Exploring the World
Contributed by Mark Mau and Henry Edmundson
Industrial growth following World War I and the proliferation of the automobile caused world oil consumption to increase dramatically in the 1920s. Oil companies began to expand their horizons and to do that they needed geologists with fresh ideas. As Wallace Pratt, the first geologist hired by Humble Oil, famously put it, “Where oil is first found, is, in the final analysis, in the minds of men.”
Since the 1880s, the anticlinal and salt doctrine had ruled rather sweepingly in the oil field. For example, in 1910 Frederick Gardner Clapp, a geologist working for the USGS, published an article entitled “A Proposed Classification of Petroleum and Natural Gas Fields Based on Structure.” This touched on anticlines and salt domes, but that was all.
A decade later things started to change. In March 1919, Johan August Udden, the Swedish-born director of The University of Texas’s Bureau of Economic Geology, spoke on “Oil Bearing Formations in Texas” at the AAPG annual convention in Dallas and expounded on two types of petroleum traps that thus far had received little attention—fault traps and stratigraphic traps, which he called “edged sands.”
Fault traps are created by a faulting movement of the earth, where two adjacent strata slip or slide against each other so that oil or gas gets trapped on the underside of the fault. Stratigraphic traps on the other hand are formed as a result of lateral and vertical variations in the reservoir rock that limit the movement of fluids. Udden was the first to recognize the importance of these two breeds of trap. Indeed, the discipline of stratigraphy developed into a central pillar of petroleum geology and spawned the discipline of petrology—the study of mineral content, grain size, texture color and fossil content.
The idea of stratigraphic traps went back to pioneering petroleum geologist and engineer John Franklin Carll who was relatively unrecognized during his lifetime. In the 1880s, Carll first articulated how stratigraphy trapped oil. Drawing upon well samples and his own field work, he constructed and published maps of the Pennsylvanian Venango Third Sand, the formation at a very shallow depth where Colonel Drake had struck oil in 1859, illustrating how oil accumulated in subsurface stratigraphic layers of sand and not for reasons related to structures such as anticlines or salt domes. Carll created some of the first cross-sectional maps, depicted from a side perspective and showing how strata are deposited and positioned relative to each other.
If Udden’s 1919 address had planted the germ of an idea in people’s minds, it was geologist Arville Irving Levorsen who gave stratigraphy the push it needed in his 1936 AAPG presidential address “Stratigraphic versus Structural Accumulation.” Levorsen emphasized the importance of stratigraphic traps, ensuring that this terminology soon became as essential to the language of petroleum geology as the word anticline. In February 1945, Stanford University appointed Levorsen professor of geology, an example of the rising importance played by petroleum geology in academia.
The First Discoveries in Saudi Arabia
One of the early geology students at Stanford was Max Steineke, a son of German immigrants who had settled in Oregon. Steineke graduated in 1921 and gained experience exploring for oil in California, Alaska, Canada, Colombia and New Zealand for Standard Oil of California (SOCAL, later becoming Chevron). In 1934, he was recruited to join a small team of geologists in Saudi Arabia. The previous year, King Ibn Saud had granted an oil concession to SOCAL, so it formed a new subsidiary, the California-Arabian Standard Oil Company (CASOC), the predecessor of Aramco, to explore for oil and gas in the vast desert country. The geology of Saudi Arabia could only be guessed at. Camel trips across the interior during World War I and the 1920s by Harry St. John Bridger Philby provided some insight. Collections made on these early travels indicated the presence of lower Kimmeridgian and Callovian carbonates, both respectively forming part of the late and middle Jurassic period. Geologists could surmise that these Jurassic rocks, were deposited in shallow waters because of fossil evidence and the widespread occurrence of evaporites, minerals caused by seawater evaporation. It was clear that at some point the sea had covered large portions of the Arabian shield.
Already in October 1933, the first two CASOC geologists in Saudi Arabia, Bert Miller and Krug Henry, had reconnoitred the limestone hills of Jebel Dhahran on the coast of the Arabian Gulf in eastern Saudi Arabia. They promptly found a favorable structure which they named the Dammam Dome, a geologic structure Miller and Henry recognized as a salt dome from their experience in the US Gulf Coast. The dome rose gently above the flat topography of the Arabian coastal plain and comprised a number of hills up to 350 feet in elevation. Early in March 1934, Richard Kerr—pilot, aerial photographer and geologist—arrived with an airplane specially designed and built by the Fairchild Aviation Corporation, New York, to conduct aerial reconnaissance to supplement the field work. Kerr took pictures of the Dammam Dome from the air while Henry and colleague J.W. “Soak” Hoover finished detailing the structure on the ground and staked a location for a test well in early June before the onset of the hot Arabian summer. Hoover noted in his diary for June 5, 1934, that they found organic-rich shale and marine fossils on one of the long, low hills of Dammam Dome, indicators that held out some possibility of an oil find. The first test well was spudded in April 1935 and drilled to a depth of 3,203 feet, resulting in some oil shows but nothing to get excited about.
Despite this early work, the task in Eastern Arabia remained daunting. The CASOC geologists made gravity surveys, benefiting from a recently developed, much simpler and faster gravity instrument than the cumbersome torsion balance. Yet, the bulk of the exploration work consisted of ordinary field geology. When Max Steineke arrived, he crossed the Arabian Peninsula in both directions, carefully surveying the landscape as he went. The information he and his party gathered became the basis for all future geologic profiles of the country. In 1936, Steineke was made CASOC chief geologist.
CASOC still believed Dammam to be the most attractive structure since it was close to a productive zone in the neighboring island of Bahrain. In December 1936, following five more dry wells at Dammam Dome, Steineke urged the drillers to go deeper with the seventh well. Throughout 1937 and into early 1938 there were still no positive results, and Steineke had to go back to San Francisco to persuade management to continue funding the Arabian operations. A meeting was scheduled for March 4, 1938, and on the very same day Dammam no. 7, now at 4,727 feet in the Upper Jurassic Arab Formation, came in at 1,585 barrels of oil per day. This discovery later became known as the “Prosperity Well.”
CASOC management were now willing to risk more investment around Dammam and decided to focus on a nearby area where a test well, Abu Hadriyah no. 1, was being drilled. In October 1938, the seismic company GSI was contracted by CASOC to obtain seismic reflection data around Abu Hadriyah, and their results indicated the potential for a vast reservoir below. However, the report was met with skepticism, and the CASOC production department wanted to abandon the well. Some even saw this as a good opportunity for getting rid of the geophysicists. But parent company SOCAL’s management had earmarked cash for the Abu Hadriyah well. By the early days of 1940 the well had reached 8,656 feet, and still there was no hint of oil. The bit cut its way down past 9,000 feet, and the hole remained dry.
About this time, George Cunningham, exploration manager of SOCAL, and Cecil Green, who supervised GSI field crews worldwide, arrived for a visit of the Saudi operations. Green watched the drilling and later recalled, “You might go that deep at home, but certainly you wouldn’t go all the way to Saudi Arabia and drill 9,000-foot holes looking for oil. It was too expensive.” In mid-February of 1940, Cunningham and Green proceeded eastward to visit SOCAL operations in India and Indonesia. While they were in the Indus basin, two telegrams arrived. Cunningham read the first: “Please return to Saudi Arabia before going on to Indonesia for the express purpose of making a post-mortem study of the loss of US$ 1.5 million on the dry hole at Abu Hadriyah.” Cunningham was crestfallen and Green didn’t feel any better. “Why don’t you read the other one?” suggested Green. Cunningham opened the second telegram. It was from Steineke and read: “Abu Hadriyah well just came in at 15,000 barrels per day at 10,115 feet.” GSI’s reflection survey had been vindicated, and Green remembered the advice Everette Lee DeGolyer had once given him: “Use all the best geology you can and all the best geophysics. But be sure to carry a rabbit’s foot in your pocket.”
Steineke died prematurely aged 54 in 1952, having discovered in 1948 the largest oil field in the world, the incomparable Ghawar field that produces today as abundantly as it did when first put on production.
Of Doodlebuggers and Roving Geologists
In the 1940s and 1950s, seismic exploration was still a job that demanded great personal flexibility. “It was common for my father to come home on Friday and say, ‘We’re moving on Monday,’” recalled Leon Thomsen, a geophysicist at the University of Houston, “So, we packed up and moved. It never occurred to me to complain, we just did it. I moved fourteen times before I left home.”
Like all geophysicists of that era, Leon’s father, Erik Thomsen, was known as a “doodlebugger,” a term borrowed from the dowser who uses a simple divining rod to locate subterranean water, minerals, oil or gas. In 1951, Erik Thomsen’s wife wrote, “The doodlebugger of earlier times claimed occult powers in the matter of locating oil by the twitch of his stick. The most modern equipment has not been able to erase the old name, and seismic doodlebuggers cling to it with stubborn affection.”
In contrast, the job of the exploration geologist was well established. Covering large areas in the field, examining outcrops and collecting rocks characterized their daily routine. Many oil companies had reconnaissance geology groups. The most famous worked for Standard Oil Company of New Jersey and was called the “Rover Boys,” a nickname derived from the official “Roving Geological Assignment Worldwide.” The Rover Boys were an elite group of geologists, carefully selected and trained. From the late 1940s to the mid-1960s, they were dispatched by Standard Oil management into the unknown sedimentary basin areas of the world to make assessments of oil prospects.
Dave Kingston, who was party chief of the Rover Boys for 15 years, conducted surface field work and regional studies in the frontier areas of South America, Europe, the Middle East and Africa. Kingston was hired into the group because of his experiences in the 1950s, performing a geologic reconnaissance of the unmapped Yukon Territory in Canada, where they even had to hunt for their own food. From this proving ground, Standard Oil did not hesitate to send him anywhere in the world. On top of this, a Rover Boy also needed the ability to learn new languages and have the knack for getting along with the locals. As Kingston remembered, “The first year I was in Turkey I was arrested five times for espionage. But after that, I learned to speak enough Turkish to be able to talk directly with the police without going through my interpreter.”
The Rover Boys explored basin areas to locate the size and shape of key structures and then work out stratigraphy from outcrops. At the very heart of the field work was measuring the angle of dip—in other words how steeply the strata were inclined to the horizontal. This allowed explorationists to estimate how deep the strata might appear in different parts of the basin. Dip was measured by a clinometer, but the measurement had to be combined with a compass reading to provide the direction the strata were dipping in.
All that changed when both dip and direction could be measured using the Brunton compass made in Riverton, Wyoming. This instrument, patented in 1894 by a Canadian-born Colorado geologist named David W. Brunton, was originally used in mining and introduced into the oil field in the early 20th century. The Brunton compass measured dip more accurately than the old hand-held clinometer and was easy to use. In the late 1940s, Bert Bally, a geologist with Shell and then Rice University in Houston, recalled the importance of the sophisticated compass: “As a student I worked in Sicily and was hired by Gulf Oil to map the whole of southeast Sicily. They hired me because I spoke Italian, so I had to map and rank various prospects in the hot summer there. Initially there was no other technology except a Brunton compass. With that and subsequently a rather limited geophysical survey, the Ragusa oil field was found.” Another fine example of the hardy exploration breed was Augusto Gansser-Biaggi, a Swiss geologist whose early work included trips to Greenland and the Himalayas. Disguised as a pilgrim, he once circumnavigated the holy mountain Mount Kailash in Tibet, discovering at the southern foot of the mountain marine sediments, a sensation at the time. After a spell working in Colombia, Venezuela and Trinidad for Shell, he joined the National Iranian Oil Company in the mid-1950s as chief geologist. Working from relief pictures taken by the Iranian Air Force, Gansser located the largest known wildcat oil gusher in the country, north of Qom, which produced 80,000 barrels per day before it caught fire August 26, 1956, and eventually collapsed on itself.
If geologists were unable to access territory from the ground, they could still be dropped there from the air. As David Jenkins, BP chief geologist from 1979 to 1982, recalled, “When I went to Papua New Guinea in the 1960s we used helicopters to take us to clearings in the forest. We then walked off with one or two assistants collecting rock samples and later got picked up again.”
From Aerial Photography to Satellites
Help from the air had been coming from the earliest days. Union Oil geologists tried to define the Santa Fe Springs and Richfield prospects in California using aerial photography soon after the close of World War I. They assembled 400 photographs, which pilots of the company’s airplane took with an ordinary camera, into a mosaic that represented an area of some 6,250 acres. Most early aerial photography supporting geology was rather haphazard and lacked any technology to fit many individual photographs into a coherent picture.
World War II changed that. In one development, called “trimetrogon” photography, British and Americans Forces operated reconnaissance airplanes, most notably the P-38 “Lightning” that had a special camera installed in its nose. The camera took vertical shots and at the same time a sideways shot on each side. The three shots gave a better view of objects on the ground as Dave Kingston remembered: “I worked up in the Canadian Rockies and these trimetrogon photographs were the first aerial photographs that we had up there; they were a big help to give the big picture and location of outcrops for further studying and mapping the surface geology.”
Another breakthrough in aerial photography was the wide-angle stereoscopic camera, combined with the technique of flying back and forth over an area taking overlapping strips of pictures. Then, equipped with a stereoscopic viewer, geologists could prepare detailed topographic maps without even visiting the territory. Martin Ziegler of Shell, one of three Swiss brothers, all of whom contributed to postwar exploration geology, recalls a trip to Nepal together with party leader Ken Glennie to study the foothills of the Himalayas in the early 1960s: “We looked at the overlapping parts of the aerial photographs stereoscopically and you’d see the ridges, you’d see the rivers and you could see how the beds were dipping . . . and then you jumped to the next photo and eventually you’d build up a whole sequence of data you’re interested in.”
Drawbacks to aerial photography included cloud cover and vegetation, which, if sufficiently dense, could mask what the geologist was looking for. In areas such as deserts with neither impediment, the technique was a godsend. Recalls Dave Kingston: “They did a lot of aerial photography, for example in North Africa. All of a sudden we could map from the air in a very short time structures that previously had taken us years to do with surface field parties.” Glennie, working in the Middle East in 1964, also has vivid memories of the benefits of aerial photogeology: “We drove on south into Oman where I managed to persuade the managing director of Petroleum Development Oman to hire a plane for me, so I could take photographs from the air. It cost me 500 pounds for a day’s flying and I spent the day taking hundreds of photographs. I’ve never spent 500 pounds of Shell’s money more usefully.”
The prevalence of aerial photogeology started to wane towards the end of the 1960s when NASA sent the first satellites into orbit able to take pictures of the earth. In 1972, the US space agency launched its Landsat program with satellites capable of repeatedly photographing practically every spot on the globe. These pictures, covering 115 miles on a side, showed immense detail about the earth and its geologic features. Dave Kingston recalled, “Satellite photographs gave us a totally new perspective on the world’s onshore basins, a massive help for international exploration.”
A natural extension of aerial photography was aeromagnetic surveys. During World War II, the US Navy developed the first airborne magnetometer for antisubmarine warfare. Gulf Research and Development Company modified and adapted this for limited use in petroleum exploration work during the war years, and by 1946 several airborne magnetometers were available and got licensed to Aero Service Corporation and Fairchild Aviation.
In 1947, full-scale commercial use of aeromagnetic surveys started, with most of the work conducted outside the US. The quality of aeromagnetic data was better than that obtained by land magnetometers because measurements at altitude averaged out minor surface and near-surface variations of no interest to petroleum exploration. Furthermore, in aerial magnetic surveys, it was possible to fly over the same area at different elevations in order to delineate better the depth of any anomalies that might be present. Another success factor was cost. Because aeromagnetic surveying usually cost a fraction of seismic surveying, the airborne magnetometer offered a rapid, cheap method of obtaining an initial assessment of the petroleum potential of large, unexplored areas. In 1964, the Soviets were the first to perform magnetic surveying from satellites; NASA followed suit the next year.
Sedimentology Makes an Impact
Both in academia and in the oil companies, sedimentary rocks were now being scrutinized to an unprecedented degree. This was triggered by the search in the years following World War II for stratigraphically trapped oil. An early example was the API Project 51 that started in 1950. API Project 51 was a multidisciplinary study of sedimentation in the northern Gulf of Mexico and the largest single project that the API had ever sponsored. It was hosted by the Scripps Institute of Oceanography in La Jolla, California, under the direction of Francis Parker Shepard.
From his earliest years Shepard had been good at questioning accepted geologic knowledge. Based at the University of Illinois in 1923, he was on the New England coast collecting seafloor samples and found something that astonished him: “To my surprise, I found almost everything brought up from the seafloor seemed to clash with the antiquated ideas that we had been taught in our geology courses. For example, we were told that sand is found along the shores and this, in turn, is replaced by finer sediments outside, and only mud occurs on the outer continental shelf. That is not what I found at all. Mud often occurred right near the shore and was replaced by sand in deeper water outside; then sometimes by gravel still farther out.” Shepard later became a renowned expert on submarine deposits and a key figure in the emerging discipline of sedimentology.
Determining the age of the sediments was a perpetual challenge. Observing and analyzing the biostratigraphy of rocks was rather difficult and cumbersome work, but a new method derived from the early days of nuclear physics significantly improved the ability to date rocks correctly. The idea, which came from two renowned physicists, Ernest Rutherford and Frederick Soddy, in 1902, was first used to date rock samples by the British geologist Arthur Holmes in 1911. The technique is based on the fact that all rocks contain tiny amounts of certain radioactive elements that are unstable and eventually decay. The decay rate is constant and known, so the age of rocks may be determined by measuring for a chosen radioactive element present in the rock, how much has decayed and how much of the original remains. This works perfectly for igneous and metamorphic rock but must be used with care for sedimentary rock because its evolution through weathering and transport is so complex. An alternative dating for sedimentary rock was already available by measuring the direction of the rock’s remnant magnetism and correlating that to the earth’s known and numerous magnetic reversals. Another major area of research was carbonates. Unlike the basic chemistry of quartz, a compound of silicon and oxygen that originates deep in the earth and is progressively weathered and ground to form sand grains, carbonate’s main constituent calcite is a compound of calcium, carbon and oxygen. Carbonates either precipitate from calcite-rich environments or originate from living organisms, for example coral reefs. In the world of sedimentology, carbonates make up 10 to 15% of all sedimentary rocks and contain some of the world’s largest oil reservoirs such as the Ghawar field in Saudi Arabia. Worldwide, carbonate reservoirs contain at least 60% of all known oil and 40% of the gas. In the Middle East, those figures rise to 70% and 90%.
In 1950, Shell recruited its first sedimentologist with a chemical and biological background, James Lee Wilson. From 1952 through 1966, Wilson applied himself to the new discipline of carbonates in Texas and New Mexico. He was followed in close order by Robert J. Dunham, who by 1962 introduced the first classification of carbonate rock in terms of its depositional fabric. This was a seminal piece of work because carbonate rocks vary in structure and appearance to a far greater extent than sandstones, and the industry badly needed some way of understanding and dealing with this important rock type. Dunham’s classification with modifications is still in use today. Petroleum geology was slowly coming of age, and the training of young geologists became a priority for oil companies. Martin Ziegler was an instructor in carbonate geology for Exxon in the late 1960s and early 1970s and describes what it took to create the right mindset: “Annually we had training sessions for geologists, geophysicists, production engineers and others. We took them on a month-long training course, starting out at the lab in Houston to get them acquainted with various types of limestones. Then we took the group out to Florida and the Bahamas—they were in small groups, no more than about 14 people or so. And there we showed them where different types of limestones were formed in the Florida Bay; we showed them how a shoreline looks, what a reef looks like. We took them in a plane over to the Bimini and Andros islands in the Bahamas, and there we showed how an island develops. They had to take cores and they had to collect fossils. They had to make cross-sections and discuss what was going on.”
Understanding Oil Migration
Success in exploration depends crucially on finding the right geologic environment for a reservoir, which is to say a porous sedimentary rock capable of containing the oil and gas. But equally important is ensuring that somewhere nearby the right conditions existed far back in geologic time for oil and gas to be created and then migrate to its resting place.
Up until the early 20th century, geologists believed oil and gas were created where they were eventually found—in the reservoir. But in 1909, Malcolm J. Munn of the USGS surmised that the oil might be squeezed out of shale source beds and then swept up by water toward a reservoir formation.
Thirty years after Munn, Vincent C. Illing, head of the petroleum department at Royal School of Mines in London, tried to reproduce this idea in the laboratory. Illing's experiments used long glass tubes filled with alternate sections of coarse and fine sand. The sands were saturated with water and then a mixture of 90% water and 10% oil was introduced at one end. He observed that oil would fill a coarse section easily but get temporarily stopped at a coarse-fine interface. The water, meanwhile, would travel without hindrance through both coarse- and fine-sand sections, eventually providing enough impetus for the oil to break through each fine-sand section and build up in the next coarse sand, and so on.
Illing measured pressure changes across the coarse-fine interfaces and tilted the tubes to simulate oil accumulating against the forces of buoyancy. These simple experiments corroborated the idea of migration and provided a foundation for explaining accumulations not only in structural traps but also in stratigraphic traps. They demonstrated that oil-water contacts in reservoirs need not be horizontal if dynamic water conditions are present during migration.
Yet, still in the 1940s and most of the 1950s, many geologists clung to the idea that oil-water interfaces were systematically horizontal. It took one extraordinary geologist named Marion King Hubbert to change people’s perceptions forever. Many just called him King Hubbert, because in many ways he acted like a king. Hubbert became well-known for the ultimate put-down: “Our ignorance is not so vast as our failure to use what we know.” He was a person of great authority and scientific rigor. He not only studied geology but also mathematics and physics and may be credited for firmly pulling geology into the quantitative sciences. In 1943, Hubbert joined Shell in Houston, where he later directed the Shell research laboratory. After retiring from Shell in 1964, he worked at the USGS until 1976.
King Hubbert was clearly difficult to work with. When Martha Lou Broussard, a 1957-Rice University geology graduate and the first female geologist graduating from Rice, went for a job interview, he asked her if she intended to have children. When she said yes, Hubbert told her to go to the blackboard and calculate at exactly what point the world would reach one person per square meter. Only a cantankerous mind such as Hubbert’s could shake up the geologic community about oil migration. In a 1940-paper on “The Theory of Ground Water Motion,” Hubbert had already published some important work discussing underground movement and segregation of two waters of different densities. At Shell, he extended this work to movements of oil, gas and salt water, and in 1953 presented a paper at the spring meeting of the AAPG entitled "Entrapment of Petroleum under Hydrodynamic Conditions."
In this paper, Hubbert demonstrated that the presence or absence of hydrocarbons in all types of traps can be explained better in almost every instance by the existence of dynamic water conditions rather than static water conditions in the subsurface. As Illing had noted, if the water is at rest, the oil and gas interfaces will be horizontal, typically the case in anticlines. If the water is in motion, the interfaces may be tilted in the flow direction, sometimes the case in stratigraphic traps that would not otherwise trap the oil or gas in static conditions.
As an example, Hubbert referred to the Rocky Mountains oil province. Here, water is typically flowing through subsurface layers from the mountains toward the Wyoming basin. He observed that in some Rocky Mountain anticlines, the seal appeared not to provide closure. Yet, because the flowing water tilted the oil-water contact, the oil did get trapped.
The Importance of Plate Tectonics
Meanwhile, at the largest possible length scale, petroleum geologists were beginning to harness the new ideas of plate tectonics. In 1897, the English geologist Richard Dixon Oldham used a seismograph to monitor a huge 8.1 earthquake in Assam, and this led to his proposal that the earth consisted of three major components: core, mantle and crust. Twelve years later, the Croatian meteorologist and seismologist Andrija Mohorovičić, following in Oldham’s footsteps, postulated the existence of a boundary surface between the mantle and the crust, which came to be known the M-discontinuity or simply “Moho.” In passing through the rocks immediately above this surface, earthquake waves reach a velocity of about 7.2 kilometers per second, whereas below the M-discontinuity the velocity suddenly jumps to above 7.9.
These results provided the basis of a wild idea first propounded by Alfred Wegener, a German meteorologist, geophysicist and polar researcher. The idea was that the continents and ocean floors forming the earth’s crust were sufficiently detached from the mantle to be able to “float” and move around. He published these ideas in 1915 in the now seminal work “The Origin of Continents and Oceans,” claiming that all the continents had once formed one supercontinent and then, approximately 200 million years ago, split up and drifted away from each other to reach their present form. Wegener provided plenty of evidence for his so-called Continental Drift theory, but was met with universal skepticism. The problem was that Wegener hadn’t been able to propose a valid mechanism behind the drift. “A lot of people pooh-poohed it because they wanted to know how it worked,” said Ken Glennie recalling his student years at the University of Edinburgh during the late 1940s. John McPhee, the popular writer about geology, remembered when he was a graduate, “Nearly all the faculty at Princeton thought continental drift was sheer baloney.” Former Exxon-geologist Walter Ziegler, the oldest of Martin’s brothers, remembered, “When I came to Calgary in 1955, the research department head of Imperial Oil told me that continental drift was European bullshit!”
By that time, clues were beginning to emerge in a discipline closely related to geology: oceanography. This discipline took form thanks to the extraordinarily ambitious British Challenger expedition, which from 1872 to 1876 sailed more than 70,000 nautical miles around the world, taking depth soundings, describing seafloor sediments and identifying thousands of new species. Fifty years later, depth surveys in the Atlantic and Caribbean were revealing a highly irregular seafloor. Especially intriguing, a line of underwater mountains seemed to dot the mid-Atlantic. The picture sharpened after World War I, when Fessenden’s echo sounding measurements revealed a long, continuous mountain chain. In the late 1940s and the 1950s, ocean surveys conducted by many nations filled in more detail.
In 1947, Maurice Ewing of Columbia University in New York led an expedition on the US research ship Atlantis and found sediment layers on the Atlantic seafloor to be far thinner than expected. Many scientists believed that the oceans had existed without much change for at least four billion years, so the sediment layer was expected to be thousands of feet deep. The seafloor therefore appeared to be much younger, in the range of 200 million years or less.
Nine years later, Ewing, together with Bruce Heezen, also from Columbia, noticed that earthquakes in the ocean floor predominantly occurred along midocean ridges. In 1962, Harry Hess, a Princeton professor of geology, associated the earthquakes with the idea that ocean crust was forming at the ridges, with molten material such as basalt oozing up from the earth’s mantle along the midocean ridges and spreading new seafloor away from the ridge in both directions. Although his theory made sense, Hess lacked convincing evidence to support it.
This was to come from another science hot spot, the University of Cambridge in England. Geoscientists Frederick Vine and Drummond Matthews started looking at the magnetic patterns of the ocean floor. It was well known that the earth’s magnetic field had reversed 171 times in the past 76 million years, so it seemed reasonable to observe this record in the vicinity of the Mid-Atlantic Ridge. What they found was crucial. Mirror image records appeared on either side of the ridge, suggesting that the seafloor was not only spreading but also documenting its age.
Matthews and Vine published their results in Nature in September 1963, making history. But other geoscientists had had similar ideas. In January 1963, the Canadian geophysicist Lawrence Whitaker Morley submitted a paper including almost identical ideas to the Journal of Geophysical Research, which rejected it summarily. Morley’s paper came back with a note telling him that his ideas were suitable for a cocktail party but not for a serious publication.
The Canadian geophysicist John Tuzo-Wilson was also skeptical of plate tectonics but eventually became one of its most famous supporters. He resolved many unanswered questions, in particular the idea of the transform fault in which plates slide past each other without any oceanic crust being created or destroyed. The most famous example is probably the San Andreas Fault between the North American and Pacific plates. For Walter Ziegler of Exxon the transform fault concept was a key turning-point: “I remember having dinner one evening in the early 60s at the house of Professor Bob Folinsbee at the University of Alberta, and Tuzo-Wilson was there. Tuzo-Wilson was involved in all sorts of oceanographic studies and was the inventor of the transform faults. And there he was sketching it at the dinner table, explaining how it worked. Slowly the American scientific community and the oil community began to wake up.”
In the US, at the Exxon research center in Houston, plate tectonics was finally becoming mainstream. A young geologist, Pete Temple, who had studied under Harry Hess at Princeton, was an early adopter. Dave White of Exxon remembers, "One day Pete and another member of the group, Tom Nelson, started looking at a seismic section from the Otway Basin off South Australia and they envisioned that what they were seeing was a pull-apart feature, where Antarctica had pulled away from Australia. Applying the theory, they then postulated that there should be a transform fault within a certain area near Tasmania at a right angle from the pull-apart. The fault turned out to be right where they thought it would be. I remember Pete coming into my office waving the seismic section in the air. He thought that was pretty neat, and I did too."
Plate tectonics had begun its slow march into the minds of oilfield geologists.
This entry is based on Groundbreakers: The story of oilfield technology and the people who made it happen, by Mark Mau and Henry Edmundson. You can find the book at www.fast-print.net/bookshop/1791/groundbreakers.