CO 2 Sequestration in a Carbonate Saline Aquifer: An Investigation into the Roles of Natural Fractures and Well Placement

CO 2 sequestration is considered one of the main pillars in achieving the ongoing decarbonization efforts. A myriad of CO 2 sequestration projects targeted sandstone reservoirs since carbonate reservoirs appeared to be unpropitious due to their geological complexity and unfavorable mineralogy and properties. This study investigates CO 2 sequestration potential in a carbonate saline aquifer while considering various geological complexities by capitalizing on numerical simulation. A synthetic anticline reservoir model examined the optimum well location and landing zone for CO 2 sequestration. Additionally, the model evaluated the role of natural fractures in the migration path of CO 2 plume and geochemical reactions throughout the storage process. The study demonstrates that placing the injection well away from the top of the structure in a low-dip region while injecting in the bottom interval would yield the optimum design. After applying a plethora of analyses, geological complexity could impede the migration path of CO 2 but eventually produce a similar path when injected in a similar region. The geochemical interactions between the injected CO 2 and reservoir fluids and minerals reduce the free and trapped CO 2 quantities by dissolving calcite and precipitating dolomite. Furthermore, natural fractures impact the CO 2 quantities during early times only when the fractures cross the top layers. Similarly, the CO 2 migration differs due to the higher permeability within the fractures, resulting in slightly different CO 2 plumes. Consequently, the role of natural fractures should be limited in carbon storage projects, specifically if they do not cross the top of the reservoir. This study reflects a unique perspective on sequestering CO 2 while capturing the roles of natural fractures and well placement in depicting the migration path of the CO 2 plume. A similar systematic workflow and holistic approach can be utilized to optimize the subsurface storage process for potential formations.