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The Illinois Basin -Decatur Project (IBDP) is a carbon capture and storage (CCS) project that is located at the Archer Daniels Midland (ADM) Company's corn processing plant in Decatur, Illinois. The IBDP has an extensive seismic program that was designed to meet site characterization and monitoring objectives that includes two-dimensional (2D) and three-dimensional (3D) surface seismic data, time-lapse 3D vertical seismic profi les (VSPs), and microseismic monitoring. As little deep subsurface data was available within a 20-mile (32-km) radius of site, the surface seismic surveys have been important to the site characterization objectives for the project. Through seismic inversion analysis, rock properties such as density, porosity, and rock lithology were derived from the surface seismic data and incorporated into the geologic and geomechanical models for the project. Time-lapse 3D VSPs are acquired with a permanent geophone array in Geophysical Monitoring Well #1 (GM1). Carbon dioxide (CO 2 ) injection commenced in November 2012, and the fi rst monitor survey was acquired in February 2012 after approximately 70 000 tonnes of CO 2 had been injected. While this is a small volume of CO 2 to detect seismically, anomalies were identifi ed that may be suggestive of CO 2 movement in the Mt Simon Sandstone at the depth of injection. Microseismic activity has been monitored using the geophone array in GM1 and two deep geophones installed in the Injection well (CCS1). A comparison of the different operation parameters with microseismic activity shows a correlation between microseismicity and pressure changes in the formation.

Microseismic monitoring at the Illinois Basin-Decatur Project (IBDP) is accomplished using a combination of commercially available components that are integrated to provide real-time analysis and remote processing capabilities by means of a purpose-built data management system and secure web portal. The processing workflow consists of real-time, remote access, and inhouse processing components, which provides a seamless path from in-field quality control to final locations with short turnaround times. Event location is performed using an adaptation of the Geiger method, which is designed to be robust for the sparse but localized observation sets typically encountered with injection monitoring. Observed microseismicity displayed distinct linear clustering and increased in distance from the injection well over time, presenting challenges for location accuracy of more distal events. The velocity model, a key component in event location and characterization, evolved through early stages of the project as new wells were drilled providing the opportunity for improved observation geometry and acquisition of additional controlled energy source points for model calibration. The experience gained at IBDP highlights the importance of field systems and processing flows that allow adaptation to evolving operational conditions and microseismic event activity.

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