Since September, engineers
in the UH Enhanced Oil Recovery Laboratory have been
enjoying X-ray vision.
"We have capabilities no one
else has," said Harry Deans,
professor of chemical engineering and EOR Director.
Deans is describing the extraordinary capabilities of the
X-Ray CT Scanning system recently acquired by the EOR
Laboratory. The device, traditionally used to diagnose body
tissue disorders, has been borrowed them medicine and
idapted for oil field research.
"We've removed a lot of
nedicine's constrantes from the
nachine," he said.
"Because our targets have
wo or three times the density
>f the human body, we need
% X-ray doses. So, we scan
onger and use high settings on
Core samples from oil fields
ire being studied with the CT
Scan to determine how oil
flows through rock.
"A lot of oil is trapped and
never gets to the well," Deans
said. Our research is focused on
improving the process of getting what's there out of the rock
and at a reasonable cost. If it
can't be done economically, it's
a waste of time."
X-Ray CT is a computer-
controlled technique for imaging cross sections inside an
Scanners have been bought
by the industry as they are replaced with Nuclear Magnetic
Resonance machines in the
UH, with a matching grant
from the National Science
Foundation, purchased EOR's
fourth-generation scanner for
$125,000, about 10 percent of
the machine's original cost.
However, EOR, which was
established in 1984, receives its
funding primarily from industrial sponsors. The research
consortium currently has 18
member companies that each
pay annual dues of $15,000.
These fees cover laboratory
operation costs, machine maintenance, theoretical research by
graduate students and proprietary research for individual
companies in the consortium.
CT is the abbreviation for
The word tomography derives
from the Greek word "tomos,"
meaning slices, and "graph"
The name is an exact description of the scanner's mode
of operation, because a CT
nondestructively "slices" and
displays the interior of the object being studied.
In CT, an X-ray source
moves in a circular path around
the object in a controlled time
rotation. At each angle of rotation, 720 detectors, which are in
a fixed array, pick up any radiation that passes through the
target and obtains a one-dimensional projection.
A computer mathematically
processes these projections to
create a two-dimensional image.
The object is then moved in
one millimeter increments and a
series of slices are imaged. From
sequential, overlapping cross
sections, any other plane
through the body can be reconstructed by the computer.
These reconstructions produce three-dimensional representations of the object.
In the EOR laboratory, an
image can be taken and reconstructed on the console in 20 to
30 seconds, Deans said. The
images are stored on disk and
Since oil is found in porous
rock such as limestone, a scan
of oil field samples with the
pores evacuated looks like Swiss
Deans said they are filling the
pores, under pressure, with xenon gas — which stops X-rays
just like rock does. As a result,
the whole sample appears solid
— except for any irregularities
in the rock itself.
Soon, tests will be conducted
in which helium, a gas that has
no X-ray absorption, is forced
in the core samples at high
pressure. Xenon will then be
flowed in to displace it.
"The speed at which it fills
all the holes will be very interesting. This is the data we're
after," Deans said.
"By working with high pressure, the displacement process
will be slow enough for us to
take repeated pictures and
watch it happen."
This process will correspond
to what's happening in the
ground when water is flowed in
to displace oil and force it out.
"It's something we need to
understand," he said.
Deans, who taught at Rice
University before coming to
UH in 1982, said they will only
be doing pure research in the
"There are no direct commercial aspects of our research."
But plans will include making the X-ray machine available
for multi-disciplinary use. The
civil engineering department already has suggested using the
scanner to study concrete stress,
Electronic Music Inc., a
company owned by the Beatles,
developed the first modern CT
— Marilyn Swanson