Pyrite effects on the oxidation of in situ crude oil

Abstract

As an enhanced oil recovery method, the air injection process (AIP) has been applied for decades. However, deviations are still being identified between laboratory tests and field applications. One possible reason for such deviations is the formation minerals of the crude oil reservoir. Some natural minerals are beneficial for the oxidation of hydrocarbons and may affect the AIP behavior. Herein, the accelerated-rate calorimetry (ARC) was adopted to study the crude oil oxidation when containing pyrite or iron oxide under adiabatic and high-pressure conditions. The temperature profiles and detailed kinetic data from the ARC tests were compared for the crude oil oxidation traits, with different ground mineral particles presented in the ARC vessel, to figure out the catalytic effects of iron minerals on the crude oil oxidation. Results indicate that iron oxide showed a catalytic effect on the high-temperature oxidation period of crude oil, whereas the pyrite could not generate enough iron oxides to catalyze crude oil oxidation under limited oxygen conditions. During the test, since pyrite oxidizes before the crude oil, the enthalpy from pyrite oxidation could benefit the onset of crude oil oxidation. Hence, this study could be beneficial for future AIP engineering design and AIP candidate reservoir screening.