Study of the catalytic effect of copper oxide on the low-temperature oxidation of Tahe ultra-heavy oil

Abstract

The heavy metal compounds existing in a reservoir have a significant catalytic effect on the low-temperature oxidation of heavy oil during the in situ combustion (ISC) process. This study focused on the thermal behavior of Tahe ultra-heavy oil and the catalytic effect of copper oxide on low-temperature oxidation to probe into the applicability of the ISC technique. For this purpose, three samples, including Tahe crude oil, oxidized oil and oxidized oil-CuO, were studied by performing thermogravimetry (TG)/derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) with three different heating rates (5–10 and 15 °C min−1) at temperatures ranging from 30 to 830 °C. The result indicated that more fuel was produced to cause more exothermic heat in the high-temperature oxidation (HTO) zone as the heating rate increased. Kinetic parameter calculation detected that the activation energy of the crude oil was 13.73 kJ mol−1 in the low-temperature oxidation (LTO) stage and 131.72 kJ mol−1 in the HTO stage, respectively. Compared with TG/DSC analysis and the activation energy of the three samples, the activation energy of oxidized oil was reduced obviously in the HTO zone by the crude oil. Additional CuO accelerated fuel deposition in the low-temperature region with no reduction in the activation energy, revealing that CuO has a catalytic effect on Tahe crude oil to cause fuel deposition in LTO. Based on the comprehensive thermal performance and kinetic characterization of the crude oil, 69.61% of the crude oil remained in the final LTO, which can be oxidized as coke to supply sufficient fuel for the HTO stage. This finding indicates that the ISC technique may be feasible for Tahe oilfield development.