An Exciting Answer to “How to simultaneously improve CO2 storage capacity & shale gas recovery ?”

Significance 

Shale gas has attracted considerable research attention as emerging clean energy. Preliminary studies project a tremendous increase in natural gas consumption in the next two decades, 20% of which will come from shale gas resources. However, the exploitation of shale gas is extremely challenging due to the low permeability and complex composition of the shale matrix. Increasing the exploitation of shale gas requires enhancing its recovery and utilization, which has remained an inherent challenge.

Generally, the carbon dioxide (CO2) adsorption capacity for both organic and inorganic shale pores is stronger than that of methane (CH4). This is the basic working principle of the CO2 storage and enhanced gas recovery (CS-EGR) technology designed to improve shale gas recovery and CO2 storage by injecting the CO2 into shale reservoirs. To this end, it is important to understand the competitive adsorption mechanism and behaviors of the CO2/CH4 mixture in the reservoir as well as the associated impacts of the key formation parameters.

Despite the substantial number of studies on the impact of different formation parameters, most have concentrated on the overall reservoir parameters rather than the individual component parameters like the gas partial pressure. Moreover, the currently used experimental and theoretical approaches fail to clearly illustrate the competitive adsorption behaviors of CO2/CH4 in shale matrix, particularly in large organic-inorganic pores. This can be attributed to the deficiencies of the adopted models and techniques emanating from multiple adsorption layers and confinement effects.

Herein, researchers at the Dalian University of Technology: Dr. Jingyue Sun, Professor Cong Chen, Dr. Yue Zhang, Professor Weizhong Li and Professor Yongchen Song analyzed the competitive adsorption characteristics and mechanism of CO2/CH4 mixture in graphene-montmorillonite heterogeneous surface shale pores via molecular dynamics simulations. The decisive factor influencing competitive adsorption was discussed to provide a basis for improving CO2 storage capacity and shale gas recovery. Their work is currently published in the Chemical Engineering Journal.

By comparing the heterogeneous and homogenous surface pores, the authors revealed that the partial pressure of the CO2 and CH4 gases played a vital decisive role in defining the competitive adsorption behavior for the cases of pore size and certain temperatures. When the partial pressure of the pores with heterogeneous surfaces is the same as that of pores with homogenous surfaces, the competitive adsorption was consistent. An observation based on the partial pressure showed that the total amount of CH4 production and the corresponding absolute CH4 adsorption amount near the graphene-montmorillonite surface was not dependent on the ratio and exhibited a linear relationship with PCH4.

Despite the presence of the multiple adsorption layers of the mixture, the good fitting results showed that each layer was satisfactorily explained by the Langmuir adsorption theory. Three key recommendations were provided to enhance CO2 storage and CH4 recovery. First, a significant reduction in the first pressure as low as possible was recommended due to its benefit in CH4 production. Second, it is important to inject and soak a given amount of CO2. The third was to decrease the pressure to the final pressure in accordance with the first pressure and maintain the CO2 injection ratio between 1.11 – 1.21.

In summary, the research team reported successfully the simulation of the competitive adsorption behavior of the CO2/CH4 mixture. The results revealed the importance of describing the competitive behaviors based on the partial pressure of the gases forming the mixture. The operation recommendations based on timing and CO2 injection amounts was effective in enhancing CO2 storage and shale gas recovery. In a statement to Advances in Engineering, Professor Cong Chen, the corresponding author stated that their findings would contribute to the design optimization of the CS-EGR technology for alleviating energy crisis and reducing CO2 emissions.

An Exciting Answer to “How to simultaneously improve CO2 storage capacity and shale gas recovery ?” - Advances in Engineering An Exciting Answer to “How to simultaneously improve CO2 storage capacity and shale gas recovery ?” - Advances in Engineering

About the author

Jingyue Sun was born in Shandong Province, China, in 1995. She graduated from the School of Mechanical and Electrical Engineering, Qingdao University,  in 2017, and received her master’s degree from the School of Energy and Power Engineering, Dalian University of Technology, in 2020. Since 2020, she has been studying for a Ph.D. at Dalian University of Technology. Up to now, she has published 4 papers including Chemical Engineering Journal and Fuel. Additionally, she gave oral presentations at the Goldschmidt Conference and the IFEDC conference in 2021. She received the “Excellent Master’s Thesis Award” issued by Dalian University of Technology in 2020. She is interested in carbon storage and utilization, and efficient extraction of unconventional energy, especially transport properties of adsorbed gas in nanopores. These studies will help to better understand the solid-fluid interactions in CCUS.

About the author

Dr. Cong Chen is a Professor of Energy and Power Engineering at Dalian University of Technology, leader of the Center for Multi-scale Control of CO2 Sequestration, and Director of DLUT-PAPRSDL Advanced Refrigeration Technology Joint Research and Development Center. His research interests are multi-scale control of CCUS from molecular to field scale with a focus on CO2 sequestration in saline aquifers, CO2 enhanced oil/gas recovery, CO2 sequestration as gas hydrates as well as digital twins of CCUS. He is winner of Invited Lecture under Advanced Materials Award of 2022. He serves as editor in Current Physics, editorial board member in Liquids, guest editor of Molecular Simulation, Convenor of Goldschmidt series conferences, member of IEECP22 technical program committee, and member of ISPEE2023 organizing committee.

Reference

Sun, J., Chen, C., Zhang, Y., Li, W., & Song, Y. (2022). Competitive adsorption characteristics based on partial pressure and adsorption mechanism of CO2/CH4 mixture in shale poresChemical Engineering Journal, 430, 133172.

Go To Chemical Engineering Journal

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