With World oil demand increasing in the face of limited supplies, increasing attention is turning towards non-conventional oil sources as a means to relieve the pressure exerted on conventional stocks. However, non-conventional oils are hard to extract, process and transport. Several technologies are already at work with differing levels of success, recovery ranging from as low as 5% through to more than 70%. This paper reviews the range of Enhanced Oil Recovery techniques, broadly classified into either thermal or non-thermal methods, and their applicability to the extraction of heavy oils and bitumens. Advantages and disadvantages are presented in terms of their recovery factors, requirements, limitations and economics. The potential benefits of additional downhole catalytic upgrading of heavy oils are also explored.

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.

The worldwide conventional crude oil demand is on the rise and because of the rising prices, unconventional oils are becoming more economically attractive to extract and refine. However, technological innovation is needed, if heavier oil supplies are to be further exploited. Toe-to-heel air injection (THAI), and its catalytic add-on (CAPRI) processes combine in-situ combustion with catalytic upgrading using an annular catalyst packed around the horizontal producer well. These techniques offer potentially higher recovery levels and lower environmental impact than alternative technologies, such as steam-based techniques. An experimental study is reported concerning the optimization of catalyst type and operating conditions for use in the THAI-CAPRI process. Experiments were carried out using microreactors containing 10 g catalyst, with oil flow of 1 ml.min -1 and gas flow of 0.5 l.min -1 , under different temperatures, pressures and gas environments. Catalysts tested included alumina supported CoMo, NiMo and ZnO/CuO. It was found that there was a trade off in operation temperature between upgrading performance and catalyst lifetime. At a pressure of 20 bar, operation at 500 °C led to an average of 6.1 °API upgrading of THAI oil to 18.9 °API, but catalyst lifetime was limited to 1.5 hours. Operation at 420 °C was found to be a suitable compromise, with upgrading by an average of 1.6 °API, and sometimes up to 3 °API, with catalyst lifetime extended to 77.5 hours. Coke deposition occurred within the first few hours of the reaction, such that the catalyst pore space became blocked. However, upgrading continued, suggesting that thermal reactions or reactions catalysed by hydrogen transfer from the coke itself play a part in the upgrading reaction mechanism. The CAPRI process was relatively insensitive to changes in reaction gas medium, gas flow rate and pressure, suggesting that the dissolution of hydrogen or methane from the gas phase does not play a key role in the upgrading reactions. By careful control of the temperature and oil flow rate in the in-situ CAPRI process, additional upgrading compared with the THAI process alone may be effected, resulting in a more valuable produced oil, which is easier to transport.

Summary The worldwide conventional crude-oil demand is on the rise, and because of the rising prices, unconventional oils are becoming more economically attractive to extract and refine. However, technological innovation is needed if heavier oil supplies are to be exploited further. Toe-to-heel air injection (THAI) and its catalytic add-on processes (CAPRI) combine in-situ combustion with catalytic upgrading using an annular catalyst packed around the horizontal producer well. These techniques offer potentially higher recovery levels and lower environmental impact than alternative technologies (e.g., steam-based techniques). An experimental study is reported concerning the optimization of catalyst type and operating conditions for use in the THAI-CAPRI process. The feed oil was supplied from the Whitesands THAI-pilot trial. Experiments were carried out using microreactors containing 10 g of catalyst, with oil flow of 1 mL/min and gas flow of 0.5 L/min, under different temperatures, pressures, and gas environments. Catalysts tested included alumina-supported CoMo, NiMo, and ZnO/CuO. It was found that there was a trade-off in operation temperature between upgrading performance and catalyst lifetime. At a pressure of 20 bar, operation at 500°C led to an average of 6.1°API upgrading of THAI oil to 18.9°API, but catalyst lifetime was limited to 1.5 hours. Operation at 420°C was found to be a suitable compromise, with upgrading by an average of 1.6°API, and sometimes up to 3°API, with catalyst lifetime extended to 77.5 hours. Coke deposition occurred within the first few hours of the reaction, such that the catalyst pore space became blocked. However, upgrading continued, suggesting that thermal reactions or reactions catalysed by hydrogen transfer from the coke itself play a part in the upgrading reaction mechanism. The CAPRI process was relatively insensitive to changes in reaction-gas medium, gas-flow rate, and pressure, suggesting that the dissolution of hydrogen or methane from the gas phase does not play a key role in the upgrading reactions. By careful control of the temperature and oil-flow rate in the in-situ CAPRI process, additional upgrading compared with the THAI process alone may be effected, resulting in a more-valuable produced oil, which is easier to transport.

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