The following is excerpted from The Oracle of Oil: A Maverick Geologist’s Quest for a Sustainable Future, by Mason Inman. Copyright © April 11, 2016. W .W. Norton & Co. Adapted from Chapter 17, “A Magical Effect.”
Author’s Note: In the mid-1950s, M. King Hubbert was the first to explain correctly how a new technique known as hydraulic fracturing—or, for short, “fracking”—actually worked. This excerpt covers how he solved the puzzle, and (with the help of his assistant) convinced others of his explanation. The study of fracking he and his assistant published in 1957 is now considered a classic, still cited often today.
AT A 1954 CONFERENCE, TWO oil companies—Stanolind on one side, Atlantic Refining on the other—got into a fierce debate about the physics behind hydraulic fracturing. This relatively new method involved pumping fluid into a well until it opened fractures in the rock surrounding the well, yielding more oil. The two sides “got a dogfight going that lasted nearly all afternoon,” Hubbert recalled, laughing. Neither side’s explanation made sense to him. Nonetheless he stayed “on the sidelines just kind of enjoying the show.”
Stanolind had introduced the new technique in 1948, under the name “the hydrafrac process”—soon shortened to simply “fracking.” The technique had been an immediate hit. In just its first several years, it was applied more than thirty thousand times, helping extract more oil, especially from older wells.
However, even after its use had become widespread, no one knew exactly how hydraulic fracturing worked. Since it was put to use at the bottom of wells, thousands of feet underground, there was no easy way to see the results of the technique. Why did the rock fracture at a particular pressure? And why did the required pressure vary so much from well to well and place to place? No one was sure.
The debate Hubbert observed at the 1954 conference was over a seemingly esoteric point, but it was central to understanding how the fracking process worked. Stanolind argued the fractures were horizontal, like pancakes. Atlantic said the fractures were vertical, along the length of the well, like the fins on a rocket. Each company had its own reasoning—and Hubbert thought they were both wrong.
Soon after that contentious conference, Shell gave Hubbert a new assignment: figure out how fracking worked.
HUBBERT HAD FIRST encountered hydraulic fracturing in 1946—although rather than trying to put it to use, it was a problem Shell wanted to avoid. The company’s engineers had come to Hubbert to see if he could solve a mystery that had arisen as they drilled offshore in the Gulf of Mexico. As with most every oil well, these engineers were using a concoction called drilling mud—a slurry of clay and other minerals. They pumped it down the hole, where it flowed around the drill bit, cooling it, and also clearing out chips of rock from the bottom of the hole.
The mud served an additional, particularly crucial purpose. As it flowed back up the hole, the mud put pressure on the walls of the well, holding back oil and gas under high pressure, which otherwise might unexpectedly blow out. In decades past, such gushers—the iconic black fountains erupting from oil derricks—had been a cause for celebration. But they were wasteful and dangerous, and so had been mostly tamed through careful use of drilling mud.
The Shell engineers told Hubbert how, in drilling along the Gulf Coast, they’d gone down some six thousand feet using very light, watery mud without encountering any problems. But in a span of one or two hundred feet, they’d encountered a zone with much higher pressure that required heavier mud to supply enough pressure to hold back the fluids in the rock. They’d worried that if they waited too long to use heavy mud, they’d risk a blowout. Yet when they put in the heavy mud too early, they suffered another problem, known as “lost circulation,” in which the drilling mud simply disappeared down the hole. This lost circulation was a major problem for drilling in this area, slowing down the process and driving up costs. Some wells suffered lost circulation so chronically that they were abandoned before they struck oil. Not sure of the dynamics underground, the Shell engineers couldn’t determine how to prevent lost circulation.
Hubbert’s first thought was that they must have hit a limestone layer that had cavernous holes in it. But the engineers told him there was no limestone in that area. Then they explained there was another aspect to the mystery. When they sent down mud at high pressure, the mud disappeared. But when they eased off the pressure, the circulation returned. The engineers and Hubbert agreed that the pressure from the heavy mud must be opening up fractures surrounding the well.
However, the pressure wasn’t enough to lift the overburden—the weight of all the rock pressing down from above—and that puzzled the engineers. Hubbert realized the engineers were imagining the fractures as pancake-like horizontal openings in the rock—and for such cracks to open, they’d have to lift the weight of all the rock above. Hubbert told them it was far more likely that the fractures were vertical, so to open up they’d only have to push neighboring rock sideways, which would usually require much less force. It was like the difference between trying to lift the heavy door of a bank vault off its hinges, compared with swinging the door on its hinges.
Hubbert had solved the problem. His explanation of the underlying physics allowed the engineers to adjust their drilling mud to avoid lost circulation and drill more efficiently.
MEANWHILE STANOLIND HAD also discovered hydraulic fracturing and devised a method for putting it to use. At first it had been experimental, using a fluid that was cheap to buy. “Due to availability and price, war-surplus Napalm has been used in the majority of experiments to date,” Stanolind reported in 1948. They mixed sand into the napalm— also known as “jellied gasoline”—which carried the sand along with it, enabling the sand to lodge deep within the newly opened fractures. Then they pumped down another fluid that dissolved the jelly, and much of the napalm flowed back to the surface. But the grains of sand remained stuck in the fractures, propping them open, allowing oil and gas to escape from the rock.
The technique quickly caught on, and companies advertised their fracturing services and equipment in industry magazines like Oil and Gas Journal and World Oil, commonly showing drawings of horizontal, pancake- like fractures. Stanolind had based this on evidence drawn from a few shallow test wells and had assumed that all fractures, even those deep down, would likewise be horizontal.
This explanation was “accepted almost universally, with rarely a dissenting voice,” as Hubbert saw it. But to him, that explanation made no sense. They’d got the physics wrong. In 1953 he had published a short commentary in the journal Petroleum Transactions, arguing that Stanolind’s explanation was mistaken and the fractures were likely vertical. At the 1954 conference where the “dogfight” broke out over fracking, both sides had explanations that differed from Hubbert’s. Although the technique was in widespread use, there was still disagreement over how it worked, and its application remained hit or miss. There was clear room for improvement.
By the time Shell tasked Hubbert with explaining how fracking worked, “we had the records of several thousand fracturing jobs, with varying degrees of reliability in their data,” he recalled. “We had to smoke out useful information.”
Hubbert had recently hired a new assistant, David Willis, who had just completed his doctorate in geology at Stanford. In the fall of 1954, Hubbert and Willis developed a theory that described the forces at work when fluid was pumped into a well at high pressures. They worked on this intensively for a few months, writing up the results for a high-level conference to be held the following summer at Royal Dutch Shell’s lab in Amsterdam. Hubbert and Willis found that in some special conditions— in shallow wells, or along faults under sideways stress, like California’s San Andreas Fault—the fractures would lie horizontal. But their analysis suggested that in most cases the fractures would be vertical, along the well’s shaft.
When Hubbert presented the results at the Amsterdam conference, “it was very well received by the highest level technical people,” he recalled, “accepted completely, with no significant criticism.” After this vote of confidence, Shell organized training sessions on the new analysis for its field engineers. When it came time for the first course, Willis was away so Hubbert gave it himself. “What I discovered was that the theoretical argument was having no effect whatever on these men,” Hubbert recalled. The engineers were absolutely sure that the fractures were horizontal. Every article, every ad on fracking showed fractures oriented that way. They had been “completely brainwashed,” Hubbert thought. “They didn’t have any real evidence, but they’d been so thoroughly indoctrinated on this thing that they knew damned well these fractures were horizontal.” It mattered, because if they didn’t understand the forces at work, they couldn’t control it precisely. The technique would remain more art than science.
When Willis returned to Houston, Hubbert told him the presentation had been a flop. Willis didn’t say much at the time. But a few days later, on a Monday morning, Willis appeared in the doorway to Hubbert’s office, looking anxious. He wanted Hubbert to come to the lab to see something. Swamped with backlogged paperwork, Hubbert told Willis it would have to wait. Willis left, then came back half an hour later, getting more and more fidgety. He’d been working on something over the weekend, he said, and Hubbert should come and see it. Hubbert relented and trudged over to the lab.
In Shell’s Bellaire lab, one of the nation’s best-funded research facilities, sat the contraption Willis had assembled at home over the weekend. It was a goldfish bowl, filled with liquid Knox gelatin and some plaster in it. Willis had used the gelatin to simulate rock—appropriate, given Hubbert’s work on laws of scaling—and had stuck an Alka-Seltzer bottle in the middle of it to mimic a well. He’d put the liquid gelatin in the fridge and let it set, then pulled out the bottle. Then he’d used a baster to pump a slurry of plaster of Paris down the hole, filling it until the plaster began to push its way into the gelatin, forming fractures. As their theory predicted, the fractures were vertical.
Although Willis’s setup was kludged together, Hubbert immediately realized it was what they needed to win over the field engineers: a clear demonstration. They’d have an opportunity to make their case at an internal Shell conference in early 1956, in several weeks’ time. They got to work on building a larger version of the model. To replace Willis’s goldfish bowl, Hubbert scoped out bigger aquariums on sale at local shops.
At the Shell conference, Hubbert and Willis explained their experiment and showed the plaster casts, first from one angle, with the fractures flaring out from either side of the well. Then they rotated the cast, so the audience could see that the fractures were thin and sharp, like a knife’s blade. And of course, they were undoubtedly vertical.
Within a week of this demonstration, field engineers began sending in data they’d collected after fracturing wells. Some of them had put rubber plugs down wells to form an impression of the wall. Others sent cameras down the hole. This field data showed the fractures were indeed vertical. The theory was right—and finally the engineers believed it. Willis’s contraption “had a magical effect,” as Hubbert put it. “It made Christians out of these people.”