Shell Western E&P Inc. is well along with a sharp expansion of its carbon dioxide enhanced oil recovery operations.
In Southwest Colorado, Shell stepped UP CO2 productive capacity to 800 MMcfd from 700 MMcfd in McElmo Dome field straddling the Dolores-Montezuma county line. McElmo Dome CO2, flowing through the 500 mile Cortez pipeline to West Texas, supplies most of the gas Shell injects in its Denver Unit. But most of the increased production will go to other operators in West Texas, New Mexico, and Utah.
In Wasson field, Yoakum County, West Texas, Shell is enlarging its Denver Unit CO2 recovery plant to almost twice the present inlet gas capacity, thereby hiking throughput to 290 MMcfd from 180 MMcfd. It also is modifying and extending to the west, inside the city limits of Denver City, its CO2 flood area (OGJ, Feb. 26, 1990, p. 106).
Shell Oil Co.'s Venture magazine said the combined Wasson field projects will boost unit recovery to about 60% of oil originally in place and extend the life of the unit by at least 25 years beyond previous expectations.
MCELMO DOME
The 100 MMcfd added productive capacity in McElmo Dome field comes from completion of a fourth CO2 processing plant at nearby Sand Canyon. Automation allows its operation as a remote site, if necessary.
The expansion plan included drilling of five wells, installation of stainless steel gathering lines and a dehydration/compression unit, expansion of the produced water disposal system, and addition of power equipment owned and operated by a utility company at a total cost of about $28 million.
However, results of the first three wells drilled in the project were better than expected. So the fourth and fifth might not be required.
Built earlier at McElmo Dome were the Yellowjacket and Hovenweep processing plants, each rated at 300 MMcfd, and the Moqui plant, rated at 100 MMcfd.
McElmo Dome field, covering 200,000 acres, produces CO2 from the 250-300 ft thick Mississippian Leadville limestone and dolomite at 8,200-9,000 ft. Reserves are more than 10 tcf of CO2, which Venture calls "one of the largest and purest accumulations of CO2 in the U.S."
Shell expects peak production of about 1 bcfd.
DENVER UNIT
Expansion of the Denver Unit CO2 recovery plant consists of two major parts: replacing and expanding the hydrogen sulfide treating capacity by installing Shell's SulFerox process and modifying and debottlenecking the existing recovery plant.
Flood expansion will require installation of more CO2 and water injection systems and other field facilities and conversion of 122 water injection wells to CO2 injection. No drilling will be required.
Completion of the projects is set for early 1992, when unit production is scheduled to start a gradual rise to a peak of nearly 50,000 b/d of oil in 1996. Current production is 38,000 b/d of oil, 207,000 b/d of water, and 195 MMcfd of gas, including CO2. Combined cost of the plant and flood expansion will be about $100 million during the next several years.
Covering 28,750 acres, the unit holds 750 producing wells, 200 CO2 injection wells, and 190 water injection wells. Injection volumes are 440 MMcfd Of CO2 and 141,000 b/d of water.
Shell's Denver Unit injection program uses a hybrid water-alternating-gas (WAG) method. That involves injecting CO2 continuously for 4-6 years, then switching to the WAG method.
Shell began injecting CO2 in 1984. It started a Wasson field waterflood in 1964.
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