A Heat Transfer Study for the In-Situ Combustion Process

Abstract

Abstract This paper deals with phenomenon of heat transport in underground combustion processes. It is assumed that heat is generated at a constant rate at a moving vertical combustion surface. This generated heat is transported in the fluid flow direction by convection and a portion is lost to the cap and base rock by portion is lost to the cap and base rock by vertical conduction. On the basis of this idealized model, temperature and energy distributions during the combustion process have been investigated. This study indicates that it is advantageous to achieve the condition such that the heat front velocity is larger than the combustion front velocity. For this case a portion of the generated heat is carried ahead of the combustion front to heat the reservoir oil in the downstream formation. If the heat front moves slower than the combustion front, then the generated heat is distributed mainly in the formation upstream of the combustion front and in the cap and base rock. The results of this study suggest that the combustion front temperature can be controlled in order to avoid damage to wells. This can be accomplished by controlling the rate and composition of the injected fluid. Introduction The in-situ combustion process is a well known method of recovering oil from an underground porous reservoir. It involves injection of a combustible fluid, e.g., air, into an oil-bearing sand. At the injection side the formation is heated by electric heaters for example for a certain period of time until the combustion becomes self-supporting. Additional heat is generated as the result of the exothermic reaction between the injected fluid and a part of the oil in place. Thus, the combustion part of the oil in place. Thus, the combustion front or reaction zone can be propagated through the formation. Simultaneously a portion of the generated heat is transported away from the combustion front. The oil is heated and its viscosity is reduced. As the result of this process, the oil moves toward the production process, the oil moves toward the production well and the flow rate is accelerated. This process has been studied both in the process has been studied both in the laboratory and in the field. It is obvious that the phenomenon of heat transport plays a significant role in the under ground combustion process. The production of oil depends strongly upon the amount and distribution of heat which can be carried downstream from the combustion front. The present work was therefore initiated in order to study some of the factors affecting the heat distribution. The effect of the fluid flow is disregarded in this investigation.