ABSTRACT
Surfactants are extremely important in the oil and gas industry [1]. Primary depletion and secondary recovery processes applied in oil reservoirs typically recover about a third of the original oil in place (OOIP); thus, nearly two trillion barrels of conventional oil and ve trillion barrels of heavy oil remain in reservoirs worldwide after these methods have been exhausted [2]. The low oil recoveries from conventional recovery methods are the result of inefcient macroscopic sweep efciencies due to the lack of mobility control and poor microscopic displacement efciencies caused by the capillary trapping of oil that is attributed mainly to wettability and interfacial forces. The enhanced oil recovery (EOR) method of choice and the expected recovery depend on many considerations such as technology, reservoir geology, reservoir uids, and overall economics that include the price of oil. It has long been an objective of the industry to develop processes to improve the overall recovery. However, the low oil prices from the mid-1980s until recently provided little incentive for research on EOR methods, especially surfactant processes that require signicant initial costs
19.1 Introduction ........................................................................................................................ 489 19.2 History of Surfactants in the Petroleum Industry ..............................................................490 19.3 Types of Surfactants Used in EOR ..................................................................................... 491 19.4 Recovery of Residual Oil ................................................................................................... 492 19.5 Effect of Surfactants on IFT .............................................................................................. 492
19.5.1 Inuence of Salinity on IFT ................................................................................... 492 19.5.2 Inuence of Surfactant Structure on IFT ............................................................... 493 19.5.3 Inuence of Oil Properties on IFT ......................................................................... 494
19.6 Effects of Surfactant on Wettability ................................................................................... 494 19.7 Variations of Surfactant Flooding ...................................................................................... 495
19.7.1 Surfactant Selection ................................................................................................ 496 19.7.2 Application of Surfactant-Based Processes in Sandstone Reservoirs .................... 496 19.7.3 Application of Surfactant-Based Processes in Carbonate Reservoirs .................... 497 19.7.4 Application of Surfactant-Based Processes in Gas Condensate Reservoirs ........... 497
19.8 Optimization of Surfactant-Based Processes ..................................................................... 498 19.9 Limitations and Challenges ................................................................................................ 499
19.9.1 Surfactant Retention ............................................................................................... 499 19.9.2 Production of High Viscosity Emulsions ................................................................500 19.9.3 Overview ................................................................................................................. 501
19.10 Economics .......................................................................................................................... 501 19.11 Summary and Prospects .....................................................................................................502 Acknowledgments ..........................................................................................................................502 References ......................................................................................................................................502
