Trenton-Black River Hydrothermal Dolomite Reservoirs in Ontario: An Assessment of Remaining Potential After 100 Years of Production

Mcfarland, Sean¹, Terry Carter², Robert Trevail³, Joseph Gorman⁴, Philip Walsh⁴, and Ed Welychka^4
1 Golder Associates, Mississauga, ON, 
² Ontario Ministry of Natural Resources, London, ON, 
³ Dallas-Morris Drilling Inc., Freedom, PA, , 
⁴ Energy Objective, London, ON

Since discovery of the first Trenton-Black River reservoir in Ontario in 1900 over 19 million barrels of oil and 31 billion cubic feet of natural gas have been produced from this play, with current production of nearly one million barrels of oil per year. Proven recoverable reserves in individual pools range up to 6 million bbl of oil and 11 bcf of natural gas at an average depth of 800 m.

Geological relationships are analogous to the giant Albion-Scipio field in Michigan. 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 several kilometres in length and several hundred metres in width. There is commonly a structural depression over the dolomitized zone, vertical displacement of the underlying Precambrian basement surface, and a change in character on seismic records within the dolomitized zone. The reservoirs are laterally bounded by non-porous limestones, and are overlain by grey marine shales of the Blue Mountain Formation.

A reassessment of the initial and remaining potential oil and gas resources of the Trenton-Black River play in Ontario is underway at the time of writing. The assessment methodology and preliminary results are summarized. The study is funded by the Targeted Geoscience Initiative of Natural Resources Canada.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004