Hydraulic fracturing can evidently improve the coalbed methane production in underground coal mines, but it is difficult to delimit the stimulated area accurately. In order to evaluate the stimulated area, microseismic (MS) monitoring technique is proposed to investigate the seismic responses of the induced fractures of hydraulic fracturing. Three coal seams were targeted to be treated in a coal mine. An array of geophones was set along the underground roadway to detect the MS signals caused by HF. In order to verify the result of MS monitoring, water content of each coal seam has been measured before and after HF treatment. The results showed that a series of MS events were detected during the entire HF process, and a sharp MS event usually occurred during the first hour of HF process. The energy of the sharp MS event had higher magnitude than others. The MS distribution exhibited complex morphological features. The directionless MS response was distributed over a radius of less than 40 m but tended to be significantly conjugated with a radius of more than 40 m. HF could stimulate both the coal seam and the rock layers nearby. The achievable stimulated area in the coal seam was determined to be 50 m × 50 m according to the MS density and water content. The stimulated area in terms of MS density was easily found to be broader than the area of water direct intrusion. The present study indicated that MS monitoring technique could potentially be used for evaluation of HF in underground coal mine.
With mine mining depth increasing, the situation of mine gas control is more rigorous, and the existing single hydraulic fracturing method often cannot achieve the ideal effect. Based on the characteristics of high gas and low permeability coal seam, this paper designed different ways of hydraulic fracturing experiment to investigate the differences of gas extraction ability, and eventually optimize the hydraulic fracturing method. The experimental results show that repeated hydraulic fracturing and directional hydraulic fracturing methods are more suitable for increasing soft coal seam permeability than conventional hydraulic fracturing method, and the gas extraction ability of repeated hydraulic fracturing is better than directional hydraulic fracturing. After repeated hydraulic fracturing, the single-hole average pure volume of gas drainage has reached 10.224m³/d, which is 2.5 times as much as the conventional hydraulic fracturing; The extraction concentration is 63% -72%, with an average of 67.8%, which is 19.2% higher than the conventional hydraulic fracturing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.