Trenton-Black River Hydrothermal Dolomite Reservoirs in Ontario: Geology, Reserves and Potential Resources

Terry R. Carter¹, Sean McFarland², Robert A. Trevail³, Joseph Gorman⁴, and Philip Walsh^4
1 Ministry of Natural Resources, London, ON
² Golder Associates, Mississauga, ON
³ Dallas-Morris Drilling, Freedom, PA
⁴ Energy Objective, London, ON

Since discovery of the Hepworth gas pool in 1900 over 19.5 million barrels of oil and 35 billion cubic feet of natural gas have been produced from Trenton-Black River hydrothermal dolomite reservoirs in Ontario. Oil and gas in these pools are trapped in Ordovician carbonates of the Trenton and Black River Groups where they have been dolomitized and fractured adjacent to vertical faults. The resulting linear hydrothermal dolomite reservoirs reach up to 14 kilometres in length and several hundred metres in width. Proven recoverable reserves in individual pools range up to 6 million bbl of oil and 13.6 bcf of natural gas at an average depth of 800 m. The last assessment of the initial and remaining potential resources in this important play was completed in 1984. Since that time 39 new Trenton-Black River oil and gas pools have been discovered in Ontario and oil production from this play has increased from only 60,000 barrels/year to over 1 million barrels/year. This study includes Trenton structure contour maps for major new pools, geophysical log cross-sections, estimates of recoverable reserves and a summary of reservoir characteristics in addition to estimates of potential resources. The assessment methodology and preliminary results are summarized. Preliminary estimates indicate that 83% of the natural gas resources and 40% of the oil resources in this play are still undiscovered. Funding for this study was provided by Natural Resources Canada under their Targeted Geoscience Initiative.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005