MGSC has partnered with the Archer Daniels Midland (ADM) Company, an agricultural product processing company, and Schlumberger Carbon Services to conduct a large-volume, saline reservoir storage field project at ADM’s agricultural products processing complex in Decatur, Illinois. The Development Phase project, also referred to as the Illinois Basin – Decatur Project (IBDP) involves the injection of 1 million metric tons of CO2 over three years into a deep saline formation of the Illinois Basin.
The project site is located on the ADM industrial facility and corporate headquarters within the city of Decatur, Illinois, a city with a population of 77,000 people. The injection well and verification wells are located in a field north of the industrial facilities (Figure 1). ADM’s Decatur complex consists of various processing facilities including a corn wet milling plant with ethanol production which is the source of the CO2 for the project. Additional primary facilities include cogeneration of electricity and steam, bioproducts, oilseed processing, and vegetable oil refining. Previously this field had been used for corn/soybean farming or had lain fallow. Other land uses within one mile of the test site include agricultural, commercial, and residential. The site is located in Bloomington Ridged Plain of the Till Plains Section of Illinois, has approximately 25 feet of relief, and is less than 2 miles west of Lake Decatur. Lake Decatur is a surface impoundment of the Sangamon River, which is the major surface water feature in east-central Illinois. The site is underlain by approximately 5 feet of loess, 30.5 feet of glacial drift (Wisconsin and Illinoisan Episode), and Pennsylvanian bedrock. The deepest Underground Source of Drinking Water (USDW) being monitored at the site is at a depth of about 140 feet in the Pennsylvanian bedrock.
Description of Geology
The target formation is the Cambrian-age Mt. Simon Sandstone, the thickest and most widespread saline reservoir in the Illinois Basin (Figure 2). It is overlain by the Eau Claire Formation, a regionally extensive, low-permeability shale, siltstone and tight limestone, and is underlain by Precambrian granitic basement. To date, the upper Mt. Simon has been used extensively for natural gas storage in the northern half of Illinois. Detailed reservoir data from a few wells at these storage sites shows that the lower Mt. Simon has the necessary porosity and permeability to be a good storage target. A regional isopach map of the Mt. Simon initially suggested there are probably more than 1,000 feet of Mt. Simon reservoir available for injection at the ADM site and 1,650 feet was actually measured. The injection well was drilled to a total depth of 2,200 meters (7,236 feet). Data from a well drilled 17 miles from the ADM site and a second well drilled 51 miles south of the ADM site indicate that there is generally good porosity in the Mt. Simon. MGSC found that the average porosity of the Mt. Simon injection zone at the IBDP site is around 12 percent. The top of the Mt. Simon Sandstone at the ADM site is estimated to lie at a depth of 5,500 feet.
Within the Illinois Basin, the Devonian-age New Albany Shale, Ordovician-age Maquoketa Formation, and the Cambrian-age Eau Claire Formation all contain shales that function as the primary confining zones. There are also many minor, thinner Mississippian- and Pennsylvanian-age shale beds that form local confinement for known hydrocarbon traps within the basin. Subsurface wireline correlations suggest the three primary confining zones are continuous within a 100-mile radius of the test site. At the injection site the Eau Claire, which will be the primary confining zone, was found to be 500 feet thick. The Ordovician Maquoketa Shale and the New Albany Shale act as secondary and tertiary confinement. There are no seismically resolvable faults and fractures within a 25-mile radius of the ADM site.
Source of CO2
The source of CO2 for the project is downstream of the product recovery scrubbers that follow the ADM ethanol fermentation units. The CO2 stream from these units is typically 99%+ pure and is saturated with water vapor at 80 °F and 1.5 psig. Common impurities are ethanol and nitrogen in the range of 600 to 1,000 parts per million by volume (ppmv) each. Other impurities in lesser amounts often include oxygen, methanol, acetaldehyde, and hydrogen sulfide (H2S).
The CO2 stream from the fermentation units is routed to a dedicated dehydration/compression facility where it is dried and compressed. The CO2 stream is routed to a multistage centrifugal blower with one 632 kW motor that raises the CO2 pressure to 18 psig. Following the blower, the CO2 is compressed to a supercritical fluid (~1,400 psig) by two 4-stage reciprocating compressors running in parallel and powered by 632 kW motors. Glycol dehydration occurs between the third and fourth stages of compression. The compressed CO2 fluid is then transported to the injection wellhead through a 6,000 foot steel pipeline. An additional pump is integrated into the system just downstream of the compressors to boost pressure above 1,400 psi if additional pressure is needed to maintain an injection rate 1,000 metric tons per day. Shakedown of the newly constructed facility was completed in October, 2011. On November 2, 2011 the Illinois EPA granted approval to begin injection operations, and on November 7, 2011 injection operations were initiated at 1,000 metric tons per day.
Simulation and Monitoring of CO2
MODFLOW and GFLOW are being used to develop a conceptual model for shallow groundwater flow and to estimate CO2 migration in the subsurface. The modeling results provide information used in developing risk mitigation strategies for nearby water supplies in the unlikely occurrence of a CO2 leak either during or following CO2 injection. Geochemical models, such as Geochemist’s workbench, PHREEQCI, and TOUGHREACT, will be used to conduct thermodynamic modeling of shallow groundwater and injection-formation brine. These models will provide insight on the long-term fate of injected CO2 and will be used to study the regional impact of multiple injection wells on flow within a saline reservoir across the Illinois Basin. At present, 55 feet of perforations have been opened in the lower Mt. Simon, and plume modeling is proceeding based on porosity and permeability data from sidewall cores and well log information. Other zones may be opened during the three-year injection period to take advantage of vertically stacked storage zones that will result in a compact plume shape. Porosities in the lower Mt. Simon are 15–25 percent, and permeabilities are primarily in the range of tens to several hundred millidarcies, up to about 1,000 millidarcies.
The IBDP has an extensive Monitoring, Verification, Accounting (MVA), and Assessment program focused on the 0.25 mi2 project site and critical locations in the surrounding area. Program goals include establishment of the environmental baseline conditions to evaluate potential impacts from CO2 injection, demonstration that project activities are protective of human health and the environment, and demonstration of an accurate accounting of stored CO2. MVA efforts are being conducted pre-, during, and post-CO2 injection. Effectiveness of long-term storage of CO2 in the Mt. Simon is being evaluated through an in-zone verification well designed to monitor the injection formation and formations immediately above the primary caprock using pressure monitoring and fluid sampling. A dedicated geophone well has been drilled to facilitate repeat seismic imaging over the life of the project. Surface deformation will be measure using InSAR satellite imagery. Monitoring of the near-surface environment includes color infrared aerial imagery, high-resolution electrical earth resistivity, shallow groundwater quality, soil CO2 fluxes, net exchange CO2 fluxes, and vadose zone CO2 concentrations. Characterization of near-surface CO2 conditions is important to determine baseline conditions for detecting any potential CO2 leakage to the atmosphere.