Cleat Orientation and Areal Hydraulic Anisotropy of a Wyoming Coal Aquifer

Abstract

The anisotropic, areal hydraulic conductivity of the Felix No. 2 coal (Eocene, Wasatch Formation) has been defined in a four‐well pump test at a site in the Powder River Basin of northeastern Wyoming. The direction of maximum hydraulic conductivity of the subbituminous coal bed bears N59°E and is associated with a horizontal hydraulic conductivity of 0.27 m/day. The direction of minimum hydraulic conductivity bears N31°W and is associated with a horizontal hydraulic conductivity of 0.15 m/day. The direction of maximum hydraulic conductivity approximately corresponds to the trend of the prominent face cleat in the coal, while the direction of minimum hydraulic conductivity corresponds to the trend of the butt cleat. The cleat orientation appears related to the alignment of major structural features of the region. Prediction of the direction of both maximum and minimum horizontal hydraulic conductivity in near‐horizontal coal beds appears possible. However, either the cleat orientation of the bed or the alignment of the controlling fold structure must be known or obtainable.

Hydrologic properties of coal-beds in the Powder River Basin, Montana. II. Aquifer test analysis

“…Previous tests (Stone and Snoeberger, 1977;Dobson, 1996) indicate that the maximum transmissivity is aligned nearly parallel to the face cleat orientation. For example, Stone and Snoeberger (1977) determined that maximum transmissivity was oriented N598E, and face cleats about N708E.…”

“…Previous tests (Stone and Snoeberger, 1977;Dobson, 1996) indicate that the maximum transmissivity is aligned nearly parallel to the face cleat orientation. For example, Stone and Snoeberger (1977) determined that maximum transmissivity was oriented N598E, and face cleats about N708E. Results of the current test are of interest, in that they show the major transmissivity tensor axis to be oriented about 558 E of the face cleat orientation of N338, but nearly parallel to the strike of a major fracture orientation in the coals and interbedded sediments that may arise from a shift in the orientation of the stress field through geologic time (Morin, this issue).…”

“…Six other aquifer tests conducted to determine the anisotropic transmissivity of coal-beds in the Powder River Basin are described by Stone and Snoeberger (1977), Stoner (1981), and Dobson (1996). Results of the test described in this paper are compared to results of those tests in Table 4.…”

Horizontal Hydraulic Conductivity Estimates for Intact Coal Barriers Between Closed Underground Mines

“…Hydraulic properties of western coal seams are reported by McCord and others (1992) in Colorado and New Mexico and by others (1978, 1980), Chadwick (1981), Stoner (1981), and Stone and Snoeberger (1977) in low-rank beds of the Fort Union Formation in North Dakota, Montana, and Wyoming.…”

“…Schubert's (1980) summary of several studies indicated a range of 2 to 10 in West Virginia coals. Stoner (1981), Vogwill (1979), Stone and Snoeberger (1977), and Erickson (1970) found anisotropic ratios of western coals to differ by a factor of 2.5 and 2.9, 2.4, 1.8, and 4.8, respectively.…”