Each month, we provide an environmental compliance tip that is based on provincial and federal regulations. However, there are environmental risks that are not covered by existing regulations, including risks associated with historical (abandoned) oil and gas exploration wells.
An Explosion
The issue of the potential significant risks associated with abandoned oil and gas wells drew public attention in 2021. In downtown Wheatley, Ontario, there was a hydrogen sulphide gas explosion (August 26, 2021). The explosion hospitalized seven and levelled two buildings (London Free Press).
On June 26, 2025, hydrogen sulphide gas was again detected in Wheatley. This was after the original emergency order was lifted on October 31, 2024. These incidents in Wheatley highlight the unpredictable, disruptive, and destructive potential of the presence of historical oil and gas exploration wells near buildings.
According to an article in the Globe and Mail (paywall), “Experts say another Wheatley is all but assured in the region. It’s just a matter of time” (our emphasis).
Human Health, Environmental, and Monetary Risks
The incident in Wheatley demonstrates not only the human health and environmental risk associated with these wells, but also the expense for municipalities, insurance companies, and individuals.
Earlier this year, CK NewsToday reported that “the costs incurred with the Wheatley emergency to date are pegged at $22 million, while the provincial funding received or committed is $16.4 million.”
Image Source and Credit: The Ontario Ministry of Natural Resources and Forestry/Ontario GeoHub https://www.ontario.ca/page/open-government-licence-ontario. See Open Government Licence – Ontario.
According to Ontario GeoHub, this map includes “The locations of wells that have been drilled for oil production, gas or salt resources or for underground storage of hydrocarbons.”
Thousands of Historical Oil and Gas Wells
There are thousands of oil and gas exploration sites (as many as 27,000) across southwestern Ontario. Unfortunately, reviewing publicly available online historical well drilling location maps is not sufficient to determine risk because there are limited or poor records in some areas.
Determining the location of these thousands of exploration wells (from the 1860s to the 1970s) using field drilling sketches and incomplete drilling records can be difficult. This is exacerbated when the metal pipe casing associated with the borehole has been removed (and would not be found with metal detection equipment).
Well location accuracy is often negatively proportional to the age of the installation. The accuracy of locating older wells is often estimated to be approximately 200 metres (drilling location should be within a 200-metre radius circle around the map plot location).
However, in reality, based on our personal experience, we have found that a few of the online map locations have been placed on the wrong property lot and/or potentially as far as 500 metres away from where locational information in the drilling records indicates. We have found that even locations plotted on the map with an estimated 20 to 50 metre radius accuracy can be found 25 to 95 metres away.
How Do You Find Abandoned Oil and Gas Exploration Wells?
Based on our project experience, we have found that a phased-investigation approach can help focus subsequent tasks towards better-defined potential former drill areas. A desktop location study is often the first phase and typically consists of a review of available historical drilling records.
As a second phase, site inspections, interviews, and a geophysical survey can each narrow (and sometimes expand) the target area.
A third phase of investigation may include other useful techniques such as a surface soil vapour survey and/or soil sampling.
Having detailed information on the position of former petroleum exploration drill locations can facilitate better decisions regarding potential risk; specifically, it may identify existing structures at risk and potential risk for future development.
Conclusion
There are thousands of historical oil and gas production and exploration wells located throughout Ontario, posing potential human health and environmental risks. With the push toward more and faster development (Protect Ontario by Building Faster and Smarter Act of 2025), a cautious and measured approach will help reduce these risks.
Environmental Assistance
If you would like to have a discussion regarding our service related to abandoned/orphaned oil and gas wells on your development or within your municipality, township, or county, please feel free us at 519-948-7300.
Allan Clifford Lawton (Cliff) co-authored this blog. Cliff is a project manager at Dragun. He has more than 35 years of experience. Cliff manages and oversees soil and groundwater investigations and works closely with and advises First Nations Communities on environmental matters. Cliff has authored articles in Environmental Science and Engineering Magazine, Lawyers Weekly, and Commercial Inc., and has spoken at conferences such as the International Municipal Lawyers Association. See Cliff’s bio.
Christopher Paré, P.Geo, co-authored this blog. Chris is a senior geoscientist and manager of Dragun’s Windsor, Ontario, office. Chris has more than 35 years of experience on projects ranging from environmental site assessments (Phase One/Two ESA), excess soils, remedial investigations, soil and groundwater remediation, Permits to Take Water, Records of Site Conditions, vapour intrusion, and site decommissioning. Chris is a frequent speaker, author, and expert witness. See Chris’ bio.
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