A NormalizedHydrophilic–LipophilicDeviation ExpressionHLD_NIs Necessary to Avoid Confusion Close to the Optimum Formulation ofSurfactant‐Oil–WaterSystems

Abstract

The physicochemical conditions to attain a minimum interfacial tension between oil and water were intensively studied in the 1970s when the chemical‐enhanced oil recovery became an emergency with the increase in petroleum cost. Correlations between the formulation variables (salinity, oil nature, surfactant and co‐surfactant nature, temperature, and pressure) required to attain a minimum interfacial tension or a three‐phase behavior, so‐called optimum formulation, were related to the chemical potential concept in the late 1970s. They were then transformed in a generalized hydrophilic–lipophilic deviation (HLD) expression in 2000. Some confusion in the ranking and classification of the surfactant parameters with different scales has occurred in recent years. The aim here is to propose a normalized HLDN expression with the alkane carbon number (ACN) variable scale to clear up the current misunderstanding in the use of different HLD expressions. The use of a single HLDN expression for all systems improves the prediction of formulation effects, but does not eliminate the limitations due to the partitioning of species in surfactant mixtures.

The Oscillatory Spinning Drop Technique. An Innovative Method to Measure Dilational Interfacial Rheological Properties of Brine-Crude Oil Systems in the Presence of Asphaltenes

“…These slight changes allowed to eliminate some confusion and to return to the original pseudo-characterization of the surfactant through the named preferred ACN (so-called Nmin or PACN) in an alkane carbon number scan carried out from the 1970s [40] to last year [41]. The normalized surfactant contribution parameter SCP N in the last proposed HLD N equation [39,42] is not a characteristic of the surfactant. Nevertheless, it allows to make some ranking in the hydrophilicity in the different species and calculate average mixtures' average effects.…”

“…The main use of the HLD equation is that it allows predicting properties of surfactant-oil-water systems with some accuracy for both equilibrated and stirred systems like emulsions and foams [43][44][45][46]. In particular, as far as EOR or dehydration are concerned, for the out of optimum cases (HLD N << 0 or HLD N >> 0) [39,42], high interfacial tensions and high emulsion stability are usual. However, at HLD N = 0 ultralow tension, very unstable emulsions and foams and very low E' and interfacial viscosity values are attained [17,18].…”

“…HLD N equation has been presented recently [39,42] with a surfactant classification parameter (SCP N ) that incorporates both the contribution of the demulsifier and natural surfactants (asphaltenes mainly). When anionic or nonionic surfactants are present HLD N can be expressed as [72]:…”

Formulation in Surfactant Systems: From-Winsor-to-HLDN

“…(2) for nonionic surfactants where S is the salinity of the aqueous phase, for instance, in %wt NaCl, and ACN the number of carbon atoms in an n-alkane oil phase. The K term value was found to considerably depend on the surfactant head group, e.g., 0.16 for alkyl benzene sulfonates, 0.10 for alkyl sulfates or carboxylates, 0.05 for some alkyl polypropoxy sulfate extended surfactants following equation (1), and 1.15 for alkyl ethoxylates following equation (2), as indicated elsewhere [2,38,67,136]. The Δ indicates the corresponding changes of the two variables to compensate each other and return to optimum formulation (B).…”

“…In the particular case of micro-heterogeneous systems, the knowledge attained after many years of research has allowed understanding better the systems' behavior, leading to predictive tools' development that permits ingredient selection to achieve products for specific needs. This has been done by introducing scientific-technical tools in the practical use of surfactant-water-oil systems such as the well-known numerical concept HLD (Hydrophilic-Lipophilic Deviation) and its normalized form HLDN, much more helpful than the previously presented HLB concept [2,38,62,[65][66][67].…”