Microseismic data acquisition, processing, and event characterization at the Illinois Basin – Decatur Project

• Description of the IBDP microseismic monitoring network.
• Description of the IBDP microseismic data processing and event characterization workflows.
• Several event clusters features displayed detectable linearity suggesting geologic control.
• The velocity model evolved and improved as new data became available.
• Velocity anisotropy had a systematic impact on event locations.

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 in-house processing components, which provides a seamless path from in-field quality control to final locations with short turn-around 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.