Washington, D.C. — Gas streams containing high levels of both carbon dioxide (CO2) and hydrogen sulfide (H2S) can be safely used for carbon capture and storage (CCS), according to results from a field test completed by the Plains CO2 Reduction (PCOR) Partnership.
The test by PCOR—one of seven members of the U.S. Department of Energy’s (DOE) Regional Carbon Sequestration Partnership (RCSP) program—also demonstrated that carbon sequestration using so-called "sour" gas streams can be combined successfully with enhanced oil recovery (EOR) and H2S disposal.
The findings help support national and global efforts to develop and deploy CCS use as one option for mitigating global climate change. CCS involves the permanent storage of human-generated CO2 emissions in geologic formations deep underground, including depleted oil and gas reservoirs, deep saline formations, and unmineable coal seams. Some of these same geologic formations may also be fit for large-scale storage of CO2 streams containing significant quantities of H2S, a toxic and flammable "sour" gas that smells like rotten eggs. Results from the Zama field test will help in determining the technical and economic viability of CO2 and sour gas storage and support the ultimate deployment of commercial-scale projects.
During the four-year field test, a gas stream composed of 70 percent CO2 and 30 percent H2S was injected at a depth of 4,900 feet in the Zama oilfield in northwestern Alberta, Canada. A total of about 33,500 tons of sour gas were injected, simultaneously sequestering CO2, disposing of H2S, and increasing oil recovery by reducing the viscosity of the crude oil and pushing it toward the production well. Apache Canada Ltd. undertook the injection and hydrocarbon recovery processes, while the PCOR Partnership conducted monitoring, verification, and accounting (MVA) activities to verify and validate the containment integrity of the reservoir.
The project’s goals, all achieved, included:
- Demonstration that the capture and injection of a sour gas stream into properly characterized and carefully selected underground reservoirs is feasible and safe within existing industry and regulatory standards.
- The design, implementation, and demonstration of cost-effective, ongoing MVA strategies.
- Confirmation that sour gas could be successfully used for EOR operations in a previously untested geologic feature (i.e., carbonate pinnacle reefs – buildups of carbonate that can contain varying amounts of oil and natural gas); incremental oil production over the course of the project was greater than 25,000 barrels.
DOE’s RCSP program is a government-industry effort that aims to determine the best approaches for capturing and storing gases that can contribute to climate change. The program is managed by the Office of Fossil Energy’s National Energy Technology Laboratory.
The PCOR Partnership brings together more than 80 partners consisting of public agencies, utilities, oil and gas companies, engineering firms, nonprofit organizations, and universities. Led by the Energy and Environmental Center in Grand Forks, N.D., the PCOR Partnership has completed four small-scale validation tests and is currently conducting two large-scale development tests.