LAUSR

A series of accelerated rate calorimeter (ARC) experiments were conducted on heavy oil mixed with a carbonate core to study the thermal behavior and oxygen uptake operating at different air fluxes of 5.0, 2.5, and 1.25 (m3(ST)/(m2h)) referred to as Runs -1, -2 and -3, respectively. As a result, evaluation of the temperature rise per unit mass of oxygen was proposed as a new approach for identifying the main contributing mechanism during in-situ combustion (ISC). The obtained findings can be used for predicting the transition occurring between low- and high-temperature ranges (LTR and HTR). For Runs -2 and -3, such a transition occurred at 280°C, whereas for Run-1, operated at the highest air flux, LTR shifted to HTR at about 300°C. The overlapping curves of O2 to COx and O2 to low-temperature oxidation (LTO) plus water were interpreted as equal contributors to energy formation. The calculated maximum values varied between 4053 for LTO reactions and 13 420 dT(°C)dmO2(g) for high-temperature oxidation (HTO) reactions depending on the air flux. The measured self-heat rates (SHRs) and oxygen uptake, further used to obtain the apparent heat of reaction, were in general agreement with the values reported in the literature, 16 000 J/g O2 consumed. These values are typical for the HTO reactions; however, in this study, the heats of reaction when the oxidation reactions are operating in the oxygen addition or LTO mode were the main interest. Depending on the run, the apparent heats of LTO reactions varied between 4422 and 7101 J/g O2 consumed.