I am very familiar with the Ontario well files and the historic records and perform historical well searches for property transfers or curious landowners.
In many areas of Ontario there were historic oil and gas wells drilled in the late 19th and early 20th century that may not be documented on the property title. Many of these historic wells were not plugged or improperly plugged and the landowner could be responsible for the plugging costs. Sometimes a search can reveal a company that should be held responsible for the well plugging costs.
A Title Search can uncover hidden truths about the property such as liens or mortgages or petroleum leases registered on title but may have nothing documenting whether any petroleum (oil and/or natural gas) wells were drilled.