Presentation Title

Macroseepage of Methane and Light Alkanes in Southern California

Faculty Mentor

Dr. Lambert Doezema

Start Date

23-11-2019 8:00 AM

End Date

23-11-2019 8:45 AM

Location

223

Session

poster 1

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Current methane budgets have broad ranges for natural geologic emissions of methane and light alkanes. Methane is an extremely potent greenhouse gas with an atmospheric lifetime of over ten years, illustrating the importance of study. In an effort to narrow this range and provide a more complete understanding of local and global methane budgets, qualitative and quantitative research regarding macroseepage of methane and light alkanes was completed. From May through June 2019, three sites with known geologic macroseepage were visited in southern California: McKittrick, Ojai, and Carpinteria. Samples were collected by placing a stainless-steel flux chamber over visible emissions with active tar bubbling. An initial air sample was taken using a sampling canister. A secondary air sample was then taken after waiting 10 minutes. These two measurements were analyzed for methane using a gas chromatography-flame ionization detector (GC-FID) system. C2-C5 were analyzed using GC-FID system fit with cryogenic pre-concentration abilities. Maximum fluxes (ppb/hr) observed were 10,254,037.6 for methane, 41,618.8 for ethane, 466.3 for propane, 82.2 for iso-butane, 49.9 for n-butane, 200.4 for iso-pentane, and 21.3 for n-pentane. Gas wetness, which is the C1/(C2+C3) ratio, and i-Butane/n-Butane ratios were then calculated and compared to previous research conducted at La Brea Tar Pits. Between all three locations studied, the average gas wetness ratio at McKittrick was the most similar to the La Brea Data at about 300, while the ratio from Carpinteria was significantly higher than Ojai and McKittrick at about 900. While both the Ojai and McKittrick i-Butane/n-Butane ratios were well below the La Brea ratio at below 2, the Carpinteria i-Butane/n-Butane ratio was higher than the La Brea ration at 20. These findings are suggestive of microbial processing as the gaseous emissions travel from the oil reservoirs up to the earth’s surface.

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Nov 23rd, 8:00 AM Nov 23rd, 8:45 AM

Macroseepage of Methane and Light Alkanes in Southern California

223

Current methane budgets have broad ranges for natural geologic emissions of methane and light alkanes. Methane is an extremely potent greenhouse gas with an atmospheric lifetime of over ten years, illustrating the importance of study. In an effort to narrow this range and provide a more complete understanding of local and global methane budgets, qualitative and quantitative research regarding macroseepage of methane and light alkanes was completed. From May through June 2019, three sites with known geologic macroseepage were visited in southern California: McKittrick, Ojai, and Carpinteria. Samples were collected by placing a stainless-steel flux chamber over visible emissions with active tar bubbling. An initial air sample was taken using a sampling canister. A secondary air sample was then taken after waiting 10 minutes. These two measurements were analyzed for methane using a gas chromatography-flame ionization detector (GC-FID) system. C2-C5 were analyzed using GC-FID system fit with cryogenic pre-concentration abilities. Maximum fluxes (ppb/hr) observed were 10,254,037.6 for methane, 41,618.8 for ethane, 466.3 for propane, 82.2 for iso-butane, 49.9 for n-butane, 200.4 for iso-pentane, and 21.3 for n-pentane. Gas wetness, which is the C1/(C2+C3) ratio, and i-Butane/n-Butane ratios were then calculated and compared to previous research conducted at La Brea Tar Pits. Between all three locations studied, the average gas wetness ratio at McKittrick was the most similar to the La Brea Data at about 300, while the ratio from Carpinteria was significantly higher than Ojai and McKittrick at about 900. While both the Ojai and McKittrick i-Butane/n-Butane ratios were well below the La Brea ratio at below 2, the Carpinteria i-Butane/n-Butane ratio was higher than the La Brea ration at 20. These findings are suggestive of microbial processing as the gaseous emissions travel from the oil reservoirs up to the earth’s surface.