TRENTON-BLACK RIVER HYDROTHERMAL DOLOMITE RESERVOIRS IN ONTARIO: AN ASSESSMENT OF REMAINING POTENTIAL AFTER 100 YEARS OF PRODUCTION

摘要

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 1200 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 present assessment of Ordovician recoverable oil and gas reserves in southwestern Ontario involved geological delineation and statistical evaluation, using the truncated discovery process model, of the established mature play. Results of the assessment suggest that total Middle Ordovician recoverable gas and oil resources is in the order of 7,960 10~6m~3 (281 bcf) and 6,313,671 m~3 (39.7 MMbbls) respectively. Eighty-five per cent of this gas volume 6,799 10~6m~3 (240 bcf) and 43 per cent of this oil volume 2,733,296 m~3 (17.2 MMbbls) remains to be discovered. This indicates that the play still has a significant upside potential with respect to undiscovered oil and gas volumes, particularly in that area between the current area of exploration and development activity and the eastern most point of the Niagara Escarpment.