DETERMINATION OF BULK PERMEABILITY WITHIN THE MORIEN GROUP USING THE FORCING OF OCEAN TIDES IN THE SYDNEY BASIN IN CAPE BRETON, NOVA SCOTIA

Abstract

Since November 1992 the Lingan Colliery in the Sydney coalfield has been steadily filling with water. At the same time the water level in the previously flooded 1B region and the No 26 Colliery has been gradually decreasing. There are no direct excavated links between the Lingan and No.26 Collieries. It is believed that influences of the longwall mining in the Phalen Colliery have caused damage to the barrier pillar between the Lingan and No 26 Collieries, resulting in a hydrological connection. The water levels in the workings in question have been monitored and recorded by the Cape Breton Development Corporation (CBDC) since 1986, but after the 1992 massive inrush the monitoring system was upgraded to provide a more complete picture of what is happening within the mine with respect to mine waters. In Lingan, water level data recorded by CBDC, show a strong tidal signal that overprints the increasing water level signal in the mine. Comparison with regional tidal records over the same time period has confirmed this correlation between water level data and the tidal signal. The differences found in the correlations will be used to determining the bulk permeability of the strata from the Harbour coal seam to the seafloor. An analysis of the phase shift and amplitude of the tidal signal in the water level records provides a direct estimate of formation permeability, based on Darcy's law and assuming that there is laminar flow through out the formation. Water level data, analyzed to remove the longer time period fluctuations in levels, are presented with tidal data. The bulk permeability based on the tidal signal differences are found to fall within the silt to sand range ( 1 o-2 to 1 o-3 em/ sec).

Key Words: bulk permeability, hydrological connection, correlation, Darcy's law, laminar flow, Colliery, phase shift, amplitude shift