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Geologists Ian Bryant
and Peter Tilke are
part of the CyberGeologist* program, sponsored by Schlumberger
and the United States Gas Research Institute. They use a
variety of methods to gather and analyze data about underground
rock formations in the never-ending search for oil and gas.
One way the scientists gather this data is by bringing up
actual samples of the rock and studying them in the laboratory,
but they also use other more sophisticated methods, such
as borehole resistivity and seismic imaging.
A borehole image of rock layers
indicating an underground point bar
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Borehole resistivity images are generated by sensors built
into the drillbit. As the drillbit passes through the layers
of rock, it runs an electric current through the rock. By
measuring changes in the electrical resistivity of the rock,
they can determine what kind of rock the bit is drilling through.
A computer is used to convert the information from the drillbit's
measurements into a graphic image of the rock layers.
Seismic imaging uses a process similiar to the sonar systems
which submarines use to navigate. Scientists create vibrations
in the rock. They can then measure the "echo" of the vibrations
as they are reflected by the underground layers of rock.
Using these methods, the scientists take a series of measurements
in a certain area. Then they "connect the dots" to create
a three-dimensional model of the underground formations.
By studying modern point bars and other sedimentary formations,
the scientists can create more accurate models from the
borehole and seismic data they collect.
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