Coal: two birds with one stone
Coalbed methane has been recognised as an important energy resource and is used as conventional natural gas. Recovery of methane can be achieved through injection of CO2 gas. This is based on the principle that coal has a stronger affinity for CO2 than for methane and as a result when CO2 is present, methane on coal is replaced by CO2. This results in methane production while CO2 is retained in the coalbeds. Therefore, injecting CO2 into coalbeds achieves not only enhanced coalbed methane recovery (ECBM), but also greenhouse gas (GHG) sequestration in underground reservoirs. The main objective of the EU ‘Monitoring and verification of CO2 storage and ECBM in Poland’ (MOVECBM) project was to improve the understanding of matters related to CO2 injection in coal. Issues that were addressed in the study included the safety of CO2 storage in coal, its adsorption rate and the physical accessibility to methane. To gain a better understanding of the adsorption kinetics and diffusivity of gases into the coal, project partners injected CO2 and with time-lapse profiling monitored its migration in the coal and the release of methane. Potential degradation mechanisms were explored and through high resolution imaging it was possible to identify corrosion phenomena and leaks while comparing different materials such as cement and steel. Continuous, near-surface monitoring was developed to ensure cost-effective public and environmental safety. Overall, the MOVECBM project developed tools for monitoring and modelling long-term CO2 and methane behaviour in coalbeds. This technology can be implemented for methane production which represents a cleaner source of energy. Additionally, CO2 sequestration in coal resources has important environmental consequences.
