Geochemical and Mineralogical Investigation for Carbon Capture and Storage, Within the Arbuckle Aquifer, Kansas

A class VI permit site under U.S. Department of Energy has been proposed for carbon sequestration in south-central Kansas. In an effort to maintain environmental stability three wells have been drilled to basement rock, two being near the injection site, KGS 1-32 and KGS 1-28, and one being to the western annex, Cutter KGS #1. The western annex site, Cutter, is being utilized as a cross-comparison for mineralogical, geochemical, and structural component to the eastern sites in Wellington. A link will be determined of the continuity of three zones of interest: the Mississippian pay zone (3670'-3700'), a potential baffle zone in the upper Arbuckle (4400'-4550'), and the proposed CO2 injection zone (4900'-5050'). 11 depths within Cutter have been swabbed, and samples taken to investigate the chemistry of the subsurface formation water. The different depths will allow for a quantitative determination of how the brine composition varies with depth, and also provides a baseline for future monitoring. Initial chemical analysis by ICP-OES and HR-ICP-MS show a hyper saline brine (50,000-190,000TDS), dominated by Cl, Na, and Ca ions. pH ranges from 6.4 to 7.5, and total alkalinity from 124 and 378 mg/L of HCO¬3-. One complex, yet intriguing, species is Iron. It could potentially allow for further precipitation of the CO2¬ from the formation of Fe carbonates, such as siderite. Cores and thin sections were taken from a variety of depths ranging from 3681.9' to 5176.9' (Wellington) and 5564.3' to 7540.2' (Cutter). Dominant mineralogy consists of dolomite with varying forms of silicic intrusions, usually in the form of chert nodules with sulfide minerals and argillaceous materials in between. Extensive vugs and microfractures allow for varying porosity within each interval. Pay zone rocks typically display fine-grained cherty dolomite with subhedral to euhedral dolomite rhombs as well as oil stains oriented in parallel blotches. Characteristics such as high porosity and small grain size could potentially lead to quicker reactions with CO2 saturated brine, releasing oil trapped in pore spaces and leading to enhanced oil recovery. The rocks of the baffle zone are characterized by a low porosity dolomitic packstone with increasing abundance of chert, argillaceous materials, and sulfide minerals towards the bottom of the zone. Baffle zone relative impermeability could also allow for improved CO2 reactivity as it would have more time to react with formation minerals. The injection zone is generally composed of dolomite with siliceous nodules that slightly increases with depth. Explicit heterogeneity exists at carbonate-chert boundaries usually occurring in fractures and heavily influencing CO2 to mobilize in a convoluted, potentially lateral fashion. Flow through experiments have been conducted in order to determine reactivity and stability of the overlying cap rocks and baffle zone. Reservoir characterization is determined through geochemical modeling, and will need to be extensively studied in order to properly determine the feasibility for carbon sequestration in Kansas. With the potential for 2.7 billion tones of CO2 to be stored in Kansas, this project could allow Kansas to play a major role in the quest for environmental stability.