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Probability of encountering coalbed discontinuities during vertical and horizontal borehole drilling.

Authors
Houseknecht-DW
Source
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8665, 1982 Jan; :1-21
NIOSHTIC No.
10002361
Abstract
Probabilities of encountering coalbed discontinuities during vertical or horizontal drilling in a specific coalbed can be estimated based on analysis of mined-out areas of the coalbed where the size, shape, orientation, and distribution of discontinuities are known. The resultant probability estimates can be applied to cost-risk evaluations of drilling programs proposed for exploratory, developmental, or methane drainage purposes in undeveloped areas of that coalbed. Data compiled from mine maive hypothetical drilling programs--one for drilling vertical boreholes. Analysis based on a mined-out area of the Beckley coalbed indicated that vertical methane drainage boreholes spaced 1,000 feet apart in a square grid pattern would each have a 29-percent probability of encountering a discontinuity in a geologically unexplored area of the coalbed. It was also determined that exploratory vertical drilling could locate most of the discontinuities if a borehole spacing of 2,500 feet were used. For horizontal drainage boreholes in the Beckley coalbed, the analysis indicated a linear relationship between hole length and the probability of encountering a discontinuity.
Keywords
Mine-gases; Mining-industry; Methanes; Methane-drainage; Methane-control; Explosive-gases; Explosive-atmospheres; Underground-mining; Coal-mining; Control-technology; Engineering-controls
CAS No.
74-82-8
Publication Date
19820101
Document Type
IH; Report of Investigations
Fiscal Year
1982
NTIS Accession No.
NTIS Price
Identifying No.
RI-8665
NIOSH Division
PRC
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8665
State
PA
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