Optimization of CO2 Huff-n-Puff in Hydrocarbon-Bearing Chattanooga Shale Reservoirs Using Reservoir Characterization and Numerical Simulation

The unprecedented growth in the exploration and production of unconventional resources in North America has sparked widespread interest worldwide. The differences in reservoir characteristics and production mechanisms between conventional and unconventional resources have provided technical, developmental, and economic challenges to the industry.;Shale formations are known to hold abundant amounts of hydrocarbons. However, extremely low permeability is a common characteristics of all unconventional shale reservoirs. Well productivity in shale oil and gas reservoirs comes from wells with transverse fractures that connect natural fracture complexity.;As the oil near the fractured area is produced the oil rate declines very sharply. This quick drop in well productivity for shale reservoirs makes it very challenging to further improve the primary production. The injection of CO2 or other gases to maintain pressure in the stimulated reservoir volume and extract oil from the organic and inorganic pore volume may prove to be the most suitable option to increase the final recovery. Among various injection modes, cyclic CO2 injection (CO2 huff-and-puff) scenarios have seen significant increase in interest for the purpose of improved oil recovery (IOR) in unconventional reservoirs. While the use of carbon dioxide in conventional reservoirs is a widely applied and well understood practice, its use for IOR in shale reservoirs is a relatively new concept.;Upper Devonian-Mississippian Chattanooga shale plays in North America are categorized as unconventional reserves with potential hydrocarbon resource accumulations. Unlike Chattanooga shale in the Appalachian region (Tennessee), less effort has been dedicated to its correspondent in the Ozark region (Oklahoma, Southeastern Kansas, Northern Arkansas and Missouri).;This thesis covers the generation of a comprehensive workflow incorporating geological well logs and seismic data to generate a complete reservoir characterization in an effort to simulate the performance of oil wells under CO2 huff-n-puff injection in Chattanooga shale. A numerical reservoir simulator has been used to evaluate the performance of CO2 injection for Chattanooga shale in Wellington Field, south-eastern Kansas. A general evaluation of primary depletion for different well locations is discussed based on sweet spot indices. A series of simulations were conducted for the study of the various parameters affecting the well productivity potential. Sensitivity analyses was conducted by using different well completions, well lengths and reservoir parameters. An economic optimization process also was made to evaluate the best gas injection design to obtain the highest Net Present Value (NPV). The cumulative oil can be notably increase by the use of the optimum injection design. The huff-n-puff injection of CO2 proved to be a viable option by increasing the final oil recovery from 10% to 53% if designed using optimal parameters.