In June 1968, ARCO-Exxon completed the Prudhoe Bay State I well, discovering the largest oil accumulation in the United States. This discovery was the result of a 4-year seismic program which began in 1963. Prior to this time, and beginning in 1943, the U.S. Navy carried out a 10-year exploration program within Naval Petroleum Reserve 4. Small accumulations of oil and gas were discovered on NPR 4 during this period. Industry exploration started on the North Slope in 1958 with geologic field work. The first industry seismic work began in 1962. Initial emphasis was between the Colville and Canning Rivers on federal acreage within the foothills belt north of the Brooks Range. By 1963, each of the three predecessor companies of Atlantic Richfield (Atlantic Refining Co., Richf eld Oil Corp., and Sinclair Oil Corp.) were involved in separate geophysical exploration programs. North-south regional seismic lines and State of Alaska land availability resulted in shifting, in 1964, the exploration effort north to the Arctic coastal area. By this time both the Prudhoe Bay and Colville structures had been delineated. In December 1964, during the first state sale on the North Slope, Sinclair in partnership with British Petroleum (now Sohio-BP) leased the entire Colville structure. By mid-1965 additional seismic control had further defined the Prudhoe Bay structure. The critical state lease sale of July 1965 determined the eventual ownership of Prudhoe Bay field. It resulted in Richfield-Humble (now Exxon) buying the top tracts, with BP acquiring flank acreage. In Janua y 1967, ARCO-Humble acquired additional offshore tracts. Prior to the Prudhoe discovery well in January 1968, 10 wells had been drilled on the North Slope by industry without commercial success.

End_of_Article - Last_Page 634------------