In August 1974 the Groundwater Division, Alberta Research Council, was approached by the Engineering Division, Physical Sciences Branch, Alberta Research Council, concerning permeability determinations for an underground coal gasification test. From subsequent discussions it was concluded that aquifer testing of the coal seam would be a viable method to obtain magnitudes, orientations and distribution of permeabilities within the coal seam and thus aid in planning a proposed underground coal gasification test. A drilling program and a 4000 minute aquifer test were completed in October 1975 and a second 4000 minute aquifer test (at a higher pumping rate) was completed in April 1976. This report describes the results obtained.
The test site is located approximately 15 miles north of Halkirk and one mile southeast of the Battle River Power Station, or approximately 130 miles southeast of Edmonton. All of the piezometers were drilled on land owned or leased by the Cordel-Vesta Mine (operated by Manalta Coal Ltd.) and are located near the high wall (bench) of an abandoned stripping excavation.
Purpose and Aims
It was felt that if an aquifer test indicated anisotropic, horizontal permeability distribution within the coal seam, the direction and magnitude of higher permeability could control the direction of burning coal during the gasification test. This would eliminate the need for mechanical linking (by drilling horizontal holes from the high wall) to ensure a known direction of air circulation (and thus burn direction) prior to ignition of the coal for gasification. In addition, any relationship established between air and water permeability within the coal seam could perhaps be applied to future underground gasification tests.
Original aims of the aquifer testing were:
1. To determine the horizontal permeability of the coal seam, anisotropy (if any), and coincidence of anisotropy with the major and/or minor cleat (fracture) directions as proposed by J. D. Campbell, Alberta Research Council.
2. To establish if hydraulic continuity exists between the water in the abandoned stripping excavation (where a portion of the coal seam had been removed) and groundwater in the coal seam.
3. To determine the vertical permeability of the caprock (above coal) and the baserock (below coal) and thus evaluate the possibility of gas leakage during gasification.
4. To determine the coefficient of storage of the coal seam, baserock and caprock.
Because the first aquifer test (1) established anisotropic permeability effects in the coal seam, and (2) did not induce a response in the piezometers completed above and below the coal seam, it was decided to conduct a second aquifer test.
The aims of the second aquifer test were:
1. To pump the coal seam at the highest possible continuous rate in an attempt to measure vertical permeability of the sediments above and below the coal.
2. To confirm the anisotropy of the horizontal permeability in the coal seam.