Effect of supercritical CO2 saturation pressures and temperatures on the methane adsorption behaviours of Longmaxi shale. (1st September 2020)

• Record Type: Journal Article
• Authors: Qin, Chao; Jiang, Yongdong; Luo, Yahuang; Zhou, Junping; Liu, Hao; Song, Xiao; Li, Dong; Zhou, Feng; Xie, Yingliang
• Is Part Of: Energy. Volume 206(2020)
• Publication Date: 2020-09-01
• Subjects: Supercritical carbon dioxide -- Shale -- Methane adsorption behaviour -- Adsorption models -- Solubility; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2020.118150
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: To investigate the effects of supercritical CO2 (SC–CO2 ) saturation pressures and temperatures on the methane adsorption capacity of shale, total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, scanning electron microscope and energy dispersive spectrometer (SEM/EDS) analysis, low-pressure N2 adsorption (LP-NA), and high-pressure methane adsorption (HP-MA) were conducted on raw and SC–CO2 –saturated (8, 12, 16 MPa; 40, 60, 80 °C) shale collected from the Sichuan Basin. Results indicate that the excess adsorption isotherm of shale to methane clearly exhibited excess adsorption characteristics with increasing adsorption pressures. This excess methane adsorption capacity decreased after SC-CO2 saturation and is mainly attributable to decreases in the TOC content, clay minerals and specific surface area (SSA) in the SC–CO2 –saturated shale. The density of adsorbed phase methane was considered at different adsorption models, and the results suggest that the Langmuir-Freundlich (LF) and Dubinin-Astakhov (DA) models better describe methane adsorption behaviours than the Langmuir and Ono-kondo models. The methane adsorption capacity of shale is closely related to the solubility of SC-CO2, which decreased significantly with increasing SC-CO2 saturation time and pressure, while the influence of SC-CO2 saturation temperatures was not evident at low-pressure (8 MPa). This study provides a theoretical reference for CO2 enhanced shale gas recovery. Highlights: HP-MA of shale was studied at various SC-CO2 saturation pressures and temperatures. TOC, clay minerals, carbonates and SSA of shale decreased after SC-CO2 saturation. The methane adsorption capacity of shale decreased after SC-CO2 saturation. The density of absorbed methane was considered and fitted well in LF and DA models. The effect of SC-CO2 saturation pressure is obvious, while that of temperature is inapparent.