Effect of CO2 foam fracturing fluid acidification on pore structure of anthracite and bituminous coal

• Published in: Fuel (Guildford) Vol. 387; p. 134384
• Main Authors: Pan, Hongyu, Chen, Hongjiao, Pan, Mingyue, Ji, Bingnan, Chen, Siyu, Han, Mingrui, Cao, Yan, Cao, Xinshuang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2025
• Subjects: Acidification; CO2 foam fracturing fluid; Mineral composition; Pore structure; Acidification; Mineral composition; Pore structure; CO2 foam fracturing fluid
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2025.134384

•CO2 foam fracturing fluid has the most significant modification effect on medium–low rank coal samples.•CO2 foam fracturing fluid has the most prominent effect on Nave and Lc,and relatively little effect on d002.•Macropore increase in medium-low rank coals transforms mainly from 5-50nm mesopores, high rank from 2-5nm micropores. The injection of CO2 foam fracturing fluid into coal seams alters the pore structure of the coal, thereby enhancing the recovery of coalbed methane. To investigate the alteration of pore structure across various coal ranks, coal samples from three different ranks were chosen as the research subjects: long-flame coal (CY), coking coal (JM), and anthracite (WY). These samples were subjected to an acid-based modification experiment with the CO2 foam fracturing fluid. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and low-temperature nitrogen adsorption tests (LP-N2A) were conducted on the coal samples before and after the acidification and modification process to investigate the changing rules in surface characteristics, mineral components and pore structure across coal ranks. The study found: The medium–low rank coal exhibits a more significant modification effect than the high rank coal samples, in terms of surface morphology, mineral composition or pore structure. The findings of this study offer theoretical insights and guidance for applying CO2 foam fracturing technology in coalbed methane reservoirs of various coal ranks.