Stratigraphic evaluation of reservoir and seal in a natural CO2 field: Lower Paleozoic, Moxa Arch, southwest Wyoming

Abstract

The Moxa Arch in the Greater Green River Basin, southwestern Wyoming, hosts two potential reservoirs for CO 2 sequestration. The Bighorn Dolomite and Madison limestone are interpreted to be independent reservoirs based on differing CO 2 compositions and production histories; the two reservoirs are separated by Devonian carbonates, siliciclastic rocks, and evaporites. On the Moxa Arch, the Bighorn ranges in thickness from 67 to 120 m with porosities from 3 to 15 percent. The massive buff-colored Steamboat Point Member comprises the bulk of the subsurface Bighorn in southwest Wyoming. Mottled dolostone (light-colored patches with higher porosity and dark-colored patches with lower porosity) is very common and is presumably the result of preferential early dolomitization of bioturbation. Core study suggests that this factor affects gas saturation and storage in this extensive reservoir. The lower Member of the Jefferson Formation is the most probable seal within the Devonian stratigraphy. Strata of this member are interpreted to have been deposited in a shallow basin semi-isolated from the deeper marine environment to the west. 87 Sr/ 86 Sr isotopic analyses of anhydrite sampled from Moxa Arch well cuttings support the interpretation of a depositional environment exposed to a mixture of seawater and freshwater. High-frequency relative sea level fluctuations superimposed on a gently sloping shelf produced alternating layers of marine carbonates, peritidal siliciclastic rocks, and evaporites. The evaporites are interpreted to seal CO 2 in the Bighorn Dolomite from the overlying Madison limestone. The lower Paleozoic strata on the Moxa Arch provide an effective trap-reservoir-seal combination for naturally occurring CO 2 with potential applications to future studies at analogous locations in the central Rocky Mountain Region.

Constraining the Fluid History of a CO2‐H2S Reservoir: Insights From Stable Isotopes, REE, and Fluid Inclusion Microthermometry

“…An estimated volume of former anhydrite nodules in the drill cores of 0.2 vol% would equate to 2.55 × 10 9 m 3 or 5.6 × 10 13 mol in the reservoir. The amount of CO 2 is estimated to be 3.15 × 10 +12 m 3 STP (De Bruin, 1991;Lynds, 2010). Based on an assumed CO 2 -H 2 S ratio of 1:13 (gas composition of 65% CO 2 and 5% H 2 S; Huang et al, 2007) and this CO 2 volume, the H 2 S gas volume is calculated to be 2.4 × 10 11 m 3 or 9.8 × 10 12 mol.…”

“…paucity of petrographic observations from the LaBarge Field. The gas forms a 250-m-thick gas column and is the largest known natural CO 2 accumulation in the world (Allis et al, 2001;Lynds et al, 2010;Stilwell, 1989). Different sources for the CO 2 and H 2 S at the LaBarge Field have been proposed including thermal degradation of hydrocarbons, breakdown of carbonates, volcanic gas migration, and TSR (De Bruin, 2001;Huang et al, 2007;Stilwell, 1989).…”

Climate instability and tipping points in the Late Devonian: Detection of the Hangenberg Event in an open oceanic island arc in the Central Asian Orogenic Belt

“…It is tempting to attribute this excursion to cratonic erosion that occurred with the widespread glaciation that developed in latest Famennian (Isaacson et al, 2008, Brezinski et al, 2010and McClung et al, 2013, resulting in increased 87 Sr input to the oceans (Clemens et al, 1993). Late Devonian basinal sediments that have local cratonic sediment sources may exhibit elevated 87 Sr/ 86 Sr values up to 0.71083 (Lynds et al, 2010), and continental weathering at the D-C boundary was exacerbated not only by changes in sea level but also the erosion of the rising Appalachians by glaciers (Brezinski et al, 2009). It has even been suggested that the tectonic uplift of the Appalachians alone could also have affected seawater 87 Sr/ 86 Sr ratios (Richter et al, 1992).…”

Cyberinfrastructure for collaborative geologic carbon sequestration research: a conceptual model

“…The study area was chosen after being identified as having significant potential for geologic sequestration of impure CO 2 in a deep reservoir environment. Several formations were identified as potentially suitable for deep reservoir storage of impure CO 2 gas, foremost among them the Ordovician Bighorn Dolomite and the Mississippian Madison Limestone (for a more detailed description of the geologic characteristics and sequestration potential of the Moxa Arch anticline, see Lynds et al (2010)). This site was also of interest for sequestration research activities due to a large abundance of natural CO 2 being produced as a byproduct of oil and gas development in the region and an already present CO 2 sequestration infrastructure and market to support enhanced oil recovery (EOR).…”