Vertically Integrated Models with Coupled Thermal Processes
S.E. Gasda, W.G.G. Gray and H.K.D. Dahle
Event name: ECMOR XIV - 14th European Conference on the Mathematics of Oil Recovery
Session: Thermal and Heavy Oil Methods
Publication date: 08 September 2014
Info: Extended abstract, PDF ( 437.82Kb )
Price: € 20
CO2 storage in geological formations involves coupled processes that affect the migration and ultimate fate of injected CO2 over multiple length and time scales. For example, coupling of thermal and mechanical process has implications for storage security, including thermally induced fracturing and loss of caprock integrity in the near wellbore environment. This may occur when CO2 is injected at a different temperature than reservoir conditions, e.g. Snøhvit injection, potentially leading to large temperature, density and volume changes within the plume over space and time. In addition, thermally induced density changes also impacts plume buoyancy that may affect large-scale migration patterns in gravity-driven systems such as Utsira storage site. This interaction becomes particularly important at temperatures and pressures near the critical point. Therefore, coupling thermal processes with fluid flow should be considered in order to correctly capture plume migration and trapping within the reservoir. A practical modeling approach for CO2 storage at the field scale is the vertical-equilibrium (VE) model, which solves partially integrated conservation equations for flow in two lateral dimensions. This class of models is well suited for strongly segregated flows, as can be the case for CO2 injection. In this paper, we extend the classical VE model to non-isothermal systems by vertically integrating the coupled heat transport equations, focusing on the thermal processes that most impact the CO2 plume. The model allows for heat exchange between the CO2 plume and the surrounding environment assuming thermal equilibrium across the plume thickness for relatively thin plumes. We investigate the validity of simplifying assumptions required to reconstruct the fine-scale thermal structure from the coarse-scale model solution. The model concept is verified for relatively simple systems. The results of this work demonstrate the potential for reduced models to advance our understanding of the impact of thermal processes in realistic storage systems.