Development and Operation of a One-Million Tonne Carbon Capture and Storage Demonstration Project: Decatur, Illinois USA

A successful carbon dioxide (CO₂) storage site is based on careful selection of the site, detailed site characterization prior to the start of injection, and an ongoing monitoring plan to ensure that the site is secure and that leakage is not taking place.  A reservoir-seal system must exist that offers capacity in terms of adequate pore space, injectivity in terms of reservoir permeability, and containment in the form of a reservoir seal.  Prospecting for such a system can be done initially using regional geologic data, then progressing to detailed site-specific geophysical imaging.  Site confirmation involves drilling to recover rock and fluid samples and determine pressures and temperatures.  Detailed well logging generates data to assess reservoir and seal matrix properties, evaluate any fractures present, and create a baseline against which post-injection changes can be further assessed.  Subsurface monitoring may involve repeat geophysical surveys, repeat cased-hole well logging, and observation wells to determine changes as CO₂ is injected over time.  All of these approaches have been implemented at a US Department of Energy-supported demonstration of carbon storage at Decatur, Illinois USA where 1 million tonnes of CO₂ is to be injected over a period of three years.  Injection began in November 2011 and is continuing at the rate of 1,000 tonnes per day. A total of 500,000 tonnes has been injected to date with no indication of CO₂ migration outside of the injection zone. Injection will continue through late fall 2014 and subsequent environmental monitoring will continue for at least another three years.

The Illinois Basin – Decatur Project (IBDP) is the saline reservoir storage project of the Midwest Geological Sequestration Consortium (MGSC), one of the Phase III projects of the US Department of Energy’s Regional Carbon Sequestration Partnership (RCSP) program. The IBDP is the first demonstration-scale (1 million tonnes permitted) RSCP project supplied from an industrial source in the United States. The major MGSC IBDP collaborators are the Illinois State Geological Survey, Schlumberger Carbon Services, Trimeric Corporation, and the Archer Daniels Midland Company (ADM). Numerous researchers contribute to multiple aspects of the project. ADM is a global agricultural products processing company and supplies the 99+ percent pure CO₂ as a byproduct of the fermentation of corn to produce ethanol as a motor fuel component. ADM also owns the injection site, operates the compression facility, and holds the Underground Injection Control (UIC) permit required under US environmental regulations.

The IBDP is an integrated industrial CCS system from the source to the reservoir.  It includes a 2,190 m deep injection well, a 2,201 m deep observation well, and a 1,050 m deep geophysical well containing a string of 31 multicomponent geophones cemented in place.  The observation well is perforated at 11 intervals, nine in the Mount Simon, and two above the primary shale seal and is fitted with the Westbay* multilevel groundwater characterization and monitoring system to allow continuous pressure monitoring and periodic fluid sampling.  The geophysical well is located on the injection well pad and the observation well is located 300 m north-northeast of the injector.  The injection well is fitted with multicomponent microseismic sensors.  Dense phase CO₂ is delivered to the injection well via a 1.9 km, 6-inch diameter pipeline supplied by two four-stage reciprocating compressors with an integrated glycol dehydration system with output pressure up to 97 bars.

Pre-injection characterization of the reservoir-seal system at the IBDP site indicated favorable capacity, injectivity, and containment that are now being confirmed.  The system consists of 500 m of Mount Simon Sandstone overlain by 151 m of Eau Claire Shale acting as the seal.  Injection is taking place through 16.7 m of perforations over a depth range of 2,117 to 2,136 m at the base of the Mount Simon with average interval porosity of 20 percent and permeability of 185 md. 

To maintain compliance with the permit, commissioning of the system involved such adjustments as flow rate (capped at 1,050 tonnes/day by permit), temperature of carbon dioxide at the wellhead, and pressure in the tubing-casing annulus, as well as accommodating system venting requirements, such as when one of the two compressors goes offline.  The reservoir readily accepted the injected CO₂ from the first day of injection and no abnormal back pressure or other adverse events occurred during startup.  Full injection rate of 1,000 tonnes/day was achieved with only 24.1 bar bottomhole pressure increase over static reservoir pressure.  A pressure response was seen at the observation well within hours after less than 200 tonnes was injected.  After 50,000 tonnes had been injected, reservoir pressure increases in the observation well up to 11 bars were observed to begin leveling off.  This response suggests very good lateral reservoir continuity at the perforation level, as might be expected for a reservoir deposited as a sand-rich braided fluvial system. 

An extensive program of subsurface and surface environmental monitoring systems is in place to define the subsurface plume and verify no impact on groundwater, soil, and air quality is occuring.  Subsurface monitoring includes repeat cased-hole logging, baseline 3D seismic, repeat Vertical Seismic Profiles (VSP), downhole and surface pressure and temperature monitoring, and microseismic monitoring. Surface monitoring includes ground water, CO₂ soil flux, CO₂ gas sampling, surface elevation change monitoring, and air monitoring.  Seventeen ground water wells at various depths sample shallow sand and gravel and bedrock aquifers and about 100 soil flux rings are monitored to assess any changes in CO₂ flux rates.

The comprehensive environmental MVA program at the site confirms there is no indication of CO₂ other than where expected - the lower one-third of the Mt. Simon and the high-quality reservoir zone into which it is being injected.  The baffling created by areas of lower permeability (less than or equal to 1 mD) within the reservoir is restricting the rise of CO₂ within the Mt. Simon.  The injected CO₂ has not reached intervals of lower reservoir quality higher up in the Mt. Simon (1,783 to 1,951 m) near the middle of the 500 m thick reservoir. Modeling conducted out to 100 years indicates that CO₂ does not cross this zone.  These observations are further confirmed by pressure readings in the observation well 304 m north of the injection well wherein a pressure increase of less than 20 psi is noted 98 m above the perforation interval.  A repeat 3D VSP was shot in early April 2013, which is expected to further define the position of the plume at the halfway point of injection. The monitoring program has given scientists, regulators, and the general public confirmation that no leakage is occurring and that the site is safe and effective.

*Mark of Schlumberger