The surfactant selection for chemical floods usually starts with an extensive lab study identifying the formulation that provides the best recovery performance. However, it is oftentimes overlooked that in a laboratory setting the requirements on product availability and applicability are less sensitive than for a field scale injection. Thus, there are various other aspects that contribute to the overall economics of chemical selection which also need to be taken into account. Aside from the molecular properties, the manufacturing aspects have to be examined carefully to allow proper planning and ensure the supply of large volumes for full field implementation on time. Furthermore, opportunities to simplify and optimize the logistics (i.e. packaging, regulatory compliances …) help to reduce the cost of a chemical injection project. This is also strongly connected with the handling properties of the selected materials when it comes to the blending of the final injection cocktail (e.g. activity, viscosity, storage conditions, etc…). This paper describes the crucial factors that impact the economics of a selected surfactant for a chemical EOR project, taking into account the production, transportation, delivery form, application performance, handling, amongst others. Another point that will be discussed, is the option to create in-country value and reduce logistic challenges by performing a final production step regionally close to the project site. In the end, we conclude that involving the suppliers at a very early stage of the screening process helps to eliminate unsuitable molecules. It also allows for proper planning and leads to the most appropriate procedure. By taking into account the whole economics picture, a win-win situation can be created and the project is beneficially optimized. Forward thinking the treatment of both injected and produced fluids can be part of this optimization process.

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Recently, research and development of EOR surfactants focused on so-called "harsh" conditions like e.g. high salinity reservoirs combined with high temperatures. It is well known and acknowledged that dealing with large amounts of dissolved electrolytes in the injection brine causes difficulties for most types of surfactants and other chemicals. Mostly overseen is the fact that, especially for surfactants, very low salinity conditions can also be quite challenging. We present a comprehensive phase behavior study based on the fundamentals of surfactant science. Surfactant flooding has highest efficiency when a surfactant is chosen whose optimum conditions match the reservoir parameters. The phase behavior of the injected surfactant slug and the crude oil depends strongly on temperature and water salinity, which directly influence the ability to reduce the interfacial tension. Near-fresh water injection brines do not have major precipitation issues, but they require surfactants of certain hydrophobicity. This is caused by the fact that decreasing salinity at constant temperature favors the interaction of the surfactant with the aqueous phase and increases its water solubility. In order to counterbalance the preference for the aqueous phase the hydrophobicity of the surfactant has to be increased to force the formation of a microemulsion middle phase. By this procedure the water – surfactant – crude oil interaction is adjusted, resulting in Winsor III type phase behavior and the desired ultra-low interfacial tension regime. However, increasing the surfactant hydrophobicity decreases its water solubility. This can disturb its transport within the injection water towards the crude oil in the formation. Our results provide a good overview of the challenges and advantages in the application of amphiphilic compounds at low salinity. The water solubility and the phase behavior of different classes of surfactants and their blends are shown. Several approaches are investigated to overcome these challenges or find ways to deal with them. The perils of blending surfactants are addressed and the question is posed how the appearance of the injection solution affects its performance. In the light of a growing interest in smart-water flooding technology the salinity in mature reservoirs is expected to drop significantly. This paper compares different approaches for the selection of appropriate surfactants when dealing with very low saline waters. To not impede the application of surfactants in a later stage of the reservoir life cycle and to achieve maximized outcome it has to be planned carefully if a smart-water flood shall be applied.

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