Influence of combination forms of intact sub-layer and tectonically deformed sub-layer of coal on the gas drainage perfo
- PDF / 2,887,483 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 30 Downloads / 151 Views
Influence of combination forms of intact sub-layer and tectonically deformed sub-layer of coal on the gas drainage performance of boreholes: a numerical study Wei Zhao1,2,4 • Kai Wang1,2 • Rong Zhang3 • Huzi Dong1,2 • Zhen Lou1,2 Fenghua An4
•
Received: 11 January 2020 / Revised: 12 February 2020 / Accepted: 2 April 2020 The Author(s) 2020
Abstract High concentration and large flow flux of gas drainage from underground coal seams is the precondition of reducing emission and large-scale use of gas. However, the layered occurrence of coal seams with tectonically deformed sub-layers and intact sub-layers makes it difficult to effectively drain gas through commonly designed boreholes. In this study, the gas drainage performance in coal seams with different combinations of tectonically deformed sub-layers and intact sub-layers was numerically analyzed. The analysis results show that the gas drainage curve changes from a singlestage line to a dual-stage curve as the permeability ratios of Zone II (kII) and Zone I (kI) increase, raising the difficulty in gas drainage. Furthermore, a dual-system pressure decay model based on the first-order kinetic model was developed to describe the dual-stage characteristics of pressure decay curves with different permeability ratios. In the end, the simulation results were verified with reference to in-situ drainage data from literature. The research results are helpful for mines, especially those with layered coal seams comprising tectonically deformed sub-layers and intact sub-layers, to choose appropriate gas drainage methods and develop the original drainage designs for achieving better gas drainage performance. Keywords Tectonically deformed coal Pressure decay Permeability Hydraulic flushing boreholes
1 Introduction Tectonically deformed coal is the coal whose chemical and mechanical properties have been dramatically altered by tectonic movements (Cheng and Pan 2020; Ju et al. 2014). Different from intact coal, it is usually characterized by a & Kai Wang [email protected] 1
Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources, China University of Mining & Technology, Beijing, Beijing 100083, China
2
School of Emergency Management and Safety Engineering, China University of Mining & Technology, Beijing, Beijing 100083, China
3
Flight Technology College, Civil Aviation University of China, Tianjin 300300, China
4
State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University), Jiaozuo 454003, China
higher gas content, a higher gas desorption rate, a lower mechanical strength and a lower permeability (Black 2019; Wang et al. 2015; Wu et al. 2019; Zhao et al. 2015, 2019; Zhi and Elsworth 2016). Tectonically deformed coal is widely distributed in China, specifically, in the west of Henan Province, the south of Shanxi Province and the middle and north of Anhui Province, etc., where intense tectonic movements occurred during coal formation. According to the statistics, there are about 457 billion tons of
Data Loading...
