PHASE AND INTERFACIAL TENSION BEHAVIOR OF NONIONIC SURFACTANTS

Novel Nonylphenol Polyethoxylated Based Surfactants for Enhanced Oil Recovery for High-Mineralization Carbonate Reservoir

Surfactant flooding can mobilize trapped oil and change the wettability of the rock to be more hydrophilic, which increases the oil recovery factor. However, the selection of surfactants is difficult in the case of high salinity conditions. In this work, we synthesized three novel anionic-nonionic surfactants based on widely used nonionic surfactant nonylphenol polyethoxylated (NPEO) and evaluated their efficiencies for enhanced oil recovery (EOR) in high salinity water (20% NaCl). The modified surfactants showed a decrease in interfacial tension (IFT) up to 10 times compared with the nonionic precursor. All surfactants had changed the wettability of rock to be more hydrophilic according to contact angle measurements. The effectiveness of surfactants was proved by spontaneous imbibition experiments, in which the synthesized surfactants showed a better displacement efficiency and increased oil production by 1.5–2 times. Filtration experiments showed an increase in oil recovery factor by 2–2.5 times in comparison with the nonionic NPEO. These promising results prove that the synthesis of new surfactants by modifying NPEO is successful and indicate that these novel surfactants have a great potential for EOR in high salinity reservoirs.

How to Use the Normalized Hydrophilic-Lipophilic Deviation (HLDN) Concept for the Formulation of Equilibrated and Emulsified Surfactant-Oil-Water Systems for Cosmetics and Pharmaceutical Products

The effects of surfactant molecules involved in macro-, mini-, nano-, and microemulsions used in cosmetics and pharmaceuticals are related to their amphiphilic interactions with oil and water phases. Basic ideas on their behavior when they are put together in a system have resulted in the energy balance concept labeled the hydrophilic-lipophilic deviation (HLD) from optimum formulation. This semiempirical equation integrates in a simple linear relationship the effects of six to eight variables including surfactant head and tail, sometimes a cosurfactant, oil-phase nature, aqueous-phase salinity, temperature, and pressure. This is undoubtedly much more efficient than the hydrophilic-lipophilic balance (HLB) which has been used since 1950. The new HLD is quite important because it allows researchers to model and somehow predict the phase behavior, the interfacial tension between oil and water phases, their solubilization in single-phase microemulsion, as well as the corresponding properties for various kinds of macroemulsions. However, the HLD correlation, which has been developed and used in petroleum applications, is sometimes difficult to apply accurately in real cases involving ionic–nonionic surfactant mixtures and natural polar oils, as it is the case in cosmetics and pharmaceuticals. This review shows the confusion resulting from the multiple definitions of HLD and of the surfactant parameter, and proposes a “normalized” Hydrophilic-Lipophilic Deviation (HLDN) equation with a surfactant contribution parameter (SCP), to handle more exactly the effects of formulation variables on the phase behavior and the micro/macroemulsion properties.

Study of the molecular array behaviour of laurel alkanolamide at the oil–water interface and the high interfacial activity enhanced by an inherent synergistic effect

Intricate H-bonds network existed between alkanolamide and water molecules in oil–water interface layer, which laid the foundation for the high interfacial density and high interfacial efficiency of alkanolamide at the oil–water interface.

How to Attain an Ultralow Interfacial Tension and a Three-Phase Behavior with a Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 2. Performance Improvement Trends from Winsor's Premise to Currently Proposed Inter- and Intra-Molecular Mixtures

The minimum interfacial tension occurrence along a formulation scan at the so-called optimum formulation is discussed to be related to the interfacial curvature. The attained minimum tension is inversely proportional to the domain size of the bicontinuous microemulsion and to the interfacial layer rigidity, but no accurate prediction is available. The data from a very simple ternary system made of pure products accurately follows the correlation for optimum formulation, and exhibit a linear relationship between the performance index as the logarithm of the minimum tension at optimum, and the formulation variables. This relation is probably too simple when the number of variables is increased as in practical cases. The review of published data for more realistic systems proposed for enhanced oil recovery over the past 30 years indicates a general guidelines following Winsor's basic studies concerning the surfactant-oil-water interfacial interactions. It is well known that the major performance benefits are achieved by blending amphiphilic species at the interface as intermolecular or intramolecular mixtures, sometimes in extremely complex formulations. The complexity is such that a good knowledge of the possible trends and an experienced practical know-how to avoid trial and error are important for the practitioner in enhanced oil recovery.

Using emulsion inversion in industrial processes

Emulsion inversion is a complex phenomenon, often perceived as an instability that is essentially uncontrollable, although many industrial processes make use of it. A research effort that started 2 decades ago has provided the two-dimensional and three-dimensional description, the categorization and the theoretical interpretation of the different kinds of emulsion inversion. A clear-cut phenomenological approach is currently available for understanding its characteristics, the factors that influence it and control it, the importance of fine-tuning the emulsification protocol, and the crucial occurrence of organized structures such as liquid crystals or multiple emulsions. The current know-how is used to analyze some industrial processes involving emulsion inversion, e.g. the attainment of a fine nutrient or cosmetic emulsion by temperature or formulation-induced transitional inversion, the preparation of a silicone oil emulsion by catastrophic phase inversion, the manufacture of a viscous polymer latex by combined inversion and the spontaneous but enigmatic inversion of emulsions used in metal working operations such as lathing or lamination.

The Phase Behavior of Simple Salt-Tolerant Sulfonates

Abstract

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.

Introduction

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.

Experimental

Secondary alkane sulfonates were prepared by the synthesis route shown in Fig. 1.

SPEJ

p. 913

Phase Partitioning of Anionic and Nonionic Surfactant Mixtures

Abstract

The efficiency of oil recovery by water flooding can begreatly unproved by the addition of judiciously selected surfactants. Under certain conditions, when surfactant solutions are mixed with oil, micro emulsions are formed that may be in equilibrium with an excess oil (Type 1). anexcess aqueous phase (Type II), or both (Type III). The partitioning of the surfactant between those coexisting equilibrium phases is important to consider in the design of micro emulsion processes for oil recovery. This is particularly true because different phases generally move at differing velocities within the pore spaces of an oil reservoir and therefore fractionation will occur in successive stages along the flow path. This leads to chromatographic separation of the surfactant molecules. The problem is complicated because all surfactant systems are blends of molecules, and chromatographic separation will result in a change in the optimal salinity of the surfactant system. Thus, a system that is initially optimized will not remain optimized during the course of the flood.

To examine the question of selective surfactant partitioning, we varied the composition of oil/water/surfactant equilibrated systems so that they would pass through the optimal formulation region. The partitioning of anionic surfactants into the oil in Type I and Type IIIphase systems was small. Furthermore, binary and ternary mixtures of these surfactants were found tocopartition; that is, little if any fractionation was detectable. Their collective behavior was intermediate between those of the pure components. Nonionic surfactants, unlike anionics, partition substantially into the oil phasein Type I and Type III phase systems. This was found to be an intrinsic properly of the surfactant structure and notunique to those nonionic surfactant systems that are polydisperse.

Selective fractionation also was found for polydispersenonionic surfactants.

Introduction

The appropriate surfactant and cosurfactant system for amicellar/polymer flood to obtain enhanced oil recovery requires careful optimization. The surfactant must beselected so that, under reservoir conditions, the interfacial tension (IFT) between oil and brine is dramatically reduced. Numerous studies have demonstrated that the surfactant/cosurfactant system that produces the required interfacial activity must have solution properties properly balanced between those in the aqueous and oleicphases. This balance is sensitive to the equivalent weight as well as the structure of the surfactant, the concentration and type of alcohol cosurfactant used, the ionic nature of the brine, and the composition of the oil.

Clearly, any mechanism that tends to change one of these factors will also tend to alter the oil recovery efficiency of a given formulation. Thus, it is imperative either to control or to allow for these disrupting mechanisms.

SPEJ

P. 301^

Evaluation of the Interfacial Tension Between a Microemulsion and the Excess Dispersed Phase

Abstract

From a consideration of the thermodynamic stability of microemulsions, one can establish a relation between the interfacial tension y at the surface of the globules and the derivative, with respect to their radius re, of the entropy of dispersion of the globules in the continuous medium. Expressions for the entropy of dispersion are used to show that gamma is approximately proportional to kT/r2e, where k is Boltzmann's constant and T is the absolute temperature. Since the environment of the interface between the microemulsion and the excess dispersed medium is expected to be similar to that at the surface of the globules, these expressions are used to evaluate the interfacial tension between microemulsion and excess dispersed medium. Values between 10 and 10 dyne/cm that decrease with increasing radii are obtained, in agreement with the range found experimentally by various authors. The origin of the very small interfacial tensions rests ultimately in the adsorption of surfactant and cosurfactant on the interface between phases. The effect on the interfacial tension of fluctuations from one type of microemulsion to the other, which may occur near the phase inversion point, is discussed.

Introduction

The system composed of oil, water, surfactant, cosurfactant, and salt exhibits interesting phase equilibria. For sufficiently large concentrations of surfactant, a single phase can be formed either as a microemulsion or as a liquid crystal. In contrast, at moderate surfactant concentrations, two or three phases can coexist. For moderate amounts of salt (NaCl), an oil phase is in equilibrium with a water-continuous microemulsion, whereas for high salinity, an oil-continuous microemulsion coexists with a water phase. At intermediate salinity, a middle phase (probably a microemulsion) composed of oil, water, surfactants, and salt forms between excess water and oil phases. Extremely low interfacial tensions are found between the different phases, with the lowest occurring in the three-phase region. These systems have attracted attention because of their possible application to tertiary oil recovery. It has been shown that the displacement of oil is most effective at very low interfacial tensions.Microemulsions have been investigated with various experimental techniques, such as low-angle X-ray diffraction, light scattering, ultracentrifugation, electron microscopy, and viscosity measurements. These have shown that the dispersed phase consists of spherical droplets almost uniform in size. While it is reasonable to assume that the microemulsions coexisting with excess oil or water contain spherical globules of the dispersed medium, the structure of the middle-phase microemulsion is more complex. Experimental evidence obtained by means of ultracentrifugation indicates, however, that at the lower end of salinity the middle phase contains globules of oil in water, while at the higher end the middle phase is oil continuous. A phase inversion must occur, at an intermediate salinity, from a water-continuous to an oil-continuous microemulsion. The free energies of the two kinds of microemulsions are equal at the inversion point. Since their free energy of formation from the individual components is very small, small fluctuations, either of thermal origin or due to external perturbations, may produce changes from one type to the other in the vicinity of the inversion point. As a consequence, near this point, it is possible that the middle phase is composed of a constantly changing mosaic of regions of both kinds of microemulsions.

SPEJ

P. 593^