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Isotopic Forensic Techniques for Methane Source Descrimination
Oral Presentation
Prepared by J. Sueker, G. Cramer
ARCADIS US., Inc., 1687 Cole Blvd, Suite 200, Lakewood, CO, 80401
Contact Information: Julie.Sueker@arcadis-us.com; 303-231-9115
ABSTRACT
Combustible gases, such as methane, in soil and shallow groundwater present a safety concern due to potential offgassing and accumulation in water well and plumbing systems that could lead to an explosion. Elevated concentrations of methane in enclosed spaces also pose an asphyxiation hazard. Methane observed in shallow subsurface environments can be derived from many potential sources including swamps, landfills, coal beds, and natural gas production and storage operations. Understanding methane provenance may be important for sites where methane hazards are present and multiple unrelated methane sources exist. Generation of methane and other light hydrocarbon gas occurs via three principal mechanisms; 1) biogenesis – microbial decomposition of organic matter (e.g., carbon dioxide reduction and acetate fermentation); 2) thermogenesis – thermal decomposition of deeply buried organic matter (associated with coal, oil, and gas formation); and 3) abiogenesis – formation of methane within Earth’s mantle. These different methane generation mechanisms result in differing compositions of light hydrocarbon gases as well as in differing stable carbon and hydrogen isotope ratios which can be used to assess methane provenance. Carbon-14 (14C) age dating can further discriminate methane sources, as thermogenic gases are “fossil” carbon sources and do not contain measureable quantities of 14C, whereas biogenic gases are typically “modern” and contain measurable quantities of 14C. Methane forensic techniques were utilized to distinguish a single source of natural gas released from a Gulf Coast region salt dome cavern storage facility from other sources of methane known to occur naturally in the region. The natural gas release was caused by a breach of a storage well casing at an elevation above the storage cavern. Natural gas escaped through the well casing breach into overlying formations and migrated to the surface. Application of methane forensic techniques resulted in delineation of a significantly smaller affected footprint than originally interpreted.
Oral Presentation
Prepared by J. Sueker, G. Cramer
ARCADIS US., Inc., 1687 Cole Blvd, Suite 200, Lakewood, CO, 80401
Contact Information: Julie.Sueker@arcadis-us.com; 303-231-9115
ABSTRACT
Combustible gases, such as methane, in soil and shallow groundwater present a safety concern due to potential offgassing and accumulation in water well and plumbing systems that could lead to an explosion. Elevated concentrations of methane in enclosed spaces also pose an asphyxiation hazard. Methane observed in shallow subsurface environments can be derived from many potential sources including swamps, landfills, coal beds, and natural gas production and storage operations. Understanding methane provenance may be important for sites where methane hazards are present and multiple unrelated methane sources exist. Generation of methane and other light hydrocarbon gas occurs via three principal mechanisms; 1) biogenesis – microbial decomposition of organic matter (e.g., carbon dioxide reduction and acetate fermentation); 2) thermogenesis – thermal decomposition of deeply buried organic matter (associated with coal, oil, and gas formation); and 3) abiogenesis – formation of methane within Earth’s mantle. These different methane generation mechanisms result in differing compositions of light hydrocarbon gases as well as in differing stable carbon and hydrogen isotope ratios which can be used to assess methane provenance. Carbon-14 (14C) age dating can further discriminate methane sources, as thermogenic gases are “fossil” carbon sources and do not contain measureable quantities of 14C, whereas biogenic gases are typically “modern” and contain measurable quantities of 14C. Methane forensic techniques were utilized to distinguish a single source of natural gas released from a Gulf Coast region salt dome cavern storage facility from other sources of methane known to occur naturally in the region. The natural gas release was caused by a breach of a storage well casing at an elevation above the storage cavern. Natural gas escaped through the well casing breach into overlying formations and migrated to the surface. Application of methane forensic techniques resulted in delineation of a significantly smaller affected footprint than originally interpreted.