In Situ Combustion is a possible method for producing heavy oil when other methods such as SAGD are not adequate (e.g. in thin beds, or when CO2 emission for steam generation is unacceptable...). Previous field trials of this process have often been unsuccessful. However, in recent years, several new well implementations have been proposed (COSH, THAI,...), exploiting the more advanced drilling capabilities available nowadays. Simulations of such configurations require a reliable representation at field scale of the oxy-combustion reactions, which is not available at the present time.
The objective of the work described in this paper is to illustrate some improvements in the description of oxycombustion reactions both at the experimental level and in the simulation models. A "ramped temperature" experiment has been conducted on an extra heavy stock tank oil (10000 cp at reservoir conditions). This experiment has been successfully matched using a commercial simulator. The improvement over classical adiabatic reactor experiments is significant: two combustion reactions are clearly observed, and the Arrhenius parameters are determined with increased accuracy. The reliability of the inferred parameter values is checked by applying them to simulations of previous adiabatic disk reactor experiments conducted under avariety of conditions.
The final part of the paper is dedicated to illustrating the impact of the new reaction scheme on the simulation results at field scale.
With the more advanced drilling capabilities now available, such as horizontal wells, several new well configurations have recently been proposed for In SituCombustion applied to heavy oil (COSH(1), THAI(2),...).
To assess the potential of these new configurations by simulation, a reliable representation of the oxycombustion reactions is required. These reactions govern the oxygen consumption and will directly influence the efficiency of the recovery process in any given configuration. Moreover, the oxygen consumption will also determine the time of oxygen breakthrough, which is one of the critical parameters of air injection. In order to improve the description of the oxy-combustion reaction scheme, both at the experimental level and at the numerical simulation level, a ramped temperature experiment was conducted on an extra heavy oil and has been successfully matched using a commercial simulator (STARS ™ from CMG).
In the final part of the paper, the impact of the new reaction scheme is evaluated at field scale by comparing numerical simulations made with the old and the new reaction schemes.
Before developing the ramped temperature experiment, two types of experiment had been developed in the TOTALFINAELF thermal methods laboratory in order to determine the kinetic parameters of the oxycombustion reactions for light oils (3):
The isothermal disk reactor experiments. These provide valuable information on the kinetic parameters at low temperatures but are less accurate at high temperatures (the required assumption of a constant concentration of reactive products is no longer valid).
The adiabatic disk reactor experiments. These provide useful information on the self-ignition temperature and on the heat released by the reactions. However, they cannot be used to determine accurate kinetic parameters above the self-ignition temperature because the temperature increase is too rapid.
