Optimisation of the THAI-CAPRI process for heavy oil upgrading: effect of hydrogen and guard bed

Toe-to-heel air injection (THAI) and its catalytic version CAPRI are relatively new technologies for the recovery and upgrade of heavy oil and bitumen. The technologies combine horizontal production well, in situ combustion, and catalytic cracking to convert heavy feedstock into light oil down-hole. The deposition of asphaltenes, coke, and metals can drastically deactivate the catalyst in the CAPRI process. A fixed bed microreactor was used to experimentally simulate the conditions in the catalyst zone of the oil well of CAPRI. In this study, oil upgrading and catalyst deactivation in the CAPRI process were investigated in the temperature range of 350–425 °C, pressure of 20 barg and residence time of 9.2 min. Additionally, a guard bed consisting of activated carbon particles prior to the active catalyst in a microreactor and/or the addition of hydrogen to the gas feed were used to minimize coke formation and catalyst deactivation through respectively removing and hydrocracking the coke precursors. It was found that depending on the upgrading temperature, the viscosity of the produced oil reduced significantly by 42–82% and (American Petroleum Institute) API gravity increased by 2 to 7 °API relative to the feedstock of 0.49 Pa·s and 13 °API, respectively. Conversely, the use of hydrogen further increased the API gravity by 2 °API and the viscosity by 5.3%. Notably, the coke content of the catalyst reduced from 57.3 wt % in nitrogen to 34.8 wt % in hydrogen atmosphere. The use of a guard bed increased the API gravity of the produced oil by a further 2° and reduced the viscosity by an average of 8.5% further than achieved with the active HDS catalyst CoMo/alumina.