document preview

Abstract
The Illinois Basin – Decatur Project (IBDP) plans to inject one million tonnes of carbon dioxide (CO2) into the Mt. Simon Formation over a three-year period, starting in late 2011. Uncertainty analyses that were conducted at successive stages of the project have been used to evaluate the impact of additional data on the uncertainty in reservoir performance predictions.

Reservoir simulators are predictive tools that help the project team evaluate the injectivity, storage capacity and containment capabilities of a reservoir for carbon capture and storage (CCS) projects. Simulation studies for IBDP started in 2008 using general regional data. Over time, reservoir models have increased in complexity and have become more representative of the Mt. Simon Formation as more data have been acquired.

An initial uncertainty analysis used models based on two-dimensional (2D) seismic data and available logs from a nearby well. After drilling the injection and monitoring wells at the storage site, petrophysical measurements were obtained that enabled a detailed sensitivity analysis to identify parameters that are critical to injectivity, CO2 migration, and corresponding pressure pulse evolution. This information helped reduce the number of uncertain parameters and their ranges for the second uncertainty analysis. Lastly, after gathering three-dimensional (3D) seismic data, results of special core analysis, and injectivity tests, the reservoir model and uncertainty ranges of other input parameters were updated for a final iteration of pre-injection uncertainty analysis.

Results of the first uncertainty analysis helped the project team identify an uncertainty envelope of possible CO2 migration scenarios. The second stage of uncertainty analysis targeted wide ranges in reservoir performance predictions, indicating several reservoir parameters on which to focus additional characterization efforts. A more complete, final round of uncertainty analysis produced manageable ranges of predicted uncertainties and a credible basis of reservoir performance expectations prior to the operational phase of the project. Results of this analysis can be used to identify the area of review (AoR) for permitting, priority and placement of monitoring tools, as well as timing of repeat surveys and scenarios for injection schemes in the near future.

Introduction
The Midwest Geological Sequestration Consortium (MGSC) is one of seven regional partnerships created by the U.S. Department of Energy (DOE) to advance carbon sequestration technologies nationwide. Led by the Illinois State Geological Survey (ISGS), in conjunction with the Indiana Geological Survey and the Kentucky Geological Survey, and covering Illinois, southwestern Indiana and western Kentucky, this partnership was established to assess geological carbon sequestration options in the 60,000 square mile geologic feature known as the Illinois Basin. MGSC’s objective is to determine the technical and economic feasibility of using these geologic formations for long-term storage.

Along with partners Archer Daniels Midland Company (ADM) and Schlumberger Carbon Services in the Illinois Basin – Decatur Project the plan to inject up to 1 million metric tons of CO2 over a 3-year period into the Mt. Simon Sandstone at a depth of about 6300-7,000 feet. The CO2 is being captured from the fermentation process used to produce ethanol at Archer Daniels Midland Company’s (ADM) corn processing complex in Decatur, Illinois.