SECARB CO2 injection test in mature coalbed methane reservoirs of the Black Warrior Basin, Blue Creek Field, Alabama

• Published in: International journal of coal geology 2015-05, Vol.144-145 (C), p.71-87
• Main Authors: Pashin, Jack C., Clark, Peter E., McIntyre-Redden, Marcella R., Carroll, Richard E., Esposito, Richard A., Oudinot, Anne Y., Koperna, George J.
• Format: Article
• Language: English
• Subjects: Black Warrior Basin; CO2 injection; Coalbed methane; Subsurface monitoring; Well testing
• ISSN: 0166-5162; 1872-7840
• DOI: 10.1016/j.coal.2015.04.003

The SECARB Black Warrior field verification test employed a diverse suite of well testing and monitoring procedures designed to determine the injectivity, capacity, heterogeneity, and performance of mature coalbed methane reservoirs. A total of 3250bbl of water and 252t of CO2 were injected into coal in a battery of slug tests. These tests demonstrate that significant injectivity exists in Black Warrior coalbed methane reservoirs and that reservoir heterogeneity is a critical factor to consider when implementing CO2 sequestration and CO2-enhanced recovery programs. The primary test well produces coalbed methane at wellhead pressures just above atmospheric, and yet desorption testing indicates that less than 20% of the original gas in place has been recovered by primary production. Injection of CO2 was conducted at sustained rates of about 90t/d of CO2. Reservoir pressure declined exponentially following the emplacement of each CO2 slug. Slug and pressure-buildup tests verify that permeability decreases exponentially with depth and also decreased during injection. Monitoring operations included multi-zone pressure logging and gas sampling in deep observation wells and groundwater sampling in a shallow observation well. Results indicate that significant permeability anisotropy exists in each coal group. In the Black Creek coal, pressure response was greatest in the dominant natural fracture direction. In the Pratt coal group, pressure response was dominated by hydrofractures. CO2 broke through to the observation wells only in the Pratt coal group and only along the major fracture directions. No significant flow of CO2 out of zone was detected, and no impact on shallow groundwater resources was identified. •A CO2 injection and well testing program conducted in Black Warrior coalbed methane reservoirs.•Multizone monitoring technology was applied to analyze pressure and fluid composition.•Results show effects of hydrofractures and natural fractures.•Post-injection performance of the coalbed methane production well improved.•Monitoring results indicate the CO2 stayed in zone and that groundwater was protected.