Horizontal trajectories of rotary-drilled holes.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9177, 1988 Jan; :1-11
This Bureau of Mines report investigates the horizontal trajectory of boreholes drilled in coalbeds using the rotary drilling technique. Test holes drilled in coalbeds showed that the path of a borehole in the horizontal plane depends on drilling assembly configuration, drill bit rotation, and coalbed geologic features. An assembly that contained an 18-ft (5.5-M) long drill collar and two centralizers had the best horizontal stability evidenced by trajectories that deviated less than 16 ft. (4.9 M) from a target at 1,000 ft (305 m). Removal of one of the centralizers resulted in a loss of control of hole trajectory in the horizontal plane. Generally, holes tended to turn to the right, presumably because of right-hand rotation of the bit. Deviations from the original bearing line were as much as 200 ft (61 m) or more at a depth of 1,000 ft (305 m).
Surface-mining; Surface-properties; Underground-mining; Mining-industry; Coal-mining; Structural-analysis; Room-and-pillar-mining
IH; Report of Investigations
NTIS Accession No.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9177