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The pioneering endeavors that led to the discovery of Prudhoe Bay In the first of a two-part series, Gil Mull recounts Richfield’s early geological and geophysical exploration on the North Slope Alan Bailey PNA Contributing Writer
A combination of teamwork and perceptive leadership underpinned the discovery of the Prudhoe Bay oil field, according to veteran geologist Gil Mull. Mull was a member of the team of geologists and geophysicists that found North America’s largest oilfield. Today, he is a petroleum geologist with the Alaska Division of Oil and Gas.
In an interview with PNA, Mull described the events that culminated in first measured flow of oil from Prudhoe Bay State No. 1 well on March 12, 1968. The well tested at more than 1,000 barrels per day. Initial exploration The story of Prudhoe Bay really began with the discovery of oil by Richfield Oil Corp. on the Kenai Peninsula in 1957. That discovery triggered a flurry of exploration activity across Alaska, Mull said.
“In the summer of 1959 Richfield had its first geological field party on the North Slope,” Mull said. That field party did some general mapping of the area.
Richfield did no further work on the North Slope for three years. Then, Harry Jamison, who was directing exploration from Richfield’s Los Angeles office, pushed the idea of another geological field party on the North Slope: Jamison understood some of the geology of the North Slope and he knew about the oil seeps there.
“I guess that you could say that he had a sort of an intuition that it looked like a good prospective petroleum basin,” Mull said. Fieldwork in 1963 And so, on June 3, 1963, Jamison dispatched Mull and Gar Pessel from its Anchorage office and two other Richfield geologists from California to Umiat, in the northern foothills of the Brooks Range. At that time, Umiat boasted the only airstrip in the area.
Jamison gave the team a free hand to do whatever it deemed appropriate.
“There was not much in the way of specific instructions, other than just go out and map what we thought needed to be mapped and to get a feel for what the geology was,” Mull said. “There was very difficult communications back to town, so nobody was going to try to do a lot of orchestrating.”
Armed with U.S. Geological Survey North Slope data and the results of the earlier Richfield exploration, Mull and the team decided to focus on the area from Umiat south to the Brooks Range mountain front and eastward into the Alaska National Wildlife Refuge.
Covering such a wide area of Arctic wilderness in a three-month field season required fast work: a Cessna 180 aircraft and a Bell G2 helicopter provided field transportation.
The field team used the helicopter to reach the rock outcrops.
“Using the air photos the previous reconnaissance mapping and doing our own reconnaissance work we could locate where the good (rock) exposures were and land on the outcrop,” Mull said. The geologists would spend part of the day assessing the rocks at the outcrop. The team would then follow the outcrops by helicopter.
Mull enjoys vivid memories of flying in the Bell helicopter, an old, two-passenger design with a goldfish bowl bubble and an open lattice tail boom.
“It would cruise at about 60 and had a rate of climb not much faster than … you could climb a stairwell,” Mull said.
The team used the Cessna 180 to stage fuel caches and set up camp.
“(The helicopter) didn’t have much of a fuel range … so we worked from fuel cache to fuel cache,” Mull said. “We started off first with the ski plane, working off the frozen lakes, and after the lakes broke up the ski plane switched to floats.” Indications of oil The geology indicated the strong possibility of an oil discovery.
“We had seen an oil sand over in ANWR — a really good oil sand,” Mull said. “We had also seen oil sand in the river bank … at Sagwon.”
On Aug. 2 Gar Pessel, the co-party chief of the field team, sent an historic note to Ben Ryan, the district geologist for Richfield, and Leo Fay, the local project supervisor in Anchorage, summarizing the field party’s conclusions: “We have a good section with excellent reservoir possibilities and positive proof of the petroliferous nature of these sands. If one cannot get an oil field out of these conditions, I give up!”
In his note, Gar followed with the party’s recommendation that Richfield carry out a seismic survey to investigate the geological structures north of Sagwon where the surface rocks disappear beneath the North Slope coastal plain.
Ryan sent Pessel’s hand-written, yellow tablet page with a short covering memo to Harry Jamison in San Francisco. “Harry took (the note) upstairs to Richfield management and said ‘We’ve got to get a decision now, we’ve got to have a seismic crew this winter,’ ” Mull said.
Thanks to Jamison’s swift and decisive action, Richfield did indeed mobilize a seismic crew for the winter of 1963-64. The first seismic survey “The seismic crew started shooting long, north-south reconnaissance lines,” Mull said. They shot three lines, he said. “The second line … ran over a pretty good looking anticline, called Susie.” Susie was located just north of Sagwon, on the Sag River. Susie would later become the site of the first Richfield exploration well on the North Slope.
The Richfield geologists returned in the summer of 1964, to extend the field mapping west to Cape Lisburne. During the following winter the seismic crew shot more reconnaissance lines.
With the North Slope exploration by a number of major companies now in full swing, Richfield raised additional funds by selling half of its North Slope interest to Humble Oil (part of Standard Oil of New Jersey).
“Humble bought a half interest in everything that Richfield had gotten,” Mull said, “a half interest in the surface work, half interest in the seismic work, and in the federal leases that Richfield had acquired in the foothills, for what had to be the all-time best deal ever — $5 million.”
Humble then became a full participating partner, with its geologists and geophysicists joining in the subsequent field studies. Humble would later become part of Exxon, thus securing Exxon’s future involvement in North Slope oil production.
“In the second winter season, in 1964-65, with Humble now as a partner with Richfield, the seismic crew worked on north up towards the coast,” Mull said. “And one of the early lines they ran crossed a big structure, now called Prudhoe Bay.” Lease sales Exploration on the North Slope also spurred leasing activity — during the first season of seismic exploration, Richfield began a really aggressive campaign of picking up federal leases in the foothills, Mull said.
In the meantime, the state of Alaska “acquired its lands along the coast — thanks to Tom Marshall, the state’s only petroleum geologist — and started selling leases in 1964 and 1965.
“The state had its first lease sale in the winter of 1964 up in what is now the Colville area,” Mull said. BP and Sinclair picked up most of those leases, he said.
In the second state lease sale in July 1965, Richfield and Humble in partnership picked up most of the leases across the structure they had found at Prudhoe Bay.
BP bought most of the leases around the flanks of the structure, and Atlantic Refining acquired some leases down the southern flank of the structure.
At the time of the lease sales, none of the companies could foresee the scale of what they were about to find. Yet it turned out that the locations of the leases would have a profound impact on the ownership of the oil and gas that lay beneath the Arctic tundra.
The stage was set for one of the most remarkable finds in the history of North American oil exploration.
Editor’s note: See part two in the next weekly edition of PNA. The information in the article was given to PNA in an interview. It was also part of a presentation by Gil Mull on March 12 at the national meeting of the American Association of Petroleum Geologists in Houston. Mull gave the presentation in place of Harry Jamison who had to cancel because of illness in his family.
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