There Are More Oil Seeps Than All The Tankers
Deep underwater, and deeper underground, scientists see surprising
hints that gas and oil deposits can be replenished, filling up again, sometimes
rapidly. Although it sounds too good to be true, increasing evidence from
the Gulf of Mexico suggests that some old oil fields are being refilled
by petroleum surging up from deep below, scientists report. That may mean
that current estimates of oil and gas abundance are far too low.
Recent measurements in a major oil field show "that the fluids were
changing over time; that very light oil and gas were being injected from
below, even as the producing [oil pumping] was going on," said chemical
oceanographer Mahlon "Chuck" Kennicutt. "They are refilling
as we speak. But whether this is a worldwide phenomenon, we don't know."
Also not known, Kennicutt said, is whether the injection of new oil from
deeper strata is of any economic significance, whether there will be enough
to be exploitable. The discovery was unexpected, and it is still "somewhat
controversial" within the oil industry.
Kennicutt, a faculty member at Texas A&M University, said it is now
clear that gas and oil are coming into the known reservoirs very rapidly
in terms of geologic time. The inflow of new gas, and some oil, has been
detectable in as little as three to 10 years. In the past, it was not suspected
that oil fields can refill because it was assumed the oil formed in place,
or nearby, rather than far below.
According to marine geologist Harry Roberts, at Louisiana State University,
"petroleum geologists don't accept it as a general phenomenon because
it doesn't happen in most reservoirs. But in this case, it does seem to
be happening. You have a very leaky fault system that does allow it to migrate
in. It's directly connected to an oil and gas generating system at great
What the scientists suspect is that very old petroleum -- formed tens of
millions of years ago -- has continued migrating up into reservoirs that
oil companies have been exploiting for years. But no one had expected that
depleted oil fields might refill themselves.
Now, if it is found that gas and oil are coming up in significant amounts,
and if the same is occurring in oil fields around the globe, then a lot
more fuel than anyone expected could become available eventually. It hints
that the world may not, in fact, be running out of petroleum.
"No one has been more astonished by the potential implications of our
work than myself," said analytic chemist Jean Whelan, at the Woods
Hole Oceanographic Institution, in Massachusetts. "There already appears
to be a large body of evidence consistent with ... oil and gas generation
and migration on very short time scales in many areas globally," she
wrote in the journal Sea Technology.
"Almost equally surprising," she added, is that "there seem
to be no compelling arguments refuting the existence of these rapid, dynamic
The first sketchy evidence of this emerged in 1984, when Kennicutt and colleagues
from Texas A&M University were in the Gulf of Mexico trying to understand
a phenomenon called "seeps," areas on the seafloor where sometimes
large amounts of oil and gas escape through natural fissures.
"Our first discovery was with trawls. We knew it was an area of massive
seepage, and we expected that the oil seeps would poison everything around"
the site. But they found just the opposite.
"On the first trawl, we brought up over two tons of stuff. We had a
tough time getting the nets back on board because they were so full"
of very odd-looking sea.floor creatures, Kennicutt said. "They were
long strawlike things that turned out to be tube worms.
"The clams were the first thing I noticed," he added. "They
were pretty big, like the size of your hand, and it was obvious they had
red blood inside, which is unusual. And these long tubes -- 3, 4 and 5 feet
long -- we didn't know what they were, but they started bleeding red fluid,
too. We didn't know what to make of it."
The biologists they consulted did know what to make of it. "The experts
immediately recognized them as chemo-synthetic communities," creatures
that get their energy from hydrocarbons -- oil and gas -- rather than from
ordinary foods. So these animals are very much like, but still different
from, recently discovered creatures living near very hot seafloor vent sites
in the Pacific, Atlantic and other oceans.
The difference, Kennicutt said, is that the animals living around cold seeps
live on methane and oil, while the creatures growing near hot water vents
exploit sulfur compounds in the hot water.
The discovery of abundant life where scientists expected a deserted seafloor
also suggested that the seeps are a long-duration phenomenon. Indeed, the
clams are thought to be about 100 years old, and the tube worms may live
as long as 600 years, or more, Kennicutt said.
The surprises kept pouring in as the researchers explored further and in
more detail using research submarines. In some areas, the methane-metabolizing
organisms even build up structures that resemble coral reefs.
It has long been known by geologists and oil industry workers that seeps
exist. In Southern California, for example, there are seeps near Santa Barbara,
at a geologic feature called Coal Oil Point. And, Roberts said, it's clear
that "the Gulf of Mexico leaks like a sieve. You can't take a submarine
dive without running into an oil or gas seep. And on a calm day, you can't
take a boat ride without seeing gigantic oil slicks" on the sea surface.
Roberts added that natural seepage in places like the Gulf of Mexico "far
exceeds anything that gets spilled" by oil tankers and other sources.
"The results of this have been a big surprise for me," said Whelan.
"I never would have expected that the gas is moving up so quickly and
what a huge effect it has on the whole system."
Although the oil industry hasn't shown great enthusiasm for the idea --
arguing that the upward migration is too slow and too uncommon to do much
good -- the search for new oil and gas supplies already has been affected,
Whelan and Kennicutt said. Now, companies scan the sea surface for signs
of oil slicks that might point to new deposits.
"People are using airplane surveys for the slicks and are doing water
column fluorescence measurements looking for the oil," Whelan said.
"They're looking for the sources of the seeps and trying to hook that
into the seismic evidence" normally used in searching for buried oil.
Similar research on known oil basins in the North Sea is also under way,
and "that oil is very interesting. There are absolutely marvelous pictures
of coral reefs which formed from seepage [of gas] from North Sea reservoirs,"
Analysis of the ancient oil that seems to be coming up from deep below in
the Gulf of Mexico suggests that the flow of new oil "is coming from
deeper, hotter formations" and is not simply a lateral inflow from
the old deposits that surround existing oil fields, she said. The chemical
composition of the migrating oil also indicates it is being driven upward
and is being altered by highly pressurized gases squeezing up from below.
This upwelling phenomenon, Whelan noted, fits into a classic analysis of
the world's oil and gas done years ago by geochemist-geologist John Hunt.
He suggested that less than 1 percent of the oil that is generated at depth
ever makes it into exploitable reservoirs. About 40 percent of the oil and
gas remains hidden, spread out in the tiny pores and fissures of deep sedimentary
And "the remaining 60 percent," Whelan said, "leaks upward
and out of the sediment" via the numerous seeps that occur globally.
Also, the idea that dynamic migration of oil and gas is occurring implies
that new supplies "are not only charging some reservoirs at the present
time, but that a huge fraction of total oil and gas must be episodically
or continuously bypassing reservoirs completely and seeping from surface
sediments on a relatively large scale," Whelan explained.
So far, measurements involving biological and geological analysis, plus
satellite images, "show widespread and pervasive leakage over the entire
northern slope of the Gulf of Mexico," she added.
"For example, Ian MacDonald at Texas A&M has published some remarkable
satellite photographs of oil slicks which go for miles in the Gulf of Mexico
in areas where no oil production is occurring." Before this research
in oil basins began, she added, "changes in reservoired oils were not
suspected, so no reliable data exists on how widespread the phenomenon might
be in the Gulf Coast or elsewhere."
The researchers, especially the Texas team, have been working on this subject
for almost 15 years in collaboration with oil industry experts and various
university scientists. Their first focus was on the zone called South Eugene
Island block 330, which is 150 miles south of New Orleans. It is known as
one of the most productive oil and gas fields in the world. The block lies
in water more than 300 feet deep.
As a test, the researchers attempted to drill down into a known fault zone
that was thought to be a natural conduit for new petroleum. The drilling
was paid for by the U.S. Department of Energy.
Whelan recalled that as the drill dug deeper and deeper, the project seemed
to be succeeding, but then it abruptly ended in failure. "We were able
to produce only a small amount of oil before the fault closed, like a giant
straw," probably because reducing the pressure there allowed the fissure
In addition to the drilling effort and the inspection of seeps, Whelan and
her colleagues reported that three-dimensional seismic profiles of the underground
reservoirs commonly show giant gas plumes coming from depth and disrupting
sediments all the way to the surface.
This also shows that in an area west of the South Eugene Island area, a
giant gas plume originates from beneath salt about 15,000 feet down and
then disrupts the sediment layers all the way to the surface. The surface
expression of this plume is very large -- about 1,500 feet in diameter.
One surprise, Whelan said, was that the gas plume seems to exist outside
of faults, the ground fractures, which at present are the main targets of
It is suspected that the process of upward migration of petroleum is driven
by natural gas that is being continually produced both by deeply buried
bacteria and from oil being broken down in the deeper, hotter layers of
sediment. The pressures and heat at great depth are thought to be increasing
because the ground is sinking -- subsiding -- as a result of new sediments
piling up on top. The site is part of the huge delta formed over thousands
of years by the southward flow of the massive Mississippi River. Like other
major deltas, the Mississippi's outflow structure is continually being built
from sands, muds and silts washed off the continent.
Analysis of the oil being driven into the reservoirs suggests they were
created during the so-called Jurassic and Early Cretaceous periods (100
million to 150 million years ago), even before the existing basin itself
was formed. This means the source rock is buried and remains invisible to
seismic imaging beneath layers of salt.
In studying so-called biomarkers in the oil, Whelan said, it was concluded
that the oil is closely related to other very old oils, implying that it
"was probably generated very early and then remained trapped at depth
until recently." And, she added, other analyses "show that this
oil must have remained trapped at depths and temperatures much greater than
those of the present-day producing reservoirs."
At great depth, where the heat and pressure are high enough, she explained,
methane is produced by oil being "cracked," and production of
gas "is able to cause sufficient pressure to periodically open the
fracture system and allow upward fluid flow of methane, with entrapment
of oil in its path."
All information posted on this web site is
the opinion of the author and is provided for educational purposes only.
It is not to be construed as medical advice. Only a licensed medical doctor
can legally offer medical advice in the United States. Consult the healer
of your choice for medical care and advice.