Chasing the oil to Kitchen
The Kitchen prospects are in 70 feet of water close to the Kenai Peninsula’s industrial complex north of Nikiski. Escopeta has 11 years of work into the prospects, including studies by geologists with Cook Inlet experience and, more recently, the reprocessing of seismic by Houston-based Apex Metalink Inc. with its proprietary technology.
Escopeta’s Kitchen acreage is east of the Middle Ground Shoal field, where XTO is doing additional development work to improve on the 12 million barrels of reserves it bought from Shell in 1998. (Shell developed the east flank of the structure in the 1960s and the west flank in the late 1980s.)
If Escopeta’s theories on oil migration in the inlet are correct, the oil in Middle Ground Shoal migrated from east to west, filling Escopeta’s Kitchen prospect traps first before moving on to Middle Ground Shoal and then on to subsequent traps.
“The theory on migration of oil is that the migrating oil finds a path, and then travels along that path, not deviating from it,” said Bob Warthen, a consulting geologist working with Escopeta. “When it leaves the source area, it migrates up dip and fills the deepest traps first. As these are filled the oil continues to migrate up dip filling the shallowest traps in turn.”
Warthen said Middle Ground Shoal is about 80 to 85 percent filled while structures farther along the migration path are less filled, supporting the idea that the Kitchen structures were filled before Middle Ground Shoal.
Warthen’s Cook Inlet experience has guided Escopeta. He has worked the inlet since 1967, first for Union Oil where he was a regional geologist for 26 years, and then as a consultant. He remembers after Prudhoe Bay was discovered, the working scenarios in the inlet shifted to a strictly a development-type scenario, resulting in very little exploration work being done.
After Warthen took an early retirement from Unocal in 1992, he began working all the available data on the inlet, including well information and seismic, and doing fieldwork, trying “to get a better understanding of the intricacies of the formations.”
He developed a basin map that was focused on the inlet’s petroleum system and potential untested habitats and traps. Geologists Walter Wells and Frank Banar, retired from Mobil, also contributed to Escopeta’s “idea map.”
Banar said one very key thing Escopeta did was to have its seismic data reprocessed using a process called wavelet energy absorption. In China, he said, the process has been used in basins which have both coal and gas, and where the gas needed to be identified on the seismic.
Because Cook Inlet has both coal and gas, the process seemed appropriate, he said. In addition to the seismic processing for gas, Apex Metalink also has a process for fluids identification.
The wavelet energy absorption processing “showed some significant gas reserves on the Kitchen and East Kitchen structures, especially in the Tertiary section, where abundant coal beds have generated major dry gas reserves,” Banar said.
Current Cook Inlet production is from Tertiary formations: dry gas from Sterling, Beluga and upper Tyonek; oil from the lower Tyonek and Hemlock. There is no production from the older Cretaceous and Jurassic in the upper Cook Inlet basin, although surface oil seeps are known from the Jurassic Tuxedni formation. The Tuxedni, said Warthen, has been identified by the USGS as the source rock for all of the oil present in the Hemlock.
Davis said potential deep gas below the Tertiary is a separate prospect. The objectives at the Kitchen prospects are the major producing Cook Inlet formations — Sterling, Beluga, Tyonek and Hemlock. Escopeta does not attribute any reserves to pre-Tertiary but considers them a very viable future target.
DOE said the inlet has been explored for structural traps but not for stratigraphic traps. East Kitchen is a structural trap, Davis said, while Kitchen is a faulted stratigraphic trap first proposed by the U.S. Geological Survey.
What Escopeta is doing matches up with DOE’s description of two-phase exploration history in mature basins, first exploration for structural traps such as East Kitchen, Davis said, and then a second phase focused on stratigraphic plays like Kitchen.
USGS theories hold that only 4 percent of the volume of oil that theoretically generated from Cook Inlet source rock has ever been identified. If Escopeta’s approach bears fruit, it will fill in many of the blanks in Cook Inlet knowledge, with a payoff for the company.
—Steve Sutherlin
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