American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

Abstract

A numerical simulation is developed to determine the temperature profiles and oil production for an inverted 5-spot pattern subjected to dry or wet in situ combustion. The basic equations required for the simulation are derived and discussed. The simulation takes into consideration the heat of combustion, the reservoir heat capacity, the conduction and convection of heat through the reservoir, and the conduction of heat between the reservoir and the cap and base rocks. Oil production is calculated through the use of the temperature-oil saturation relationships, a production delay factor and a well-capturing factor.

Examples of temperature profiles and oil production for the dry and wet combustion processes are presented. The features of the temperature profiles produced from the simulation appear to produced from the simulation appear to be in agreement with those reported by others in the literature. For the same injection rate of steam or water simultaneously with air there is not much difference in the temperature profiles ahead of the combustion front. However, behind the front there is definitely a better utilization of heat (i.e., heat scavenging effect) in the case of water injection.

Introduction

In situ combustion is one of the promising techniques for the recovery of promising techniques for the recovery of heavy oil. With this process, air is injected into the formation to burn a part of the oil in-place. Heat part of the oil in-place. Heat generated by combustion is used to heat up the formation and its contents. The increase in temperature reduces the oil viscosity and thus increases its mobility. Ahead of the combustion front, the formation water is vaporized and together with water generated by combustion produces a steam zone. Further ahead, this steam condenses and produces a hot condensate zone. Hence, the in situ combustion process includes both steam and water flooding mechanisms.

Many processes for in situ combustion have been studied and reported in the literature. Among these are forward combustion, reverse combustions and wet combustion.

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