The Midwest Regional Carbon Sequestration Partnership (MRCSP) was founded in 2003 as part of the U.S. Department of Energy?s (DOE?s) Regional Carbon Sequestration Partnership initiative. Since its founding, MRCSP has made significant strides toward making CCUS a viable option for states in the region. The public/private consortium, funded through the DOE Regional Carbon Sequestration Initiative, brings together nearly 40 industry partners and 10 states. Battelle, as the project lead, oversees research, development and operations and coordinates activities among the partners. The incremental, phased approach has built a valuable knowledge base for the industry and paved the way for commercial-scale adoption of CCUS technologies. From 2008 to 2020, MRCSP Phase III focused on the development of large-scale injection projects. This report is part of a series of reports prepared under the Midwestern Regional Carbon Sequestration Partnership (MRCSP) Phase III (Development Phase). These reports summarize and detail the findings of the work conducted under the Phase III project. During the MRCSP Phase III monitoring period, over 1 million metric tons of CO<
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was injected into ten Silurian-age (Niagaran) pinnacle reef reservoirs in Otsego County, Michigan that are operated by Core Energy, LLC. There are over 800 pinnacle reefs in northern Michigan, and collectively, these geologic features have sufficient capacity to store several hundred million metric tons of CO<
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. Moreover, most of the reefs are oil-bearing and went through primary production in the 1970s and 1980s
therefore, by injecting CO<
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into the reefs, there is a real opportunity to realize additional (enhanced) oil recovery (EOR) and to permanently store CO<
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after EOR. A key objective of the MRCSP Phase III project is to evaluate the effectiveness of various technologies for monitoring CO<
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that has been injected into deep geologic formations. Monitoring may be required at CO<
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storage sites for a variety of reasons, including to meet UIC Class II (EOR sites) or Class VI (storage only sites) permit requirements or EPA greenhouse gas reporting rule requirements or to qualify for tax credits under the 45Q tax credit rule. The results of this monitoring study should prove useful to operators considering using carbonate pinnacle reefs of Northern Michigan for CO<
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storage.