Distribution, Origin, Fate, and Transport of Methane and Ethane in Shales Using High-Resolution Profiles: The Williston Basin Example.
Lecture venue: Room 329, Level 3 IS&T Building
Flinders Uni, Bedford Park campus (Car park 15)
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Seminar: M. Jim Hendry
Distribution, Origin, Fate, and Transport of Methane and Ethane in Shales Using High-Resolution Profiles: The Williston Basin Example
M. Jim Hendry, Erin Schmeling, S. Lee Barbour, M. Huang, Scott Mundle
Rigorous baseline characterization of the distribution of natural gas concentrations across low hydraulic conductivity (K) sandstones and shales is required to evaluate the potential for leaks of fugitive natural gases into potable groundwater resources. Similar characterizations are also required for conventional gas and oil activities, and carbon capture and geological storage. This study presents the first, detailed profiling of natural gases in low K argillaceous cap rock through which stray gases must migrate to reach shallow groundwater resources. The gas profiles were interpreted to define the origin, distribution, fate, and transport of the gases, with a focus on CH4. The study was conducted at five sites across a 200-km2 area of laterally extensive, thick (700 m) low K Pierre Shale of the Cretaceous in the Williston Basin (WB), Canada to a maximum depth of 250 m below ground. High-resolution vertical profiles of conservative Cl- concentrations from squeezed core samples and CH4 and C2H6 gas headspace analyses of core samples collected at 3-10 m and 1-3 m intervals, respectively, exhibited linearly increasing depth trends in the shale. Baseline gasand Cl- concentration profiles in the Pierre Shale exhibited a strong linear relationship (R2=0.90). These data and 1D transport modeling suggested that the profiles are at or near steady state, the result of long-term (>20 Ma), upward diffusion of both Cl- and gases from sources located below the shale. The data also showed there is minimal production or consumption of CH4 and C2H6 in the profile. Measurements of δ13C-CH4 and δ2H-CH4 showed that the hydrocarbon gases are bacterial in origin. The isotopic depth profiles were consistent with isotopic diffusion. The similarities of the physical and chemical hydrogeology (including CH4) at the study sites to other studies within the Cretaceous shales of the 250,000 km2 WB suggest that our findings may be generally applicable across the WB and possibly to other shallow shale gas plays.
Biography - M. Jim Hendry
Dr. Jim Hendry is a professor at the University of Saskatchewan where he holds two research chairs. A focal area of Hendry’s research program is the migration of contaminants through clay-rich media (aquitards). Much of this research is directly relevant to the mining and agricultural sectors, as well as nuclear-waste disposal. He has authored or co-authored over 170 refereed scientific publications.
Dr. Hendry is a Fellow of the GSA and GAC. His research expertise has been recognized by the international scientific community through such prestigious awards as the Distinguished Henry Darcy Lectureship (2000) and the Synergy Award from NSERC, an annual prize that honors the most outstanding achievements resulting from university-industry collaboration in Canada (2008).