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Rotary drilling holes in coalbeds for degasification.

Authors
Cervik-J; Fields-HH; Aul-GN
Source
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8097, 1975 Jan; :1-21
NIOSHTIC No.
10000710
Abstract
Coal is a soft and brittle material. Drilling rates in the Pittsburgh coalbed using a drag bit exceed 3 ft/min at 2,500-pound thrust. However, maintaining the bit on a horizontal trajectory or parallel to bedding planes to attain lengths of 1,000 feet is difficult. This Bureau of Mines report presents a drill string configuration that can be guided through the coalbed. The angle of the borehole is measured periodically and by proper combinations of bit thrust and rotational speed (r/min), bit trajectory can be lifted or dropped to keep the bit in the coalbed. An example of a hole drilled to 2,126 feet is presented to show levels of thrust and rotational speed used to lift or drop the bit, the seemingly unexplainable events that occur, and the strategy used during drilling. Thrust levels during drilling range from 600 to 2,500 pounds. Hydraulic motors powered by a 30-hp, 440-volt motor provide ample power for drilling horizontal holes 2,000 feet long.
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
19750101
Document Type
IH; Report of Investigations
Fiscal Year
1975
NTIS Accession No.
PB-250693
NTIS Price
A03
Identifying No.
RI-8097
NIOSH Division
PRC
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8097
State
PA
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