This thesis presents geological, geochemical and petrophysical descriptions of the La Luna Shale in Colombia with a view to build a reservoir simulation model for investigating the potential of primary recovery, enhanced oil recovery by huff and puff gas injection and safe storage of CO2. The investigation is performed in the Middle Magdalena Valley (MMV) and Catatumbo Basins. The injection gases considered in this thesis are methane (CH4) and carbon dioxide (CO2). Reservoir modelling using a commercial compositional simulator provides a baseline scenario of primary oil recovery. This is important as there is no oil production from La Luna Shale at present. Original contributions of this thesis include demonstrating that: 1. Oil recovery can be obtained from the La Luna Shale and increased significantly by CH4 and CO2 injection while simultaneously and safely storing CO2. 2. There is “geologic containment” in the La Luna Shale in both the MMV and Catatumbo Basins.The concept of geologic containment applies when hydrocarbon fluids are in an inverted position vis-a-vis gravity, i.e., oil is at the top, condensate is in the middle and natural gas is at the bottom within the same shale strata (Ramirez and Aguilera, 2016; Fragoso et al., 2018). 3. Under favourable conditions it is possible to obtain oil production from the La Luna Shale without implementing hydraulic fracturing. 4. A modified Pickett plot helps to establish hydrocarbons maturity in the La Luna Shale. The win-win scenario of improving oil recovery while simultaneously storing carbon dioxide (CO2) in the shale is critically important as oil will be needed in Colombia for several decades while the country is striving to reduce the environmental impact. The “Utilization” and “Storage” of CO2, two important as aspects of CCUS (Carbon Capture, Utilization and Storage), can be successfully attained in the La Luna Shale in Colombia. The “Capture” aspect of CCUS is beyond the scope of this study.