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The borehole monitoring experiment: field measurements of reservoir conditions and responses in longwall panel overburden during active mining.

Authors
Schatzel-SJ; Karacan-CÍ; Goodman-GVR; Mainiero-R; Garcia-F
Source
Proceedings of the 12th U.S./North American Mine Ventilation Symposium, Reno, Nevada, June 9-11, 2008. Wallace KG Jr., ed., Reno, NV: University of Nevada - Reno, 2008 Jun; :93-101
NIOSHTIC No.
20034033
Abstract
In order to better understand the effects of longwall mining on the methane reservoir overlying the panel, the National Institute for Occupational Safety and Health/Pittsburgh Research Laboratory (NIOSH/PRL) designed and implemented a vertical borehole monitoring experiment (BME) on an active longwall panel. The mine operates in the Pittsburgh Coalbed in Greene County. Pennsylvania. The BME site was located away from either end of the panel to avoid mechanical influences caused by the draping of overburden in this region and was positioned at the same distance from the tailgate gateroad as the mine's gob gas venthole sites. The borehole drilling depths and monitoring intervals were chosen to address a different stratigraphic zone in each of the three planned holes. The monitoring boreholes were positioned perpendicular to face advance using a close spacing pattern of about 15 m (50 ft) between collars. Boreholes were instrumented downhole and on the surface for various measurements. It was observed from the field data that the gob gas venthole fracture network formed 24-46 m (80-150 ft) ahead of the mining face. Overburden permeability's within the same test zones increased 100 to 500 times following undermining. The borehole test interval within the fractured rock responded to overburden gas pressure while the test interval in the caved zone responded to mine ventilation conditions. Eight months after the boreholes were undermined, slug testing indicated permeabilities had increased further in the fractured rock zone. Measurements of surface movement indicate that the permeability development observed in the boreholes is a product of vertical subsidence without lateral movement within the tensional rock mechanics zone on a supercritical longwall panel. Results from this study suggest that maximum permeability in the longwall panel overburden is achieved 58 to 190 m (190 to 620 ft) behind the longwall following maximum compaction of the overburden. PowerPoint and MP3 files are available.
Keywords
Mining-industry; Underground-mining; Coal-mining; Longwall-mining; Methane-control; Methane-drainage; Methanes
CAS No.
74-82-8
Publication Date
20080609
Document Type
Conference/Symposia Proceedings
Editors
Wallace-KG Jr.
Fiscal Year
2008
NTIS Accession No.
NTIS Price
ISBN No.
9780615200095
NIOSH Division
PRL
Priority Area
Mining
Source Name
Proceedings of the 12th U.S./North American Mine Ventilation Symposium, Reno, Nevada, June 9-11, 2008
State
PA; NV
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