Recent Advances in Carbon Dioxide Sequestration in Deep Unmineable Coal Seams Using CO₂-ECBM Technology: Experimental Studies, Simulation, and Field Applications

Abstract

CO 2 -enhanced coalbed methane (CO 2 -ECBM) technology helps to store CO 2 while producing a clean source of energy (CH 4 ) through the sorption process. This technique can sequester much CO 2 at low temperatures and pressures while recovering CH 4 , which will help offset the associated costs, such as capturing injection gases, drilling and completion infrastructure, compression, and injection expenses. This review paper critically analyzes the CO 2 sequestration potentiality in deep unmineable coal seams. The results revealed that, despite several researchers' insights from proposed concepts, experimental data, modeling and simulations, and pilot tests, there are no reported full field CO 2 -ECBM technology applications for CO 2 sequestration and CH 4 recovery because implementing the projects is uneconomical. Also, CO 2 sequestration and CH 4 recovery effectiveness on coal seams depend on wettability changes of the CO 2 −H 2 O−coal system. The identified research gaps and challenges in this paper are going to help various researchers and shareholders in conducting extra investigations toward full field application of CO 2 sequestration while simultaneously producing a clean source of energy (CH 4 ) in deep unmineable coal seams to meet the Paris climate summit agreement to achieve net zero emissions by 2050 and a maximum global temperature rise of 1.5 °C.

Investigation on the Gas Emission Law of Water-Containing Coal across the Rank Range

“…With the depletion of shallow resources, coal mining is gradually marching to deep areas. − The occurrence conditions of deep coal seams are complicated, such as high ground stress, high gas, high heterogeneity, low permeability, low strength, and multiple structures, which undoubtedly increase the difficulty of gas control in coal mines in China. − As an effective means to prevent and control coal and gas outbursts, hydraulic antireflection technology (hydraulic fracturing, hydraulic punching, and hydraulic cutting) has been gradually promoted in China since the 1960s and has achieved good control effects. − …”

Coal Wettability: A Holistic Overview of the Data Sets, Influencing Factors, and Knowledge Gaps

“…Carbon capture and storage (CCS) is considered an effective and scientifically proven technique for reducing anthropogenic CO 2 emissions in a safe manner. − This approach involves the injection of captured CO 2 into suitable subsurface geological formations, such as saline aquifers and depleted oil/gas reservoirs. − The secure confinement of CO 2 within these geological media is facilitated through various trapping mechanisms, including residual trapping, structural trapping, dissolution trapping, and mineral trapping. − Notably, shale formations and unmineable coal seams have also been tested for their suitability for geological storage of CO 2 . − Coal seams and shales can trap enormous volumes of CO 2 via adsorption trapping. , Particularly, the injection of CO 2 into the coal seams has been receiving increasing attention due to its dual advantages in geological CO 2 storage and enhanced coalbed methane (ECBM) recovery. − Coal seams have also been tested for their suitability for hydrogen (H 2 ) storage in the context of the transition toward clean energy . Indeed, studies have shown the potential of H 2 adsorption in coals as well, albeit much lower than CO 2 . , …”