A NEW SEMI ANALYTICAL MODELING OF TOE TO HEEL AIR INJECTION IN IN SITU COMBUSTION PROCESS

Laboratory combustion tube experiments can be operated far more rapidly and cheaply than to be operated in the field. Forecasts of reservoir response to the application of thermal methods are necessary before starting a project. Thermal numerical models are available to provide forecasts. However, these models are expensive and consume a great deal of computer time. An alternative to numerical modeling is to use a semi‑analytical model. Toe to heel air injection (THAI) is studied in this research and the temperature distribution as well as the consequential oil production rate have been formulated and compared against the experimental data. The main objective was to investigate thermal applications of horizontal wells for displacement and gravity drainage processes using analytical modeling as well as experiment. The main novelties presented in the paper are: a) Regarding the Bailey‑Larkin's and Penberthy‑Ramey's work, the differential equations of heat transfer process around a moving combustion front in a vertical combustion tube is derived, b) using the Laplace Transform method the solution of these equations are introduced, c) the temperature distribution ahead and behind the moving combustion front is obtained and it is resulted that the temperature distribution ahead of the front is a function of dimensionless time and dimensionless front velocity while the distribution behind the front is only a function of dimensionless time, d) the average temperature over the oil column from the combustion front to the underburden is formulated, e) the recorded temperatures ahead and behind the front are compared against the proposed analytical temperature distribution models, f) new "type curves" are set up for approximating the front velocity while propagating beyond the injection well to the lower boundaries, and g) an indirect formulation method for evaluating the combustion front velocity into the reservoir is introduced.