International Journal of Petroleum and Petrochemical Engineering (IJPPE) Volume 2, Issue 2, 2016, PP 22-31 ISSN 2454-7980 (Online) DOI: http://dx.doi.org/10.20431/2454-7980.0202005 www.arcjournals.org ©ARC Page | 22 Alkali and Hybrid-Alkali Flooding as a Tertiary Oil Recovery Mode: Prospects and Challenges Nithin Chacko Thomas 1 , Bisweswar Ghosh 2 , Waleed S. AlAmeri 3 , Alibi Kilybay 4 1,2,3,4 The Petroleum Institute, Abu Dhabi, UAE Abstract: Discovery of new oil being in declining trend and demand being on the rise, EOR technologies has to play a bigger role in the future to meet the energy demand and economics. This paper presents a comprehensive review of EOR technologies related to alkaline flooding and its hybrids. Alkaline flooding is one of the chemical enhanced oil recovery techniques in which high pH alkaline chemicals are injected to the reservoir for recovering the residual oil. It is among the oldest EOR techniques and its history started way back in the early 20 th century. The history of alkaline flooding, mechanisms by which it recovers oil, different process variations, the effectiveness and costs of different alkalis, problems associated with alkaline flooding and its application in carbonates are briefly reviewed in this paper. This paper also focuses on the reviews of the application of various hybrid floods developed along with alkali and their advantages, limitations both in clastic and carbonate reservoirs. The technical solutions to some of these challenges will be discussed. 1. INTRODUCTION Alkaline flooding is an enhanced oil recovery technique in which an alkaline chemical such as sodium hydroxide, sodium orthosilicate or sodium carbonate is injected during polymer flooding or water flooding operations. The alkaline chemical reacts with certain types of oils, forming surfactants inside the reservoir. Eventually, the surfactants reduce the interfacial tension between oil and water and trigger an increase in oil production. Alkaline flooding is not recommended for carbonate reservoirs because of the abundance of calcium: the mixture between the alkaline chemical and the calcium ions can produce hydroxide precipitation that may damage the formation. Alkaline flooding is also known as caustic flooding”. However, recent researches and f ield application has added more knowledge to this very important area of EOR there is much more to alkaline flooding than what has been described in the Schlumberger Oilfield Glossary. This article is an effort to update the reader with the past and recent development on Alkali for EOR application. 2. HISTORY Alkali or caustic flooding is a process of enhanced oil recovery technique in which usually high pH alkaline solutions are injected into the reservoir. The injected alkaline chemicals react with the acidic component present in the crude oil and generate surfactants in-situ, which acts favorably for recovering the residual oil left after secondary oil recovery phase. Alkaline flooding is an established EOR technique which started in the early 20 th century. Squires F (1917) found that the oil displacement could be made more efficient by the introduction of an alkaline chemical into the flood water and also increasing the temperature of the water. This was the first ever published report which stated about the possibility of alkaline flooding for enhancing oil recovery. In the following years many laboratory investigations were conducted (Nutting, P.G. 1925-1928, cited by Johnson, C.R. 1976) which detailed the use of other alkaline chemicals like sodium silicate and sodium carbonate for increasing the recovery of oil by enhancing the performance of water flooding process. In 1927, Atkinson received the first patent right (in USA) for application of caustic/alkali for improving the oil recovery (Atkinson, 1927). Atkinson in his patent explained the advantages of using strong alkalis like hydroxides of potassium and sodium in increasing oil recovery from oil bearing sands. Many laboratory studies and field tests were conducted and reported in subsequent years, of which Beckstrom and Van Tuyl (1927) (cited by Johnson, C.R. 1976) is worth mentioning, who also advocated for use of strong alkalis like sodium carbonate, sodium hydroxide and potassium hydroxide. In 1942, another patent was issued for the use of sodium hydroxide, as an emulsifying agent that could be injected to the reservoir for improving oil recovery (Subkow, 1942). Being proved