Micro-Emulsion Phase Behavior of a Cationic Surfactant at Intermediate Interfacial Tension in Sandstone and Carbonate Rocks (original) (raw)
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All Days, 2014
Test results from mixtures of anionic-cationic surfactants significantly broaden the application scope for conventional chemical Enhanced Oil Recovery methods; these mixtures produced ultra low Critical Micelle Concentrations (CMC) as well as ultra-low interfacial tension (IFT) and high oil solubilization that promote high oil recovery.Mixtures of anionic and cationic surfactants with molar excess of anionic surfactant for EOR applications are described herein. Physical chemistry properties, such as surface tension, CMC, surface excess and area per molecule of individual surfactants and their mixtures were measured by Wilhelmy Plate Method. Morphologies of surfactant solutions, both surfactant-polymer (SP) and alkaline-surfactant-polymer (ASP), were studied by Cryo TEM. Phase behaviors were recorded by visual inspection including with crossed polarizers at different surfactant concentrations and different temperatures. Interfacial tensions between normal octane, crude oil and surfac...
The 1973 Arab oil embargo dramatically called the public's attention to the seriousness and urgency of the energy problem. Oil had been, for several decades, the cheapest energy source and the warnings of farsighted individuals were not sufficient to force the industrial world into considering a long lasting energy policy. The oil embargo did it. Since then governments, industrials and consumers all around the world, particularly in developed western countries, have realized the need for an overall and longterm energy policy. However the problem is extremely complex, even when limited to those of a single nation. The long-term goal is to develop technology to economically utilize solar energy and nuclear fusion as well as some other secondary resources (Considine: 1977; Halacy: 1977). However, this seems to belong to a distant future. Because of the decreased availability of cheap oil, other fossile fuels are becoming economically attractive again; it is probable that coal, lignite, tar sands, oil shales and the like are going to be exploited more and more during the next decades. But tapping these reserves will require the mastering of new processes such as in-situ combustion which may take quite a while. However the large scattering in the reported data dealing with the correlation NCa-Recovery suggest that an ultra low tension might not be the unique criterion. It should be also pointed out that a low tension may be transient, and that the bulk of the reported data deal only with interfacial tension between effluent fluids at equilibrium, which might be misleading with regard to the actual displacement mechanism. The actual shape of the pore and the contact angle or wettability of the rock might be quite important as shown recently by analyzing mobilization mechanism on simplified models (Oh and Slattery: 1976). II.3.1. Low interfacial tension The low tension mobilization mechanism rests on the concept that if the interfacial tension is sufficiently low, then the viscous forces are larger than the capillary forces and thus the oil ganglion can be dragged out (Foster: 1973; Whiteley and Ware: 1976; Widmyer et al: 1976). Conditions for mobilization are reported to be sufficient for displacement (Reed and Healy: 1976). Eventually the tension might reach a zero value i.e., the two liquids become miscible (Davis: 1968; Gogarty: 1968); however this regime cannot be maintained during the flooding because of physical degradation of the surfactant slug front by diffusion, dispersion and adsorption. II.3.2. Spontaneous emulsification The so-called spontaneous emulsification has been proposed as a mobilization mechanism able to displace oil from a porous rock (Jones: 1975; Cayias et al: 1975). This phenomenon has been reported a long time ago for both low and high tension
Energy & Fuels, 2017
In-situ emulsification/solubilization is an oil recovery technique routinely used to mobilize residual oil after the secondary oil production (waterflooding). The oil is produced after a subsequent reduction of interfacial tension (IFT) between stranded crude oil and water in the reservoir. Herein is presented a recovery method for heavy crude oils whose scheme consists of the injection of a fully solubilized (or emulsified) oil. Theoretically, the fully solubilized oil, referred hereinafter as microemulsion formulation, reduces the viscous forces that keep residual oil stranded. Different microemulsion formulations were prepared ex-situ from two heavy oils (API 11.5 and 16.6), micellar
Surfactant Phase Behavior and Retention in Porous Media
Society of Petroleum Engineers Journal, 1979
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. 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 an...
SPE Improved Oil Recovery Symposium, 2014
Unconventional shale oil resources have emerged as a significant source of fossil fuels in recent years. The oil contained in shales is held in natural microfractures, micropores, and inside nanopores of the organic matter. The strong capillary forces in these pores can bind the oil to the surface with strengths that are inversely proportional to the pore radius. In order to recover more oil from these pores, it is beneficial to reduce the capillary pressure by manipulating the interfacial tension and contact angle of oil/brine/shale systems using surfactant solutions. The main consideration in surfactant flooding is to optimize brine salinity and surfactant concentration while minimizing their adsorption on rock surfaces. Although the effect of some surfactants on recovery in shale oil reservoirs has been studied in the past, the mechanism is still unclear. Moreover, the limited data available in the literature is not representative of the actual reservoir conditions. The objective of this study is to elucidate the oil displacement mechanisms in shale oil by surfactant flooding. The phase behavior of several anionic surfactants was studied in the presence of crude oil at reservoir temperature (i.e. 80 °C). The results of these tests were used to screen the best surfactants. Dynamic interfacial tensions (IFT) and contact angles (CA) of selected surfactant-in-brine/oil/shale systems were measured by the rising/captive bubble technique using a state-of-the-art IFT/CA apparatus. The apparatus was thoroughly validated with various systems using the axisymmetric drop shape analysis technique. Using the same methodology, the effects of surfactant concentration (0.01 to 0.1 wt%) and brine salinity (0.1 to 5 M NaCl) on IFT and CA at ambient and reservoir conditions (i.e. 80 °C and 3000 psig) were studied. Surfactant adsorption on shale samples was also measured in brines at ambient conditions. Our data reveal that the most effective surfactant was able to reduce the oil-brine IFT from its original value (23 mN/m) down to 0.3 mN/m at reservoir condition. A reduction in the IFT value and an increase in the dynamic contact angle of oil drop on polished shale surface were observed with the addition of surfactant and salt to the system. A trend between these parameters, pressure, and temperature was also reported.
Adsorption of nonionic surfactants in sandstones
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
Adsorption of surfactants from aqueous solutions in porous media is very important in enhanced oil recovery (EOR) of oil reservoirs because surfactant loss due to adsorption on the reservoir rocks impairs the effectiveness of the chemical slurry injected to reduce the oil-water interfacial tension (IFT) and renders the process economically unfeasible. In this paper, two nonionic surfactants with different ethoxylation degrees were studied, ENP95 with ethoxylation degree 9.5 and ENP150 with ethoxylation degree 15. The experiments were carried out in a surfactant flooding apparatus, with a pressure gradient of 30 psi. The concentration of the injected solutions were 30% above the critical micelle concentration, to assure micelle formation. The results from the flow experiments of surfactant solutions in porous media showed that the adsorption extent was higher for ENP95 than for ENP150 because the previous surfactant has a smaller ethoxylation degree, that is, a smaller polar part.
The Effect of Oil/Brine Ratio on Surfactant Adsorption From Microemulsion
Static adsorption measurements of petroleum sulfonates on crushed Bell Creek and Berea cores were made using fluids with the same active sur-factant concentration but varying brine/oil mass ratios. The salinity of the brine was chosen such that a significant three-phase region existed in the oiIlbrine/surfactant/aIcohol system. The surfactant adsorption was found to be independent of the structural and compositions differences among the fluids. A series of oil recovery tests in which middle-phase microemulsions were injected into waterflooded cores also were performed. The cores used in these tests had been treated to remove divalent ions accessible to fluid flow. Microemulsion slugs (1.75 to 146070 PV) of equal active surfactant concentration but differing brine/oil mass ratios were injected. The total surfactant retention for this system was also found to be independent of the brine/oil mass ratio.
Role of Wettability on the Adsorption of an Anionic Surfactant on Sandstone Cores
The removal of excess water content in produced oil that contains non-ionic surfactant stabilized emulsion is challenging by conventional chemical treatment. A new approach is developed to examine, characterize, and demulsify the non-ionic surfactant (C12 _ 14EO22) stabilized emulsions. Crude oil in water (O/W) emulsions are formed and stabilized by surfactant in the upper layer. Emulsion viscosity measurements show that emulsion viscosity is independent of prepared water oil ratio. Water content in upper layer emulsions can be separated by heating the system. However, the bottom layer contaminated with crude oil cannot be treated via heating. An amino silane functionalized magnetic nanoparticle is characterized and evaluated for de-emulsification and water treatment. The mixing of the nanoparticle with the contaminated water cannot treat contaminated water, the water still has total organic carbon (TOC) as high as 1470 ppm. When an external magnetic field applies to the nanoparticle-emulsion mixture, the TOC level in water is significantly decreased. Water treatment and nanoparticle recycle can be simultaneously achieved.
Open Journal of Applied Sciences
In chemical enhanced oil recovery, surfactants are injected into the reservoir with the intention to lower interfacial tension (IFT) between the water and oil phases, and thereby bring about efficient displacement of oil. However, the adsorption of the surfactants to reservoir rock surfaces leads to the loss and reduction in concentration of the surfactants, which in turn reduces the overall efficiency of the oil recovery process, with attendant financial losses. In this work, the adsorption of Quillaja Saponaria (QS), a novel, natural, non-ionic surfactant, on crushed sandstone reservoir rock is investigated. X-ray diffraction (XRD) study of clean sandstone particles has been undertaken to determine the main components present in the sand particles. The conductivity method was used to measure CMC and the surfactant concentrations in aqueous solutions. Batch adsorption experiments were used to determine the amount of QS adsorbed on rock surface. Equilibrium conditions were reached after almost 5 days. From the results of the study, the Langmuir isotherm model is more suited for predicting the adsorption behaviour of QS on sandstone. The kinetic adsorption of QS obeys the pseudo-second order model. This study is particularly relevant in surfactant selection for chemical EOR processes.
Petroleum Science, 2011
Reservoir wettability plays an important role in various oil recovery processes. The origin and evolution of reservoir wettability were critically reviewed to better understand the complexity of wettability due to interactions in crude oil-brine-rock system, with introduction of different wetting states and their infl uence on fl uid distribution in pore spaces. The effect of wettability on oil recovery of waterflooding was then summarized from past and recent research to emphasize the importance of wettability in oil displacement by brine. The mechanism of wettability alteration by different surfactants in both carbonate and sandstone reservoirs was analyzed, concerning their distinct surface chemistry, and different interaction patterns of surfactants with components on rock surface. Other concerns such as the combined effect of wettability alteration and interfacial tension (IFT) reduction on the imbibition process was also taken into account. Generally, surfactant induced wettability alteration for enhanced oil recovery is still in the stage of laboratory investigation. The successful application of this technique relies on a comprehensive survey of target reservoir conditions, and could be expected especially in low permeability fractured reservoirs and forced imbibition process.