Scientific drilling and downhole fluid sampling of a natural CO<sub>2</sub> reservoir, Green River, Utah

Abstract

Abstract. A scientific borehole, CO2W55, was drilled into an onshore anticline, near the town of Green River, Utah for the purposes of studying a series of natural CO2 reservoirs. The objective of this research project is to recover core and fluids from natural CO2 accumulations in order to study and understand the long-term consequences of exposure of supercritical CO2, CO2-gas and CO2-charged fluids on geological materials. This will improve our ability to predict the security of future geological CO2 storage sites and the behaviour of CO2 during migration through the overburden. The Green River anticline is thought to contain supercritical reservoirs of CO2 in Permian sandstone and Mississippian-Pennsylvanian carbonate and evaporite formations at depths > 800 m. Migration of CO2 and CO2-charged brine from these deep formations, through the damage zone of two major normal faults in the overburden, feeds a stacked series of shallow reservoirs in Jurassic sandstones from 500 m depth to near surface. The drill-hole was spudded into the footwall of the Little Grand Wash normal fault at the apex of the Green River anticline, near the site of Crystal Geyser, a CO2-driven cold water geyser. The hole was drilled using a CS4002 Truck Mounted Core Drill to a total depth of 322 m and DOSECC’s hybrid coring system was used to continuously recover core. CO2-charged fluids were first encountered at ~ 35 m depth, in the basal sandstones of the Entrada Sandstone, which is open to surface, the fluids being effectively sealed by thin siltstone layers within the sandstone unit. The well penetrated a ~ 17 m thick fault zone within the Carmel Formation, the footwall damage zone of which hosted CO2-charged fluids in open fractures. CO2-rich fluids were encountered throughout the thickness of the Navajo Sandstone. The originally red sandstone and siltstone units, where they are in contact with the CO2-charged fluids, have been bleached by dissolution of hematite grain coatings. Fluid samples were collected from the Navajo Sandstone at formation pressures using a positive displacement wireline sampler, and fluid CO2 content and pH were measured at surface using high pressure apparatus. The results from the fluid sampling show that the Navajo Sandstone is being fed by active inflow of CO2-saturated brines through the fault damage zone; that these brines mix with meteoric fluid flowing laterally into the fault zone; and that the downhole fluid sampling whilst drilling successfully captures this dynamic process.

Determining noble gas partitioning within a CO2–H2O system at elevated temperatures and pressures

“…Additionally storage of anthropogenic CO 2 in geological structures as part of national CCS (Carbon Capture and Storage) strategies has further stimulated much recent interest in supercritical CO 2 -water systems (Kharaka et al, 2006;Bickle et al, 2007;Cole et al, 2010). With this focus noble gases have been used extensively to understand the processes controlling CO 2 behaviour in the subsurface (Gilfillan et al, 2008(Gilfillan et al, , 2009Dubacq et al, 2012;Zhou et al, 2012;Kampman et al, 2013) and they offer the potential to trace in-reservoir processes and subsurface leakage from engineered systems (Nimz and Hudson, 2005;Mackintosh and Ballentine, 2012).…”

Metagenomic analysis of a high carbon dioxide subsurface microbial community populated by chemolithoautotrophs and bacteria and archaea from candidate phyla

“…the dissolution of limestones from the Paradox and/or Navajo Sandstone Formations), with a ∼ 20% contribution from mantle degassing (Wilkinson et al ., ). Drilling near CG revealed in situ CO 2 concentrations close to saturation (> 900 mmol l −1 ) near the base of the Navajo Sandstone Formation (∼ 330 m) and decreasing but still quite high (∼ 700 mmol l −1 ) towards the top of the formation (∼ 220 m), presumably because of mixing with meteoric water (Kampman et al ., ). For additional descriptions of CG, the reader is referred to Baer and Rigby (), Barnes () and Waltham (); for a stratigraphic column of this area, see chart 67 in Hintze (), and for a geologic map, see Doelling ().…”

A siltstone reaction front related to CO2- and sulfur-bearing fluids: Integrating quantitative elemental mapping with reactive transport modeling

“…Near the town of Green River, natural CO 2 -bearing fluids are hosted in a series of fault bounded Jurassic sandstone reservoirs in the footwall blocks of the southerly dipping Little Grand Wash and Salt Wash normal faults, where they intersect the apex of the Green River anticline (e.g., Heath et al 2009;Dockrill and Shipton 2010;Kampman et al 2009Kampman et al , 2012Kampman et al , 2013Shipton et al 2004;Wigley et al 2012). The CO 2 -bearing fluids escape to the surface through the fault damage zones of the faults as well as several abandoned petroleum exploration and water wells ( Fig.…”

“…Geological map of the Green River anticline showing locations of the Little Grand Wash and Salt Wash Graben normal fault systems, CO 2 -springs and location of drill-hole CO2W55. Structure contours are for the top surface of the Navajo Sandstone, the main CO 2bearing reservoir (modified after Kampman et al 2013).…”

“…Scientific drilling adjacent to the Little Grand Wash fault in 2012 has allowed study of CO 2 transport mechanisms and long-term reactions between S-bearing, CO 2 -saturated brines and formation minerals in shallow aquifers ( Fig. 1; Kampman et al 2013Kampman et al , 2014Kampman et al , 2016Busch et al 2014). Drill-core collected in this 2012 drilling campaign exhibits bleaching in the reservoir sandstone, basal sections of the cap rocks related to these migrating fluids.…”