The noble gas geochemistry of natural CO2 gas reservoirs from the Colorado Plateau and Rocky Mountain provinces, USA

Abstract

Identification of the source of CO 2 in natural reservoirs and development of physical models to account for the migration and interaction of this CO 2 with the groundwater is essential for developing a quantitative understanding of the long term storage potential of CO 2 in the subsurface. We present the results of 57 noble gas determinations in CO 2 rich fields (>82%) from three natural reservoirs to the east of the Colorado Plateau uplift province, USA (Bravo Dome, NM., Sheep Mountain, CO. and McCallum Dome, CO.), and from two reservoirs from within the uplift area (St. John's Dome, AZ., and McElmo Dome, CO.). We demonstrate that all fields have CO 2 / 3 He ratios consistent with a dominantly magmatic source. The most recent volcanics in the province date from 8 to 10 ka and are associated with the Bravo Dome field. The oldest magmatic activity dates from 42 to 70 Ma and is associated with the McElmo Dome field, located in the tectonically stable centre of the Colorado Plateau: CO 2 can be stored within the subsurface on a millennia timescale.The manner and extent of contact of the CO 2 phase with the groundwater system is a critical parameter in using these systems as natural analogues for geological storage of anthropogenic CO 2 . We show that coherent fractionation of groundwater 20 Ne/ 36 Ar with crustal radiogenic noble gases ( 4 He, 21 Ne, 40 Ar) is explained by a two stage re-dissolution model: Stage 1: Magmatic CO 2 injection into the groundwater system strips dissolved air-derived noble gases (ASW) and accumulated crustal/radiogenic noble gas by CO 2 /water phase partitioning. The CO 2 containing the groundwater stripped gases provides the first reservoir fluid charge. Subsequent charges of CO 2 provide no more ASW or crustal noble gases, and serve only to dilute the original ASW and crustal noble gas rich CO 2 . Reservoir scale preservation of concentration gradients in ASW-derived noble gases thus provide CO 2 filling direction. This is seen in the Bravo Dome and St. John's Dome fields. Stage 2: The noble gases re-dissolve into any available gas stripped groundwater. This is modeled as a Rayleigh distillation process and enables us to quantify for each sample: (1) the volume of groundwater originally 'stripped' on reservoir filling; and (2) the volume of groundwater involved in subsequent interaction. The original water volume that is gas stripped varies from as low as 0.0005 cm 3 groundwater/cm 3 gas (STP) in one Bravo Dome sample, to 2.56 cm 3 groundwater/cm 3 gas (STP) in a St. John's Dome sample. Subsequent gas/groundwater equilibration varies within all fields, each showing a similar range, from zero to $100 cm 3 water/cm 3 gas (at reservoir pressure and temperature).

Experimental determination of noble gases and SF6, as tracers of CO2 flow through porous sandstone

“…used as part of mixture to fingerprint individual CO 2 storage sites that may be in close proximity to one another. Noble gases and their isotopes are able to provide unique constraints on certain geological processes (Gilfillan et al, 2014;Burnard et al, 2013;Holland and Gilfillan, 2012;Wilkinson et al, 2010;Gilfillan et al, 2008;Gilfillan et al, 2017). Understanding their predicted arrival times in relation to each other can help determine ownership of CO 2 storage sites and thus the party responsible to rectify any unplanned effects.…”

“…Noble gases (He, Ne, Ar, Kr and Xe) exist in trace amounts in geological environments and they can be used as tracers within natural CO 2 reservoirs (Gilfillan et al, 2008;Gilfillan et al, 2009;Zhou et al, 2012;Sathaye et al, 2014) and for CO 2 used in EOR projects (Nimz and Hudson, 2005;Györe et al, 2015;Györe et al, 2017). As such, small amounts of noble gas blends can also be intentionally added to the CO 2 being injected for storage or be measured in the captured CO 2 stream and used as tracers to monitor CO 2 movement (Hovorka et al, 2013;Flude et al, 2016;Flude et al, 2017).…”

A Phase-Partitioning Model for CO2–Brine Mixtures at Elevated Temperatures and Pressures: Application to CO2-Enhanced Geothermal Systems

“…The solubility of CO 2 in water has obvious implications for long-term carbon sequestration and water-rock interactions (e.g., Gilfillan 2008;Moore et al 2005;Rosenbauer et al 2005;Palandri et al 2005;Kaszuba et al 2003). The solubility of water into CO 2 is also of importance, because it affects the reactivity of CO 2 with surrounding rocks (e.g., Regnault et al 2005;Rimmelé et al 2008;Lin et al 2008;Suto et al 2007) and determines the capacity of injected CO 2 to dry the rock formations adjacent to injection wells (Giorgis et al 2007;Hurter et al 2007;Pruess and Müller 2009).…”

The Relevance of Geochemical Tools to Monitor Deep Geological CO2 Storage Sites

“…Isotopic compositions of mantle-derived carbon are indeed contained between −3 and −8‰ Pee Dee Belemnite (PDB) and isotopic compositions of bulk crustal carbon correspond to a range of −5 to −7‰ PDB. Noble gases can then be used to distinguish between decarbonatation/magmatic sources, by comparing for example the measured CO 2 / 3 He ratios in the gas phase with the known values of the crustal and mantle ranges (Sherwood Lollar et al, 1997;Ballentine et al, 2001;Gilfillan et al, 2008;Jeandel et al, 2010).…”