(Tech Connections Column, February 2007, American Oil and Gas Reporter)

The Permian Basin’s annual “carbon dioxide conference week” continues to grow in stature with the Carbon Management Workshop moving to Houston (and simulcast to Midland, Tx.), a packed field trip and short course, and case history sessions in Midland. The Midland CO₂ Conference drew 350 people from 196 organizations, including 50 from 10 foreign countries. There now are more than now 80 commercial CO₂ improved oil recovery projects.

Although interrelated, the Carbon Management Workshop and CO₂ Conference draw different audiences, as evidenced by attendee responses to the statement: “Climate change/global warming is a serious problem that merits a serious response.” Eighty-five percent of the carbon management attendees said yes. Attendees at the Midland conference answered a question focused more specifically on CO₂: “Do you think CO₂ causes global warming?” Responses were nearly evenly split among “yes,” “no” and “not sure.” Whatever the perspective, the reality is that anthropogenic CO₂ sources are becoming the emerging option for many oil fields previously precluded from CO₂ IOR.

The focus in Midland was on operations and flood results. Anadarko Petroleum showed that with planning on the front end, all aspects of producing and controlling a state-of-the-art CO₂ project could be automated. Fiberspar presented a case study demonstrating the time savings and cost advantages of continuously spooled flowlines in Encana’s Weyburn CO₂ project.

At the SACROC Oil Field, the hydrocarbon gas/oil ratio (HCGOR) varies with time and flooding stage. HCGOR doubles during the active CO₂ injection phase. Kinder Morgan shared how predicting and optimizing HCGOR helped optimize revenues from 15,000 barrels a day of natural gas liquids. Kinder Morgan samples its SACROC injection wells monthly to make sure they have the right pressure and composition to maximize sweep.

Occidental Petroleum described the process by which it identified and mitigated several large “short-circuiting features” leached or fractured between several injectors and producers in its Anton Irish Unit. There has been a learning curve because void spaces have been much larger than anticipated, but the polymer gel/foamed cement treatments (SPE 103044) have yielded positive results, and insights gained now are being applied elsewhere.

Denbury Resources compared early results between its Little Creek and West Mallalieu projects in Mississippi. These deep sandstones have much higher operating and miscibility pressures, and both fields are under continuous injection rather than WAG (water alternating gas). At $0.25 an Mcf for the CO₂, operating expenses for both are $12-$14 a barrel. An atypically large amount (four-five hydrocarbon pore volumes of CO₂) ultimately will be injected in each field.

Little Creek, which underwent waterflooding, had produced 38 percent of the original oil in place prior to CO₂ flooding. West Mallalieu, which has a weak water drive and had only recovered 22 percent of OOIP, went directly from primary to tertiary. It now is producing at higher rates (6,900 bbl/d versus 2,600 bbl/d) and likely will produce 22 percent or more of the remaining oil versus the expected tertiary recovery of 17 percent at Little Creek. However, West Mallalieu is forecasted to ultimately recover only 44 percent of OOIP versus 55 percent expected for Little Creek because it is thicker (harder to sweep) and three channels have been identified.

Apache Canada presented the results of a unique CO₂ pilot project in Northern Alberta in which acid gas–65 percent carbon dioxide and 35 percent hydrogen sulfide–is being injected in a series of pinnacle reefs. This project is part of the Energy and Environmental Research Center and the U.S. Department of Energy’s Plains CO₂ Reduction Partnership. The initial pilot consisted of 10 pinnacles, but there is expansion potential with more than 25 pinnacles identified in the area.

Anadarko presented early results from its Salt Creek Field project, which it began in 2004. The oil response was quick in the first and second phases (of 12) within the Wall Creek 2 formation, becoming self-funding in 2005. Pilot response in the shallower, immiscible Wall Creek 1 has been sufficiently promising to expand as well. Oxy then highlighted the significant improvement in its Denver Unit CO₂ flood brought about by modifying patterns, altering WAG, developing the transition zone, and optimizing individual patterns. Another mature flood–Chevron’s Vacuum Field–was improved through infill drilling, expanding the area of the flood, and defining and exploiting the top of the transition/residual oil zone.

The Permian Basin is the source of proven CO₂ flood practices, since it accounts for more than 75 percent of CO₂ IOR. The solid technical program, operator willingness to share, and the networking environment make the CO₂ Conference the premier event of its type. More information is available at www.spe-pb.org. The 2007 conference is planned for the week of Dec. 3.