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Primary Author-Presenter
Bryan Szatkowski obtained a BSc Geology from the University of Saskatchewan. Bryan is president and founder of GCHEM Ltd who over the past +25 years has worked with academia, industry, government regulators and landowners developing chemical and isotopic fingerprinting applications (Energy-Forensics) to resolve oil and gas development and exploitation questions related to exploration, production and environmental detection and monitoring. In this presentation, Bryan will provide case studies using Energy-Forensics to classify, characterize and determine the geological origins of leaking gases in surface casing vents (SCVF) and soils outside casing (GM) on resource wells impacted with natural gas leakage.

Secondary Author-Presenter
Brad Johnston obtained a BSc in Chemistry from the University of Saskatchewan. Brad has worked at GCHEM Ltd for 24 years, is the Operations Manager and was instrumental in developing chemical and isotopic fingerprinting (Energy-Forensics) and applications for the energy industry. In this presentation, Brad will provide case studies using Energy-Forensics to classify, characterize and determine the geological origins of leaking gases in surface casing vents (SCVF) and soils outside casing (GM) on resource wells impacted with natural gas leakage.

Presentation Summary

In western Canada, many oil and natural gas wells are leaking gas into surface casing vents and into soils around the well-head. This undesired leakage, or migration of natural gases from deep (thermogenic) sources may pose significant operational, safety and environmental concerns. Fugitive gases may migrate into shallower strata and, ultimately, may be released to atmosphere contributing to greenhouse gas emissions (GHG). Gaseous hydrocarbons may enter a well bore at points of poor cement bonding with wall rock, in small, and possibly gas induced, channels within the cement itself, or in micro-annuli at the contact between casing and cement. When gas is detected in the vent between the production and surface casing, it is considered to be surface casing vent flow (SCVF) and when found in soils outside the casing, it is termed active gas migration (AGM). In addition to thermogenic gas associated with drilling and hydrocarbon exploitation activities, gases may be present in soils from biological activity, contamination, or natural background processes. Identifying the geological source or origin of migrating gases has proven to be a difficult and challenging task, but is essential for successful intervention and remediation of a leaking well bore.

Chemical and isotopic chemistry has proven to be a powerful tool in forensic science for detecting the alteration in alcohols or wines, confirming the origin of ancient artifacts and detecting or tracing the origin of contraband substances. The same principals can be applied to fingerprint and/or characterize natural gas related to surface gas migration (SCVF & AGM) at resource well bores. Stable carbon (δ13C) and hydrogen (δD) isotopic compositions of light-alkane gases change systematically with stratigraphic depth therefore, individual geological formations contain gases with unique or characteristic isotopic compositions. By comparing molecular, δ13C and δD isotopic compositions of migrating gases collected at or near surface to established ‘BASELINE-CONTROL’ fingerprints of subsurface gases, a source for the migrating gases can be identified to focus intervention-repair operations. In this presentation stray gas case studies are provided where the geological source of leaking gases is determined using molecular and stable isotopic compositions of carbon and hydrogen in light alkane/ene gases.

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