Fundamental Basis for Action of a Chemical Demulsifier Revisited after 30 Years: HLD_Nas the Primary Criterion for Water-in-Crude Oil Emulsion Breaking

Abstract

In the past four decades, many experimental studies have confirmed the systematic events occurring at the so-called optimum formulation of surfactant−oil−water systems. At this particular formulation, the adsorbed surfactant at the interface interacts equally with water and oil phases, which is supposed to occur according to Winsor theory to attain a three-phase behavior. A low minimum interfacial tension has been confirmed to take place at optimum in hundreds of reports on enhanced oil recovery (EOR). It also coincides with a very definite minimum in emulsion stability, which is looked after for chemical dehydration or crude oil desalting. A normalized hydrophilic−lipophilic deviation (HLD N ) equation was proposed as a multivariable expression that numerically estimates the difference of the surfactant interactions with oil and water. This concept can be applied in crude oil emulsion breaking by considering asphaltenes as being in part a lipophilic surfactant whose effect must be compensated by a hydrophilic demulsifier surfactant to reach the optimum formulation. This is attained through equivalence effects by changing two or more variables, particularly asphaltenes and demulsifier type and concentration, which can be measured through different techniques. Furthermore, in recent studies, asphaltenes are found to exhibit two different lipophilicity levels depending on their self-gathering at or close to the interface, for example, as flat bidimensional nanoaggregates or as three-dimensional clusters. This review presents the know-how reached after 30 years of studying water-incrude oil emulsion breaking (also known as chemical dehydration) using a formulation approach with the HLD multivariable expression. The first part reviews the fundamental concepts and advances on the HLD equation in relation to simple and complex mixtures. The second part presents several strategies aimed at increasing performance and decreasing demulsifier dosification using the HLD N normalized equation in a qualitative way as well as a quantitative way.

Outlook on the Role of Natural Surfactants on Emulsion Stability and Gas Hydrate Antiagglomeration in Crude Oil Systems

“…The presence of two immiscible phases (water and crude oil), emulsifiers (natural-occurring surfactants present in the crude oil, mainly asphaltenes) and mixing energy (pumping, chokes, valves) makes the dispersion of small water droplets into the oil phase possible. While the amount of dispersed water varies, it normally resides in the range of ∼1–90 vol % in the form of droplets whose size lies between 0.1 and 100 μm. − ,, Asphaltenes and other natural surfactants are lipophilic, hence crude oil acts as the emulsion external phase. − Crude oil natural surfactants and some fine-solid particles consolidate an interfacial film that covers water droplets and can avoid/delay coalescence. Therefore, the emulsion stability depends mainly on the nature of that film. ,, Table summarizes the main effects of natural surfactants on crude oil emulsion stability.…”

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

“…Mainly, the optimization of the formulation to attain performance and robustness in the formulation, strategies to minimize chemical dehydrant (demulsifier) dosification, and even the relationship between dilational interfacial rheology and the stability of emulsions in the vicinity and at optimum formulation [113][114][115][116][117][118][119][120][121][122]. Herein, we will not expand on the subject because there are many references, and the current state-of-theart can be found in an actualized review that has been published recently [123]. 7.…”

“…This is why the optimum formulation is the proper interfacial situation to break an emulsion as in crude oil dehydration or wastewater treatment, as discussed elsewhere in the past 30 years [113,114,[116][117][118]253]. More information on the instability at optimum formulation is not included here because it has been recently reviewed elsewhere [254]. Let us now include the effects of the composition, i.e., the surfactant concentration Cs and the water/oil ratio WOR, which locate the situation in a Winsor ternary diagram.…”

“…The demulsifier formulation, i.e., the product to attain an optimum formulation to considerably reduce the W/O emulsion stability, i.e., 10,000 times or more, has been discussed in several hundred papers over the past 40 years. It is not treated here because an extensive review on the chemical demulsifying has been just published [254], showing how much progress has been made in the past decades applying the HLD concept. The review also reports that there are still difficulties because of the complexity of crudes oils and the lack of numerical evaluation of the asphaltenes as lipophilic surfactants.…”

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

“…Mainly, the optimization of the formulation to attain performance and robustness in the formulation, strategies to minimize chemical dehydrant (demulsifier) dosification, and even the relationship between dilational interfacial rheology and the stability of emulsions in the vicinity and at optimum formulation [113][114][115][116][117][118][119][120][121][122]. Herein, we will not expand on the subject because there are many references, and the current state-of-theart can be found in an actualized review that has been published recently [123].…”