The geologist who helped lead the historical discovery of the Prudhoe Bay oilfield in 1968 and who carved a path for later discoveries that provided invaluable resources for the United States has passed.
Charles “Gil” G. Mull, died at age 86 from complications of Parkinson’s Disease in Salt Lake City on Oct. 3.
Known as a “pioneer” of Alaskan geology, Mull leaves behind a great number of AAPG peers and friends who, for decades, took inspiration from his passion for exploring Alaska’s North Slope and made careers in his footsteps.
Often called “a giant among us” with an “encyclopedic memory” of Alaskan outcrops, Mull was among the first group of modern North Slope explorers who battled extreme weather conditions in uncharted territory to find the resources needed by a country in a continuous hunt for fuel.
The 25 billion-barrel Prudhoe Bay oilfield ultimately lifted the economic status of Alaska and helped power a nation. It remains the largest conventional oilfield in North America and, at the time of its discovery, provided the United States with 25 percent of its oil reserves. The promising geology of the North Slope continues to attract explorers from all over the world.
Mull, an outdoorsman at heart, spent his 40-plus year career in the wilderness of the remote Brooks Range, carted from site to site by a Cessna 180 on floats or skis, and brought into the bush daily by a vintage helicopter with wooden rotor blades. During summer field mapping seasons, he lived in an 8-by-10-foot canvass tent, slowly piecing together a comprehensive geologic framework of the subsurface. His and others’ work helped lead to many subsequent discoveries that to date have produced more than 18 billion barrels of oil that continue to pump through the 800-mile Trans-Alaska Pipeline, constructed after Prudhoe Bay was found.
Oilfield of the Century
Born in 1935 in Edwardsville, Ill., Mull moved to Colorado in 1947, falling in love with the Southwest for its rocks – rich in geologic history. While at the University of Colorado in 1954, Mull changed his major from chemistry to geology, lured by the beauty of the Flatirons and longing for a career in the outdoors.
While earning his master’s degree, Mull found summer jobs in the Southwest as a geological field assistant with Richfield Oil Corporation, a small oil and gas company that sparked an exploration boom in Alaska after its Swanson River discovery near Cook Inlet in 1957. Richfield later hired Mull and sent him to Alaska in 1961.
Although much of the action was taking place near Cook Inlet, Mull and his mapping partner, Gar Pessel, were sent to the virtually unexplored North Slope in 1963 alongside senior geologists from major oil companies who had larger budgets and doctoral degrees. In a former interview, Mull said he always wondered why Richfield selected a pair of “punk kids” to map an area that some began to believe held the oilfield of the century.
Harry Jamison, who headed regional exploration in Alaska for Richfield, caught wind of the promising geology on the North Slope and believed Mull’s natural affinity for field mapping would help the company become more aggressive in its exploration.
Using data from the U. S. Geological Survey as a guide, Mull and Pessel compiled reconnaissance maps that conveyed the structural geology and stratigraphy of much of the eastern North Slope and Brooks Range. In fact, they identified high-quality oil source rocks and oil-saturated sandstones not previously reported by the USGS.
Upon identifying potential reservoir rocks, organic-rich shales and a prominent geologic structure that looked to be a viable trap, the pair convinced Jamison to send a seismic crew to image the subsurface. An unconformity that looked especially promising was found near a place few had heard of at the time: Prudhoe Bay.
In 1965, Richfield gobbled up the majority of leases in a state lease sale near this structural high. Richfield, after merging with the Atlantic Refining Company to become ARCO, drilled a wildcat well in 1967 in partnership with Humble Oil (now ExxonMobil). Around this time, Mull accepted a position at Humble Oil as a field and wellsite geologist, which placed him at the Prudhoe Bay State No. 1 well on Dec. 26, 1967. As the well was drilled, the sixth core sample Mull requested from the Sadlerochit Formation came up covered in porous sandstone and conglomerate.
“It had some nice features, to put it mildly,” Mull said. “Merry Christmas!”
A drill stem test confirmed his suspicions. Gas and fluids “flowed to the surface at a furious rate. It was like a rumble, a roar, like a jet plane overhead shaking the ground. It was obvious there was the potential for a major oilfield,” he recalled. “This flowed for eight to 10 hours. The flare burned for 24 hours. It was exciting.”
At this point, Mull could no longer make daily reports from the field by ham radio, for fear of interception. Instead, he made daily, 700-mile roundtrips by plane to Fairbanks or Barrow to convey his findings by telephone.
In May 1968, the Sag River State No. 1 well was drilled approximately 7 miles away and 400 feet structurally lower, confirming that Prudhoe Bay was a Persian Gulf-sized oilfield.
Prudhoe Bay made global headlines and jumpstarted ongoing exploration efforts on the North Slope still taking place with success today. It also generated billions of dollars in tax revenue for Alaska, providing an avenue for indigenous populations in Arctic Alaska to – for the very first time – build modern homes with running water, fire houses and schools.
After the discovery, Mull remained in the mountains, leading field parties and mapping the vast stretches of the North Slope from Point Hope to Canada.
“To me, the real excitement was going out and wandering around the hills to places nobody had ever been before and putting together a geologic map,” he said.
Hearing that he might be sent to Houston to run operations from a skyscraper, Mull dodged the office job and joined the USGS’s Branch of Oil and Gas Resources in California in 1975. Then, in 1977, when the USGS announced plans to explore the National Petroleum Reserve – Alaska, Mull returned to the Frontier State to continue his field mapping work, assessing oil and gas potential and working for the USGS in Anchorage.
He joined the Alaska Department of Natural Resources’ Division of Geological and Geophysical Surveys in 1981 to further the state’s assessment of its prolific resources. In 2001, he joined the Department’s Division of Oil and Gas. Throughout his career, he authored or co-authored an estimated 60 technical papers and maps on North Slope geology and was a mentor to dozens of geology graduate students at the University of Alaska Fairbanks.
He returned to his Southwestern roots in 2003 when he retired with his wife, Yvonne, to Santa Fe. Yet as he said to the Petroleum News, an Alaskan publication, “I tell people that I’m not retiring from geology, I’m just moving my files to a different location.”
His intentions, which he kept well into his 80s – even after a diagnosis of Parkinson’s – were to continue geological consulting and to work with the USGS as it digitized his geological maps.
He gave his collection of oil samples from Alaskan exploration wells, including Prudhoe Bay, to the USGS, which published the results of their geochemical analyses in 2021 to help further exploration in the state.
When the oil and gas industry began enduring intense criticism, Mull stressed that the industry’s benefits to humanity should not be disregarded.
“In general, we’d have to say it’s oil and gas that fuels the country and keeps the country going,” he said. “Petroleum supplies are to the overall benefit of the public as a whole – not just the companies.”
Making History and Memories
The geological community of Alaska and beyond consider Mull a legend and have long held on to photos and stories of the man who, rock by rock, permanently wove himself into the Alaskan landscape.
After his death, an outpouring of messages through numerous channels revealed the many ways he inspired colleagues and friends:
“His expertise on the North Slope is basically unrivalled. From that standpoint, he occupies a unique niche in the geological fraternity. We remained close friends throughout his career, and in the last 15 years or so, revisited southern Utah almost every year to visit rock art sites and enjoy the geology and scenery of that unique area. Gil was a giant of his profession, but a gentle and humble friend.” – Harry Jamison, retired, former president of ARCO Exploration Co.
“Always such an ox and powerhouse. He had an exceptional life and is the perfect example of someone who would have lived on happily forever if given the choice to be immortal.” – Dolores van der Kolk, senior lecturer at Texas State University.
“Upon encountering Gil, it took most people about 30 seconds to realize that he was an honest, humble, authentic person. Gil had no airs about him, he didn’t care about titles or honorifics. He valued passionate, hard work and he loved being with others.” – Tom Homza, senior staff geologist at Shell Exploration & Production Company.
“He had an almost photographic memory regarding details of outcrops he’d visited in the past, including outcrops he saw only once 30 to 35 years earlier. He had a natural way of making you feel like your thoughts and ideas were valuable and mattered.” – David LePain, petroleum geologist, Alaska DGGS.
“His enthusiasm and energy in the field and his encyclopedic knowledge of Brooks Range-North Slope outcrops was amazing. If you wanted to see and walk out a critical stratigraphic relationship, just ask Gil. He would say something like, ‘Go up “X” river, take the second drainage on the right, and look along the third ridge.’” – Arlene Anderson, retired geologist, ExxonMobil.
“I was always impressed, no questions asked, by his prodigious works and breadth of knowledge.” – Ken Bird, retired supervisory research geologist, USGS.
“Even in some of his last days when I mentioned Gil’s discovery of Prudhoe Bay to one of his health aides, Gil was careful to say he was part of the team that had an incredible adventure. Those Alaska days were memories he highly cherished.” – Marjorie Chan, distinguished professor of Geology, University of Utah.
“I was awed by his dual accomplishments of being a well-site geologist for the Prudhoe Bay discovery well and the guy who first recognized the regional tectonic importance of large-scale northward-directed thrusting of the Endicott Mountains allochthon in the Mt. Doonerak fenster in the central Brooks Range. I think Gil’s spirit still lives in northern Alaska someplace and I will always picture him wearing a puffy, red down jacket at a field camp on the tundra smiling, and in a rising voice saying his welcoming greeting ‘howdy-howdy-howdy!’” – Thomas Moore, scientist emeritus and retired research geologist, USGS.
“Gil had unmatched knowledge and experience in the geology of northern Alaska, but what truly made him unique was his passion to selflessly share those insights with any student or colleague. Gil had a keen appreciation for beauty, whether it was laying down on the tundra to photograph diminutive “belly flowers” or passionately describing the intricate weave of a Navajo basket.” – Marwan Wartes, geologist, Alaska DGGS.
“Already a giant of Brooks Range geology in his own right, Gil became my time traveler, a living link to the generation of giants who preceded him. In the nearly 30 years that were to follow, I never tired of his tales of the geology or the departed souls who unraveled the secrets.” – Greg Wilson, retired exploration manager, ConocoPhillips Alaska, Inc.
“Gil Mull was a mentor and friend to an entire generation of North Slope geologists. He was a great field geologist and stratigrapher who believed that to really understand our planet’s history and map its resource potential one had to invest their time with the rocks, no matter how remote the outcrop. Both literally and metaphorically, Gil’s legacy left giant footprints on Alaska.” – Mark Myers, consulting geologist and commissioner with the U.S. Arctic Research Commission, and former director of the USGS, State Geologist, director of the Division of Oil and Gas of the Alaska Department of Natural Resources, commissioner of the DNR, vice chancellor for Research at the University of Alaska Fairbanks and field geologist.
“The company (Richfield) had thrown us together in one of the most intense working relationships I could imagine. During those years, we were mapping the geology, writing lengthy geologic reports and producing maps of our exploration for the company. Gil’s patience with the demanding process of writing reports and coming to agreement about our mapping and conclusions about the geology is the one thing that I remember most about this part of our careers. For that, I will be ever grateful.” – Gar Pessel, retired geologist, Alaska DGGS, former professor of field geology at the University of Alaska Fairbanks.
“For many years after he retired, when planning field work in a new area, I would call Gil and ask if he could recommend specific sites that might benefit my objectives. Invariably, a few days later I would receive an email with an 18- or 25-page attachment containing typed observations and interpretations, scans of 20- or 40-year-old field notes, and annotated topographic maps and air photos. These always were accompanied by a quote, something like this one from 2007: ‘This is based on an old map that Gar Pessel and I did years ago, but it was done when our knowledge of regional stratigraphic trends and structural style was rudimentary at best, so I urge great caution in using any of that old mapping.’ His modesty was obvious but, of course, those notes and interpretations were among the most useful tools we carried to the field each year.” – David Houseknecht, senior research geologist, USGS.
“Although it’s risky, exploration is still the heart of science. And science is the heart of exploration.” – Gil Mull.