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Summary

The Pump Canyon CO₂-enhanced coalbed methane (ECBM)/sequestration demonstration in New Mexico has the primary objective of demonstrating the feasibility of CO₂ sequestration in deep, unmineable coal seams through a small-scale geologic sequestration pilot. This project is not the first of its kind; several small- or large-scale pilots were already conducted previously in the United States [Allison Unit (Reeves et al. 2003) in the San Juan, Appalachian, and Warrior basins] as well as internationally [the Recopol (Reeves and Oudinot 2002) project in Poland, and the Yubari project in Japan, Canada, and Australia]. Additional pilots are currently under way.

At the project site, a new CO₂-injection well was drilled within an existing pattern of coalbed-methane-production wells. Primarily operated by ConocoPhillips, these wells produce from the Late Cretaceous Fruitland coals. CO₂ injection into these coal seams was initiated in late July 2008 and ceased in August 2009. A variety of monitoring, verification, and accounting (MVA) methods were employed to track the movement of the CO₂ in order to determine the occurrence of leakage. Within the injection well, MVA methods included continuous measurement of injection volumes, pressures, and temperatures. The offset production wells sampled gas-production rates, pressures, and gas composition through CO₂ sensors, tracers in the injected CO₂, time-lapse vertical seismic profiling, and surface tiltmeter arrays. A detailed study of the overlying Kirtland shale was also conducted to investigate the integrity of this primary caprock. This information was used to develop a detailed geologic characterization and reservoir model that has been used to further understand the behavior of this reservoir.

The CO₂-injection pilot has ended with no significant CO₂ buildup occurring in the offset production wells. However, a small but steady increase in CO₂ and N₂ at two of the offset wells may have been an indication of imminent breakthrough. More recent gas samples are, however, showing a decrease in CO₂ and N₂ content at those wells. This paper describes the project, covering the regulatory process and injection-well construction, the different techniques used to monitor for CO₂ leakage, and the results of the modeling work.