The Greater Aneth Oil Field is the largest producing oil field in the State of Utah, with current production of approximately 10,000 bbls of oil per day, and is the 86th largest oil field in the United States by proven reserves as ranked by the US Energy Information Administration. The Greater Aneth Oil Field covers over 48,000 acres (19,500 ha) and is also one of the three biggest CO2 EOR projects in the US Rocky Mountains. Greater Aneth is located in the southern Rocky Mountains in south-eastern Utah near the Colorado and New Mexico borders in an area known as the Four Corners Region. The field was discovered in 1956 and is the largest oil field in the Paradox Basin.
Elk Petroleum is the operator and NNOGC has a 36% interest. The Greater Aneth Oil Field is comprised of three contiguous operating units: the Aneth Unit, the McElmo Unit and the Ratherford Unit. Collectively these three operating units are known as the Greater Aneth Oil Field.
At its peak, the Greater Aneth Oil Field produced over 100,000 bbls of oil per day and currently produces from 444 wells. As of 1 January 2017, cumulative production was 483.1 million BO of the estimated 1.5 billion bbls of original oil in place (“OOIP”) and 440.2 billion cubic feet of gas (BCFG), (Utah Division of Oil, Gas and Mining, 2017a).
Extensive EOR development both, secondary recovery through waterflood and tertiary recovery through carbon dioxide (CO2) flooding, have been implemented across the Greater Aneth Oil Field. The implementation of these secondary and tertiary enhanced oil recovery developments makes the Greater Aneth Oil Field the largest waterflood program and the only CO2 enhanced oil recovery operation in Utah.
Waterflood (secondary recovery) operations began in 1961 and have been implemented in all the Greater Aneth Oil Field units and carbon dioxide flooding (tertiary recovery) through a water alternating gas (WAG) EOR program began in the McElmo Creek Unit in 1985 by Texaco Oil Company and were further expanded by Resolute Energy into the Aneth Unit starting in 2007. CO2 EOR operations have not been extended into the Ratherford Unit which is under extensive waterflood recovery. Overall, there are 333 injection wells exist in the field as of the end of 2016. Oil is exported via the Running Horse Oil Pipeline to Western Refining’s Gallup, New Mexico refinery.
Extensive and successful horizontal drilling programs have also been conducted across the Greater Aneth field. These drilling programs were carried out primarily in the Aneth (in 1996) and Ratherford (in 1994) Units in the northwest and southeast parts of the field, respectively. Horizontal wells in the primary Desert Creek zone have successfully increased production in these units.
CO2 is supplied to the Greater Aneth Oil Field by Kinder Morgan under long-term contract from the McElmo Dome CO2 Field located in southwestern Colorado via a 28 mile 8-inch pipeline which is owned and operated by the Greater Aneth Joint Venture. The McElmo Dome CO2 Field is the largest source, producer and supplier of CO2for CO2 EOR operating in the US producing over 1.1 BCF of CO2 a day with over 6 TCF of remaining proven CO2 gas reserves.