Petroleum Research (Sep 2022)
Simulation of catalytic upgrading in CAPRI, an add-on process to novel in-situ combustion, THAI
Abstract
Based on the analysis of recent projections by the International Energy Agency (IEA), to meet the growing and subsequently declining demands of oil from now to 2040, we need up to around 770 billion barrels of oil. Since the worldwide total proved reserves of easy-and-cheaper-to-produce conventional oils is roughly only 520.2 billion barrels, the remaining 249.8 billion barrels must be obtained from unconventional petroleum resources (i.e. heavy oils and bitumen). These resources are however very difficult and costly to upgrade and produce due to their inherently high asphaltene contents which are reflected in their very high viscosities and large densities. However, still they should prove attractive development prospects if, as much as practicably possible, their upgrading can be performed in conjunction with in situ or downhole catalytic upgrading processes. Such projects will contribute significantly towards smoother and greener transition to full decarbonisation. Advanced technologies, such as the toe-to-heel air injection coupled to its add-on in situ catalytic process (i.e. THAI-CAPRI processes), have the potential to develop these reserves, but require further developmental understanding to realise their full capability. In this work, a new detailed procedure for numerically simulating the THAI-CAPRI processes is presented. The numerical model is made-up of Athabasca-type bitumen and it has a horizontal producer (HP) well that is surrounded by an annular layer of alumina-supported cobalt-oxide-molybdenum-oxide (CoMo/γ-Al2O3) catalyst. The simulation is performed using the computer modelling group (CMG) reservoir simulator, STARS. This new work has shown that the choice of the frequency factor of the catalytic reactions allowed model validation based on the degree of catalytic upgrading in form of API gravity. Overall, the work herein identifies the important parameters, such as API gravity, peak temperature, oil production rate, cumulative oil production, produced oxygen concentration, temperature distribution profile, extent of coke deposition on the catalyst surface, etc., governing the successful operation of the THAI-CAPRI processes. In particular, this study has shown that even in the vicinities of the mobile oil zone (MOZ) where the catalytic upgrading is expected to be taking place, the catalyst surfaces are covered with high concentration of coke. This finding is in parallel to the observations reported from experiment of CAPRI process alone. Therefore, it is concluded that when experimental studies of the THAI-CAPRI processes are to be conducted, a catalyst regeneration mechanism must be put in place in order to prolong the effectiveness and thus the life of the catalyst so that proper field operation design can be made. Additionally, the study has also shown that the temperature of the MOZ is less than 306 °C and that implies that an external source of heating the annular catalyst layer must be provided in order to effect the catalytic upgrading in the THAI-CAPRI processes. Thus, a new study should look at the feasibility of targeted heating (in the case of microwave) or conductive or resistive heating (in the case of electrical heating) to raise the temperature of the annular catalyst layer to that required to achieve the catalytic upgrading.
