Thermal transients during nonisothermal fluid injection into oil reservoirs

Abstract

During hot fluid injection into oil reservoirs, the importance of determining the temperature profile to estimate the thermal efficiency is well known. In addition, the resultant temperature distribution due to cold water injection into a hot reservoir during waterflooding may significantly influence the stress distribution in the reservoir. Owing to these facts, in this work we present a new two-dimensional analytical model for analyzing the thermal transients during nonisothermal fluid injections into oil reservoirs that may provide a better insight into the mechanisms of heat transfer in oil reservoirs. The new model has several distinguishing aspects. Primarily, it is the first analytical solution of an unsteady state two-dimensional heat transport process in a laterally/vertically confined layer. In addition, both finite longitudinal and transverse heat dispersions have been accounted for in the model as well as the heat loss to the bounding layers. Thus, the model allows one to observe the roles of both boundary conditions and fluid mechanics controls simultaneously, a feature not possessed by the previous analytical models that assume either boundary conditions or fluid mechanics controls. Hydrodynamic heat dispersion concept has also been incorporated in the new model in order to account for the much larger temperature transition zones observed in the field than that would be caused by pure conduction. Finally, since the solution is free of numerical dispersion and nonphysical oscillations, especially in two-dimensional domains, it serves as a higher stepping stone for validation of numerical models.