Improving the Efficiency of the THAI-CAPRI Process by Nanocatalysts Originated from Rock Minerals

摘要

Toe-to-heel air injection method is a modified pattern in situ combustion which is applicable for the recovery of heavy oil reservoirs. A fixed bed of catalyst around the production well can improve performance and quality of the produced oil; however, pilot tests revealed rapid deactivation of the catalyst bed. Dispersion of fine catalyst particles (ideally nanoparticles) around the production well by carrier fluids may reduce the deactivation problem. In the first step of this study, three nanoparticles, namely calcite, montmorillonite (MMT), and Cloisite 20A, were dispersed in a heavy oil as candidate catalysts and subjected to simultaneous thermal analysis. Kinetic parameters of different reaction zones were obtained by the Coats and Redfern model, and it was observed that 0.5 wt % of the MMT more effectively catalyzed the combustion reactions. In the second step, selected sample was subjected to multiple heating rate experiments to study detailed kinetic effects. Results were analyzed by Vyazovkin isoconversional kinetic modeling, and mechanism of different steps was determined. Results showed that all reaction regions follow nucleation growth models. It was found that low-temperature oxidation (LTO) reactions follow a power law model (n = 1/3) which means an acceleratory nucleation process. Nanoclay did not change the reactions mechanism of both fuel deposition (FD) and high-temperature oxidation (HTO) regions (both followed A(0) but E-0 and Ao in the FD step were increased from 187.3 +/- 19.0 kJ/mol and 51.2 +/- 3.4 min(-1) to 235.0 +/- 21.8 kJ/mol and 59.7 +/- 3.3 min(-1), respectively. In contrast to FD, Nanoclay decreased E-0 and A(0) of HTO from 100.1 +/- 17.2 kJ/mol and 34.6 +/- 2.1 min(-1) to 81.3.0 +/- 18.5 kJ/mol and 31.0 +/- 2.3 min(-1) respectively. In other words, MMT intensified LTO and catalyzed FD step and consequently altered the residual coke. It also decreased energy barriers and changed mass loss pattern of HTO which could be caused by change of reactant (coke) and resistance of MMT nucleation sites to heat in contrast to ingested nucleation sites of residual coke. Altogether, MMT improved LTO and prevented formation of excessive fuel; at the same time, MMT catalyzed HTO step and caused more uniform temperature profile which could sustain combustion.