Carbon dioxide sequestration effects on coal's hydro-mechanical properties: a review

Abstract

SUMMARY Carbon dioxide (CO2) sequestration in deep un‐minable coal seam causes the seam's permeability and strength to be significantly reduced because of CO2 adsorption‐induced matrix swelling. This paper reviews this swelling process in coal and its influence on coal's flow and strength properties. The amount of swelling depends on the properties of both the gas and the coal mass. The swelling caused by CO2 adsorption is higher compared with that caused by CH4 and N2 and greatly depends on the state of the CO2 phase. The super‐critical state of CO2 adsorption causes greater swelling compared with the sub‐critical state. It has been observed that the swelling rate increases with increasing CO2 pressure; however, high saturation pressures may cause the coal matrix to shrink. The swelling rate reduces with increasing temperature, and the effect of coal rank on swelling still remains unclear. The CO2 adsorption‐induced swelling effect causes the coal mass permeability to be significantly reduced, and the reduction is significant for super‐critical CO2.The effect of swelling on coal permeability reduces with increasing temperature. The coal matrix swelling and associated polymer structure re‐arrangement occur in the coal mass during and after the CO2 injection, resulting in the weakening of the coal mass strength. The strength reduction is much higher for high rank coal compared with low rank coal. It is also observed that the influence of super‐critical CO2 on strength is more powerful than that of sub‐critical CO2. Although CO2 sequestration in deep coal seams has been carried out in several main coal seams in the USA, Australia and some other countries, none of these projects has achieved the original target of storing large amounts of CO2, possibly because initial analysis did take into account the effects of coal seam property changes because of the adsorption of CO2 during and after injection. Copyright © 2012 John Wiley & Sons, Ltd.

Characteristics of Clay-Abundant Shale Formations: Use of CO2 for Production Enhancement

“…However, CO 2 has higher affinity to adsorb into many rock masses including shales [97][98][99]. Therefore, the injection of CO 2 into shale causes its adsorbed methane to be replaced by the injected CO 2 , resulting in greater shale gas production.…”

Effect of Coal Rank on Various Fluid Saturations Creating Mechanical Property Alterations Using Australian Coals

“…The process of enhanced coal bed methane (ECBM) recovery is being implemented and tested as a viable option to store and reduce the amount of anthropogenic carbon dioxide (CO 2 ) in the Earth's atmosphere, as well as for the recovery of useful coal bed methane (CH 4 ) gas [1][2][3][4][5][6][7]. Overall, the ECBM process involves introducing CO 2 through injecting wells into deep coal seams and this CO 2 then acts as a displacing gas, which allows the already adsorbed CH 4 to be desorbed from the coal matrix.…”

“…However, according to previous studies [1][2][3]6,[8][9][10][11][12], this CO 2 -ECBM process leads to CO 2 adsorption-induced coal matrix alterations, which in turn affect its hydro-mechanical properties. Particularly in the geomechanical respect, the coal mass becomes weaker with the substitution of existing adsorbate CH 4 with the highly chemically potential CO 2 [13,14].…”

Laboratory investigation of gas permeability and its impact on CBM potential

“…The coal tends break along the cleat direction (the face cleat, also known as main or master cleat, and butt cleat, also known as cross or board cleat). There exist many reports that predict the seam behaviour post-production from the determination of permeability in the laboratory using triaxial condition (Xiao et al 2005;Yang and Zoback 2011;Wang et al 2012;Perera and Ranjith 2012;Zheng et al 2012;Zhu et al 2013;Ghanizadeh et al 2014;Maffucci et al 2015). Laboratory-measured permeability anisotropies exhibited 2:1 contrast in the face and butt cleats and a 100:1 contrast between face cleat and vertical permeability (Gash et al 1993).…”