Radar images of the surface of an oil field are helping
scientists understand how rocks deep within the field behave,
which may help oil companies reduce costs and increase

In this pilot study, the researchers are monitoring
where and how much the ground surface sinks as oil is pumped
from a large oil field.

Subsidence means that rocks are collapsing deep
underground. It can damage oil wells and reduce the amount of
oil that can be pumped from a field. In their study,
geophysicist Dr. Eric Fielding, of NASA’s Jet Propulsion
Laboratory, Pasadena, Calif., and Dr. Tadeusz Patzek,
associate professor of petroleum engineering at the
University of California, Berkeley, looked at Chevron’s Lost
Hills oil field. Lost Hills is located about 40 miles
northwest of Bakersfield in California’s San Joaquin Valley.
About a mile wide and more than three miles long, parts of
the oil field have subsided 3 meters (10 feet) since 1989.

The researchers compared radar images of the oil field
taken during 1995, 1996, 1998 and 1999, using a technique
called radar interferometry. This involves precisely aligning
two radar images taken at different times. It produces
accurate measurements of topography and of surfaces that may
have changed in the time between collection of the data.

Using these radar data, scientists found that parts of
the oil field were subsiding unusually rapidly, more than 3
centimeters (1.2 inches) a month, in 1995 and 1996. They also
discovered that while the ground subsidence rate decreased in
the center part of the oilfield, it increased in the northern
part in every year observed between 1995 and 1999.

“This is an exciting new application for synthetic
aperture radar, monitoring subsidence over an oil field from
space,” said Fielding. “We’re now working with Chevron to
combine these subsidence maps with the records of oil and
water extraction and injection to understand how oil-
containing rock is behaving beneath the surface.”

The project is a collaboration supported by NASA, the
University of California, Berkeley, the Department of Energy
and Chevron U.S.A. The results were presented in October 2001
at the Society of Petroleum Engineers Annual Technical
Conference and Exhibition. JPL is a division of the
California Institute of Technology in Pasadena.