Competitive adsorption phenomenon in shale gas displacement processes

Abstract
Displacement of methane (CH4) by injection gas is regarded as an effective way to exploit shale gas and sequestrate carbon dioxide (CO2) simultaneously. To remarkably enhance the rupture and extension of fractures, an original and comprehensive simplification for the real shale composition model is established to study the shale gas displacement by gas injection. In the present model, besides the consideration in the existence of organic matter in shale, the choice of silica as inorganic minerals is firstly taken into account considering its brittleness characteristic to meet the demand of fracture stretch. Based on the model, the displacement methane process and competitive adsorption behaviors were studied by using the grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) respectively. As the results, the strong interaction between carbon dioxide and shale results in the higher efficiency of displacing methane. We also find that the optimum operating conditions for CO2 and N2 displacing methane are at the pore width of 30 Å, the result being slightly different from the previous studies indicating that the displacement efficiency of small pores is higher. Moreover, the displacement efficiency by using different gases can all reach higher than 50% when the injection pressure is greater than 30 MPa. It is expected that this work can reveal the mechanisms of competitive adsorption between shale gas and gases, and provide a guidance for displacement exploitation of shale gas by gas injection and sequestration of carbon dioxide.

Citation
Shi, J., Gong, L., Sun, S., Huang, Z., Ding, B., & Yao, J. (2019). Competitive adsorption phenomenon in shale gas displacement processes. RSC Advances, 9(44), 25326–25335. doi:10.1039/c9ra04963k

Acknowledgements
The work was supported in part by the National Natural Science Foundation of China (51676208), the Fundamental Research Funds for the Central Universities (18CX07012A, 18CX05029A, 19CX05002A) and the grants BAS/1/1351-01, URF/1/2993-01, and REP/1/2879-01 from King Abdullah University of Science and Technology (KAUST)

Publisher
Royal Society of Chemistry (RSC)

Journal
RSC Advances

DOI
10.1039/c9ra04963k

Additional Links
http://xlink.rsc.org/?DOI=C9RA04963K

Permanent link to this record