Editor's Note: Leonardo Maugeri is group senior vice president for corporate strategies and planning at the Italian energy company ENI as well as the author of the forthcoming book The Age of Oil: The Mythology, History and Future of the World's Most Controversial Resource.

In this article, a rough draft of which appears below, Maugeri points out that Earth does, in fact, hold a lot more oil beneath its surface than most people think, and the key to tapping that crude is the development of new technologies.

What is your reaction to Maugeri's assertion that "most of the planet’s known resources are left unexploited in the ground, and even more await to be discovered," which seems counterintuitive given the view by many experts that we have already reached "peak oil" and that today's focus should be on new sources of renewable energy?

Does Maugeri present a persuasive case that "the difficult oil of today will be tomorrow's easy oil, thanks to the learning curve of technology expertise"?

What are your thoughts on the author's estimation that the world has enough oil for the rest of the 21st century?

What other oil extraction technologies might Maugeri want to consider addressing?

What effect will the state of the economy have on Maugeri's observations and predictions? Would a look at this same issue a year from now likely yield very different results?

Your feedback will be considered by the writer and editors as they complete the final draft of this article, which will appear in an upcoming edition of
Scientific American magazine.

On 20 dry, flat square miles of California’s Central Valley, more than 8,000 horseheads—as old-fashioned oilmen call them—slowly rise and fall as they suck oil from underground. Glittering pipelines crossing the whole area reveal that the place is not merely a relic of the past. But even to an expert’s eyes, Kern River Oil Field betrays no hint of the miracle that has enabled it to survive decades of dire predictions.

Kern River Oil Field was discovered in 1899, and initially it was thought that only 10 percent of its heavy, viscous crude could be recovered. In 1942, after more than four decades of modest production, the field was estimated to still hold 54 million barrels of recoverable oil. As pointed out in 1995 by Morris Adelman, professor emeritus at the Massachusetts Institute of Technology and one of the few remaining energy gurus, “in the next forty-four years, it produced not 54 million barrels but 736 million barrels, and it had another 970 million barrels remaining.” But even this estimate was wrong. In November 2007 U.S. oil giant Chevron announced that cumulative production had reached two billion barrels. Today, Kern River still puts out more than 80,000 barrels per day, and Chevron reckons that the remaining reserves are about 480 million barrels.

Chevron began to achieve its miracle in the 1960s by injecting steam into the ground, a novel technology at the time. Later, a new breed of exploration and drilling tools—along with steady steam injection—turned the field into a sort of oil cornucopia. Yet, Kern River is not an isolated case. Most of the world’s oilfields have revived over time. New exploration methods have revealed more of the Earth’s secrets. And leaps in extraction technology have led to tapping oil in once-inaccessible areas and in places where drilling was once uneconomic. In a way, technology is the real cornucopia.

All That You Can't Leave Behind

At a time when the world increasingly fears an approaching peak and subsequent decline in oil production (even if the current economic crisis has temporarily obscured this view), it may be surprising to learn that most of the planet’s known resources are left unexploited in the ground, and that even more still wait to be discovered.

In 2008, just before the economic meltdown that slashed oil consumption, the world consumed around 30 billion barrels of oil per year, or roughly 85 million barrels per day, with the U.S. leading the rush with more than 21 million barrels consumed every day. Our planet’s proven oil reserves are estimated at between 1.1 trillion and 1.3 trillion barrels, more than the amount we have consumed so far, which is less than one trillion barrels.

These 2.3 trillion barrels are only a slice of the Earth’s original petroleum deposits, which the U.S. Geological Survey estimates to be around seven trillion to nine trillion barrels. But with today’s technology, know-how and prices, only part of that oil can be recovered economically and is thus classified as a proven reserve.

The world’s average oil recovery rate today is around 35 percent. That means that about two thirds of the original oil remains underground; that resource is rarely mentioned in the debate on the future of oil. And there is more.

First, proven reserves are only estimates and not fixed numbers. The definition of what can be recovered economically changes as technology develops and as the price of crude goes up. That’s why most oilfields have produced much more than the initial estimates of their reserves assumed, and even more than the initial estimates of their total content. Second, these data do not include unconventional oils, such as ultra-heavy oils, tar sands and bituminous schist, which together are at least as abundant as conventional oil. Finally, only one third of the sedimentary basins of our planet—the geological formations that may contain oil—have been thoroughly explored with modern technologies.

Even a mature oil country such as the U.S., whose oil production has been declining since the 1970s, still holds huge volumes of unexploited oil under its surface. According to a recent report by the National Petroleum Council (NPC), of the 582 billion barrels of known oil, 208 billion already have been produced or proven, leaving 374 billion barrels underground. What’s more, all this oil is only a fraction of the country’s total original amount, which the NPC estimates at more than a trillion (1,124 billion). Meanwhile, U.S. proven oil reserves are 29 billion barrels, and the country’s annual production is about three billion barrels, less than half of the seven billion barrels it consumes every year.

Thus, a country or a company may increase its reserves of black gold even without tapping new areas and frontiers, if it is capable of recovering more oil from known fields. Still, that does not mean that it is easy.

A Rocky Start

Contrary to common belief, oil is not held in great underground lakes or caves. If you could “see” an oil reservoir, you would only notice a rocky structure, in which there seems to be no room for oil. But beyond the reach of the human eye, a world of often-invisible pores and microfractures entrap minuscule droplets of oil, together with water and natural gas.

Nature created these formations over millions of years. It started when huge deposits of vegetation and dead microorganisms piled up at the bottom of ancient seas, decomposed and got buried under successive layers of rock. High temperatures and pressures then slowly transformed the organic sediments into today’s oil and gas.

When such a reservoir is drilled, it is a bit like uncorking a champagne bottle. Freed from its ancient rocky prison, the reservoir’s internal pressure pushes oil to the surface (along with stones, mud and other debris). The process goes on until the pressure peters out. From then on, recovery must be assisted.

About one third of the oil in a reservoir is “immobile oil,” isolated drops trapped by strong forces within the pores of the rock. The remaining two thirds, though mobile, will not necessarily flow into the wells. In fact, usually about half of the mobile oil is stuck inside the reservoir because of geological barriers or low permeability. The situation is even worse when the oil is not a light liquid, but a heavy, viscous molasses-like substance. In that case, only a limited amount of it may be recovered through conventional technologies.

I Drink Your Milkshake

In the past, oilmen generally recognized that the development of a reservoir entailed three subsequent stages. First, they exploited the internal pressure of the oilfield. This early phase was referred to as primary recovery and usually yielded between 10 and 15 percent of the total oil in place. Secondary recovery consisted of injecting natural gas and water into the reservoir. The reason for the use of water is not obvious at first, but is quite simple. Because oil is lighter than water, oil will be uplifted when water is injected in the reservoir, just as pouring water in a glass filled with olive oil would push the oil upward. The first and second recovery stages could bring the recovery rate to between 20 and 40 percent, for good-quality reservoirs. Beyond that, textbooks indicated a third stage—tertiary recovery—based on the application of thermal, mechanical, chemical or biological processes.

One of the most important developments so far has been the horizontal well, a dramatic breakthrough compared with the traditional vertical drilling used since the inception of the oil industry. Commercially adopted in the 1980s, this technique is particularly suitable for reservoirs where oil and natural gas occupy thin, horizontal strata, or in sections where vertical drilling can no longer be useful. With their flexible “L” shapes, horizontal wells can change direction and penetrate a reservoir horizontally, thus “assaulting” virgin sections of a reservoir.

The revolution in exploration, computing and drilling tools has also allowed for going deeper and deeper into the oceans to push the frontiers of oil search.

Developed after World War II, offshore technologies seemed to have reached their most daunting milestone in the 1970s, when they were essential to the development of North Sea oil. At that time, production came from fields that lay below 300 to 600 feet of water and 3,000 feet under the seabed. But in the last few years, the industry has succeeded in striking oil at depths below 10,000 feet of water and 20,000 feet below the seabed—as it occurred in the Gulf of Mexico and the Brazilian offshore.

Moreover, new technologies have enabled geologists to see what lies beneath layers of underground salt, which are unevenly distributed beneath the seabed and sometimes thicker than 15,000 feet. Similar to frozen waters, salt formations represented a formidable obstacle because they blurred the seismic waves used in exploration, making it impossible to reconstruct an accurate image of the underground. The removal of this obstacle has led to at least three major ultra-deep offshore discoveries: Thunder Horse and Jack in the Gulf of Mexico and Tupi in Brazil. These areas are what people in the field call “elephants”—fields holding more than one billion barrels of oil and natural gas.

Wringing Out Every Drop

Although wells have gone farther and deeper than ever before, technologies have evolved to get more oil out of the rock, using heat, gas injection, chemical processes and even microbes.

Steam injection, among the oldest heat-based methods, was decisive in the revival of the Kern River Oil Field back in the early 1960s. The basic principle of this technology is that the injected steam heats the overlying formation, allowing oil to move, so that it becomes recoverable. In simpler words, it is like heating crystallized honey to get it into a liquid, less viscous form.

To this day, Kern River’s steam injection represents the largest project of this kind in the world. A variant of steam-assisted recovery has been applied to tar sand deposits in Alberta that are too deep to be surface-mined.

Another heat-based process that has been field-tested is burning a fraction of the reservoir’s hydrocarbons. The fire generates heat and carbon dioxide, both of which make oil less viscous. At the same time, the fire itself breaks the larger and heavier molecules of oil, once again making it mobile.

Another technique involves the injection at high pressure of gases such as carbon dioxide (CO2) or nitrogen into the reservoir. In simple terms, these gases mix with oil, reducing both its viscosity and the forces that trap oil into its prison. CO2 can also be injected simply to restore or maintain the reservoir’s pressure.

In the U.S., CO2 has been applied to oil recovery since the 1970s, and is in use in about 100 ongoing projects, with a dedicated pipeline network of more than 2,500 kilometres. The know-how accumulated in CO2 injection has opened the way for carbon capture and sequestration, a promising technique for storing this greenhouse gas in the subsoil for hundreds of years. The first commercial carbon capture and sequestration project has been active in Sleipner, Norway, since 1996, and is storing 1.5 million tonnes of CO2 per year. A small step, considering that human activity alone is estimated to eject into the atmosphere around 50 billion tonnes of carbon dioxide every year.

Ironically, however, one of the main problems in using CO2 for oil recovery is its scarcity. Capturing the gas from large power station smokestacks or volcanoes is not cheap, and the cost of capturing it from smaller sources such as cars or even most industrial plants is prohibitive. Another hurdle is transportation, which can be too costly if the oil fields are in remote regions.

Another method to help recovery is to use chemistry. Chemicals can mix with trapped oil and make it less viscous, so that it can flow toward the well. Although the chemistry terminology can be quite esoteric, these chemicals all work based on the same principle, which is similar to how layers of soap molecules can engulf fatty substances and help remove grease from your hands. The most successful chemical process so far has been applied in China, where the national oil company PetroChina has injected a polymer substance in its Daqing oilfield since the mid 1990s. The technique is credited for helping get out an extra 10 percent of the reservoir’s oil. A variation on this process employs a caustic solution to generate the soap-like materials from components present within the oil itself, thereby lowering the overall cost.

Microbial enhanced oil recovery is still in its infancy, with experiments being conducted the U.S., Mexico, Norway, Venezuela and Trinidad. This technology consists of pumping considerable amounts of specialized microbes into the reservoir, together with nutrients and in some cases also oxygen. The microbes grow in the interface between the oil and the rock, helping to release the oil. The revolution underway in genetic engineering opens up the possibility of modifying bacteria and other microorganisms to make them more efficient at breaking up the heavier and more viscous oil molecules so as to make them mobile.

A New Era Ahead?

Technological breakthroughs in the oil industry have always been the result of very long, drawn-out processes. Horizontal drilling was first tested in the 1930s, and some of the more advanced recovery methods have existed at least since the 1950s. For most of the industry’s history, however, oil has been overabundant, so its price has been too low to justify significant and costly innovations. A new era is coming, and not only because oil prices are historically high—even after a dramatic plunge that slashed them from $147 per barrel in July 2008 to around $45. Other more important factors are at work.

First of all, many of the largest and most productive oil basins in the world are approaching what I call technological maturity: their production limits using conventional technology. These basins include reservoirs from Persian Gulf countries, Mexico, Venezuela and Russia that started producing oil in the 1930s, ’40s and ’50s. For these fields to keep producing in the future, new technologies will be required.

The second factor is the limited opportunities for new exploration and development for Western oil companies. Although in the early 1970s the major oil companies controlled around 80 percent of global oil reserves, today more than 90 percent of the world’s oil and 80 percent of the world’s natural gas is under the direct control of producing countries, through their national oil companies. The current wave of resource nationalism can only worsen this situation, because several important producers are already able to manage the development of their “easy” oil on their own, having attained an adequate level of technical and management skills. Recovering more oil from mature oilfields and discovering it in new, daunting frontiers is the only way to open up new growth opportunities in an otherwise shrinking world for Western oil companies.

Easy oil is probably running out because it was the first to be discovered and burned. But it wasn’t so “easy” when it was discovered. By the same token, the difficult oil of today will be tomorrow’s easy oil, thanks to the learning curve of technology expertise. Overall, “difficult oil” exploitation will be the survival and even prosperity key for many Western oil companies in a world that will be increasingly dominated by national oil companies.

It will take time, but I dare to make a prediction. By 2030 more than 50 percent of the known oil will be recoverable. Also, by that time the amount of known oil will have grown significantly, and a larger portion of unconventional oils will be commonly produced, bringing the total amount of recoverable reserves to something between 4,500 billion to 5,000 billion barrels of oil. What’s more, a significant part of “new reserves” will not come from new discoveries, but from a new ability to better exploit what we already have.

To be sure, by 2030 we will have consumed another 650 billion to 700 billion barrels of our reserves, for a total of around 1,600 billion barrels used up from the 4,500 billion to 5,000 billion figure. Yet, if my estimates are correct, we will have oil for the rest of the 21st Century. The real problem will be how to use that oil without wasting it through unacceptable consumption habits such as we have done so far, and—above all—without endangering the environment and climate of our planet.