Probability of encountering coalbed discontinuities during vertical and horizontal borehole drilling.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8665, 1982 Jan; :1-21
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.
Mine-gases; Mining-industry; Methanes; Methane-drainage; Methane-control; Explosive-gases; Explosive-atmospheres; Underground-mining; Coal-mining; Control-technology; Engineering-controls
IH; Report of Investigations
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8665