Unconventional Analytical Techniques for Unconventional Gas: A Case Study of a Late Cretaceous–Tertiary Ardley Gas-Charged Coal in the Pembina-Warburg Exploration Area, Alberta, Canada

Shane M. Harrison¹, Thomas Gentzis², and Mickey Payne^2
1 SH Consulting, Calgary, AB
² CDX Canada, Calgary, AB

An evaluation of fluid and reservoir parameters of a 200 m deep key test-well completed in the uppermost Ardley coal was undertaken in the Pembina–Warburg exploration area, Alberta Basin, Alberta, Canada. Downhole measurements showed a build-up of fluid (water) pressure within the coal to approximately 1470 kPa. Drawdown of the fluids showed that the permeability of the coal is less than 5mD and likely in the order of 1 mD. Formation waters are Na-HCO₃ type with salinities of approximately 1920 mg/L TDS (calculated). Detailed isotopic analyses of the fluids showed that anomalously high bicarbonate concentrations of up to 1650 mg/L are characterized by enriched δ¹³C_DIC of +22.50‰ . Dissolved methane concentrations of up to 36 mg/L are characterized by depleted δ¹³C_CH4 of -48.32‰. Formation fluids δ¹⁸O and δ²H plot along the local groundwater line (LGWL) for Edmonton, Alberta indicating a meteoric origin. The ¹³C isotopes for DIC and methane, coupled with ¹⁸O and ²H isotopes for associated groundwater and regional hydraulic and hydrochemical data suggest that the uppermost Ardley Coal Zone lies within a regional, topographically driven, dynamic flow system in which methanogenic processes are gas charging the coal and modifying groundwater chemistry in the eastern part of the exploration area.