Economic considerations for the design of in situ combustion projects

Recent technical advances in the understanding of in situ combustion have m ade it worthwhile to consider this process as a serious means of recovering heavy oil. However, it must first prove itself to be economically viable, particularly in comparison with steam based recovery processes. This paper examines the factors that are necessary to make in situ combustion work in the field, including the need to ensure operation at high temperatures,opti mal well layouts and spacing, and why economies of scale must be used to en sure competitive economics. Based on these requirements, an in situ combust ion process is then compared to a similarly designed steam process and the comparative economics are discussed. The results of this work show that in situ combustion should be laid out in a line drive pattern, based on a 4 ha (10 acres) well spacing. Sufficient air injection capacity must be installed to best ensure high temperature co mbustion, thus achieving reasonable oil production rates. It is recognized that in situ combustion has higher front end costs than steam processes, bu t recovery factors for in situ combustion can be as much as 60% higher. The cost comparison for a 20 well combustion project and a I comparable steam project set in Western Canada yields a per m(3) cost of $104.10 for steam a nd $78.00 for in situ combusiton (%16.55 for steam and $12.40 for in situ c ombustion).