ANALYSIS OF THE POTENTIAL FOR CARBON SEQUESTRATION IN THE SUBSURFACE TUSCALOOSA GROUP, SOUTHWESTERN ALABAMA

Geologic carbon sequestration refers to the process of capturing CO₂ from the atmosphere, or industrial processes, and storing it within a porous zone of a host rock formation, which is overlain by a cap rock unit. Studying the consequences of carbon sequestration is of great importance because analyzing the reaction of the process is fundamental for understanding the process of carbon sequestration and its efficacy. It is also important to understand the chemical trapping mechanisms for designing successful CO₂ storage projects. In this project the Upper Cretaceous Tuscaloosa Group of the subsurface of southern Alabama will be the geological unit that will be analyzed for carbon sequestration purposes. An important part of this study has been to observe and analyze how the injected CO₂ fluid interacts with porous rocks, specifically with the mineral glauconite, and what type of pore-occluding cement develops, and how does it change the porosity of the rocks. Glauconitic sands, sometimes referred to greensand formations, are associated with continental shelf sediments typically deposited during the Cambrian and the Cretaceous. Previous studies suggest that they may be adequate reservoirs for geologic CO₂ storage. Samples from the drill core Julian F. McGowin #1, in Mobile County Alabama, have been collected for observing lithological changes, sedimentary structures and textures, vertical changes in grain size and mineralogy as well as measuring porous thickness. The reason this core was selected to collect samples is because it is thought to be the most complete core that contains the Tuscaloosa Group. Petrographic thin sections as well as core observations show evidence of glauconite throughout most of the core. XRD results show mineralogical bulk composition of mostly quartz, calcite, kaolinite, and chlorite. Data obtained from XRD and SEM analyses was used to design an experimental plan for a hydrothermal experiment. This part of the experiment took place inside a rocking autoclave apparatus and the software Geochemist’s Workbench is being used to analyze the reaction path. According to previous studies, the Tuscaloosa Group qualifies as a near limitless reservoir for storing CO₂ because of its composition, porosity, permeability, and depth.