Are Oil and Gas Renewable?

A long-time reader of this blog sent me a link to a New York Times article highlighting the diverse scientific pursuits of Jesse Ausubel of Rockefeller University, among which is the exploration of the "deep carbon cycle". Although much is known about the behavior of carbon in the first seven miles or so of the earth's crust into which we routinely mine and drill for resources, relatively little is known about the flows of carbon-based compounds in the other 99.6% of earth's total volume. Increasing our knowledge in this area could have momentous implications for our long-term energy supplies, while expanding our understanding of the processes affecting climate change. It's also just plain fascinating.

Mr. Ausubel was already well-known in energy circles for his assessment of the progressive decarbonization of our energy consumption since the start of the industrial revolution and continuing into the future. Some colleagues at Texaco introduced me to his work on that subject in the mid-1990s. However, until I read the Times article I was unaware of his involvement with the Deep Carbon Observatory, an international project of the Carnegie Institution to investigate the organic and inorganic carbon cycles deep in the earth. Although this involves such esoteric questions as the disposition of the carbon content of the "planetesimals" that accreted to form the earth billions of years ago, it also has much more practical aspects, such as the origins of oil and gas. That includes both the fuels we consume and the methane and other hydrocarbons released into the environment without human intervention.

Most experts in the oil and gas industry accept the traditional Western view of these substances as fossil fuels, the remains of ancient forests and dinosaurs that have been processed into their present form by exposure to high pressures and temperatures over the course of millions of years. Although most hydrocarbons weren't formed in the reservoirs where they are found today, it's generally assumed that they were generated from organic material in sedimentary rock elsewhere and migrated until they reached the various geological structures that trapped and stored them for subsequent discovery and exploitation. The shale gas that has been the subject of so much activity and debate in the last few years is a special case, for which the source and trap are one in the same: organic-rich rock with such low porosity that the gas can't escape without assistance.

However, there's another, more controversial theory of the origins of at least some oil and gas, suggesting that they were formed by chemical or biological activity much deeper in the earth, and then migrated long distances before being trapped. If correct, that would mean that not only aren't these fuels truly fossils--and thus essentially static and finite--but that they might actually be continuously regenerated by natural processes in much shorter time spans. A number of academics appear to hold this view, and it was a common theory of petroleum origin among Soviet scientists. Much of this is explored in a lengthy white paper on the Deep Carbon Observatory site, including the shortcomings of current analytical techniques in determining definitively whether a given sample of methane originated from organic material in sedimentary rock or from some other source.

Finding gas or oil in deposits much deeper than those we already know about, or in places that aren't consistent with our present understanding of petroleum geology, would represent an even bigger potential energy revolution than the one begun by the recent development of the means of unlocking shale gas resources. It would also shift our perspective on the nature and required speed of the energy transition on which we've embarked. If oil and gas weren't finite--at least in human terms--it might alter the urgency of deploying some of the alternative energy technologies now in our repertoire. At the same time, it would have enormous implications for climate change, by greatly increasing the ultimate quantity of carbon we could eventually emit to the atmosphere.

From my reading of the material on the Deep Carbon Observatory site, it would be extraordinarily premature either to celebrate or panic--depending on one's perspective--over this prospect. The possibility of extracting useful quantities of hydrocarbons from unknown reservoirs in the deep earth remains speculative and might never come to pass. As a presenter from Shell put it in a slide deck from a conference on the subject, "Shell is not interested in drilling exploration wells into Earth's mantle in search of petroleum fluids." But despite understandable skepticism about the underlying theory of deep carbon and the failure of previous efforts to prove it, I don't see how it can be disproved without a much more detailed picture of the earth's interior than we are likely to possess for a long time.

The likelier near-term outcomes of the work of the DCO's multi-disciplinary researchers from industry, government and academia are both more benign and far less polarizing than the cornucopia of hydrocarbons it might someday uncover. Better techniques and instruments for analyzing the carbon and hydrogen isotopes in methane and other hydrocarbons could have wider application in many fields, including pharmaceuticals, while a better understanding of the physics and chemistry of the deep carbon cycle could lead to lower-cost and more widely acceptable means of sequestering the CO2 emissions from our use of "fossil fuels", regardless of their origin. I look forward to hearing about the progress of these efforts.