Exploration and development activity in eastern Canada had a dramatic decline in 1986, especially in the offshore regions of the east coast, and Lake Erie in the province of Ontario. Reasons for the decline include the current depressed prices for oil on international markets, the termination of the Canadian government-sponsored Petroleum Incentives Program, and completion of exploratory drilling required to validate exploration agreements on the east coast offshore. In addition, uncertainties connected with deregulation of the Canadian natural gas industry had a major negative effect on exploration and development of natural gas in Ontario.

In the Canadian east coast offshore region, drilling was completed at 10 exploratory wells and 6 delineation wells, drilling was suspended at 1 well, and drilling was in progress at another well at year end. Three new discoveries were reported: 1 gas and 1 oil discovery offshore Nova Scotia, and 1 oil discovery offshore Newfoundland. Discovered resources in the region are currently estimated at 198.6 million m³ (1.25 billion bbl) of oil and condensate, and 297.4 billion m³ (10.5 tcf) of gas.

In Ontario, a total of 113 wells were drilled in 1986: 60 exploratory, 29 development, and 24 service wells. Only 4 wells were drilled in Lake Erie, compared to 75 in 1985. Forty-five percent of the exploratory wells and 83% of the development wells were successfully completed as oil and/or gas producers. Oil production increased substantially for the second year in a row, to 135,816 m³ (854,257 bbl), compared to 112,953 m³ in 1985. The increase in 1986 was again due almost entirely to new production from Trenton-Black River carbonate rocks of Ordovician age. Production of natural gas declined by 10% to 532.435 million m³ (18.8 bcf).

Only 9 wells were drilled in Quebec in 1986, compared to 23 wells in 1985. These consisted of 4 development wells, 4 service wells, and 1 exploratory well. Gas production from Saint Flavien field increased marginally to 13.95 million m³ (492.5 mmcf).

In New Brunswick, 1 exploratory well was drilled in 1986, and it was abandoned without encountering any hydrocarbons. Production from Stoney Creek field totaled 640 m³ (4,025 bbl) of oil and 1.822 million m³ (64.3 mmcf) of natural gas.

There was no drilling onshore Newfoundland, Nova Scotia, or Prince Edward Island in 1986.