Combustion kinetics of Athabasca bitumen from 1D combustion tube experiments

There are two basic requirements for heavy-oil recovery processes: first, mobilize the bitumen, and second, have a drive mechanism deliver the mobilized bitumen to a production wellbore. In situ combustion has the potential to be an important heavy-oil recovery method. Before design of in situ combustion recovery processes can start, it is necessary as a first step to understand the kinetics of various complex chemical reactions and determine kinetic constants associated with the reactions. Even with modern reservoir simulation capabilities, this is a significant challenge. In this research, an Athabasca bitumen combustion tube experiment, conducted by the ISC Research Group at the University of Calgary, was history matched by using a reservoir thermal simulator to determine a set of kinetic parameters as well as the transport parameters for the system. The main results of the history match was a match of air injection rate, bitumen and gas production volumes, average product gas compositions, temperature profiles along the tube through time, and pressure. Gridding sensitivities were examined to determine if the derived kinetic and transport parameters were dependent on gridblock size. The results revealed that the grid was refined enough to sufficiently capture thermal, mass transfer, and reaction length scales. After this single match was achieved, the same constants were used to successfully predict several other combustion tube experiments. The results suggest that the fuel (coke) for high-temperature oxidation (HTO) originates mainly from low-temperature oxidation (LTO) and not from thermal cracking. This implies that the major control on HTO is upstream oxygen transfer into the LTO region. If LTO does not occur, then a relatively small amount of coke is deposited in the matrix due to thermal cracking and this may be insufficient to start or sustain HTO. © 2009 International Association for Mathematical Geology.