The Impact of the Initiators on Heavy Oil Oxidation in Porous Media during In Situ Combustion for In Situ Upgrading Process

In situ combustion (ISC) is an effective way to recover heavy oils, where initiation at an early stage of the low-temperature oxidation (LTO) process is crucial. A porous medium thermo-effect cell (PMTEC) was applied to conduct oxidation experiments on heavy oil in porous medium in the presence of several different initiators. The addition of initiators promoted heavy oil oxidation, resulting in reduced peak temperatures and reaction intervals for LTO. According to our results, oleic acid is the most effective initiator of heavy oil oxidation, reducing oxidation temperatures from 244-367 to 233-354 degrees C in LTO. Furthermore, electron paramagnetic resonance examination revealed that oleic acid stimulated heavy oil oxidation and resulted in higher concentrations of free radicals in the early stage of LTO. The visual combustion tube (VCT) was also used to investigate the effect of the initiator on in situ upgrading (ISU) of heavy oil. According to the results, the addition of oleic acid as an efficient initiator at concentrations of 1 and 2% reduced the viscosity of heavy oil from 2071 to 141 and 57 mPa s, respectively. Furthermore, SARA analysis of recovered oil showed that the ISC process on heavy oil in a porous medium in the presence of 1 and 2% oleic acid reduced the fractions of heavy molecular weight, such as asphaltene, from 6.04 to 3.08 and 2.32%, and light components, including saturated oil, increased from 29.64 to 38.40 and 41.05%, respectively. Additionally, gas chromatography evaluation of gaseous products revealed that the amount of the produced H2S decreased from 0.152 to 0.084 and 0.047% in the presence of oleic acid at 1 and 2% concentrations, respectively. In summary, we can conclude that heavy oil oxidation in porous media can be improved by inexpensive initiators. This process may be highly effective not only for improving enhanced oil recovery but also for improving ISU.