Thermodynamics and Kinetics of CO2/CH4 Adsorption on Shale from China: Measurements and Modeling

Abstract

CO2-enhanced shale gas recovery (CO2-ESGR) sequestrates anthropogenic CO2 and improves the profitability of shale gas exploitation. This work investigated the adsorption behaviors of CO2 and CH4 on shale from China at 20, 40, 60 and 80 °C. The pressure ranges for CO2 and CH4 were 1–5 and 1–15 MPa, respectively. The excess adsorbed amount of CH4 increased with increasing pressure from the beginning to the end, while the maximum excess CO2 adsorption was observed at approximately 4 MPa. The absolute average deviations (AADs) of CO2 and CH4, determined by the Langmuir + k model, were 2.12–3.10% and 0.88–1.11%, respectively. Relatively good adsorptivity for CO2 was exhibited when the pressure was less than 5 MPa, which was beneficial to the implementation of CO2-ESGR. With continuous increases in pressure, the adsorption capacity of CO2 was weaker than that of CH4, suggesting that the injected CO2 would reduce the partial pressure of CH4 for CO2-ESGR and the displacement effect would no longer be significant. In addition, the adsorption rate of CO2 was much faster than that of CH4. CO2 was more active in the competitive adsorption and it was advantageous to the efficiency of CO2-ESGR.

Exploring a New Method to Study the Effects of Surface Functional Groups on Adsorption of CO2 and CH4 on Activated Carbons

“…In this study, the nonlinear regression coefficient ( R 2 ) and the average relative error (ARE) were employed. The average relative error, which can describe the deviation between the experimental data and the fitted data, is given by eq . where q exp is the experimental data and q cal represents the values calculated by the models, mmol/g.…”

Experimental Study on the Kinetics of Adsorption of CO2 and CH4 in Gas-Bearing Shale Reservoirs

“…The concept of enhanced CH 4 gas recovery with simultaneous CO 2 geological storage in shale gas reservoirs has been proposed and researched over the past few years. − Based on the stronger adsorption ability of CO 2 over CH 4 on the shale matrix, CO 2 can competitively replace preadsorbed CH 4 out of adsorption sites and subsequently be trapped in the inner pore space. , With respect to the technique of enhanced shale gas recovery by injecting CO 2 (CO 2 -ESGR), knowledge of the gas transport and storage properties of CH 4 and CO 2 on gas-bearing shale reservoirs is significant for improving CH 4 production and sequestrating substantial amounts of CO 2 in a geological timescale.…”

Advances and Prospects of Supercritical CO2 for Shale Gas Extraction and Geological Sequestration in Gas Shale Reservoirs

“…This suggests that the adsorption phase density plays an important role in the adsorption process. 49 Due to the matrix expansion caused by gas adsorption, the adsorption deviation of CO 2 is more pronounced than that of CH 4 . 50 The adsorption rate of CH 4 is faster at low pressure than at high pressure, and this adsorption behavior can be explained by a type I isotherm.…”

“…Compared with CO 2 , the density of CH 4 in the free state changes more slowly, and thus no such critical pressure is observed. 49 The effect of different TOC contents in shales on CH 4 and CO 2 varies. This effect is illustrated in Figure 3, which shows that CO 2 adsorption is more sensitive to changes in the TOC content.…”