CO2 sequestration in an unmineable coalbed -: San Juan Basin, Colorado, USA

BP Amoco (BPA) is investigating the sequestration of approximately 464 tonnes per day of vented CO2 by injecting the CO2 into a non-mineable natural gas producing coal in the Colorado portion of the San Juan Basin. Removed CO2 from this production will be re-injected into the coalbed for sequestration. Using an already operating nitrogen enhanced coalbed methane (ECBM) recovery project's infrastructure, this project would further the scientific understanding of geologic CO2 sequestration. Because of utilization of the existing ECBM wells, the reservoir is already well understood and extensive reservoir modeling has already been established. This project will improve the understanding of the sequestration processes involved in coalbed methane reservoirs and will help determine technical and economic feasibility of future projects. BPA has concentrated efforts on utilizing nitrogen to enhance the recovery of methane from coals and currently operates the largest and most significant project of its kind. On a pilot basis, CO2, as an enhanced recovery process for Fruitland coals, has also been undertaken in the San Juan Basin (SJB). The two gases, CO2 and N-2, behave differently in coals. CO2 is readily adsorbed on the coal and therefore displaces the methane whereas the nitrogen strips the methane from the coals by reducing the partial pressure of the methane. Injection, production, and reservoir data will be gathered and reviewed to evaluate the success of the CO2 sequestration. BPA will use it's proprietary GCOMP Reservoir Model to investigate the flow and adsorption of CO2, simulate the process, compare field results with model predictions, and adjust the model to better match actual field performance. Preliminary reservoir simulations indicate that some incremental methane production will be recovered, while sequestering nearly all of the injected CO2 in the coal seams. This project provides an unique opportunity to test effective sequestration of CO2 in coalbeds resulting in reduced greenhouse gas emissions.