Determination of Fracture Initiation Locations during Cross-Measure Drilling for Hydraulic Fracturing of Coal Seams

Yiyu Lu, Yugang Cheng, Zhaolong Ge, Liang Cheng, Shaojie Zuo and Jianyu Zhong
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Yiyu Lu: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Yugang Cheng: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Zhaolong Ge: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Liang Cheng: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Shaojie Zuo: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Jianyu Zhong: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

Energies, 2016, vol. 9, issue 5, 1-13

Abstract: When drilling coal-bearing sequences to enhance coal seam permeability by hydraulic fracturing (HF), the location where fractures are initiated is important. To date, most research on fracture initiation has studied the problem in two dimensions. In this study, a three-dimensional model to assess initiation location is developed. The model analyzes the stress state of both the borehole wall and the coal-rock interface and the model shows that the fracture initiation location is affected by in situ stress, the dip of the coal seam, and the angle between the borehole and the coal seam. How the initiation location changes near different types of geological faults is calculated by assuming typical in situ stresses for the faults. Following these calculations, physical experiments were carried out to emulate cross-measure hydraulic fracturing under stress conditions equivalent to those in the Chongqing Tonghua coal mine, China. Fracture initiation during the experiments was monitored by an acoustic emission system. The experimental results were consistent with the theoretical calculations. This implies that the three-dimensional model for assessing the locations of fracture initiation can be applied to forecast the initiation location of fractures generated by cross-measure drilling. The assessment model provides reference values for this type of drilling in underground mines.

Keywords: hydraulic fracturing (HF); initiation location; crack propagation; acoustic emissions (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2016
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (7)

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