark H. Thomas, available through NTIS Publication No. DE92001278; American Association of Petroleum Geologists Bulletin vol. 76, no. 10, October 1992 paper entitled "The Southern Washington Cascades Conductor-A Previously Unrecognized Thick Sedimentary Sequence?" by W. D. Stanley, W. J. Gwilliam, Gary Latham, and Keith Westhusing, 16 p., 11 figs.


Tags: 1993, AAPG, DOE, Gas, Geochemistry, Geology, METC, MT, Morgantown Energy Technology Center, Oil, Open File Report 92-714, SEG-Y format seismic data, Types, UNIX, USGS, Washington, Well Data, geochemical, hydrocarbons, location, magnetotellurics, natural gas, petroleum, seismic line, subduction, velocity