Effects of Electrolyte pH on the Electro-Osmotic Characteristics in Anthracite

Abstract

Accelerating the drainage of water in coal reservoirs can significantly improve the extraction efficiency of coalbed methane (CBM). The movement of water with different pH values in anthracite was tested and analyzed. The results showed that the electro-osmotic flow velocity increased first and then slightly decreased with the increase of time up to 120 h. The electro-osmotic flow was markedly strengthened under a strong acid (pH 2) or strong alkaline (pH 13) environment, and the direction of electro-osmosis was reversed at a pH of 3−4. The changes in zeta potential, surface groups, and minerals in anthracite were tested to analyze the mechanism of electroosmotic characteristics. The results obtained from this work will provide a basis for the process of drainage and depressurization during the CBM extraction.

Effect of Cyclical Microwave Modification on the Apparent Permeability of Anthracite: A Case Study of Methane Extraction in Sihe Mine, China

“… 32 The peak near 1030 cm –1 is attributed to the stretching vibrations of Si–O–Si and Si–O–C. 33 The peak near 540 cm –1 corresponds to the vibrations of S–S. 33 The adsorption peaks near 2925, 2855, and 1430 cm –1 are slightly smaller for modified samples than unmodified samples, indicating that some of the methyl and methylene groups were removed and the adsorption capacity of coal was weaker.…”

“… 33 The peak near 540 cm –1 corresponds to the vibrations of S–S. 33 The adsorption peaks near 2925, 2855, and 1430 cm –1 are slightly smaller for modified samples than unmodified samples, indicating that some of the methyl and methylene groups were removed and the adsorption capacity of coal was weaker. 71 The decrease in CH 4 adsorption indicated that the gas seepage performance in coal was improved because of the coal matrix shrinkage effect.…”

“…The peak at 1430 cm –1 is identified as the bending vibration of −CH 3 and the antisymmetric stretching vibration of carbonate groups . The peak near 1030 cm –1 is attributed to the stretching vibrations of Si–O–Si and Si–O–C . The peak near 540 cm –1 corresponds to the vibrations of S–S .…”

“…Methods other than CO 2 substitution and N 2 displacement will have a significant effect on reservoir permeability . One approach is fluid injection, which includes hydraulic, high energy gas, , supercritical CO 2 , , liquid nitrogen, − and steam injection fracturing. , Another approach is the application of external acoustic, − electric, electromagnetic, − or electrochemical fields. − Although these methods have achieved enhancements, there are still some limitations, such as water locking damage, construction costs, complex operations, ecological environmental pollution, and even the possibility of inducing earthquakes by hydraulic fracturing. , At present, microwave modification technology has been successfully used for coking, , reduction of energy for pulverization, lignite dehydration, coal desulfurization, low-rank coal pyrolysis, biomass pyrolysis, enhancing floatation, auxiliary rock breaking, heavy oil exploitation, and oil shale exploitation …”

Electrochemical Modification on CH4 and H2O Wettability of Qinshui Anthracite Coal: A Combined Experimental and Molecular Dynamics Simulation Study

“…Electrochemical modification on coal, rock, and clay has attracted increasing interest all over the world. − The electrochemical method can accelerate methane seepage by removing filling matters like calcite and pyrite. − Meanwhile, the CH 4 adsorption decreased after electrochemical treatment due to the increase of carboxyl and other oxygen-containing groups, and the desorption ratio and diffusion coefficient increased after modification due to the strength of interaction of methane and anthracite weakened. , Unfortunately, the previous research studies mainly described the phenomena of the electrochemical process and the results, the molecular mechanism of electrochemical modification involved was limited. The molecular mechanism of the gas–liquid wetting characteristics of coal surfaces in successful CBM extraction cannot be overstated.…”