Abiotic oil : a scientific inquiry


Richard Moore

This old article refers to an upcoming conference, back in 2003. 
I wasn't able to find anything about how the conference turned out. 



Gas Origin Theories to be Studied 

The debate about cooking up hydrocarbons keeps getting hotter.

Some scientists insist that all petroleum comes from abiogenic
processes, with hydrocarbon development occurring in the
Earth's mantle.

Most geochemists and petroleum geologists remain convinced
that crude oil and natural gas have organic origins.

Look for this dispute to intensify in 2003, with new heat
coming from an unexpected venue. In June, AAPG's typically
sleepy Hedberg Conference could be the spark that sets off
scientific fireworks.

Hedberg conferences address topics proposed by AAPG's Research
Committee. They take place in informal settings, with
attendance limited to 80-100 persons.

On June 9-12, however, a Hedberg Conference will be held in
London with the theme "Origin of Petroleum -- Biogenic and/or
Abiogenic and Its Significance in Hydrocarbon Exploration and

"The timing is right," said Barry Katz, a ChevronTexaco Fellow
in Houston and a member of the conference's program committee.
"Historically, what has been the big issue is that there's
essentially a Western and an Eastern school of thought.

"On the Western side, we've gone through what you've typically
done in the scientific method," he noted. "The Russian
arguments have been just that, arguments. We have yet to get
them in a room to see what they have on the table."

Katz said he hopes the leading theorists from both sides will
attend, so "we can have a balanced view and get everybody to
talk to each other. That's what the Hedberg conferences are
all about."

* Is It Commercial?

An explorationist might dismiss the entire controversy over
petroleum origination, except for two key points:

    Theorists of abiogenic petroleum tend to see hydrocarbons as
    not just abundant but super-abundant, with no possibility of
    constrained supply.
    Petroleum generated by abiogenic processes could occur
    anywhere, so exploration need not be limited to sedimentary
    basins, or to depths of only a few miles.

Modern theory directly links petroleum origination to organic
detritus, according to Michael Lewan, a research geochemist
for the U.S. Geological Survey in Denver.

"The modern, organic theory of the origin of petroleum states
that a portion of the lipid fraction of micro-organisms
deposited in anaerobic sediments is the original source of
petroleum," he said.

Proteins and carbohydrates make up 85-95 percent of the weight
of these micro-organisms, and are rapidly degraded by
microbial activity, Lewan said.

The remaining 5-15 percent can be preserved in anaerobic
sediments, representing "unique depositional conditions that
result in organic-rich, sedimentary-rock intervals in some
stratigraphic sequences," he explained.

Lipid material preserved in the original sediments polymerizes
into kerogen, an insoluble organic material, Lewan said.

"As these organic-rich rock intervals are heated with burial
in sedimentary basins, the hydrocarbon polymers within the
kerogen thermally crack through a free-radical mechanism to
yield liquid and gaseous petroleum hydrocarbons," he said.

Research in the lab and in the field demonstrates that
petroleum development can and does take place in the earth's
crust, he stated.

"I feel we've done a very good job of simulating production of
petroleum in the laboratory," Lewan said. "Between the lab
work and the fieldwork, we've put together a very good

Although hydrocarbons can be produced from inorganic sources,
a 1993 study based on helium isotopes found that abiogenic
hydrocarbons account for less than 200 parts per million of
cumulative global production to date, Lewan said.

"Is it so diffuse that it never really accumulates? Is it
focused in certain areas where it can be accumulated?" he

"I don't think anybody has ever doubted that there is an
inorganic source of hydrocarbons. The key question is, 'Do
they exist in commercial quantities?'"

* From Russia, With Love

Various other theories oppose the organic-origin explanation.
The principal counter-theory is often called the abyssal,
abiotic Russian-Ukrainian theory of petroleum.

In 1951, a group of Russian scientists issued a challenge to
the theory of organic petroleum origination. They claimed that
hydrocarbons are produced from inorganic materials, at
upper-mantle to lower-crust depths.

New controversy over that proposal resulted from a paper
published in August 2002 in the Proceedings of the National
Academy of Sciences (U.S.), "The evolution of multi-component
systems at high pressures: IV. The thermodynamic stability of
the hydrogen-carbon system: The genesis of hydrocarbons and
the origin of petroleum."

This paper, written by J.F. Kenney of Gas Resources Corp. in
Houston and three Russian co-authors, rejects the proposal
that petroleum can derive from "highly oxidized biotic
molecules of low chemical potential."

Drawing on scaled particle theory and simplified perturbed
hard-chain theory, Kenney et al. present an evaluation of the
chemical potentials and related thermodynamic affinities for
n-alkanes. They conclude:

"The H-C system does not spontaneously evolve heavy
hydrocarbons at pressures less than about 30 kbar, even in the
most favorable thermodynamic environment. The H-C system
evolves hydrocarbons under pressures found in the mantle of
the Earth and at temperatures consistent with that

They also briefly describe the experimental production of
petroleum hydrocarbons using only wetted marble (CaCO 3) and
solid iron oxide (FeO), in an apparatus allowing investigation
at pressures up to 50 kbar and temperatures up to 1,500°

Kenney said there is no real debate about petroleum

"There has not been any 'debate' about the origin of
hydrocarbons for over a century," he stated. "Competent
physicists, chemists, chemical engineers and men knowledgeable
of thermodynamics have known that natural petroleum does not
evolve from biological material since the last quarter of the
19th century."

In their paper, Kenny et al. contrast the H-C system with the
H-C-O system, "which manifests consistently decreasing
chemical potentials with increasing polymerization."

They then discuss reactions involving C 6H12 O6, or glucose,
as a "typical biotic reagent." In response, Lewan noted that
neither carbohydrates nor proteins are now thought to have a
part in petroleum formation.

"Significant scientific advances over the last 40 years have
tested, modified and refined the organic theory for petroleum
formation in the Earth's crust," Lewan said.

"It is unfortunate that Kenney et al. have chosen to ignore
these efforts of other competent scientists, and elevate their
inorganic theory on the misconception that the organic theory
is based on carbohydrates being the source of petroleum."

* The Golden Touch

No one in the United States has been more associated with the
theory of abiogenic petroleum than Thomas Gold, a professor of
astronomy at Cornell University, now retired.

"The only real opponents to this story (of abiogenic origin)
are in Western Europe and in the United States, and they are
the professional petroleum geologists," he said.

"The subject of organic chemistry was wrongly taken by
petroleum geologists long ago to mean chemistry of biologic
origins. You can still have a book of organic chemistry that
has nothing to do with organisms at all."

Gold most recently explained his theories of the origin of
petroleum in his 1999 book The Deep Hot Biosphere, which
presents the view that life on Earth exists to a depth of many

That helps him explain the apparent organic constituents of
petroleum. In Gold's view, hydrocarbons form at a depth of 100
to 300 kilometers and take on some organic attributes as they
migrate upward.

"Oil is a very good nutrient for microbiology. In 1972, I
began to realize that the oil had soaked up biological
molecules that the petroleum itself had fed," he said.

Migration also explains another commonly offered piece of
evidence for organic petroleum, depletion of the carbon 13 C
isotope, according to Gold.

Photosynthesis and other organic activity favor the stable 12
C isotope over the stable 13 C isotope. The resulting 13 C
deficiency is taken as an indicator of organic processes.

Petroleum shows the 13 C depletion to an even greater degree
than its supposed organic source matter, but in a ratio
similar to that of the lipid fractions of those organisms.

Gold theorizes that carbon-bearing molecules diffusing through
a porous mass, in any process, results in fractionation that
favors the lighter 13 C isotope.

"Biology is not a nuclear reactor. It can't make carbon-13 or
carbon-12. But it's treated in the literature that the 12 C-
13 C preference is strictly a plant matter," Gold said. "It's
quite clear that there is an isotopic fractionation occurring
in the migration path."

More evidence of upward hydrocarbon migration from great depth
comes from the prevalent occurrence of helium with petroleum,
Gold said.

"We have two conflicting pieces of evidence. Petroleum
contains helium, which the plants cannot have concentrated,"
he said. "Petroleum also contains purely biological molecules,
which petroleum-fed biology deep in the ground could

"This (upward migration from great depth) is the only
explanation I've ever heard of to account for the amount of
helium brought up with petroleum."

Petroleum explorationists have good reason to care about the
true origin of hydrocarbons, Gold noted.

"For one thing, they always avoid drilling into the basement
rock," he said. "They've probably avoided drilling into a
large amount of very productive rock."

Also, in Gold's theory hydrocarbons continue to well up from
the mantle. He believes depleted petroleum reservoirs are
refilling, all over the world.

* Seeing Is Believing?

A new perspective on isotopic analysis of abiogenic
hydrocarbons appeared in a letter to Nature magazine in April
2002, "Abiogenic formation of alkanes in the Earth's crust as
a minor source for global hydrocarbon reservoirs."

Barbara Sherwood Lollar and four co-authors from the Stable
Isotope Laboratory at the University of Toronto reported their
analysis of gas from the Kidd Creek mine in Ontario, typical
of hard rock mines operating throughout the Canadian Shield.

"These gases had been known historically in the mines for a
very long period, up to 100 years, but nobody had investigated
them until the 1980s. In Precambrian rock, it's not
intuitively obvious where these hydrocarbons come from," said
Sherwood Lollar, a professor of geology at the university.

According to the authors, the Kid Creek gases were composed of
methane, ethane, H 2and N 2, with minor concentrations of
helium, propane and butane.

"We knew that these were unusual in composition. They don't
look like thermogenic. They don't look like microbial,"
Sherwood Lollar said.

An unusual pattern of d 13 C values among C 1-C 4alkanes
provided evidence of abiogenic formation. Additional support
came from study of d 2H values.

"The inverse relationship of 13 C isotope depletion and 2H
isotope enrichment between C 1and C 2for the Kidd Creek
samples supports a polymerization reaction as the first step
in the creation" of higher hydrocarbons, the authors

Because the isotopic signature differed markedly from that of
thermogenic or bacteriogenic hydrocarbons, Sherwood Lollar
theorized an origin in water-rock interactions.

"The gases are found intimately associated with these saline
groundwaters and brines, with up to 10 times the saline
content of oceans," she said.

Identification of the 13 C- 2H inverse relationship in
abiogenic gas allowed comparison with isotopic ratios in
commercial gas reservoirs. The study found no meaningful
presence of abiogenic hydrocarbons in commercial natural gas

"Based on the isotopic characteristics of abiogenic gases
identified in this study, the ubiquitous positive correlation
of d 13 C and d 2H values for C 1-C 4hydrocarbons in economic
reservoirs worldwide is not consistent with any significant
contribution from abiogenic gas," the authors said.

"The key point is that abiogenic hydrocarbons have been talked
about for a long time, but until now we didn't have a very
good constraint on what they looked like," Sherwood Lollar

Katz said Western science recognizes that abiogenic
hydrocarbons can result from natural processes, including the
possibility of hydrocarbons originating at great depth.

"I don't think anybody's arguing that gas couldn't be
generated from the mantle," he said.

However, even the Russian scientists he has worked with accept
the organic origin of petroleum found in large, commercial

"I've worked with geochemists and basin modelers at what was
the Soviet Union's Institute for Foreign Geologic Studies.
They were working with the same concepts we were," he said.

If abiogenic petroleum exists in amounts large enough for
economic production, he hopes details of the science involved
will be presented at the London Hedberg .

"I have yet to have anyone show me that there are commercial
quantities of these hydrocarbons," Katz said.

"I'm a scientist, so I have to keep an open mind. But I need
to see some evidence." 


"Apocalypse Now and the Brave New World"

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