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November 2008

Vol. 13, No. 46 Week of November 16, 2008

40 Years at Prudhoe Bay: Remembering the unsung heroes

The seismic crews and interpreters who crisscrossed the vast tracts of frozen tundra in the mid-1960s deserve special recognition

C.G. “Gil” Mull

For Petroleum News

Seismic crews who collected critical subsurface data and the specialists who interpreted this information are the unsung heroes who led to the discovery of the giant Prudhoe Bay oil field and most of the subsequent discoveries on the North Slope. Only in the Brooks Range foothills belt are outcrops continuous enough that anticlines and major faults can be mapped solely on the basis of surface data, but even there, seismic data is needed to resolve structural and some stratigraphic details in the subsurface. The small Umiat oil field, which was discovered by the U.S. Navy in the mid-1940s in the southeast corner of NPR-4, was found on the basis of surface mapping by United States Geological Survey and Navy geologists who mapped the structure on foot. They mapped the area after hearing of the small oil seeps at the base of Umiat Mountain from the nomadic Nunamiut Eskimos who had long known of their presence. However, subsequent exploration programs by the Navy and the oil industry began with surface geological mapping and then quickly continued with acquisition of geophysical data.

After the federal government released the first North Slope lands to exploration in 1958, many companies, including British Petroleum, Sinclair Oil & Gas, and Richfield Oil, sent surface parties north to evaluate the lands. BP and Sinclair, in partnership, mobilized a United Geophysical Co. seismic crew in 1962, and then drilled several relatively shallow wells on foothills anticlines.

The 1963 Richfield surface field party also realized that seismic data would be needed to explore the lands beneath the coastal plain north of the foothills outcrop belt, and this resulted in Richfield’s first seismic crew in the winter of 1963-64. This crew from United Geophysical was supervised by Charlie Selman, Richfield’s district geophysicist in Anchorage, and shot three north-south reconnaissance lines from the foothills north onto the coastal plain.

In addition to the crews from United Geophysical, other oil companies, including Atlantic Refining, also had seismic crews from National Geophysical Co. and Western Geophysical Co. operating in the winter of 1963-64. In the spring of 1964, Richfield added a second seismic crew, contracted from Western Geophysical.

Yet a third crew, from United Geophysical, was mobilized in the winter of 1964-65 to provide coverage to the north on lands to be selected by the State of Alaska following a partnership agreement with Humble Oil in the fall of1964. This crew shot the first lines across the Prudhoe Bay structure for Richfield-Humble, although other companies also saw the feature in their seismic data.

Map interpretations of the structure by geophysicists Paul Bolheimer, Rudy Berlin, and Pete Clara led to the final interpretation that was used for the 1965 state sale in which Richfield-Humble acquired its leases across the top of the Prudhoe Bay structure.






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