ABSTRACT
This paper presents a method for lowering the permeability of thief zones in oil reservoirs to improve recovery during waterflood operations. The method consists of preheating the thief zone around the injection or production well by injecting hot water or steam and then injecting a hot, saturated chemical solution. If the chemical has a lower solubility at reservoir temperature than at injection temperature, cooling within the formation will result in the precipitation of solids in the pore spaces.
Several chemicals were identified as having a suitable temperature-dependent solubility with a low environmental toxicity, including potassium carbonate and sodium borate. The porosity and permeability reduction from temperature-dependent precipitation of these chemicals was then experimentally determined and a correlation between the permeability and porosity reduction was obtained. A theoretical analysis of this promising new process and how it can be applied are also presented.