BAKERSFIELD, CA - An abandoned Bakersfield, California
oil lease, brought back to life in 1995 by a joint government-industry
experimental project, has produced more than a million barrels of oil
once thought unrecoverable.
|Improved technology made possible
by a joint DOE and private industry field test helped bring the
Pru Lease back into production.
Because of the success, oil is now flowing from 100 new privately funded
wells in the immediate vicinity, and experts predict that the advanced
technologies demonstrated in the federally co-funded field test could
lead to millions more barrels of oil recovered from fields around the
"This is oil from a U.S. field that otherwise would have remained
beyond the reach of conventional technologies," said Secretary of
Energy Spencer Abraham. "The Energy Department is committed to making
successes like this become more commonplace. Clearly, new technologies
and advances in oil exploration and production techniques contributed
to the successful recovery of oil that would otherwise be unreachable
with conventional technologies."
The project took place on the Pru Fee lease, part of the giant Midway-Sunset
field roughly 30 miles southwest of Bakersfield. Support from the U.S.
Department of Energy, in coordination with the University of Utah, Aera
Energy LLC, and ARCO Western Energy, made testing of the improved technologies
possible when normal commercial practices were no longer effective.
In the last five years, the million barrels of "new" oil that
has flowed from the field is more than half as much oil as the property
produced in all of its first 80 years of operation. Project sponsors predict
that the advanced technologies ultimately will result in more than 4 million
barrels of oil being produced - all from a 40-acre property once thought
to be dead from an oil producer's perspective.
The project is one of several supported by the Energy Department in its
Reservoir Class Oil Field Recovery Program. Begun in 1991, the program
targeted geologic classes of U.S. oil fields that were on the verge of
being prematurely abandoned. With federal matching funds allowing higher-risk
technologies to be tried, many operators have been able to keep oil flowing
from these fields long after conventional wisdom labeled them "depleted."
The Pru Fee project in the Midway-Sunset field was selected in the third
round of the program in 1995. The Energy Department provided $2.2 million,
and the University of Utah and its industry partners contributed $3.6
Discovered in 1894, the Midway-Sunset Field was booming by the early
1900s. The Pru lease was a major part of the early oil surge, coming into
production in 1906. But by the late 1960s, output from the lease had dropped
off greatly, and operators began injecting steam to thin the heavy oil
in an attempt to keep it flowing.
The technique worked for a while - the field was producing 300 barrels
per day in1972 - but by 1985, production had dropped to less than 10 barrels
per day. The lease was abandoned. But there was tantalizing evidence that
as much as 90 percent of the property's oil remained behind. Other Midway-Sunset
tracts continued to produce, but oil trapped in the 200- to 300-foot-thick
sand formation beneath the Pru lease seemed beyond the capabilities of
Using modern advances, engineers ran seismic surveys, compiled new information
on rock properties, and analyzed cores and outcrops to create a geologic
profile of the reservoir in unprecedented detail. They fed the data into
advanced computer programs that simulated how the reservoir would respond
to various production strategies. The computer helped pinpoint the optimal
patterns where new wells should be drilled to inject steam and recover
the most oil.
Initially, ARCO Western evaluated the previously tried technique of "cyclic
steam flooding" - using an 8-acre section of the lease to alternately
inject steam, then recover oil. But after two steam cycles, production
dropped off. The research team then turned to continuous steam injection,
sending a steady flow of steam down one set of wells and recovering oil
from other wells. Production picked up and stayed up, eventually reaching
more than 1,500 barrels per day.
By early 1999, 37 new wells on the lease had been put on line. Aera Energy,
which acquired the lease from ARCO, began applying the technologies to
leases surrounding the Pru field. Currently 54 new wells have been placed
into production, the most recent at the Lilly lease, which is twice as
large as Pru and could hold up to 10 million barrels of recoverable oil.
The Energy Department's National Petroleum Technology Office, which oversaw
the project, now estimates that applying the new methods to only half
the 26 currently shut-in Midway-Sunset properties could produce another
80 million barrels of oil. The federal taxes on this oil alone would total
more $10 million, nearly five times the government's original investment
in the Pru Fee project.