The Abandoned Works Program, SW Ontario: identifying the sources of leaking natural gases

Abstract

The Abandoned Works Program (AWP) in SW Ontario was initiated by the Ontario Ministry of Natural Resources (MNR) in 2005 to lead remediation efforts, when required, for a legacy of unplugged petroleum wells, many of which were drilled prior to provincial regulation of this activity. The first oil well was drilled in Oil Springs, Ontario in 1858. The first provincial legislation requiring plugging of unused petroleum wells was enacted in 1892 and legislation of well drilling not until 1924. Of the ∼50,000 wells dispersed across the region ∼27,000 are on record at the MNR. For many wells, there is no information on drilling depth or producing formation and a large number have not been plugged properly. On occasion, due to the lack of records, plugging these wells has been problematic and extremely costly. As part of the solution to this problem, we are determining the geochemical fingerprints of the Paleozoic natural gas reservoirs and aquifers in southwestern Ontario. The goal is to determine whether or not known reservoirs/aquifers can be differentiated using geochemical signatures, and if this approach can be used to identify leaking gas or formation water from wells with no records. Success would yield considerable cost savings in remediating undocumented leaking wells. The study area straddles the Algonquin Arch, which separates the Appalachian and Michigan basins, and hence has a diverse hydrostratigraphic history. Here, we present carbon- and hydrogen-isotope compositions (GC-IRMS) for these data. We have observed that there are distinct reservoir characterstics, from potential microbrial reaction and water infitration in the Guelph of the Lambton area to distinct hydrogen-isotope signatures in the Lower Ordovician Trenton/Black River reservoirs that might indicate mixing with other reservoirs. Carbon-isotope analyses alone can not discriminate in this regard. Current results show great promise. The isotopic data provide a useful tool for discriminating among different Paleozoic reservoirs/aquifers on a stratigraphic and geographic basis, and the results have already led to successful evaluation and plugging of a challenging, leaking well.

AAPG Datapages/Search and Discovery Article #90195 © 2014 Eastern Section Meeting, London, Ontario, Canada, September 27-30, 2014