Trends to Attain a Lower Interfacial Tension in a Revisited Pure Alkyl Polyethyleneglycol Surfactant–Alkane–Water Ternary System. Basic Concepts and Straightforward Guidelines for Improving Performance in Enhanced Oil Recovery Formulations

Abstract

Surfactant–oil–water systems exhibit a low interfacial tension minimum when the interactions between the adsorbed surfactant with water exactly coincide with its interactions with oil. This occurrence takes place at the so‐called optimum formulation, which was conceptually derived by Winsor in the 1950s and rendered by numerical correlations for enhanced oil recovery in the 1970s. The actual low value of the interfacial tension minimum has been found to increase or decrease with formulation variables and though some hints are available, no general relationship has been reported up to now, probably because too many variables are involved in complex interactions. It is shown in the present article that a linear relationship between low‐tension performance and formulation variables can be found for very simple ternary systems containing a pure ethoxylated alcohol, n‐alkane and water at variable temperature, i.e., when there are only four degrees of freedom. In such a case the iso‐performance contours studied in bi‐dimensional spaces are reported to be almost straight lines and as a consequence the path to lower the tension through formulation adjustments is easy to find as being perpendicular as possible to the contours. On the other hand, it is shown that displacing the limit of restrictions like the surfactant precipitation boundary is a priority issue, thus justifying many trends which have been proposed on empirical grounds in the past years. The reported simple guidelines for a simple surfactant–oil–water ternary is likely to considerably facilitate the formulator's work in a real system with a score of formulation variables.

Complexation of Surfactant/β‐Cyclodextrin to Inhibit Surfactant Adsorption onto Sand, Kaolin, and Shale for Applications in Enhanced Oil Recovery Processes. Part III: Oil Displacement Evaluation

“…Thus, the optimum concentration of SDS was considered to be 0.5 wt% for this system. According to Salager et al ([9], p. 199) ''surfactant-oilwater systems exhibit a low interfacial tension minimum when the interactions between the adsorbed surfactant with water exactly coincide with its interactions with oil…The actual low value of the interfacial tension minimum has been found to increase or decrease with formulation variables and …no general relationship have been reported up to now, probably because too many variables are involved in complex interactions'' [8].Therefore, the experimental observations for the specific system evaluated in this work indicates that the lowest interfacial tension (minimum IFT value) for the SDS-Stoney Creek Oil-Brine (2 wt% brine) system is 0.056 mN/m at the experimental conditions of this work. Figure 3 presents the IFT as a function of b-CD/SDS molar ratio, in which the IFT decreases as the b-CD/SDS molar ratio increases until an equimolar ratio is reached, after which the reverse process takes place, thus the IFT increases as the b-CD/SDS ratio is further increased.…”

“…The mechanism of oil recovery via surfactant flooding is the reduction of the interfacial tension (IFT) between the aqueous phase (brine) and crude oil to ultralow interfacial tension values. The values of IFT are commonly reduced from 30 mN/m (dyne/cm) to as low as 0.001 mN/m (dyne/ cm) or less, which are several orders of magnitude below the typical IFT values of brine-crude oil systems within oil reservoirs [3,[8][9][10].…”

Ethylation of Di‐rhamnolipids: A Green Route to Produce Novel Sugar Fatty Acid Nonionic Surfactants

“…By separating the contributions of different formulation parameters, the HLD concept can define the surfactant characteristics with high accuracy, about ±0.1 units, which is much better than the usual ±2 unit approximation attainable by the HLB value [41]. According to the above concept, it has been recently shown that for pure n-alcohol ethoxylate-alkane-water systems, without salt and alcohol, the HLD values can be calculated by the following equation [44]:…”

Complexation of Surfactant/β‐Cyclodextrin to Inhibit Surfactant Adsorption onto Sand, Kaolin, and Shale for Applications in Enhanced Oil Recovery Processes. Part I: Static Adsorption Analysis

“…On a pore scale, surfactants reduce the interfacial tension between oil and water to ultralow values, which decreases capillary forces and releases oil from the rock into the driving fluid. Therefore, under the condition of a high capillary number, oil droplets can be efficiently mobilized [1][2][3].…”