Alaska: A History in Geophysics

An understated masterpiece

The exploration expeditions in Alaska beginning in the late 1800s trump most other places in the world: The nuances of geology and geophysics required to find oil and gas in America’s last frontier tell the technical side of the journey, but mix in a history of Native Americans and Russians leading explorers to oil seeps, Hollywood investors, sled dog exploration teams, and rigs disassembled and transported by air for the first time – and science inevitably becomes a bit of lore.

Exploration: An Understated Masterpiece

Oozing from the ground, natural oil seeps marked the beginning of geological and geophysical study in Alaska for purposes of mapping its unknown structures and for finding “black gold” after the Klondike Gold Rush reached its peak in the late 1800s. Oil seeps prompted the formation of the Alaska Petroleum Co. and Alaska Oil Co., which began drilling at Oil Bay and Dry Bay off the Alaska Peninsula near the turn of the 20th century.

Later, U.S. Geological Survey (USGS) exploration teams dispersed across the icy land, sometimes taking four months to arrive at their starting location to record regional topography, the generalized distribution of major rock formations, and fossils, said Gil Mull, an AAPG member and retired employee of the Alaska Division of Geological & Geophysical Surveys and Division of Oil and Gas, after an earlier career with the USGS and the oil industry.

Eventually, their work led them to the more hostile climate of the North Slope of the Brooks Range north of the Arctic Circle. The USGS’ first geological transect across the Brooks Range began in 1901.

In the summer, they gathered information on outcrop distributions and rock formations on the mountains. In the winter, they walked behind a team of sled dogs that pulled their gear to the crest of the range and waited until spring for rivers to flow again. They boarded canoes, floated down the Anaktuvuk and Colville rivers, and gathered geological data along the Arctic Coast – a virtually unexplored wilderness, Mull said. USGS geologists F.C. Shrader and W.J. Peters confirmed the presence of coal in a 1904 report.

“These guys were incredible, exploring in an area in which little was known, even of the geography and topography. How did they get to these remote places?” Mull commented. “They spent months in the field in temperatures of 40 and 50 degrees below zero, isolated and living off the land. They titled their report simply, ‘A Reconnaissance in Northern Alaska.’ I find that a masterpiece of understatement.”

The First Maps

Surface mapping produced the first geologic map of Alaska in 1904 by Alfred H. Brooks, after whom the Brooks Range was named.

It confirmed the presence of a sedimentary basin beneath the North Slope. The presence of petroleum was confirmed four years later after USGS geologist Ernest de Koven Leffingwell collected oil from a major seep on the coastal plain near Cape Simpson.

Disappointment loomed despite the discovery, as echoed in the words of Brooks: “Were the region not so inaccessible, it would certainly be worthwhile to investigate these occurrences, but as it is, even if petroleum is found, it could not be brought to market.”

Leffingwell continued to explore from 1907 to 1914 on a privately funded expedition in what today is the Arctic National Wildlife Refuge. His final report, which was based on bedrock geologic mapping, attracted the attention of the U.S. Navy.

During World War I, the Navy, which had converted its warships from coal to oil, had concerns about dwindling fuel supplies. Based on Leffingwell’s reports of oil seeps, the Naval Petroleum Reserve No. 4 (NPR-4) was established in an area near the central and western North Slope beginning in 1923.

USGS reconnaissance field teams continued to explore NPR-4 in a systematic approach of field mapping.

“Some of these explorations, in an era before the availability of any detailed maps, air support or motorized tundra transportation, were sagas of discovery, adventure and survival,” Mull said.

The work led to a broad outline of the geological framework of northwestern Alaska and became the base for a second geologic map of the state produced in 1939 by the USGS.

Seismic Debuts in Alaska

When World War II commenced, the Navy once again looked to Alaska for fuel, with further assistance from the USGS.

During and immediately after World War II, single-fold seismic data was acquired in Alaska for the first time. Blasts of dynamite sent shock waves into the earth and revealed how the subsurface of rock strata beneath the Arctic coastal plain were folded and faulted, Mull said.

This technology relied on one shot and one receiver with no folding or stacking, said Tom Plawman, an AAPG member and geophysicist with BP in Alaska. In those days, seismic data was recorded on paper.

“There was a time when a computer in the seismic industry was a person,” he said. “Processing was done graphically with a pencil and paper. It was a very different world.”

All the technical information gathered from field mapping and seismic data during the 1940s and 1950s was published in USGS professional papers, technical reports and journal articles – all invaluable to the next wave of explorers: the commercial oil industry.

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The exploration expeditions in Alaska beginning in the late 1800s trump most other places in the world: The nuances of geology and geophysics required to find oil and gas in America’s last frontier tell the technical side of the journey, but mix in a history of Native Americans and Russians leading explorers to oil seeps, Hollywood investors, sled dog exploration teams, and rigs disassembled and transported by air for the first time – and science inevitably becomes a bit of lore.

Exploration: An Understated Masterpiece

Oozing from the ground, natural oil seeps marked the beginning of geological and geophysical study in Alaska for purposes of mapping its unknown structures and for finding “black gold” after the Klondike Gold Rush reached its peak in the late 1800s. Oil seeps prompted the formation of the Alaska Petroleum Co. and Alaska Oil Co., which began drilling at Oil Bay and Dry Bay off the Alaska Peninsula near the turn of the 20th century.

Later, U.S. Geological Survey (USGS) exploration teams dispersed across the icy land, sometimes taking four months to arrive at their starting location to record regional topography, the generalized distribution of major rock formations, and fossils, said Gil Mull, an AAPG member and retired employee of the Alaska Division of Geological & Geophysical Surveys and Division of Oil and Gas, after an earlier career with the USGS and the oil industry.

Eventually, their work led them to the more hostile climate of the North Slope of the Brooks Range north of the Arctic Circle. The USGS’ first geological transect across the Brooks Range began in 1901.

In the summer, they gathered information on outcrop distributions and rock formations on the mountains. In the winter, they walked behind a team of sled dogs that pulled their gear to the crest of the range and waited until spring for rivers to flow again. They boarded canoes, floated down the Anaktuvuk and Colville rivers, and gathered geological data along the Arctic Coast – a virtually unexplored wilderness, Mull said. USGS geologists F.C. Shrader and W.J. Peters confirmed the presence of coal in a 1904 report.

“These guys were incredible, exploring in an area in which little was known, even of the geography and topography. How did they get to these remote places?” Mull commented. “They spent months in the field in temperatures of 40 and 50 degrees below zero, isolated and living off the land. They titled their report simply, ‘A Reconnaissance in Northern Alaska.’ I find that a masterpiece of understatement.”

The First Maps

Surface mapping produced the first geologic map of Alaska in 1904 by Alfred H. Brooks, after whom the Brooks Range was named.

It confirmed the presence of a sedimentary basin beneath the North Slope. The presence of petroleum was confirmed four years later after USGS geologist Ernest de Koven Leffingwell collected oil from a major seep on the coastal plain near Cape Simpson.

Disappointment loomed despite the discovery, as echoed in the words of Brooks: “Were the region not so inaccessible, it would certainly be worthwhile to investigate these occurrences, but as it is, even if petroleum is found, it could not be brought to market.”

Leffingwell continued to explore from 1907 to 1914 on a privately funded expedition in what today is the Arctic National Wildlife Refuge. His final report, which was based on bedrock geologic mapping, attracted the attention of the U.S. Navy.

During World War I, the Navy, which had converted its warships from coal to oil, had concerns about dwindling fuel supplies. Based on Leffingwell’s reports of oil seeps, the Naval Petroleum Reserve No. 4 (NPR-4) was established in an area near the central and western North Slope beginning in 1923.

USGS reconnaissance field teams continued to explore NPR-4 in a systematic approach of field mapping.

“Some of these explorations, in an era before the availability of any detailed maps, air support or motorized tundra transportation, were sagas of discovery, adventure and survival,” Mull said.

The work led to a broad outline of the geological framework of northwestern Alaska and became the base for a second geologic map of the state produced in 1939 by the USGS.

Seismic Debuts in Alaska

When World War II commenced, the Navy once again looked to Alaska for fuel, with further assistance from the USGS.

During and immediately after World War II, single-fold seismic data was acquired in Alaska for the first time. Blasts of dynamite sent shock waves into the earth and revealed how the subsurface of rock strata beneath the Arctic coastal plain were folded and faulted, Mull said.

This technology relied on one shot and one receiver with no folding or stacking, said Tom Plawman, an AAPG member and geophysicist with BP in Alaska. In those days, seismic data was recorded on paper.

“There was a time when a computer in the seismic industry was a person,” he said. “Processing was done graphically with a pencil and paper. It was a very different world.”

All the technical information gathered from field mapping and seismic data during the 1940s and 1950s was published in USGS professional papers, technical reports and journal articles – all invaluable to the next wave of explorers: the commercial oil industry.

In the 1950s, areas near Cook Inlet and the Kenai and Alaska peninsulas were explored as well.

An observation made by an air photo interpreter working for Richfield Oil Corp. left the gates for exploration wide open. The interpreter noticed an anomalous oxbow-like bend in the Swanson River in a heavily timbered area on the Kenai Peninsula. It suggested the possibility of a significant structure beneath the surface. In a “gutsy” move, Richfield shot a single, short seismic line running east to west by helicopter, Mull said. It revealed a subsurface anticline that corresponded with the stream anomaly.

So, a well was drilled.

On July 23, 1957, the Anchorage Daily Times printed the first of many newspaper-selling headlines: “Richfield Hits Oil.”

The 200-million barrel discovery “really got the attention of everyone,” said Mull, who would eventually work for Richfield as a geologist in the 1960s.

“Companies had field parties all over Alaska looking for oil,” he said.

Hollywood came to Alaska, too.

In the 1950s, famous Hollywood investors included Walt and Roy Disney, Mae West and Boris Karloff, said Robert B. Blodgett, an AAPG member and consulting paleontologist in Anchorage. In a March 19, 1957 article in the Anchorage Daily Times, it was reported that Karloff flew to the lower Cook Inlet to inspect operations of the Havenstrite Drilling Company, owned by Russell Havenstrite, a multi-millionaire Californian and pioneer Alaska oil explorer.

Head North, Young Man

The Swanson River discovery prompted the U.S. Department of the Interior’s Bureau of Land Management to allow acquisition of land on the North Slope for federal and state lease sales beginning in 1958, according to a geophysical case history written by geophysicists R.N. Specht, A.E. Brown, C.H. Selman and J.H. Carlisle (Specht et al) in 1986. During the next three years, seven oil companies made the tumultuous journey north. Some acquired a substantial amount of federal acreage near the Colville River delta and in the foothills of the Brooks Range.

In 1959, after Alaska became a state, it began selecting roughly 100 million acres – including 1.5 million acres on the Arctic Coast – for the sale of leases that could provide revenue for Alaska.

Despite the North Slope’s challenging climate, major oil companies committed to long-term exploration there. Reconnaissance surface geological field parties, which were dropped off and picked up by helicopters, operated from tent camps on lakes scattered through the foothills and northern flank of the Brooks Range, according to Specht et al. USGS maps served as the framework for their additional surface and stratigraphic studies.

By the late 1950s, sufficient geological and geophysical data had been gathered to establish a broad outline of the general distribution of the rocks on the North Slope. However, that wasn’t enough to strike oil. Companies needed to know if the rocks had structural traps with reservoir potential. In the early days of exploration, the USGS did not gather a substantial amount of information on porosity, permeability and grain size – characteristics needed to help determine reservoir potential. Bringing seismic into the picture allowed the players to map structure and increase the odds of a discovery.

In 1962, BP and Sinclair Oil began the first seismic work performed by industry on the North Slope with a geophysical crew at Umiat. Atlantic Petroleum began seismic operations at the South Ocean Point a year later.

Initially, Richfield was hesitant to perform seismic, Mull said. It was costly, and the North Slope’s potential for large accumulations remained in question. However, Harry Jamison, then exploration supervisor for the Pacific Northwest and Alaska for Richfield, made the call when he read a note on yellow tablet paper from field crews insisting that seismic was needed.

“That was one of the advantages of working for a smaller company,” Mull said. “Decisions could be made very quickly.”

Old Technology, New Finds

Although common depth point (CDP) shooting had just been developed and was being used in other places in the 1960s, the seismic used on the North Slope was the “old-style” single-fold shooting, leaving interpreters to battle with noise interference. During the summer, thawed conditions produced poor geophone coupling and high noise levels from vegetation movement caused by the wind. In addition, “ice breaks,” or abrupt fracturing of the permafrost, caused additional noise. The most serious problem was interpreting the permafrost velocity effect that distorts seismic reflections, Plawman said. Before drilling, reflection identification was made strictly by educated guess, he added.

It was soon learned that seismic data was best acquired in the winter. Winter conditions also prevented heavy equipment from tearing up Alaska’s tundra, which became soggy in the summers, and damaging the underlying layers of permafrost.

Despite its issues, seismic was the best technology available, and its use was eventually extended north across the coastal plain to the Beaufort Sea.

Lease sales allowed large companies such as BP, in a partnership with Sinclair, to buy significant amounts of acreage. In 1963, BP and Sinclair shot the first line across a location thought to be very obscure at the time: Prudhoe Bay. They completed a seismic grid survey that was 17 miles by 17 miles.

Richfield and Humble Oil (now Exxon) signed a joint exploratory agreement, and by the end of 1964 the companies had acquired sufficient seismic control to delineate two major structures on state acreage: the Colville River delta and Prudhoe Bay. The seismic reflections in both structures roughly correlated with the existing stratigraphic framework, Mull said.

In a 1964 state lease sale, BP and Sinclair acquired a large tract on the Colville structure. In a subsequent sale, Richfield and Humble Oil acquired the majority of leases on the crestal area of the Prudhoe Bay structure, while BP – bidding alone – bought the majority of leases on the flank of the structure, Mull said.

In 1966, BP and Sinclair drilled a deep well near the Colville delta. A dry hole produced much disappointment. In fact, it is rumored that one discouraged manager offered to “drink all the oil that would ever be found on the North Slope,” as published in an AAPG paper by W.D. Masterson and J.T Eggert in 1992.

On the Brink of Discovery

About the same time, Richfield – now ARCO after it merged with Atlantic Petroleum in 1966 – and Humble flew in a rig from Fairbanks in a manner unlike ever before. They disassembled the rig, loaded it on a C-130 Hercules cargo plane they leased from the U.S. Air Force, along with the entire drilling camp, drill pipe, casing and supplies, and flew to the North Slope.

The operation required 80 roundtrips.

Mull was one of the well-site geologists for ARCO and Humble’s first well, the Susie No. 1, in the Brooks Range foothills about 60 miles south of Prudhoe Bay.

Susie turned out to be a dry hole and was abandoned, and the rig moved by a “cat train” northward to a drill site on the Prudhoe Bay structure.

In the winter of 1967-68, ARCO and Humble drilled the Prudhoe Bay State No. 1 well.

Working as one of the well-site geologists, this time for Humble, Mull recalled a spectacular drill stem test that produced a strong flow of natural gas from the thick and prolific reservoir in the Sadlerochit Formation the day after Christmas.

Drilling continued and in the spring showed that the formation contained both oil and gas. A long seven miles away and 400 feet stratigraphically lower than the discovery well, the Sag River State No. 1 well was drilled that same winter by the ARCO and Humble partnership, hitting the jackpot.

It was official: Prudhoe Bay was a world-class oil field.

Newspapers across the country heralded the news on their front pages. “The wildcat well, known as Prudhoe Bay State No. 1, is the first commercial oil discovery on the bleak Arctic Slope, and the announcement spurs hope of the beginning of a new oil boom for Alaska,” read an article in the Feb. 16, 1968 Anchorage Daily Times.

Needed for production were equipment for airstrip construction, camp expansion, construction equipment, additional aircraft, fuel supplies, seismic crews, drilling rigs, security measures and a host of other items – all of which were brought in by air or cat train around the clock for days, Mulls recalled.

Production, however, did not begin until 1977 because of Prudhoe Bay’s remote location and the need for the TransAlaska Pipeline to be built to transport the oil to Valdez.

Luck vs. Science

While some attributed the discovery to luck, Jamison, who served as Alaska district manager for ARCO at the time of the discovery, had other opinions.

In a speech he prepared in 2008 for a celebration of the 40th anniversary of the Prudhoe Bay discovery, he wrote, “I knew we had been lucky, but I also knew our good luck was based on 10 years of excellent exploration, land acquisition efforts, logistical and operational know-how and management level support all the way to the top … We gave ourselves the opportunity for serendipity through hard, intelligent, persevering work and the guts to back our collective judgment. And it paid off.”

The Prudhoe Bay oil field became the largest in North America with an estimated 16 billion barrels of total recoverable oil, overshadowing the East Texas oil field by twice the amount, comprising an estimated 25 percent of the nation’s oil reserves.

“The event kicked off the wave of exploration and discovery on the North Slope and adjacent offshore areas that continue today,” Mull said. “Prudhoe Bay now has produced more than 13 billion barrels of oil and its 26 trillion cubic feet of natural gas await a pipeline to markets.”

Prudhoe Bay was initially discovered using single-fold seismic technology. However, after the discovery, there was an increased incentive to bring better technology to Alaska to help guide development of the field, Plawman said.

Additional wells were drilled to help confirm the size of the field as well as shooting more modern 2-D CDP over the field. Geophysical Service Inc. (GSI) shot the first CDP line over Prudhoe Bay in 1969.

Seismic data also helped lead to the discovery of the Kuparuk River oil field on the North Slope in 1969. It became the second largest oil field in North America and produces approximately 230,000 barrels of oil per day with an estimated 2 billion barrels of recoverable oil reserves.

Kuparuk was discovered by Sinclair Oil

at the Ugnu No. 1 well, named for the nearby Ugnuravik River.

Make Way for the Modern

The first 3-D seismic performed on the North Slope was the Gas Cap 3-D Survey at Prudhoe Bay in 1977, Plawman said.

“Initially, 3-D was very expensive technology. It was mainly used to shoot known oil fields in the development drilling process. It wasn’t used for exploration because that was too speculative,” Plawman said.

“You had to already know you had a money maker.”

With time, however, the acquisition and processing of 3-D seismic data improved and became less expensive, making it more feasible to use as an exploratory tool.

“3-D has gone from being a special thing for big companies with major discoveries like Prudhoe Bay to where even relatively small companies can use it today,” Plawman said.

Today, using 3-D seismic to explore Alaska’s North Slope is a mainstream activity, he added. He suspected companies are looking for another Alpine Field – a good-sized field with a subtle trap, west of Prudhoe Bay and Kuparuk.

Amplitude versus offset, a variation in seismic reflection amplitude, also is widely used for exploration on the North Slope. And, 4-D seismic is now being used in Alaska by some companies to guide development of known oil fields on the North Slope, Plawman said.

Waning Winters

While technology used in exploration may be advancing, weather patterns are becoming more challenging.

“Climate change is a controversial issue, but there is no question that the Arctic is getting warmer,” Plawman said. “It’s had some interesting impacts on geophysical work.”

Namely, the time window for shooting onshore seismic in the winter season is becoming narrower, making it more difficult for companies to mobilize their crews and complete their surveys. Shooting seismic naturally becomes more risky when windows of time shrink in an area where shooting seismic is more expensive, as equipment and people must be transported to remote areas and appropriately weatherized.

On the other hand, the shrinking summer sea ice has made offshore seismic easier to acquire, Plawman said.

On a more positive note, some technology has made shooting seismic during the winter less dangerous. Decades ago, crews performed “hard water surveys” by driving seismic vibrators on the sea ice. This was done to tie onshore seismic data to offshore marine seismic data. As the vibrators moved farther from the coast, the ice became thinner.

Plawman recalled an incident in 1985 when a 2-foot-wide lead on the ice, which was covered in snow, opened up during the night, unbeknownst to the seismic crew. One of the geophone crew members accidentally stepped into the crack and fell in to his waist before catching himself.

“As far as I know, nobody ever died doing those ice shoots, but there were certainly some close calls,” he said. “I recall hearing a story that GSI once lost a cat when it broke through the ice. The driver escaped before the cat completely sank, as all the vehicles have an escape hatch in the roof. I don’t know of more details about that incident. It’s just part of the ‘oral tradition’ of North Slope exploration.”

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