The in-situ combustion (ISC) is highly effective thermal enhanced oil recovery process in which high displacement efficiencies can be accomplished. While several physical and chemical factors affect the ISC performance, there is a little knowledge about how each parameter changes the ISC fate. In this study, we investigate the catalytic effect of clay on different crude oil types.
Six one-dimensional combustion tube experiments were conducted on three different crude oil samples; one from Mexico and two from Alberta, Canada. The combustion behavior of each crude oil sample was tested with two combustion runs; by preparing reservoir rock with only sand (E1, E3, and E5) and by preparing reservoir rock with 3 wt% clay and 97 wt% sand mixture (E2, E4, E6). The combustion characteristics were monitored with temperature profiles, produced gas compositions, and produced liquid yields. The level of in-situ oil upgrading were determined by comparing the viscosities of produced oil samples with the original ones.
The results showed that the catalytic effect of the clay controls the combustion front propagation, the fuel formation, and the produced oil quality. Clays visualized on postmortem samples in the shape of lumps indicate that clay alteration occured at elevated temperature due to interaction of clay with crude oil and due to thermal decomposition of clay. It was observed that the lump formation was associated with mainly saturates and asphaltene contents of initial oil and asphaltene-clay interaction during fuel formation.
Our results support that the clay presence in reservoir rock had an impact on ISC performance. However, this impact did not have a linear trend and the response of the catalytic effect of clays were different from one crude oil to another; while one crude oil favored combustion more with the presence of clay, the other did not and led to lower oil production by producing more gas.