O. Abunumah, P. Ogunlude, E. Gobina
Centre for Process Integration and Membrane Technology, School of Engineering, The Robert Gordon University, Aberdeen,
Keywords: CCS, climate change, enhanced oil recovery, reservoirs, carbon, CO2
Summary:Reservoir entities can be classified into geological, geometrical and fluidic. To complicate matters, reservoirs are usually set in geological layers, such that each layer interacts with injected and resident fluids differently. Carbon dioxide (CO2) is one of the fluids injected in reservoirs. This injection process achieves both economic and environmental benefits. On the one hand, the CO2 injection increases oil production in a process called CO2 Enhanced Oil Recovery (CO2 EOR). On the other hand, it engenders the storage of CO2 in subsurface geological sites to reduce greenhouse gas and mitigate global warming in a process called Carbon Capture and Sequestration (CCS). Consequently, CO2 injection has to effectively couple with these reservoirs entities individually and collectively to achieve CO2 EOR and sequestration optimisations. Other investigators have not properly documented the CO2 sequestration optimisation subject area in light of its response to reservoirs entities. Hence the purpose of this study is to offer information on this area. Rigorous data mining and experimental methods have been applied to characterise and determine CCS response to the petrophysical quantities of reservoirs. The data mining analysis phase indicate that reservoirs' suitability to CO2 EOR application can be characterised by reservoir petrophysical quantities, such as permeability, porosity, oil viscosity and API gravity. In the experimental phase, five analogous core samples with varying structural quantities were used. The empirical analysis investigated the response of CCS to 20 reservoir quantities. Reservoirs are natural replicas of industrial materials such as nano, ceramics and silicate materials. Although reservoirs are made of sedimentations of sandstones, shale and carbonate, they however, significantly share similar physical property characteristics with the aforementioned industry material. The characterisation of reservoir rock pores size includes nanopores in shale and microspores in sandstone rocks. Similarly, authors characterisation of permeability in reservoir rocks is similar to that of industrial materials such as ceramic membranes. Consequently, these materials can be aptly used to study the carbon capture and sequestration CCS in reservoir rock to a significant degree of accuracy. The series of graphs generated in the course of the investigation show that the relationship between CCS and the petrophysical quantities ranges from linear to higher-order polynomial. The results demonstrated that CCS directly responds to pore size and gas density. CSS inversely responds to the aspect ratio, pore density, specific surface area, and displacement pressure. Furthermore, CCS is found to be responsive to porosity, tortuosity and permeability in the third-order polynomial. The research outcome provides a deeper understanding of CCS optimisation in structurally complicated multilayer reservoirs. The result also provides utility in investigating CCS response to the variability encountered in reservoir systems.