Carbon Dioxide Sequestration in Coal Formations

Abstract

Carbon dioxide (CO 2 ) is the major greenhouse gas emitted in all activities. CO 2 sequestration in coal seams has become an attractive carbon sequestration technology where the injection of CO 2 enhances methane production from coalbeds (ECBM), in addition to storing CO 2 . CO 2 can be retained in coal via three ways: free gas within the pore space or fractures in the coal, adsorbed molecules on the organic surface of coal, and dissolved in groundwater within the coal.This study investigates the effects of the salinity (NaCl) of coal seam water, injection flow rate, and CO 2 state (formation pressure) on the CO 2 sequestration in volatile bitumen coal. To achieve this objective; coreflood tests were conducted on different coal cores. The change in the effective water-coal permeability after CO 2 injection was examined. Also, the displacement efficiency of water by CO 2 was estimated. The experimental data was cross-matched with numerical simulation to estimate the relative permeability curves.The coreflood experiments showed that the effective water permeability in coal decreased during CO 2 injection due to its adsorption onto the coal surface, and reduction of the relative water permeability. Higher formation pressure led to permeability reduction as a result of higher CO 2 adsorption onto the coal surface. The effective water permeability decreased by 8% at 50 psi back pressure, compared to 48% at 1100 psi back pressure. Furthermore, as the injection flow rate increased, the contact time of CO 2 to the coal surface decreased. Hence, the CO 2 adsorption to the coal matrix decreased and the change on effective water permeability slightly decreased. Specifically, the effective water permeability decreased by 48% at 1 cm 3 /min comparing to 41% at 4 cm 3 /min. As salt concentration increased, the change in pressure drop across the core slightly increased, but this effect decreased as formation pressure increased. As the water salinity increased, the coal become more CO 2 wet, and the residual gas saturation increased. Based on these observations, the injection of CO 2 into highly volatile bitumen coal seams for CO 2 sequestration and ECBM purposes is more efficient as the salt concentration increases and high injection pressure.

A review of carbon dioxide adsorption to unconventional shale rocks methodology, measurement, and calculation

“…Firstly, CO 2 injection, either through flooding of cyclic huff-n-puff, can increase oil recovery significantly [3,4]. Secondly, CO 2 can be stored in several types of hydrocarbon reservoirs as part of the carbon storage initiative to reduce greenhouse emissions [5][6][7][8]. Recently, CO 2 injection in unconventional low permeability shale reservoirs has been investigated for both enhanced oil recovery from these reservoirs, and CO 2 storage Jin and Firoozabadi [9].…”

A model of cement-formation interface failure length in supercritical CO2-ECBM and storage injection well considering the coal swelling effect under high pressure

“…However, the carbon dioxide emissions from fossil fuels represent about 60% greenhouse effect Fang et al 2017). One effective technology to reduce and utilize the emitted CO 2 is to inject it into the unmineable coal seam and increase methane production, or CO 2 -ECBM in addition to CO 2 storage/sequestration (Zhang et al 2015;Ibrahim and Hisham 2015). This technology can improve the recovery of coalbed methane, realize the geological storage of CO 2 , and achieve the purpose of easing greenhouse gas emissions.…”