| Title | Deep groundwater circulation and associated methane leakage in the Northern Canadian Rocky Mountains |
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| Author | Grasby, S E ;
Ferguson, G; Brady, A; Sharp, C; Dunfield, P; McMechan, M |
| Source | Applied Geochemistry; Chemical Geology vol. 68, 2016 p. 10-18, https://doi.org/10.1016/j.apgeochem.2016.03.004 |
| Image |  |
| Year | 2016 |
| Alt Series | Earth Sciences Sector, Contribution Series 20150144 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | British Columbia; Alberta |
| NTS | 84L/03; 84L/04; 84L/05; 84L/06; 84L/11; 84L/12; 84L/13; 84L/14; 84M/03; 84M/04; 84M/05; 84M/06; 84M/11; 84M/12; 84M/13; 84M/14; 85D/03; 85D/04; 85D/05; 85D/06; 94I; 94J; 94K/01; 94K/02; 94K/07; 94K/08;
94K/09; 94K/10; 94K/15; 94K/16; 94N/01; 94N/02; 94N/07; 94N/08; 94N/09; 94N/10; 94N/15; 94N/16; 94O; 94P; 95A/01; 95A/02; 95A/03; 95A/04; 95A/05; 95A/06; 95A/07; 95A/08; 95B/01; 95B/02; 95B/03; 95B/04; 95B/05; 95B/06; 95B/07; 95B/08; 95C/01; 95C/02;
95C/07; 95C/08 |
| Area | Liard Line; Larsen Fault |
| Lat/Long WENS | -125.0000 -119.0000 60.5000 58.0000 |
| Subjects | environmental geology; fossil fuels; hydrogeology; groundwater; groundwater geochemistry; springs; oil shales; shales; geothermal temperatures; geothermal fluids geochemistry; hydrocarbon gases; gas
seeps; hydraulic fracturing; fracturing; environmental impacts; health hazards; hydrocarbon gases; hydrocarbon migration; hydrothermal systems; reservoir fluids; Ordovician; Devonian |
| Illustrations | location maps; thermal maps; isotope graphs; ternary diagrams; tables; cross-sections, structural; cross-sections, stratigraphic |
| Program | Geoscience for New Energy Supply (GNES) Shale Reservoir Characterization |
| Released | 2016 05 01 |
| Abstract | Concern over potential impact of shale gas development on shallow groundwater systems requires greater understanding of crustal scale fluid movement. We examined natural deeply circulating groundwater
systems in northeastern British Columbia adjacent to a region of shale gas development, in order to elucidate origin of waters, depths of circulation, and controls on fluid flow. These systems are expressed as thermal springs that occur in the
deformed sedimentary rocks of the Liard Basin. Stable isotope data from these springs show that they originate as meteoric water. Although there are no thermal anomalies in the region, outlet temperatures range from 30 to 56 \'01C, reflecting depth
of circulation. Based on aqueous geothermometry and geothermal gradients, circulation depths up to 3.8 km are estimated, demonstrating connection of deep groundwater systems to the surface. Springs are also characterised by leakage of thermogenic gas
from deep strata that is partly attenuated by methanotrophic microbial communities in the spring waters. Springs are restricted to anomalous structural features, cross cutting faults, and crests of fault-cored anticlines. On a regional scale they are
aligned with the major tectonic features of the Liard Line and Larsen Fault. This suggests that while connection of surface to deep reservoirs is possible, it is rare and restricted to highly deformed geologic units that produce permeable pathways
from depth through otherwise thick intervening shale units. Results allow a better understanding of potential for communication between deep shale gas units and shallow aquifer systems. |
| Summary | (Plain Language Summary, not published)
Controls on natural occurrence of deep crustal circulation systems and methane leakage to surface were examined to elucidate controls on connection of
deep fluids to shallow groundwater systems in regions adjacent to shale gas development. In the study areas the rocks are highly deformed by mountain building processes and are equivalent to those in the undeformed sedimentary basin to the east that
host the Horn River shale gas play. Results show that natural groundwater systems circulate to depths of 2.9 km and allow leakage of thermogenic gas to surface. However, these natural systems are rare and restricted only to areas of highly deformed
rock. This suggests that while connection of deep fluid systems to surface are possible, they are uncommon even where rock are highly deformed. |
| GEOSCAN ID | 296807 |
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