Liquid Catalysts (LCs) have been used in surface upgrading of heavy oil for a long time, but their in - situ application in heavy oil reservoirs has been considered only recently. There are four main types of LCs for in - situ applications: water-soluble, oil-soluble, mineral, and dispersed. This paper reviews various types of water-soluble liquid catalysts applied for in - situ upgrading of heavy oil. These LCs have shown great potential in terms of reducing viscosity and in - situ upgradation of heavy oil, thus facilitating recovery and transport of heavy oil in experimental studies and in the field pilot implementation. These studies show that the water-soluble LCs have great potential in becoming an economically and environmentally competitive alternative enhanced oil recovery technique to the established conventional heavy oil recovery EOR techniques, such as thermal and solvent injection. However, further research is needed in studying and developing suitable LCs in terms of their behaviour under the heavy oil reservoir pressure and temperature conditions, and to develop efficient water-soluble LCs with desirable properties.
KeywordsWater-Soluble Liquid CatalystEnhanced Heavy Oil RecoveryIn - Situ Heavy Oil Upgrading
OPEC World Oil Outlook 2025. https://www.opec.org/assets/assetdb/woo-2025.pdf
Guo, K., Li, H. and Yu, Z. (2016) In - Situ Heavy and Extra-Heavy Oil Recovery: A Review. Fuel , 185, 886-902. https://doi.org/10.1016/j.fuel.2016.08.047
Zhao, F., Liu, Y., Lu, N., Xu, T., Zhu, G. and Wang, K. (2021) A Review on Upgrading and Viscosity Reduction of Heavy Oil and Bitumen by Underground Catalytic Cracking. Energy Reports , 7, 4249-4272. https://doi.org/10.1016/j.egyr.2021.06.094
Bello, S.S., Wang, C., Zhang, M., Gao, H., Han, Z., Shi, L., et al . (2021) A Review on the Reaction Mechanism of Hydrodesulfurization and Hydrodenitrogenation in Heavy Oil Upgrading. Energy & Fuels , 35, 10998-11016. https://doi.org/10.1021/acs.energyfuels.1c01015
Nguyen, M.T., Nguyen, D.L.T., Xia, C., Nguyen, T.B., Shokouhimehr, M., Sana, S.S., et al . (2021) Recent Advances in Asphaltene Transformation in Heavy Oil Hydroprocessing: Progress, Challenges, and Future Perspectives. Fuel Processing Technology , 213, Article 106681. https://doi.org/10.1016/j.fuproc.2020.106681
Rana, M.S., Sámano, V., Ancheyta, J. and Diaz, J.A.I. (2006) A Review of Recent Advances on Process Technologies for Upgrading of Heavy Oils and Residua. Fuel , 86, 1216-1231. https://doi.org/10.1016/j.fuel.2006.08.004
Dong, X., Liu, H. and Chen, Z. (2021) Hybrid Enhanced Oil Recovery Processes for Heavy Oil Reservoirs. Elsevier.
Alarbah, A., Shirif, E., Jia, N. and Bumraiwha, H. (2021) A New Approach Utilizing Liquid Catalyst for Improving Heavy Oil Recovery. Journal of Energy Resources Tech nology , 143, Article 073006. https://doi.org/10.1115/1.4050693
Alarbah, A. (2023) Novel Synthesized Transition Metals Liquid Catalysts for Heavy Oil Recovery. Ph.D. Thesis, University of Regina. https://hdl.handle.net/10294/16024
Greaves, M., Xia, T.X., Imbus, S. and Nero, V. (2004) THAI-CAPRI Process: Tracing Downhole Upgrading of Heavy Oil. Canadian International Petroleum Conference , Calgary, 8-10 June 2004, PETSOC-2004-067. https://doi.org/10.2118/2004-067
Elahi, S.M., Scott, C.E., Chen, Z. and Pereira-Almao, P. (2019) In - Situ Upgrading and Enhanced Recovery of Heavy Oil from Carbonate Reservoirs Using Nano-Catalysts: Upgrading Reactions Analysis. Fuel , 252, 262-271. https://doi.org/10.1016/j.fuel.2019.04.094
Hyne, J.B., Clark, P.D., Clarke, R.A., Koo, J. and Greidanus, J.W. (1982) Aquathermolysis of Heavy Oils.
Aliev, F.A., Mukhamatdinov, I.I., Sitnov, S.A., Ziganshina, M.R., Onishchenko, Y.V., Sharifullin, A.V., et al . (2021) In - Situ Heavy Oil Aquathermolysis in the Presence of Nanodispersed Catalysts Based on Transition Metals. Processes , 9, Article 127. https://doi.org/10.3390/pr9010127
Chao, K., Chen, Y., Liu, H., Zhang, X. and Li, J. (2012) Laboratory Experiments and Field Test of a Difunctional Catalyst for Catalytic Aquathermolysis of Heavy Oil. Energy & Fuels , 26, 1152-1159. https://doi.org/10.1021/ef2018385
Maity, S.K., Ancheyta, J. and Marroquín, G. (2010) Catalytic Aquathermolysis Used for Viscosity Reduction of Heavy Crude Oils: A Review. Energy & Fuels , 24, 2809-2816. https://doi.org/10.1021/ef100230k
Muraza, O. and Galadima, A. (2015) Aquathermolysis of Heavy Oil: A Review and Perspective on Catalyst Development. Fuel , 157, 219-231. https://doi.org/10.1016/j.fuel.2015.04.065
Li, C., Huang, W., Zhou, C. and Chen, Y. (2019) Advances on the Transition-Metal Based Catalysts for Aquathermolysis Upgrading of Heavy Crude Oil. Fuel , 257, Article 115779. https://doi.org/10.1016/j.fuel.2019.115779
Jaseer, E.A., Musa, A., Al Otaibi, B.M., Aldossary, M.R., Tanimu, A., Maity, N., et al . (2025) Homogeneous Catalysis in Aquathermolysis for Heavy Oil Upgrading: A Critical Review of Advances, Challenges, and Perspectives. Energy & Fuels , 39, 7941-7966. https://doi.org/10.1021/acs.energyfuels.5c00263
Abdelsalam, Y.I.I., Aliev, F.A., Mirzayev, O.O., Sitnov, S.A., Katnov, V.E., Akhmetzyanova, L.A., et al . (2023) Aquathermolysis of Heavy Crude Oil: Comparison Study of the Performance of Ni(CH 3 COO) 2 and Zn(CH 3 COO) 2 Water-Soluble Catalysts. Catalysts , 13, Article 873. https://doi.org/10.3390/catal13050873
Alharthy, R.D., El-Nagar, R.A., Ghanem, A., et al . (2022) Laboratory Experiments on the in Situ Upgrading of Heavy Crude Oil Using Catalytic Aquathermolysis by Acidic Ionic Liquid. Materials , 15, Article 5959. https://doi.org/10.3390/ma15175959
Fan, Z., Wang, T. and He, Y. (2009) Upgrading and Viscosity Reducing of Heavy oil by [BMIM][AlCl 4 ]. Journal of Fuel Chemistry and Technology , 37, 690-693. https://doi.org/10.1016/s1872-5813(10)60015-1
Tunnish, A., Shirif, E. and Henni, A. (2017) The Influence of Ionic Liquid Type, Concentration, and Slug Size on Heavy Oil Recovery Performance. Brazilian Journal of Petroleum and Gas , 11, 15-29. https://doi.org/10.5419/bjpg2017-0002
Schacht-Hernández, P., Quintana-Solórzano, R., Morelos-Santos, O., Soto-Escalante, I. and Ancheyta, J. (2022) In Situ Upgrading of Heavy Crude Oil: Comparative Study of the Performance of Cu-, Fe-, Ni-, or Zr-Containing Water-Based Catalysts. Energy & Fuels , 36, 12580-12590. https://doi.org/10.1021/acs.energyfuels.2c02675
Alarbah, A., Rahman, A., Shirif, E. and Jia, N. (2025) Production Optimization of Heavy Oil Recovery Utilizing Mo-Ni Based Liquid Catalysts: A Simulation Approach. Petroleum Research , 10, 57-65. https://doi.org/10.1016/j.ptlrs.2024.08.005
Nares, H.R., Schachat, P., Ramirez-Garnica, M., Cabrera, M. and Noe-Valencia, L. (2007) Heavy-Crude-Oil Upgrading with Transition Metals. Proceedings of Latin Am erican & Caribbean Petroleum Engineering Conference , Buenos Aires, 15-18 April 2007, SPE-107837-MS. https://doi.org/10.2523/107837-ms
Wen, S., Liu, Y., Song, Y. and Li, F. (2004) Effect of Silicotungstic Acid on Catalytic Vis-Breaking of Extra Heavy Oil from Shengli Oilfield. Journal of Daqing Petroleum Institute , 28, 25-27.
Chen, Q., Enezi, S. and Yousef, A. (2019) Geochemical Modeling of Low Salinity Water Flooding EOR Mechanism. SPE / IATMI Asia Pacific Oil & Gas Conference and Exhibition , Bali, 29-31 October 2019, SPE-196497-MS. https://doi.org/10.2118/196497-ms
Suwaid, M.A., Al-Mishaal, O.F., Al-Muntaser, A.A., Varfolomeev, M.A., Djimasbe, R., Reyimkulyyeva, S.U., et al . (2024) Water-Soluble Catalysts Based on Nickel and Iron for in Situ Catalytic Upgrading of Boca De Jaruco High-Sulfur Extra-Heavy Crude Oil. Energy & Fuels , 38, 1098-1110. https://doi.org/10.1021/acs.energyfuels.3c03868
Bondarenko, A.A., Rogachev, M.K., Skvortsov, A.S. and Dmitriev, K.V. (2026) Catalytic Conversion of Heavy Oil Using Molybdenum Based Water-Soluble Catalyst. International Journal of Engineering , 39, 1821-1828. https://doi.org/10.5829/ije.2026.39.08b.04
Wang, J., Gao, K., Zhong, Y., Nan, J., Li, X., Zhao, H., et al . (2025) In - Situ Formation of Molybdenum Disulfide Nanoparticle and Its Catalytic Performance in Heavy Oil Long-Term Aquathermolysis. Colloids and Surfaces A : Physicochemical and Engineering Aspects , 707, Article 135861. https://doi.org/10.1016/j.colsurfa.2024.135861
Vakhin, A., Sitnov, S., Mukhamatdinov, I., Varfolomeev, M., Rojas, A., Sabiryanov, R., et al . (2022) Improvement of CSS Method for Extra-Heavy Oil Recovery in Shallow Reservoirs by Simultaneous Injection of In - Situ Upgrading Catalysts and Solvent: Laboratory Study, Simulation and Field Application. SPE Conference at Oman Petroleum & Energy Show , Muscat, 21-23 March 2022, SPE-200082-MS. https://doi.org/10.2118/200082-ms