Surfactant Phase Behavior and Retention in Porous Media

Abstract

Glover, C.J.,* SPE-AIME, Exxon Production Research Puerto, M.C., SPE-AIME, Puerto, M.C., SPE-AIME, Exxon Production Research Co. Maerker, J.M., SPE-AIME, Exxon Production Research Co. Sandvik, E.L., SPE-AIME, Exxon Production Research Co. Abstract Surfactant retention in reservoir rock is a major factor limiting effectiveness of oil recovery using microemulsion flooding processes. Effects of salinity and surfactant concentration on microemulsion phase behavior have a significant impact on relative phase behavior have a significant impact on relative magnitudes of retention attributed to adsorption vs entrapment of immiscible microemulsion phases.Surfactant retention levels were determined by effluent sample analyses from microemulsion flow tests in Berea cores. Data for single surfactant systems containing NaCl only and multicomponent surfactant systems containing monovalent and divalent cations are included. Retention is shown to increase linearly with salinity at low salt concentrations and depart from linearity with higher retentions above a critical salinity. This departure from linearity is shown to correlate with formation of upper-phase microemulsions. The linear trend, therefore, is attributed to surfactant adsorption, and retention levels in excess of this trend are attributed to phase trapping.Divalent cations are shown to influence microemulsion phase behavior strongly through formation of divalent-cation sulfonate species. A useful method for predicting phase behavior in systems containing divalent cations is described. This method combines equilibrium expressions with a relationship defining the contribution of each surfactant component to optimal salinity. Observed experimental data are compared with predicted data. Introduction Two essential criteria that must be met for successful recovery of residual oil by chemical flooding arevery low interfacial tensions between the chemical bank and residual oil and between the chemical bank and drive fluid andsmall surfactant retention losses to reservoir rock. If retention is excessive, interfacial tensions eventually will become high enough to retrap residual oil in the remainder of the reservoir.Previous studies have described several mechanisms responsible for surfactant retention in porous media. These include adsorption, porous media. These include adsorption, precipitation, partitioning into a residual oil phase, precipitation, partitioning into a residual oil phase, and entrapment of immiscible microemulsion phases. Of particular interest is Trushenski's discussion of microemulsion phase trapping as a consequence of surfactant-polymer interaction, and a supporting statement that similar behavior often was observed when microemulsions were diluted with polymer-free brine. Here, we attempt to provide some understanding of this surfactant dilution phenomenon by examining phase behavior as a function of salinity, divalent-ion content, and surfactant concentration. Experimental Procedures Surfactant Systems Two surfactant systems were used in this study. (Specific microemulsion compositions are discussed later.) One system was the 63:37 volumetric mixture of the monoethanol amine salt of dodecylorthoxylene sulfonic acid and tertiary amyl alcohol (MEAC12OXS/TAA) described by Healy et al. The oil component for these microemulsions was a mixture of 90% Isopar M TM and 10% Heavy Aromatic Naptha.(TM)** The brine contained NaCl only. SPEJ P. 183

Microemulsions: a novel approach to enhanced oil recovery: a review

“…Healy and Reed (1977) Nonyl surfactant (anionic) It was reported that ultralow interfacial tension between microemulsion-oil systems increases the oil recovery efficiency 4. Glover et al (1979) Monoethanol amine salt of dodecylorthoxylene sulfonic acid (anionic)…”

“…For good efficiency of microemulsions and reasonable oil recovery efficiency, the surfactant must be chemically stable, reduce the interfacial tension between brine and crude oil and displace the oil without significant surfactant loss by adsorption on the reservoir rocks. Retention of surfactant is a most restrictive factor that affects the efficiency of the oil recovery process by microemulsion flooding (Glover et al 1979). The microemulsion slug partitions into three phases such as a surfactant-rich middle-phase and surfactant-lean brine and oil phases Reed 1974, 1977;Healy et al 1976) in the intermediate salinity range.…”

Chemical Flooding in Naturally Fractured Reservoirs: Fundamental Aspects and Field-Scale Practices

“…These factors include the surfactant types (Hayes et al, 1979), chemistry (Enedy et al, 1982;Hirasaki et al, 1983;Krumrine et al, 1982), phase behavior (Glover et al, 1979;Novosad, 1982), chemicals adsorption (Austad et al, 1997), surfactant precipitation and redissolution (Somasundaran et al, 1984), chromatographic separation of chemicals (Li et al, 2009), surfactant convection (Ramirez et al, 1980), surfactant stability (Handy et al, 1982), chemicals loss (Friedmann, 1986), dispersion (Hirasaki, 1981), surfactant systems formulation (Salager et al, 1979), wettability , reservoir rock structure and morphology (Dullien et al, 1972;Yadali Jamaloei and Kharrat, 2009;Yadali Jamaloei et al, 2011a), and reservoir heterogeneity (Ma et al, 2007). The morphology and heterogeneity of the reservoir rock play a significant role in the behavior of chemical flooding processes.…”

Biosurfactants Produced From Agriculture Process Waste Streams To Improve Oil Recovery in Fractured Carbonate Reservoirs

“…Adsorption of surfactants considered for EOR applications has been studied extensively. [16][17][18][19][20][21] Surfactant retention was evaluated by comparing the adsorption isotherm of surfactin with that of the benchmark chemical surfactant.…”