Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

NIOSHTIC-2 Publications Search

Search Results

Reconciling longwall gob gas reservoirs and venthole production performances using multiple rate drawdown well test analysis.

Authors
Karacan-C÷
Source
Int J Coal Geol 2009 Dec; 80(3-4):181-195
NIOSHTIC No.
20036109
Abstract
Longwall mining is an underground mining method during which a mechanical shearer progressively mines a large block of coal, called a panel, in an extensive area. During this operation the roof of the coal seam is supported only temporarily with hydraulic supports that protect the workers and the equipment on the coal face. As the coal is extracted, the supports automatically advance and the roof strata cave behind the supports. Caving results in fracturing and relaxation of the overlying strata, which is called "gob." Due its highly fractured nature, gob contains many flow paths for gas migration. Thus, if the overlying strata contain gassy sandstones or sandstone channels, gas shales or thinner coal seams which are not suitable for mining, then the mining-induced changes can cause unexpected or uncontrolled gas migration into the underground workplace. Vertical gob gas ventholes (GGV) are drilled into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment. Thus, it is important, first to understand the properties of the gas reservoir created by mining disturbances and, second, to optimize the well parameters and placement accordingly. In this paper, the production rate-pressure behaviors of six GGVs drilled over three adjacent panels were analyzed by using conventional multi-rate drawdown analysis techniques. The analyses were performed for infinite acting and pseudo-steady state flow models, which may be applicable during panel mining (DM) and after mining (AM) production periods of GGVs. These phases were analyzed separately since the reservoir properties, due to dynamic subsidence, boundary conditions and gas capacity of the gob reservoir may change between these two stages. The results suggest that conventional well test analysis techniques can be applicable to highly complex gob reservoirs and GGVs to determine parameters such as skin, permeability, radius of investigation, flow efficiency and damage ratio. The insights obtained from well test analyses can be used for a better understanding of the gob and for designing more effective gob gas venthole systems.
Keywords
Coal-gas; Coal-gasification; Coal-mining; Coal-workers; Control-technology; Engineering-controls; Gases; Longwall-mining; Methane-control; Methanes; Mine-gases; Mining-industry; Underground-mining; Ventilation; Ventilation-systems; Work-environment; Author Keywords: Well testing; Drawdown test; Multi-rate test; Longwall mining; Gob gas ventholes; Production performance; Methane control
Contact
C. ÷zgen Karacan, National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory, Pittsburgh, PA 15236, USA
CODEN
IJCGDE
CAS No.
74-82-8
Publication Date
20091201
Document Type
Journal Article
Email Address
cok6@cdc.gov
Fiscal Year
2010
NTIS Accession No.
NTIS Price
Issue of Publication
3-4
ISSN
0166-5162
NIOSH Division
PRL
Priority Area
Mining
Source Name
International Journal of Coal Geology
State
PA
TOP