Immiscible Microemulsion Flooding

1977 ◽  
Vol 17 (02) ◽  
pp. 129-139 ◽  
Author(s):  
Robert N. Healy ◽  
Ronald L. Reed
Keyword(s):  
Interfacial Tension ◽  
Oil Recovery ◽  
Surfactant Concentration ◽  
Miscible Displacement ◽  
Immiscible Displacement ◽  
Microemulsion System ◽  
Core Flooding ◽  
Middle Phase ◽  
Interfacial Tensions ◽  
Excess Water

Abstract Economical microemulsion flooding inevitably involves microemulsion phases that are immiscible with water, oil, or both. Oil recovery is largely affected by displacement efficiency in the immiscible regime. Therefore, it is pertinent to study this immiscible aspect in relation to variables that affect phase behavior and interfacial tension between phases. This is accomplished through core flooding experiments wherein microemulsions immiscible with oil and/or water are injected to achieve enhanced oil recovery. One advantage of such an immiscible microemulsion flood is that surfactant concentration can be small and slug size large, thereby reducing deleterious effects of reservoir heterogeneity; a disadvantage is that the temporary high oil recovery accompanying locally miscible displacement before slug breakdown is reduced. Final oil saturation remaining after lower, middle, and upper-phase microemulsion floods is studied as a function of salinity, cosolvent, temperature, and surfactant structure; and results are related to interfacial tension, phase behavior and solubilization parameters. A conclusion is that immiscible microemulsion flooding is an attractive alternative to conventional microemulsion processes. Oil recovery obtained from microemulsion slugs is correlated with capillary number based on what is called the controlling interracial tension. Physically, this means the least effective of the Physically, this means the least effective of the displacement processes at the slug front or rear determines the flood outcome. Finally, a screening procedure is developed that is useful for either immiscible or conventional microemulsion floods and that can reduce the number of core floods required to estimate oil recovery potential for a candidate microemulsion system. potential for a candidate microemulsion system Introduction This is the fourth in a sequence of papers dealing with miscible and immiscible aspects of microemulsion flooding. The first of these papers identified micellar structures above the binodal curve and showed how the region of miscibility could be maximized at the expense of the multiphase region, thereby prolonging locally miscible displacement. This was accomplished by varying salinity, and the notion of optimal salinity was introduced as that which minimized the extent of the multiphase region. Interfacial tensions within the multiphase region were measured and found to vary nearly three orders of magnitude, depending on WOR and surfactant concentration. Careful isothermal pre-equilibration of bulk phases was a requisite to all interfacial tension measurements. The second paper emphasized core flooding behavior and distinguished locally miscible displacement before slug breakdown, from immiscible displacement occurring thereafter. Fractional oil flow was correlated with capillary number and it was found that an effective immiscible displacement cannot be distinguished from the locally miscible case. Further, during an effective flood, the greater part of the oil was recovered during the immiscible regime. Finally, it was shown that micellar structure within the miscible region is not of itself an important variable. Having determined that the immiscible aspect of a microemulsion flood was important and dominant, the third paper dealt extensively with the multiphase region. Microemulsions were classified as lower-phase (1), upper-phase, (u), or middle-phase (m) in equilibrium with excess oil, excess water, or both excess oil and water, respectively. Transitions among these phases were studied and systematized as functions of a number of variables. Solubilization parameters for oil and water in microemulsions were introduced and shown to correlate interfacial tensions. The middle-phase was identified as particularly significant because microemulsion/excess-oil and microemulsion/ excess-water tensions could be made very low simultaneously. In this paper, the sequence is continued by introducing the notion of an immiscible microemulsion flood as one having an injection composition in the neighborhood of the multiphase boundary. SPEJ P. 129

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

1981 ◽  
Vol 21 (05) ◽  
pp. 593-602 ◽  
Author(s):  
E. Ruckenstein
Keyword(s):  
Interfacial Tension ◽  
Oil Recovery ◽  
Phase Inversion ◽  
The Other ◽  
Dispersed Phase ◽  
Middle Phase ◽  
Inversion Point ◽  
Interfacial Tensions ◽  
Dispersed Medium ◽  
Oil Water

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^

Interfacial Tension and Phase Behavior of Surfactant Systems

1978 ◽  
Vol 18 (04) ◽  
pp. 242-252 ◽  
Author(s):  
W.H. Wade ◽  
James C. Morgan ◽  
R.S. Schechter ◽  
J.K. Jacobson ◽  
J.L. Salager
Keyword(s):  
Molecular Weight ◽  
Interfacial Tension ◽  
Crude Oil ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Surfactant Concentration ◽  
Low Molecular Weight ◽  
Middle Phase ◽  
Surfactant Systems ◽  
Low Tension

Abstract The conditions necessary for optimum low tension and phase behavior at high surfactant concentrations are compared with those required at low surfactant concentrations, where solubilization effects are not usually visible. Major differences in tension behavior between the high and low concentration systems may be observed when the surfactant used contains a broad spectrum of molecular species, or if a higher molecular weight alcohol is present, but not otherwise in the systems studied. We compared the effects of a number of aliphatic alcohols on tension with phase behavior. An explanation of these results, and also of other observed parameter dependences, is proposed in terms of changes in surfactant chemical potential. Surfactant partitioning data is presented that supports this concept. Introduction Taber and Melrose and Brandner established that tertiary oil recovery by an immiscible flooding process should be possible at low capillary process should be possible at low capillary numbers. In practice, the required capillary number, which is a measure of the ratio of viscous to capillary forces governing displacement of trapped oil, may be achieved by lowering the oil/water interfacial tension to about 10(-3) dyne/cm, or less. Subsequent research has identified a number of surfactants that give tensions of this order with crude oils and hydrocarbon equivalents. Interfacial tension studies tended to fall into two groups. Work at low surfactant concentrations, typically 0.7 to 2 g/L, has established that a crude oil may be assigned an equivalent alkane carbon number. Using pure alkanes instead of crude oil has helped the study of system parameters affecting low tension behavior. Important parameters examined include surfactant molecular structure, and electrolyte concentration, surfactant concentration, surfactant molecular weight, and temperature. At higher surfactant concentrations, interfacial tension has been linked to the phase behavior of equilibrated systems. When an aqueous phase containing surfactant (typically 30 g/L), electrolyte, and low molecular weight alcohol is equilibrated with a hydrocarbon, the surfactant may partition largely into the oil phase, into the aqueous phase, or it may be included in a third (middle) phase containing both water and hydrocarbon. Low interfacial tensions occur when the solubilization of the surfactant-free phase (or phases) into the surfactant-containing phase is maximized. Maximum solubilization and minimum tensions have been shown to be associated with the formation of a middle phase. Both the high and low surfactant concentration studies have practical importance because even though a chemical flood starts at high concentration, degradation of the injected surfactant slug will move the system toward lower concentrations. This study investigates the relationship between tension minima found with low concentration systems, and low tensions found with equivalent systems at higher surfactants concentrations, particularly those in which third-phase formation occurs. Many of the systems studied here contain a low molecular weight alcohol, as do most surfactant systems described in the literature or proposed for actual oil recovery. Alcohol originally was added to surfactant systems to help surfactant solubility, but can affect tensions obtained with alkanes, and with refined oil. Few systematic studies of the influence of alcohol on tension behavior exist. Puerto and Gale noted that increasing the alcohol Puerto and Gale noted that increasing the alcohol molecular weight decreases the optimum salinity for maximum solubilization and lowest tensions. The same conclusions were reached by Hsieh and Shah, who also noted that branched alcohols had higher optimum salinities than straight-chain alcohols of the same molecular weight. Jones and Dreher reported equivalent solubilization results with various straight- and branched-chain alcohols. In this study, we fix the salinity of each system and instead vary the molecule; weight of the hydrocarbon phase. SPEJ P. 242

scholarly journals The Importance of Microemulsion for the Surfactant Injection Process in Enhanced Oil Recovery

2021 ◽  
Author(s):  
Rini Setiati ◽  
Muhammad Taufiq Fathaddin ◽  
Aqlyna Fatahanissa
Keyword(s):  
Interfacial Tension ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Recovery Process ◽  
Injection System ◽  
Type I ◽  
Middle Phase ◽  
Interface Tension ◽  
Lower Phase ◽  
Injection Process

Microemulsion is the main parameter that determines the performance of a surfactant injection system. According to Myers, there are four main mechanisms in the enhanced oil recovery (EOR) surfactant injection process, namely interface tension between oil and surfactant, emulsification, decreased interfacial tension and wettability. In the EOR process, the three-phase regions can be classified as type I, upper-phase emulsion, type II, lower-phase emulsion and type III, middle-phase microemulsion. In the middle-phase emulsion, some of the surfactant grains blend with part of the oil phase so that the interfacial tension in the area is reduced. The decrease in interface tension results in the oil being more mobile to produce. Thus, microemulsion is an important parameter in the enhanced oil recovery process.

Optimization of Surfactant and Polymer for SP Flooding of Zahra Oil

2014 ◽  
Vol 535 ◽  
pp. 701-704 ◽  
Author(s):  
Peng Lv ◽  
Ming Yuan Li ◽  
Mei Qin Lin
Keyword(s):  
Interfacial Tension ◽  
Polymer Solution ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
High Viscosity ◽  
Oil Field ◽  
Interfacial Tensions

Producing ultra-low interfacial tensions and maintaining high viscosity is the most important mechanism relating to SP flooding for enhanced oil recovery. The interfacial tension between surfactant (PJZ-2 and BE)/polymer solution and Zahra oil was evaluated in the work. Based on the evaluatiojn of interfacial tension, the polymer FP6040s/surfactant BE system was selected as the SP flooding system for Zahra oil field.

Low Interfacial Tensions Involving Mixtures of Surfactants

1977 ◽  
Vol 17 (02) ◽  
pp. 122-128 ◽  
Author(s):  
W.H. Wade ◽  
J.C. Morgan ◽  
J.K. Jacobson ◽  
R.S. Schechter
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Surfactant Concentration ◽  
Electrolyte Concentration ◽  
Hydrocarbon Mixture ◽  
Surfactant Mixtures ◽  
Interfacial Tensions ◽  
System Variables ◽  
Low Tension ◽  
Scaling Rule

Abstract The interfacial tension of surfactant mixtures with hydrocarbons obeys a simple scaling rule. Many apparently inert surfactants give low tensions when in mixtures; the scaling rule still applies to these mixtures. The influence of surfactant structure and molecular weight on low-tension behavior is examined, and the application of these results to the optimization of surfactant flooding systems is discussed. Introduction It has been shown that the interfacial-tension behavior of a given crude oil with a surfactant solution of the sulfonate type may be modeled by replacing the crude oil with one particular alkane. The number of carbon atoms in the alkane is referred to as the equivalent alkane carbon number (EACN) of the crude oil, and this EACN is independent of the surfactant used (at fixed standard conditions). This equivalency of a crude oil and an alkane is a result of the simple averaging behavior of hydrocarbons when mixed. Any hydrocarbon may be assigned an EACN value. For instance, when homologous series of alkyl benzenes and alkanes are run against the petroleum sulfonate TRS 10-80 at 2 gm/liter of surfactant with 10 gm/liter NaCl present, heptyl benzene and heptane, respectively, give minimum interfacial tensions, a. The EACN of heptyl benzene is 7, since it is equivalent to heptane. A simple averaging rule will give the EACN of a hydrocarbon mixture : (1) where x is the mole fraction of the ith component. Thus, an equimolar mixture of undecane (EACN 11) and heptyl benzene (EACN 7) has an EACN of 9. If a surfactant gives a low (minimum) sigma against nonane (EACN 9), it will also give a low sigma against the above mixture. Eq. 1 implies that a crude oil, which is a multicomponent hydrocarbon mixture, may be assigned an EACN. This has been verified experimentally. For example, Big Muddy field crude oil has an EACN of 8.5. Therefore, any surfactant phase giving a minimum tension against an equimolar mixture of octane and nonane gives a low tension against Big Muddy crude. All crude oils rested to date have EACN's ranging from 6 to 9. For a given surfactant, the alkane of minimum tension (min) may be affected by the electrolyte concentration or type, the temperature, the surfactant concentration, or the presence of a cosurfactant. These system variables may be adjusted until the nmin for a surfactant matches exactly the EACN of a crude oil. For any particular surfactant, many different combinations of variables will give the same n min value; therefore, there are many possible systems, each with n = EACN, available for crude oil recovery. In practice, however, the system variables may be manipulated to a limited extent only. The temperature of an oil field is fixed, and the surfactant concentration is limited by considerations of solubility and expense. The electrolyte concentration and type is partly determined by oilfield conditions and is limited by the effect on surfactant solubility. These limitations mean that many of the surfactants presently available on a large enough scale for use in low-tension flooding will not give minimum tensions in the range required (n of 6 to 9). This paper shows how minimal sigma's in the required range may be found for some of these "off-scale" surfactants when they are used in surfactant mixtures. The hypothesis tested here is that surfactant mixtures average in a manner analogous to the averaging of hydrocarbons in the oil phase. It will be shown that each surfactant component may be assigned an n value and that the alkane of minimum tension of a mixture of surfactants, (n), is then given by (2) where x is now the mole fraction of the ith component of the surfactant mixture. This greatly extends the number of surfactants that may be considered as candidates for use in low interfacial-tension flooding. SPEJ P. 122

Competing Roles of Interfacial Tension and Surfactant Equivalent Weight in the Development of a Chemical Flood

1982 ◽  
Vol 22 (04) ◽  
pp. 472-480 ◽  
Author(s):  
S.L. Enedy ◽  
S.M. Farouq Ali ◽  
C.D. Stahl
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Oil Recovery ◽  
Salt Concentration ◽  
Surfactant Concentration ◽  
Evolutionary Process ◽  
Chemical Flooding ◽  
Equivalent Weight ◽  
Residual Oil ◽  
Tertiary Oil Recovery

Abstract This investigation focused on developing an efficient chemical flooding process by use of dilute surfactant/polymer slugs. The competing roles of interfacial tension (IFT) and equivalent weight (EW) of the surfactant used, as well as the effect of different types of preflushes on tertiary oil recovery, were studied. Volume of residual oil recovered per gram of surfactant used was examined as a function of these variables and slug size. Tertiary oil recovery increased with an increase in the dilute surfactant slug size and buffer viscosity. However, low IFT does not ensure high oil recovery. An increase in surfactant EW used actually can lead to a decrease in oil recovery. Tertiary oil recovery was also sensitive to preflush type. Reasons for the observed behavior are examined in relation to the surfactant properties as well as to adsorption and retention. Introduction Two approaches are being used in development of surfactant /polymer-type chemical floods:a small-PV slug of high surfactant concentration, ora large-PV slug of low surfactant concentration. This study deals with the latter-i.e., dilute aqueous slugs (with polymer added in many cases) containing less than or equal 2.0 wt% sulfonates and about 0. 1 wt% crude oil. Because the dilute slug contains little of the dispersed phase, an aqueous surfactant slug usually is unable to displace the oil miscibly; however, residual brine is miscible with the slug if the inorganic salt concentration is not excessive. The dilute, aqueous petroleum sulfonate slug lowers the oil/water IFT. overcoming capillary forces. This process commonly is referred to as locally immiscible oil displacement. Objectives The objective of this work was to develop an efficient dilute surfactant/polymer slug for the Bradford crude with a variety of sulfonate combinations. Effects of varying the slug characteristics such as equivalent weight, IFT, salt concentration, etc. on tertiary oil recovery were examined. Materials and Experimental Details The petroleum sulfonates and the dilute slugs used in this study are listed in Tables 1 and 2, respectively. The crude oil tested was Bradford crude 144 degrees API (0.003 g/cm3), 4 cp (0.004 Pa.s)]. The polymer solutions were prefiltered and driven by brines of various concentrations (0.02, 1.0, and 2.0% NACl). In many cases, the polymer was added to the slug. Conventional coreflood equipment described in Ref. 3 was used. Berea sandstone cores (unfired) 2 in, (5 cm) in diameter and 4 ft (1.3 m) in length were used for all tests, with a new core for each test. Porosity ranged from 19.3 to 21.0%, permeability averaged 203 md, and the waterflood residual oil saturation averaged 33.1%. IFT's were measured by the spinning drop method. Viscosities were measured with a Brookfield viscosimeter and are reported here for 6 rpm (0.1 rev/s). The dilute slugs containing polymer exhibited non-Newtonian behavior. Without polymer the behavior was Newtonian. Sulfonate concentration in the oleic phase was determined by an infrared spectrophotometer, while the concentration in the aqueous phase was measured by ultraviolet (UV) absorbance analysis. Discussion of Results Slug development in this investigation was an evolutionary process. Dilute slugs were developed and core tested in a sequential manner (Table 2). Slugs 100 through 200 yielded insignificant ternary oil recoveries (largely because of excessive adsorption and retention), but the results helped determine improvements in slug compositions and in the overall chemical flood. This paper gives results for the more efficient slugs only. SPEJ P. 472^

scholarly journals Characterization and oil recovery enhancement by a polymeric nanogel combined with surfactant for sandstone reservoirs

2020 ◽  
Author(s):  
Mustafa Almahfood ◽  
Baojun Bai
Keyword(s):  
Interfacial Tension ◽  
Oil Recovery ◽  
Suspension Polymerization ◽  
Sodium Dodecyl ◽  
Polymerization Process ◽  
Core Flooding ◽  
A Value ◽  
Fixed Concentration ◽  
Oil In Water ◽  
Recovery Mechanisms

Abstract The characterization and enhanced oil recovery mechanisms of a nanosized polymeric cross-linked gel are presented herein. A negatively charged nanogel was synthesized using a typical free radical suspension polymerization process by employing 2-acrylamido 2-methyl propane sulfonic acid monomer. The synthesized nanogel showed a narrow size distribution with one peak pointing to a predominant homogeneous droplet size. The charged nanogels were also able to adsorb at the oil–water interfaces to reduce interfacial tension and stabilize oil-in-water emulsions, which ultimately improved the recovered oil from hydrocarbon reservoirs. In addition, a fixed concentration of negatively charged surfactant (sodium dodecyl sulfate or SDS) was combined with different concentrations of the nanogel. The effect of the nanogels combined with surfactant on sandstone core plugs was examined by running a series of core flooding experiments using multiple flow patterns. The results show that combining nanogel and SDS was able to reduce the interfacial tension to a value of 6 Nm/m. The core flooding experiments suggest the ability of the nanogel, both alone and combined with SDS, to improve the oil recovery by a factor of 15% after initial seawater flooding.

scholarly journals Experimental Investigation of Surfactant Partitioning in Pre-CMC and Post-CMC Regimes for Enhanced Oil Recovery Application

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2319 ◽  
Author(s):  
Ahmed Fatih Belhaj ◽  
Khaled Abdalla Elraies ◽  
Mohamad Sahban Alnarabiji ◽  
Juhairi Aris B M Shuhli ◽  
Syed Mohammad Mahmood ◽  
...  
Keyword(s):  
Surface Tension ◽  
High Temperature ◽  
Interfacial Tension ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
High Performance ◽  
Surfactant Concentration ◽  
Effect Of Temperature ◽  
Sweep Efficiency ◽  
Partitioning Coefficient

The applications of surfactants in Enhanced Oil Recovery (EOR) have received more attention in the past decade due to their ability to enhance microscopic sweep efficiency by reducing oil-water interfacial tension in order to mobilize trapped oil. Surfactants can partition in both water and oil systems depending on their solubility in both phases. The partitioning coefficient (Kp) is a key parameter when it comes to describing the ratio between the concentration of the surfactant in the oil phase and the water phase at equilibrium. In this paper, surfactant partitioning of the nonionic surfactant Alkylpolyglucoside (APG) was investigated in pre-critical micelle concentration (CMC) and post-cmc regimes at 80 °C to 106 °C. The Kp was then obtained by measuring the surfactant concentration after equilibration with oil in pre-cmc and post-cmc regimes, which was done using surface tension measurements and high-performance liquid chromatography (HPLC), respectively. Surface tension (ST) and interfacial tension (IFT) behaviors were investigated by performing pendant and spinning drop tests, respectively—both tests were conducted at high temperatures. From this study, it was found that APG was able to lower IFT as well as ST between water/oil and air/oil, and its effect was found to be more profound at high temperature. The partitioning test results for APG in pre-cmc and post-cmc regimes were found to be dependent on the surfactant concentration and temperature. The partitioning coefficient is directly proportional to IFT, where at high partitioning intensity, IFT was found to be very low and vice versa at low partitioning intensity. The effect of temperature on the partitioning in pre-cmc and post-cmc regimes had the same impact, where at a high temperature, additional partitioned surfactant molecules arise at the water-oil interface as the association of molecules becomes easier.

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