The Phase Behavior of Simple Salt-Tolerant Sulfonates
- Y. Barakat (U. of Texas) | L.N. Fortney (U. of Texas) | C. LaLanne-Cassou (U. of Texas) | R.S. Schechter (U. of Texas) | W.H. Wade (U. of Texas) | U. Weerasooriya (U. of Texas) | S. Yiv (U. of Texas)
- Document ID
- Society of Petroleum Engineers
- Society of Petroleum Engineers Journal
- Publication Date
- December 1983
- Document Type
- Journal Paper
- 913 - 918
- 1983. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 4.3.4 Scale, 5.2.1 Phase Behavior and PVT Measurements, 4.1.5 Processing Equipment
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Alkane and olefin sulfonates can be used to produce optimal microemulsion formulations having very high salinity tolerance (including divalent ion) while maintaining large solubilization parameters and low interfacial tensions (IFT's). Such molecules require elevated temperatures or higher alcohol concentrations to suppress liquid crystal formation, As in other species, solubilization is inversely related to width of the three-phase regime, and IFT and solubilization are strongly coupled.
Because of their availability in commercial quantities, their ease of manufacture. and their relatively low cost, sulfonates, either petroleum or synthetic, were the surfactants first selected for extensive evaluation and study in polymer/micellar flooding. As, the apparent surfactants of choice, they have been studied extensively in our laboratory. These studies recently culminated in correlations that interrelate the width of the three-phase region, the solubilization parameter ( *), and the IFT ( *), both at optimum, for specific alkyl benzene sulfonate structures. In this latter study, it was found that branching in the surfactants hydrocarbon tail influenced both * and *; specifically, decreasing the branching tended to increase * and decrease *. In other words, surfactants with linear tails perform better if minimal IFT is the prime consideration. Other potential serious problems remain in the use of either petroleum or synthetic sulfonates. In particular. they will seldom tolerate salinities greater than 5% or calcium ion concentrations greater than 0.05%. This, of course, would remove many fields from consideration for surfactant flooding. One method for reducing the sensitivity of sulfonates to increased ionic strengths is to blend nonionic surfactants with the sulfonates. For this reason we have examined the relationship that exists between the structural features of polyethyleneoxide alkyl phenols and the performance of these nonionic surfactants. phenols and the performance of these nonionic surfactants. Although it is possible to achieve a high level of tolerance to cations. two other potential problems are introduced i.e., the possible chromatographic separation of the sulfonates and nonionics and fractionation within the nonionic species itself between oil and aqueous phases. This problem has been recognized and recently a number of patents have been issued wherein the nonionic and anionic patents have been issued wherein the nonionic and anionic polar groups are built into the same molecule. As a polar groups are built into the same molecule. As a specific example, octadecyl phenol first has ethylene oxide added, followed by sulfonation. Such molecules represent a new level of sophistication. Thus the ideal surfactant system would be one that, if possible, consists of a single molecular species or of possible, consists of a single molecular species or of structures that are very similar, so that chromatographic effects can be avoided, and that will function at high ionic strength, tolerate divalent ions, and exhibit reasonable, if not outstanding, performance. Such a system has not yet been reported. In this paper we report some results for the simplest possible surfactant structure, alkane sulfonates, and show that, unexpectedly, its values of solubilization are much larger than those found for alkyl benzene sulfonates and that it also functions well at both high ionic strengths and in the presence of large concentrations of divalent ion. In presence of large concentrations of divalent ion. In addition, results are presented to demonstrate that -olefin sulfonates exhibit similar performance to the pure monoisomeric surfactants studied in this paper.
Secondary alkane sulfonates were prepared by the synthesis route shown in Fig. 1.
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