Christopher Smith, Timothy Smith, Patrick Gordon, Michael Smith, Advanced Hydrocarbon Stratigraphy; Franek Hasiuk, Eugene Houbnyak, Sahar Mohammadi, Kansas Geological Survey
Characterization of reservoir and seal quality at potential carbon storage sites is currently a costly and time-consuming process, yet these data are required for successful permits to commission CO₂ storage facilities. This study assessed the ability of rock volatiles stratigraphy (RVS) to provide a “quick-look” methodology for derisking sites before seismic surveying or drilling. Patterson KGS 5-25 and Hartland KGS 6-10 were drilled in the summer of 2020 as part of the Kansas Geological Survey’s CarbonSAFE Phase II program to evaluate the Patterson site in Kearny county (KS) as a carbon capture and storage (CCS) site with a capacity to hold 50 Mt of CO₂ injected over 25-30 years. As part of the program to evaluate the Osage, Viola, and Arbuckle carbonates as potential saline aquifer CO₂ storage formations and the Morrow shale as the major sealing feature RVS data were collected on fresh and legacy cuttings from these wells. RVS gently extracts volatile chemistries entrained in rocks such as CO₂, water, and hydrocarbons (HCs) among others and then identifies and quantifies them on a unique cryo-trap mass spectrometry system; the nature of how readily volatiles are extracted also provides information on rock properties such as permeability. A regional baseline for CO₂ content linked to reservoir pressure and subsurface CO₂ migration had previously been established in the Mississippian Lime, which includes the Osage. Based on comparisons to this CO₂ baseline and stratigraphic trends, the RVS data showed there was no apparent history of reservoir pressure loss, subsurface CO₂ migration, or obvious communication of HCs between the shallower oil-bearing formations and the deeper saline aquifers. However, the decision to commence drilling operations to collect data represented a significant risk as data relating the target formations and the integrity of the caprocks and seals was not readily available beforehand. While the data collected on the Patterson and Hartland wells are important for the development of US EPA UIC Class VI permits, if the site was found to be wanting, for example a leaky seal, the drilling and associated science collection costs would represent lost funds as much of the same work would need to be redone at a new site. The Patterson site has produced oil since the 1960s and some wells penetrate the target carbonate formations. Legacy cuttings from Gates O. Patterson Unit 1-23 covering the target formations were analyzed with RVS to demonstrate the potential of prescreening the site before drilling. Using RVS on legacy materials from a neighboring well offers a simple, fast, and cost-effective way to derisk CO₂ storage sites by evaluating cuttings—material often warehoused at geological surveys, operators, and service companies—for evidence of past reservoir pressure loss, seal failure, or CO₂ migration based on the volatiles data from the CO₂ and associated compounds. The RVS analysis typically represents approximately 1% of the well and science costs and can be used to help direct drilling and science collection activities to sites that are most likely to be suitable for a Class VI well.