Unlocking Oil Reserves Sustainably : CO2 Injection for Enhanced Oil Recovery (EOR) in the Sarir C-Field

Abstract The ever rising global demand for energy and the need to reduce greenhouse emissions have led to the exploration of sustainable oil extraction methods. At the forefront of these methods, Carbon Dioxide ( O2) Injection for Enhanced Oil Recovery (EOR) has peaked the interest of many throughout the industry as a means of Carbon Sequestration while still increasing production rates. This thesis will explore the feasibility and potential of CO2 injection and sequestration in a mature reservoir that has been exhibiting declining production rates as of late. The Upper Sarir Sandstones has tremendous potential for EOR and given the petrophysical and fluid properties of the reservoir, it is the perfect case study to assess the feasibility of CO2 injection and sequestration in a mature oil reservoir. This study will be carried out by reservoir characterisation and modelling in which a 3D Model of the Upper Sarir Sandstones will be built and CO2 injection simulation will be employed. This thesis canters on optimizing production rates in the Upper Sarir Sandstones, with a specific focus on the Sarir C Field. The study employs modelling techniques to evaluate the efficacy of immiscible and miscible CO2 injection methods in enhancing oil recovery over a 20-year production cycle. Comparative analysis reveals that while natural production achieves an EOR of 34.2%, both miscible and immiscible CO2 injection methods significantly elevate the recovery factor (RF) to 47.9% and 43.5%, respectively, emphasizing the substantial production benefits of both approaches. An in-depth exploration of the underlying mechanisms influencing RF enhancement distinguishes the pressure-based displacement mechanism of immiscible CO2 injection, which improves reservoir fluid mobility, from the solubility-driven approach of miscible CO2 injection, reducing oil viscosity and fostering sustained high production rates. Despite the initial advantage of immiscible injection, the thesis underscores the superior long-term recovery and sequestration suitability of miscible CO2 injection, attributed to its solubility trapping potential. A preliminary model assessing CO2 trapping capabilities, rooted in rock-fluid hysteresis, indicates the Sarir C Field's promise for trapping injected CO2. Although lacking certain geological considerations, the field demonstrates increasing dynamically trapped gas saturation across the 20-year production cycle, suggesting its viability for future sequestration initiatives. The findings of this thesis aims to contribute and deepen the knowledge in the CO2 injection and sequestration methodology while promoting sustainable and responsible practices in the Oil & Gas Industry