- Email: [email protected]
Spreading behavior of crude oil over limestone substrate
Journal of Colloid and Interface Science 262 (2003) 435–441 www.elsevier.com/locate/jcis
Spreading behavior of crude oil over limestone substrate Mamdouh T. Ghannam Department of Chemical and Petroleum Engineering, College of Engineering, United Arab Emirates University, P.O. Box 17555, Al-Ain, United Arab Emirates Received 24 May 2002; accepted 6 February 2003
Abstract Wetting characteristics of crude oil droplets over limestone substrates in the presence of different aqueous solutions are investigated in terms of wetting length, droplet depth, contact angle, and spreading coefficient. A wide range of concentration of NaOH, Alcoflood polymer, and nonionic Triton X-100 surfactant are used as a continuous phase for the crude oil droplet. NaOH and Triton X-100 significantly enhanced the spreading characteristics of the crude oil droplet; however, AF1235 polymer caused a huge reduction in the spreading behavior of crude oil. 2003 Elsevier Science (USA). All rights reserved. Keywords: Spreading; Contact angle; Interfacial tension; Crude oil; Limestone substrate
1. Introduction Spreading behavior of crude oil plays an important role in oil production in most oil reservoirs. Understanding the mechanism of spreading of a liquid over a solid substrate is crucial in several engineering applications. Some of these applications are enhanced oil recovery, lubrication emulsion, and film coating as in pulp and paper, photographic emulsions, and plastic. Spreading behavior reflects the ability of a liquid to wet or spread over a solid surface in the presence of another immiscible fluid. The angle which the liquid–liquid interface makes with the solid surface is called the contact angle, θ . Interfacial tension, γ , strongly influences the transport of crude oil in an oil reservoir. Under normal reservoir conditions, interfacial tension is considered one of the important factors that cause one-third of the total crude oil in place and cannot be recovered by either gas drive or water flooding [1]. It is important to define whether an aqueous solution can displace crude oil from a rock surface and how often the displacement takes place. If the free energy/unit area of aqueous solution–solid interface is lower than the free energy/unit area of crude oil–solid interface, the aqueous solution will displace the crude oil from the solid surface. Most experimental investigation of spreading studies have been carried E-mail address: [email protected].
out in systems where the spreading liquid displaces air from a solid surface. Some of these investigations [2–6] concluded that the viscous forces and the apparent contact angle of the spreading liquid influenced the liquid spreading velocity. The diffusion mechanism in which a molecule moves from one potential site to another when it gains enough activation energy has discussed by several researchers [7–10]. Petrov and Radoev [5] studied the drag forces that existed in a primary film heading a bulk liquid. Starov et al. [11] investigated the spreading of surfactant solutions over hydrophobic substrates. They concluded that the transfer of surfactant molecules from a water droplet onto a hydrophobic surface changes the wetting characteristics in front of the water droplet on the three-phase contact line. Brown and Neustadter [12] studied the dynamic displacement of the water–crude oil contact line in a glass capillary tube under external applied forces. Strom et al. [13] studied oil displacement by an aqueous solution from a stainless steel blade coated with a polystyrene film. The interaction between oil and solid substrate in the presence of surfactant solutions have been investigated by several researchers. Among these studies are the works carried out by Cutler and Davis [14], Lucassen-Reynders [15], Schick [16], Lewin and Sello [17], De Gennes [18], Churaev and Starov [19], and Kao et al. [20]. These investigations have suggested that the wettability properties of the solid substrates and the properties of the aqueous film formed
0021-9797/03/$ – see front matter 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0021-9797(03)00176-0
436
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
between the solid surface and the oil phase are important characteristics for oil droplet removal mechanism. The spreading of the crude oil–aqueous solution interface is more complicated than the spreading of the interface between liquid and air over a rock surface. Spreading behavior demonstrates the affinity of a rock for either oil phase or aqueous phase. Wetting properties can be measured experimentally from the angle of contact and the interfacial tension using Young’s capillary equation [21] as γas − γos = γao cos θ,
(1)
where γas , γos , and γao are the interfacial tension of related surfaces of aqueous solution–solid, oil–solid, and aqueous solution–oil, respectively. Spreading coefficient (SC) can be defined in terms of interfacial tension of the three phases as SC = γas − γos − γao .
Asphaltene content (wt%) Sulfur content (wt%) Dynamic viscosity at 25 ◦ C (mPa s) Density at 25 ◦ C (kg/m3 )
0.42 1.33 4.79 827
Table 2 Interfacial tension of crude oil–aqueous solutions Triton sol. (wt%) 0.0 0.025 0.05 0.10 0.20 0.3
IFT
Polymer sol. (wt%)
IFT
NaOH sol. (wt%)
IFT
26.55 1.011 0.981 0.976 0.985 0.942
0.0 0.1 0.2 0.3 0.4 0.5
26.55 158 173 158 129 124
0.0 2.5 5.0 7.5 10.0 –
26.55 2.972 1.944 2.762 2.923 –
(2) 2.3. Physical properties of crude oil
From Eqs. (1) and (2), spreading coefficient will be: SC = γao (cos θ − 1).
Table 1 Physical properties of Bu-Hasa crude oil
(3)
2. Experimental The objective of this investigation is to study the spreading behavior of crude oil over a limestone substrate in the presence of different type of aqueous solutions. A wide range of concentrations of NaOH, Alcoflood polymer, and nonionic Triton X-100 surfactant are examined in this study. 2.1. Experimental set-up A Plexiglas tank with dimensions 10 × 10 × 13 cm is designed to accommodate a limestone substrate, a crude oil droplet, and an environment of aqueous solution. One liter of aqueous solution is used to fill the tank. The solid substrate is placed over a Plexiglas carrier with dimensions 3 × 3.5 × 4 cm. A constant volume crude oil droplet of 10 µl is injected underneath the solid substrate. A highresolution color video camera from SONY (DCR-PC100E) is used to record the crude oil droplet behavior over time. A 200-W light source is placed on the opposite side of the tank. All measurements are recorded at room temperature. Measurements and analysis of experimental data are completed utilizing Sigma Scan Pro 5 Software from SPSS Science Software GmbH, Germany. 2.2. Solid substrate A cylindrical shape of limestone with diameter 3.8 cm and thickness 0.3 cm from Jebel Hafit, United Arab Emirates, was employed as the solid substrate in all the experimental investigations. The porosity and permeability of the solid substrate are 15% and 5 md, respectively.
Crude oil from the Bu-Hasa oil field, United Arab Emirates, is used. The physical properties of the crude oil are listed in Table 1. 2.4. Physical properties of the aqueous solutions Several types of aqueous solutions are employed as continuous phases which the crude oil droplet will be in contact with. Nonionic Triton X-100 surfactant (isooctylphenoxypolyethoxyethanol from BDH Middle East L.L.C., United Arab Emirates) in a range of 0–0.3 wt%, Alcoflood polymer solution of AF1235 (from Ciba Specialty Chemicals, Bradford, West Yorks, England) in a range of 0–0.5 wt%, and sodium hydroxide solution (from BDH Laboratory Supplies, Poole, England) in a range of 0–10 wt% are studied. Alcoflood polymer of AF1235 is a high-molecular-weight polyacrylamide copolymer with a bulk density of 800 kg/m3 and an intrinsic viscosity of 12. The interfacial tensions (IFT) of the crude oil–aqueous solutions are measured by spinning drop tensiometer (from Core Laboratories Inc., Model 1500, Dallas, USA). The interfacial tension in mN/m is listed in Table 2. Rheological behavior of the Alcoflood aqueous solutions is studied using RheoStress RS100 from Haake of cone and plate sensor. The cone diameter is 35 mm, the cone tip gap is 0.137 mm, and the cone angle is 4◦ . Figure 1 shows the flow behavior of AF1235 aqueous solution in terms of viscosity versus shear rate over the examined polymer concentration. The viscosity of the Alcoflood polymer solution is heavily dependent upon polymer concentration and shear rate. Viscosity gradually decreases with shear rate, providing non-Newtonian behavior for all the tested solutions. A power law model fits the flow behavior of AF1235 solutions very sufficiently over the examined polymer concentration of 0.1–0.5 wt%, τ = mγ˙ n ,
(4)
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
Fig. 1. Flow behavior of AF1235 polymer solution.
437
Fig. 3. Wetting length behavior for Triton X-100.
Table 3 Fitting analysis for polymer solutions Polymer conc. (wt%)
m
n
0.1 0.2 0.3 0.4 0.5
0.083 0.410 0.830 1.350 2.0
0.600 0.460 0.396 0.358 0.340
Fig. 4. Wetting length behavior for AF1235.
Fig. 2. Wetting length behavior for NaOH.
where τ is shear stress in Pa, γ˙ is shear rate in s−1 , m is consistency index in Pa sn , and n is the flow behavior index. The results of the modeling analysis are reported in Table 3.
3. Results and discussion Spreading behavior of crude oil droplets over a limestone substrate is investigated in terms of wetting length (WL ), droplet depth (Dd ), contact angle (θ ), and spreading coefficient (SC) versus time in the presence of different aqueous solutions of NaOH, Triton X-100, and AF1235. 3.1. Wetting length of crude oil droplet (WL ) The wetting length of a crude oil droplet is defined as the instantaneous droplet diameter of the oil droplet placed on the limestone substrate. Figure 2 shows the wetting length behavior versus time in the presence of different
concentrations of NaOH solution. In general, WL sharply increases over a short period of time (around 3 min) and then slowly approaches a constant value. Wetting length increases significantly in the presence of NaOH aqueous solution. NaOH aqueous solution enhances wetting behavior by almost 75% for 2.5% NaOH. This enhancement of wetting length can be attributed to the ability of NaOH aqueous solution and crude oil to form a self-wetting agent to enhance the spreading behavior of the crude oil droplet. Sodium hydroxide solution reacts with naturally available organic acids in crude oil to produce soaps at the aqueous solution–oil interface. The effect produced appears to be similar to that of surfactant solutions. The difference is that NaOH aqueous solution reduces interfacial tension due to in situ generated surfactant [22]. Figure 3 shows the behavior of WL versus elapsed time for different concentrations of Triton X-100. WL increases gradually over time and significantly with Triton X-100 concentration up to a concentration of 0.2%. However, Fig. 4 shows an opposite trend for the effect of AF1235 polymer on the wetting length of crude oil droplets. Wetting length of crude oil droplets decreases gradually with polymer concentration over a concentration range of 0–0.3%. This behavior can be attributed to the ability of the network structure of the polymer solution to avoid the self-spreading of the crude oil droplet over the limestone substrate. Table 2 shows the interfacial tension measurements of crude oil in the presence
438
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
Fig. 5. Droplet depth versus time for NaOH.
of the three examined aqueous solutions of NaOH, Triton X-100, and AF1235. NaOH and Triton X-100 show a great ability to reduce the interfacial tension from 26.55 mN/m for a crude oil–water system to much lower values of about 2.0 and 1.0 mN/m for NaOH and Triton X-100, respectively, depending upon their concentrations. However, in the presence of AF1235, the interfacial tension increases significantly from 26.55 mN/m to 158.05 mN/m at 0.1% polymer concentration. Therefore, NaOH and Triton X-100 offer a strong influence to lower the values of interfacial tension, enhancing the wetting length and spreading behavior of crude oil droplet over the limestone substrate significantly. However, the presence of AF1235 polymer solution increases the interfacial tension, which limits the spreading behavior of the wetting length and therefore negatively affects the spreading behavior of the crude oil droplet. 3.2. Droplet depth of crude oil (Dd ) Droplet depth is one of the important geometrical dimensions of the crude oil droplet to investigate. It is very beneficial to measure the dynamic values of Dd of crude oil in the presence of different aqueous solutions to record the spreading characteristics in different directions. Figure 5 shows Dd of crude oil droplets versus elapsed time for different concentrations of NaOH. The droplet depth of the crude oil in the presence of pure water drops from 0.225 cm to 0.2 cm in about 3 min, which then is constant for 2 h. The addition of NaOH forms a self-active agent to lower the IFT of crude oil–water, as can be concluded from Table 2. Therefore, the presence of NaOH in the aqueous solution causes a strong reduction for Dd from 0.225 cm to 0.08 cm over a short period of time as a result of WL increases over the solid substrate. The effect of surface-active agents on the Dd behavior can be concluded clearly from Fig. 6, in which Triton X-100 is added to the aqueous phase. Figure 6 shows that 0.025% Triton X-100 gradually reduces the droplet depth to 0.075 cm over 40 min, however, 0.1% Triton X-100 causes similar behavior in much shorter time. NaOH and Triton X-100 on one hand enhance the WL values of crude oil droplet and on the other reduce the Dd values. Therefore,
Fig. 6. Droplet depth versus time for Triton X-100.
Fig. 7. Droplet depth versus time for AF1235.
both NaOH and Triton X-100 are considered to be very efficient for improving the spreading behavior of crude oil droplets over a limestone substrate. A similar investigation was carried out in presence of polymer aqueous solution to study the effect of polymer on the spreading behavior of crude oil. Figure 7 shows that the polymer concentration influences the Dd values very slightly over the elapsed time. This behavior can be attributed in the effect of AF1235 in raise significantly the IFT of crude oil–water, which decreases the WL values. Again, this observation supports that the effect of polymer strongly decreases the spreading of crude oil droplets over the a limestone substrate. 3.3. Contact angle (θ ) The interfacial crude oil–aqueous solution–solid substrate interactions is characterized by the formation of a contact angle θ . Understanding contact angle behavior, in general, is one of the challenging problems in surface science due to its role in all processes involved in three-phase interfacial phenomena. Two fundamental problems can be associated with contact angle behavior. The first is related to solid substrate surface structure, whereas the second is associated with the mutual interactions of immiscible liquids in contact with the solid substrate. The fundamental problems related to crude oil–aqueous solution interfacial interactions in the close vicinity to the contact line with solid substrate will be the focus of the current investigation.
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
Fig. 8. Effect of NaOH on the dynamic behavior of the contact angle.
Fig. 9. Effect of Triton X-100 on the dynamic behavior of the contact angle.
Fig. 10. Effect of AF1235 on the dynamic behavior of the contact angle.
Figure 8 shows the contact angle behavior versus time of rest on the limestone substrate for crude oil droplets in the presence of NaOH aqueous solution. For 0% NaOH concentration, the contact angle decreases slightly over the period of 3 min; then it approaches an almost constant value. Due to the ability of NaOH to lower significantly the IFT between crude oil and water, the contact angle decreases sharply over the first 10 min and then gradually till the end of the experiment. Figure 8 also shows that contact angle decreases with NaOH concentration. The effect of Triton X-100 on the contact angle behavior of the crude oil is given in Fig. 9. Slight concentration of Triton X-100 has a strong influence in lowering the value of contact angle
439
Fig. 11. Behavior of θ –Ca in the presence of NaOH.
over a short period of 3 min followed by almost timeindependent behavior up to 2 h. Contact angle decreases sharply from 133◦ to 84◦ with surfactant concentrations up to 0.1%; however, the contact angle starts to increase with more addition of Triton X-100 due to the formation of micelle structures. Figure 10 shows the effect of AF1235 polymers on the contact angle behavior. AF1235 increases significantly the value of the contact angle due to the polymer structure in the aqueous solution, which avoids the crude oil spreading over the limestone substrate. Previous discussion of the investigated parameters WL , Dd , and θ shows that the NaOH and Triton X-100 play two important roles in enhancement of spreading behavior. The first role for NaOH and Triton X-100 is their ability to reduce the interfacial tension between crude oil and the aqueous phase. The second role is the adsorption that can take place at the crude oil droplet–aqueous solution and aqueous solution–solid substrate interfaces. Hence, the transfer of the surfactant molecules from the aqueous phase to the crude oil and solid phases improves the spreading characteristics of the three-phase contact line. Therefore, the addition of NaOH or Triton X-100 enhances the spreading of the crude oil droplet over the limestone substrate. Previous work shows that the spreading of the threephase contact line can be modeled either by adsorption– desorption kinetics models [7] or through the hydrodynamics of the three phase contact line [2,23,24]. The adsorption– desorption mechanism is recommended at extremely low values of the spreading velocity of the three-phase contact line. Blake and Haynes [7] reported that the experimental data deviate from the adsorption–desorption model when the viscous forces are comparable with the surface tension forces, which means that the hydrodynamics has a significant effect in the movement of the three-phase contact line. Figure 11 shows the behavior of the contact angle of crude oil droplet on the limestone substrate versus the capillary number, Ca, in the presence of different concentrations of NaOH. The capillary number is defined as Ca = µv/γao , where µ is crude oil viscosity, v is the contact line velocity, and γao is the interfacial tension of the crude oil– aqueous phase system. The contact angle behavior of crude oil droplets in the presence of pure water shows behavior in-
440
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
droplet. Table 6 reports spreading coefficient, which is defined by Eq. (3), for low concentration of NaOH, Triton X-100, and AF1235 polymer. The presence of NaOH and Triton X-100 enhance the SC over limestone substrate significantly over short time from −43.78 dyn/cm in the presence of water to −4.12 dyn/cm and −1.48 dyn/cm, respectively. However, the addition of AF1235 severely reduces the SC of crude oil droplet on limestone substrate due to the effect of AF1235 network structure on the spreading of crude oil. Table 6, also, shows that the SC is almost time independent behavior. The wetting improvement parameter, WIP [25], can be used to recognize the magnitude of spreading enhancement introduced by different investigated materials,
Fig. 12. Behavior of θ –Ca in the presence of Triton X-100. Table 4 Fitting analysis for NaOH aqueous solution continuous phase
WIP = (SCi − SCf ) × 100/SCi ,
Concentration (%)
a
b
c
0.0 2.5 5.0 7.5
73.183 76.278 79.694 59.138
68.888 250.045 186.217 154.363
0.0132 0.1933 0.2206 0.1433
Table 5 Fitting analysis for Triton X-100 aqueous solution continuous phase Concentration (%)
a
b
c
0.0 0.05 0.1 0.2
73.183 94.368 87.189 105.764
68.888 156.707 51.605 166.699
0.0132 0.1866 1.027 0.3678
dependent of Ca, which means that the hydrodynamic forces play no role in the movement of the three-phase contact line. Therefore, the spreading behavior under these conditions is very limited. However, the situation is completely improved when NaOH is added to the pure water, as can be concluded from Fig. 11. The addition of NaOH gradually reduces the contact angle of the crude oil droplet. Figure 11 also shows a strong dependency of contact angle on Ca in the presence of NaOH solution, which means that the spreading of the three-phase contact line is significantly influenced by the hydrodynamic forces. Figure 12 shows similar behavior in the presence of low concentrations of surfactant, which provides a great tendency to enhance the movement behavior of the three-phase contact line. Fitting analysis is carried out to model the relationship between contact angle and Ca. A power law model of three parameters provides excellent fitting results, θ = a + b(Ca)c ,
(6)
where SCi is the spreading coefficient of the crude oil droplet within water phase and SCf is the spreading coefficient of the crude oil droplet within aqueous solutions of different materials. WIP is calculated at elapsed time of 2 h. Table 7 shows the values of WIP for different concentration of the examined materials. Equation (6) provides good prediction tools for the complete spreading situation; i.e., if SCf reaches a value of 0.0 (complete spreading behavior) the WIP approaches 100%, whereas, if SCf does not change from SCi , the WIP will equal zero. Table 7 shows that the NaOH and Triton X-100 provide the appropriate environment to enhance the spreading behavior of the crude oil droplet significantly. However, AF1235 polymer causes a huge reduction in the crude oil spreading; for example, the presence of 0.1% polymer reduces the spreading coefficient by about five and half times from the spreading of crude oil alone. One way to improve the spreading performance of crude oil droplets within the polymer solution is the addition of the surfactant material to the AF1235 aqueous solution. The addition of 0.1% Triton X-100 is investigated for the spreading behavior of crude oil droplets within the continuous phase of 0.2% AF1235 polymer solution. Under these conditions, the IFT is dropped from 173.67 mN/m with polymer alone to 1.134 mN/m in the presence of Triton X-100. Therefore, the presence of Triton X-100 enhances the spreading characteristics of crude oil droplets significantly. The SC increases from −270.74 mN/m for AF1235 alone to −1.83 mN/m when Triton X-100 is added. The WIP rises strongly from the lowest reported value of −532.74% to 95.73%, which indicates almost complete spreading.
(5)
where a, b, and c are fitting parameters. The fitting analyses of NaOH and Triton X-100 aqueous solutions are reported in Tables 4 and 5, respectively. 3.4. Spreading coefficient (SC) Spreading coefficient displays the combined actions of both interfacial tension and contact angle of crude oil
4. Conclusions Spreading behavior of crude oil droplets is studied over a limestone substrate in the presence of aqueous solutions of NaOH, Triton X-100, and AF1235 polymer. The spreading behavior is investigated in terms of wetting length, droplet depth, contact angle, and spreading coefficient. The following conclusions can be made:
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
441
Table 6 Spreading coefficient parameter for crude oil droplet Time (min)
Water
2.5% NaOH
0.05% surfactant
0.1% polymer
0.5 1 5 10 20 30 40 50 60 75 90 105 120
−43.78 −43.48 −43.27 −43.23 −43.21 −42.98 −42.17 −42.64 −42.41 −42.08 −42.81 −41.57 −42.79
−4.12 −4.02 −3.94 −3.12 −3.03 −2.93 −2.72 −2.65 −2.58 −2.47 −2.43 −2.14 −2.21
−1.48 −1.44 −1.28 −1.31 −1.24 −1.28 −1.34 −1.31 −1.28 −1.31 −1.28 −1.32 −1.34
−270.73 −267.46 −267.29 −266.82 −265.21 −265.39 −266.03 −265.42 −270.52 −266.34 −267.40 −267.21 −267.15
Acknowledgment
Table 7 Wetting improvement parameter for crude oil droplet NaOH (%)
WIP (%)
Triton X-100 (%)
WIP (%)
AF1235 (%)
WIP (%)
0.0 2.5 5.0 7.5 10.0 –
0.0 94.84 95.75 95.32 93.43 –
0.0 0.05 0.1 0.2 0.3 –
0.0 96.87 97.81 97.18 97.26 –
0.0 0.1 0.2 0.3 0.4 0.5
0.0 −524.4 −532.7 −520.3 −392.4 −373.8
1. Aqueous solutions of NaOH and Triton X-100 enhance the wetting length of crude oil droplets significantly; however, the presence of AF1235 solution reduces the wetting length gradually with polymer concentration. 2. NaOH and Triton X-100 decrease the values of droplet depth significantly due to the effect of surface-active behavior on the crude oil droplet. However, AF1235 polymer shows an insignificant influence on the droplet depth behavior. 3. The contact angle of the crude oil droplet over the limestone substrate decreases strongly in the presence of NaOH or Triton X-100. On the other hand, the presence of AF1235 polymer solution raises the experimental measurements of contact angle. 4. The presence of NaOH or Triton X-100 increases the velocity of the three-phase contact line of the crude oil droplet on the limestone substrate. Therefore, NaOH and Triton X-100 improve the spreading of crude oil droplets. 5. Both SC and WIP are improved significantly in the presence of NaOH and Triton X-100. However, AF1235 polymer causes a huge reduction for both SC and WIP. 6. The addition of 0.1% Triton X-100 enhances the spreading of 0.2% AF1235 (i.e., the lowest reported spreading behavior) significantly. WIP increases from −532.74% (polymer alone) to 95.73% when 0.1% of Triton X-100 is added.
The author is grateful for financial support from the United Arab Emirates University under Grant 03-02-711/03.
References [1] H.Y. Jennings, G.H. Newman, SPE J. (1971) 171. [2] R.L. Hoffman, J. Colloid Interface Sci. 50 (1975) 228. [3] G. Strom, M. Fredriksson, P. Stenius, B. Radoev, J. Colloid Interface Sci. 134 (1990) 107. [4] A.M. Schwarts, S.B. Tejada, J. Colloid Interface Sci. 38 (1972) 359. [5] J.G. Petrov, B.P. Radoev, Colloid Polym. Sci. 259 (1981) 753. [6] G.N. Clifton, V. Dussan, J. Fluid Mech. 118 (1982) 27. [7] T.D. Blake, J.M. Haynes, J. Colloid Interface Sci. 30 (1969) 421. [8] B.W. Cherry, C.M. Holmes, J. Colloid Interface Sci. 29 (1969) 174. [9] R.L. Hoffman, J. Colloid Interface Sci. 94 (1983) 470. [10] E. Ruckenstein, C.S. Dunn, J. Colloid Interface Sci. 59 (1977) 135. [11] V. Starov, S. Kosvintsev, M. Velarde, J. Colloid Interface Sci. 227 (2000) 185. [12] C.E. Brown, E.L. Neustadter, J. Can. Pet. Techol. 19 (3) (1980) 100. [13] G. Strom, M. Fredriksson, P. Stenius, J. Colloid Interface Sci. 134 (1990) 117. [14] W.G. Cutler, R.C. Davis (Eds.), Detergency—Theory and Test Methods, Part III, Dekker, New York, 1981. [15] E.H. Lucassen-Reynders (Ed.), Anionic Surfactants—Physical Chemistry of Surfactant Action, Dekker, New York, 1981. [16] M.J. Schick, Nonionic Surfactant, Dekker, New York, 1967. [17] M. Lewin, S.B. Sello, Handbook of Fiber Science and Technology, Vol. 2, Part B, Dekker, New York, 1984. [18] P.G. De Gennes, Rev. Mod. Phys. 57 (1985) 827. [19] N.V. Churaev, V.M. Starov, J. Colloid Interface Sci. 103 (1985) 301. [20] R.L. Kao, D.T. Wasan, A.D. Nikolov, D.A. Edwards, Colloids Surf. 34 (1988) 389. [21] J.F. Padday, in: K.L. Mittal (Ed.), Contact Angle, Wettability and Adhesion, VSP, Utrecht, 1993. [22] A. Carcoana, Applied Enhanced Oil Recovery, Prentice–Hall, Englewood Clifs, NJ, 1992. [23] R.G. Cox, J. Fluid Mech. 186 (1986) 169. [24] V. Dussan, J. Fluid Mech. 77 (1976) 665. [25] M.T. Ghannam, J. Chem. Eng. Data 47 (2002) 274.
Spreading behavior of crude oil over limestone substrate Mamdouh T. Ghannam Department of Chemical and Petroleum Engineering, College of Engineering, United Arab Emirates University, P.O. Box 17555, Al-Ain, United Arab Emirates Received 24 May 2002; accepted 6 February 2003
Abstract Wetting characteristics of crude oil droplets over limestone substrates in the presence of different aqueous solutions are investigated in terms of wetting length, droplet depth, contact angle, and spreading coefficient. A wide range of concentration of NaOH, Alcoflood polymer, and nonionic Triton X-100 surfactant are used as a continuous phase for the crude oil droplet. NaOH and Triton X-100 significantly enhanced the spreading characteristics of the crude oil droplet; however, AF1235 polymer caused a huge reduction in the spreading behavior of crude oil. 2003 Elsevier Science (USA). All rights reserved. Keywords: Spreading; Contact angle; Interfacial tension; Crude oil; Limestone substrate
1. Introduction Spreading behavior of crude oil plays an important role in oil production in most oil reservoirs. Understanding the mechanism of spreading of a liquid over a solid substrate is crucial in several engineering applications. Some of these applications are enhanced oil recovery, lubrication emulsion, and film coating as in pulp and paper, photographic emulsions, and plastic. Spreading behavior reflects the ability of a liquid to wet or spread over a solid surface in the presence of another immiscible fluid. The angle which the liquid–liquid interface makes with the solid surface is called the contact angle, θ . Interfacial tension, γ , strongly influences the transport of crude oil in an oil reservoir. Under normal reservoir conditions, interfacial tension is considered one of the important factors that cause one-third of the total crude oil in place and cannot be recovered by either gas drive or water flooding [1]. It is important to define whether an aqueous solution can displace crude oil from a rock surface and how often the displacement takes place. If the free energy/unit area of aqueous solution–solid interface is lower than the free energy/unit area of crude oil–solid interface, the aqueous solution will displace the crude oil from the solid surface. Most experimental investigation of spreading studies have been carried E-mail address: [email protected].
out in systems where the spreading liquid displaces air from a solid surface. Some of these investigations [2–6] concluded that the viscous forces and the apparent contact angle of the spreading liquid influenced the liquid spreading velocity. The diffusion mechanism in which a molecule moves from one potential site to another when it gains enough activation energy has discussed by several researchers [7–10]. Petrov and Radoev [5] studied the drag forces that existed in a primary film heading a bulk liquid. Starov et al. [11] investigated the spreading of surfactant solutions over hydrophobic substrates. They concluded that the transfer of surfactant molecules from a water droplet onto a hydrophobic surface changes the wetting characteristics in front of the water droplet on the three-phase contact line. Brown and Neustadter [12] studied the dynamic displacement of the water–crude oil contact line in a glass capillary tube under external applied forces. Strom et al. [13] studied oil displacement by an aqueous solution from a stainless steel blade coated with a polystyrene film. The interaction between oil and solid substrate in the presence of surfactant solutions have been investigated by several researchers. Among these studies are the works carried out by Cutler and Davis [14], Lucassen-Reynders [15], Schick [16], Lewin and Sello [17], De Gennes [18], Churaev and Starov [19], and Kao et al. [20]. These investigations have suggested that the wettability properties of the solid substrates and the properties of the aqueous film formed
0021-9797/03/$ – see front matter 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0021-9797(03)00176-0
436
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
between the solid surface and the oil phase are important characteristics for oil droplet removal mechanism. The spreading of the crude oil–aqueous solution interface is more complicated than the spreading of the interface between liquid and air over a rock surface. Spreading behavior demonstrates the affinity of a rock for either oil phase or aqueous phase. Wetting properties can be measured experimentally from the angle of contact and the interfacial tension using Young’s capillary equation [21] as γas − γos = γao cos θ,
(1)
where γas , γos , and γao are the interfacial tension of related surfaces of aqueous solution–solid, oil–solid, and aqueous solution–oil, respectively. Spreading coefficient (SC) can be defined in terms of interfacial tension of the three phases as SC = γas − γos − γao .
Asphaltene content (wt%) Sulfur content (wt%) Dynamic viscosity at 25 ◦ C (mPa s) Density at 25 ◦ C (kg/m3 )
0.42 1.33 4.79 827
Table 2 Interfacial tension of crude oil–aqueous solutions Triton sol. (wt%) 0.0 0.025 0.05 0.10 0.20 0.3
IFT
Polymer sol. (wt%)
IFT
NaOH sol. (wt%)
IFT
26.55 1.011 0.981 0.976 0.985 0.942
0.0 0.1 0.2 0.3 0.4 0.5
26.55 158 173 158 129 124
0.0 2.5 5.0 7.5 10.0 –
26.55 2.972 1.944 2.762 2.923 –
(2) 2.3. Physical properties of crude oil
From Eqs. (1) and (2), spreading coefficient will be: SC = γao (cos θ − 1).
Table 1 Physical properties of Bu-Hasa crude oil
(3)
2. Experimental The objective of this investigation is to study the spreading behavior of crude oil over a limestone substrate in the presence of different type of aqueous solutions. A wide range of concentrations of NaOH, Alcoflood polymer, and nonionic Triton X-100 surfactant are examined in this study. 2.1. Experimental set-up A Plexiglas tank with dimensions 10 × 10 × 13 cm is designed to accommodate a limestone substrate, a crude oil droplet, and an environment of aqueous solution. One liter of aqueous solution is used to fill the tank. The solid substrate is placed over a Plexiglas carrier with dimensions 3 × 3.5 × 4 cm. A constant volume crude oil droplet of 10 µl is injected underneath the solid substrate. A highresolution color video camera from SONY (DCR-PC100E) is used to record the crude oil droplet behavior over time. A 200-W light source is placed on the opposite side of the tank. All measurements are recorded at room temperature. Measurements and analysis of experimental data are completed utilizing Sigma Scan Pro 5 Software from SPSS Science Software GmbH, Germany. 2.2. Solid substrate A cylindrical shape of limestone with diameter 3.8 cm and thickness 0.3 cm from Jebel Hafit, United Arab Emirates, was employed as the solid substrate in all the experimental investigations. The porosity and permeability of the solid substrate are 15% and 5 md, respectively.
Crude oil from the Bu-Hasa oil field, United Arab Emirates, is used. The physical properties of the crude oil are listed in Table 1. 2.4. Physical properties of the aqueous solutions Several types of aqueous solutions are employed as continuous phases which the crude oil droplet will be in contact with. Nonionic Triton X-100 surfactant (isooctylphenoxypolyethoxyethanol from BDH Middle East L.L.C., United Arab Emirates) in a range of 0–0.3 wt%, Alcoflood polymer solution of AF1235 (from Ciba Specialty Chemicals, Bradford, West Yorks, England) in a range of 0–0.5 wt%, and sodium hydroxide solution (from BDH Laboratory Supplies, Poole, England) in a range of 0–10 wt% are studied. Alcoflood polymer of AF1235 is a high-molecular-weight polyacrylamide copolymer with a bulk density of 800 kg/m3 and an intrinsic viscosity of 12. The interfacial tensions (IFT) of the crude oil–aqueous solutions are measured by spinning drop tensiometer (from Core Laboratories Inc., Model 1500, Dallas, USA). The interfacial tension in mN/m is listed in Table 2. Rheological behavior of the Alcoflood aqueous solutions is studied using RheoStress RS100 from Haake of cone and plate sensor. The cone diameter is 35 mm, the cone tip gap is 0.137 mm, and the cone angle is 4◦ . Figure 1 shows the flow behavior of AF1235 aqueous solution in terms of viscosity versus shear rate over the examined polymer concentration. The viscosity of the Alcoflood polymer solution is heavily dependent upon polymer concentration and shear rate. Viscosity gradually decreases with shear rate, providing non-Newtonian behavior for all the tested solutions. A power law model fits the flow behavior of AF1235 solutions very sufficiently over the examined polymer concentration of 0.1–0.5 wt%, τ = mγ˙ n ,
(4)
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
Fig. 1. Flow behavior of AF1235 polymer solution.
437
Fig. 3. Wetting length behavior for Triton X-100.
Table 3 Fitting analysis for polymer solutions Polymer conc. (wt%)
m
n
0.1 0.2 0.3 0.4 0.5
0.083 0.410 0.830 1.350 2.0
0.600 0.460 0.396 0.358 0.340
Fig. 4. Wetting length behavior for AF1235.
Fig. 2. Wetting length behavior for NaOH.
where τ is shear stress in Pa, γ˙ is shear rate in s−1 , m is consistency index in Pa sn , and n is the flow behavior index. The results of the modeling analysis are reported in Table 3.
3. Results and discussion Spreading behavior of crude oil droplets over a limestone substrate is investigated in terms of wetting length (WL ), droplet depth (Dd ), contact angle (θ ), and spreading coefficient (SC) versus time in the presence of different aqueous solutions of NaOH, Triton X-100, and AF1235. 3.1. Wetting length of crude oil droplet (WL ) The wetting length of a crude oil droplet is defined as the instantaneous droplet diameter of the oil droplet placed on the limestone substrate. Figure 2 shows the wetting length behavior versus time in the presence of different
concentrations of NaOH solution. In general, WL sharply increases over a short period of time (around 3 min) and then slowly approaches a constant value. Wetting length increases significantly in the presence of NaOH aqueous solution. NaOH aqueous solution enhances wetting behavior by almost 75% for 2.5% NaOH. This enhancement of wetting length can be attributed to the ability of NaOH aqueous solution and crude oil to form a self-wetting agent to enhance the spreading behavior of the crude oil droplet. Sodium hydroxide solution reacts with naturally available organic acids in crude oil to produce soaps at the aqueous solution–oil interface. The effect produced appears to be similar to that of surfactant solutions. The difference is that NaOH aqueous solution reduces interfacial tension due to in situ generated surfactant [22]. Figure 3 shows the behavior of WL versus elapsed time for different concentrations of Triton X-100. WL increases gradually over time and significantly with Triton X-100 concentration up to a concentration of 0.2%. However, Fig. 4 shows an opposite trend for the effect of AF1235 polymer on the wetting length of crude oil droplets. Wetting length of crude oil droplets decreases gradually with polymer concentration over a concentration range of 0–0.3%. This behavior can be attributed to the ability of the network structure of the polymer solution to avoid the self-spreading of the crude oil droplet over the limestone substrate. Table 2 shows the interfacial tension measurements of crude oil in the presence
438
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
Fig. 5. Droplet depth versus time for NaOH.
of the three examined aqueous solutions of NaOH, Triton X-100, and AF1235. NaOH and Triton X-100 show a great ability to reduce the interfacial tension from 26.55 mN/m for a crude oil–water system to much lower values of about 2.0 and 1.0 mN/m for NaOH and Triton X-100, respectively, depending upon their concentrations. However, in the presence of AF1235, the interfacial tension increases significantly from 26.55 mN/m to 158.05 mN/m at 0.1% polymer concentration. Therefore, NaOH and Triton X-100 offer a strong influence to lower the values of interfacial tension, enhancing the wetting length and spreading behavior of crude oil droplet over the limestone substrate significantly. However, the presence of AF1235 polymer solution increases the interfacial tension, which limits the spreading behavior of the wetting length and therefore negatively affects the spreading behavior of the crude oil droplet. 3.2. Droplet depth of crude oil (Dd ) Droplet depth is one of the important geometrical dimensions of the crude oil droplet to investigate. It is very beneficial to measure the dynamic values of Dd of crude oil in the presence of different aqueous solutions to record the spreading characteristics in different directions. Figure 5 shows Dd of crude oil droplets versus elapsed time for different concentrations of NaOH. The droplet depth of the crude oil in the presence of pure water drops from 0.225 cm to 0.2 cm in about 3 min, which then is constant for 2 h. The addition of NaOH forms a self-active agent to lower the IFT of crude oil–water, as can be concluded from Table 2. Therefore, the presence of NaOH in the aqueous solution causes a strong reduction for Dd from 0.225 cm to 0.08 cm over a short period of time as a result of WL increases over the solid substrate. The effect of surface-active agents on the Dd behavior can be concluded clearly from Fig. 6, in which Triton X-100 is added to the aqueous phase. Figure 6 shows that 0.025% Triton X-100 gradually reduces the droplet depth to 0.075 cm over 40 min, however, 0.1% Triton X-100 causes similar behavior in much shorter time. NaOH and Triton X-100 on one hand enhance the WL values of crude oil droplet and on the other reduce the Dd values. Therefore,
Fig. 6. Droplet depth versus time for Triton X-100.
Fig. 7. Droplet depth versus time for AF1235.
both NaOH and Triton X-100 are considered to be very efficient for improving the spreading behavior of crude oil droplets over a limestone substrate. A similar investigation was carried out in presence of polymer aqueous solution to study the effect of polymer on the spreading behavior of crude oil. Figure 7 shows that the polymer concentration influences the Dd values very slightly over the elapsed time. This behavior can be attributed in the effect of AF1235 in raise significantly the IFT of crude oil–water, which decreases the WL values. Again, this observation supports that the effect of polymer strongly decreases the spreading of crude oil droplets over the a limestone substrate. 3.3. Contact angle (θ ) The interfacial crude oil–aqueous solution–solid substrate interactions is characterized by the formation of a contact angle θ . Understanding contact angle behavior, in general, is one of the challenging problems in surface science due to its role in all processes involved in three-phase interfacial phenomena. Two fundamental problems can be associated with contact angle behavior. The first is related to solid substrate surface structure, whereas the second is associated with the mutual interactions of immiscible liquids in contact with the solid substrate. The fundamental problems related to crude oil–aqueous solution interfacial interactions in the close vicinity to the contact line with solid substrate will be the focus of the current investigation.
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
Fig. 8. Effect of NaOH on the dynamic behavior of the contact angle.
Fig. 9. Effect of Triton X-100 on the dynamic behavior of the contact angle.
Fig. 10. Effect of AF1235 on the dynamic behavior of the contact angle.
Figure 8 shows the contact angle behavior versus time of rest on the limestone substrate for crude oil droplets in the presence of NaOH aqueous solution. For 0% NaOH concentration, the contact angle decreases slightly over the period of 3 min; then it approaches an almost constant value. Due to the ability of NaOH to lower significantly the IFT between crude oil and water, the contact angle decreases sharply over the first 10 min and then gradually till the end of the experiment. Figure 8 also shows that contact angle decreases with NaOH concentration. The effect of Triton X-100 on the contact angle behavior of the crude oil is given in Fig. 9. Slight concentration of Triton X-100 has a strong influence in lowering the value of contact angle
439
Fig. 11. Behavior of θ –Ca in the presence of NaOH.
over a short period of 3 min followed by almost timeindependent behavior up to 2 h. Contact angle decreases sharply from 133◦ to 84◦ with surfactant concentrations up to 0.1%; however, the contact angle starts to increase with more addition of Triton X-100 due to the formation of micelle structures. Figure 10 shows the effect of AF1235 polymers on the contact angle behavior. AF1235 increases significantly the value of the contact angle due to the polymer structure in the aqueous solution, which avoids the crude oil spreading over the limestone substrate. Previous discussion of the investigated parameters WL , Dd , and θ shows that the NaOH and Triton X-100 play two important roles in enhancement of spreading behavior. The first role for NaOH and Triton X-100 is their ability to reduce the interfacial tension between crude oil and the aqueous phase. The second role is the adsorption that can take place at the crude oil droplet–aqueous solution and aqueous solution–solid substrate interfaces. Hence, the transfer of the surfactant molecules from the aqueous phase to the crude oil and solid phases improves the spreading characteristics of the three-phase contact line. Therefore, the addition of NaOH or Triton X-100 enhances the spreading of the crude oil droplet over the limestone substrate. Previous work shows that the spreading of the threephase contact line can be modeled either by adsorption– desorption kinetics models [7] or through the hydrodynamics of the three phase contact line [2,23,24]. The adsorption– desorption mechanism is recommended at extremely low values of the spreading velocity of the three-phase contact line. Blake and Haynes [7] reported that the experimental data deviate from the adsorption–desorption model when the viscous forces are comparable with the surface tension forces, which means that the hydrodynamics has a significant effect in the movement of the three-phase contact line. Figure 11 shows the behavior of the contact angle of crude oil droplet on the limestone substrate versus the capillary number, Ca, in the presence of different concentrations of NaOH. The capillary number is defined as Ca = µv/γao , where µ is crude oil viscosity, v is the contact line velocity, and γao is the interfacial tension of the crude oil– aqueous phase system. The contact angle behavior of crude oil droplets in the presence of pure water shows behavior in-
440
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
droplet. Table 6 reports spreading coefficient, which is defined by Eq. (3), for low concentration of NaOH, Triton X-100, and AF1235 polymer. The presence of NaOH and Triton X-100 enhance the SC over limestone substrate significantly over short time from −43.78 dyn/cm in the presence of water to −4.12 dyn/cm and −1.48 dyn/cm, respectively. However, the addition of AF1235 severely reduces the SC of crude oil droplet on limestone substrate due to the effect of AF1235 network structure on the spreading of crude oil. Table 6, also, shows that the SC is almost time independent behavior. The wetting improvement parameter, WIP [25], can be used to recognize the magnitude of spreading enhancement introduced by different investigated materials,
Fig. 12. Behavior of θ –Ca in the presence of Triton X-100. Table 4 Fitting analysis for NaOH aqueous solution continuous phase
WIP = (SCi − SCf ) × 100/SCi ,
Concentration (%)
a
b
c
0.0 2.5 5.0 7.5
73.183 76.278 79.694 59.138
68.888 250.045 186.217 154.363
0.0132 0.1933 0.2206 0.1433
Table 5 Fitting analysis for Triton X-100 aqueous solution continuous phase Concentration (%)
a
b
c
0.0 0.05 0.1 0.2
73.183 94.368 87.189 105.764
68.888 156.707 51.605 166.699
0.0132 0.1866 1.027 0.3678
dependent of Ca, which means that the hydrodynamic forces play no role in the movement of the three-phase contact line. Therefore, the spreading behavior under these conditions is very limited. However, the situation is completely improved when NaOH is added to the pure water, as can be concluded from Fig. 11. The addition of NaOH gradually reduces the contact angle of the crude oil droplet. Figure 11 also shows a strong dependency of contact angle on Ca in the presence of NaOH solution, which means that the spreading of the three-phase contact line is significantly influenced by the hydrodynamic forces. Figure 12 shows similar behavior in the presence of low concentrations of surfactant, which provides a great tendency to enhance the movement behavior of the three-phase contact line. Fitting analysis is carried out to model the relationship between contact angle and Ca. A power law model of three parameters provides excellent fitting results, θ = a + b(Ca)c ,
(6)
where SCi is the spreading coefficient of the crude oil droplet within water phase and SCf is the spreading coefficient of the crude oil droplet within aqueous solutions of different materials. WIP is calculated at elapsed time of 2 h. Table 7 shows the values of WIP for different concentration of the examined materials. Equation (6) provides good prediction tools for the complete spreading situation; i.e., if SCf reaches a value of 0.0 (complete spreading behavior) the WIP approaches 100%, whereas, if SCf does not change from SCi , the WIP will equal zero. Table 7 shows that the NaOH and Triton X-100 provide the appropriate environment to enhance the spreading behavior of the crude oil droplet significantly. However, AF1235 polymer causes a huge reduction in the crude oil spreading; for example, the presence of 0.1% polymer reduces the spreading coefficient by about five and half times from the spreading of crude oil alone. One way to improve the spreading performance of crude oil droplets within the polymer solution is the addition of the surfactant material to the AF1235 aqueous solution. The addition of 0.1% Triton X-100 is investigated for the spreading behavior of crude oil droplets within the continuous phase of 0.2% AF1235 polymer solution. Under these conditions, the IFT is dropped from 173.67 mN/m with polymer alone to 1.134 mN/m in the presence of Triton X-100. Therefore, the presence of Triton X-100 enhances the spreading characteristics of crude oil droplets significantly. The SC increases from −270.74 mN/m for AF1235 alone to −1.83 mN/m when Triton X-100 is added. The WIP rises strongly from the lowest reported value of −532.74% to 95.73%, which indicates almost complete spreading.
(5)
where a, b, and c are fitting parameters. The fitting analyses of NaOH and Triton X-100 aqueous solutions are reported in Tables 4 and 5, respectively. 3.4. Spreading coefficient (SC) Spreading coefficient displays the combined actions of both interfacial tension and contact angle of crude oil
4. Conclusions Spreading behavior of crude oil droplets is studied over a limestone substrate in the presence of aqueous solutions of NaOH, Triton X-100, and AF1235 polymer. The spreading behavior is investigated in terms of wetting length, droplet depth, contact angle, and spreading coefficient. The following conclusions can be made:
M.T. Ghannam / Journal of Colloid and Interface Science 262 (2003) 435–441
441
Table 6 Spreading coefficient parameter for crude oil droplet Time (min)
Water
2.5% NaOH
0.05% surfactant
0.1% polymer
0.5 1 5 10 20 30 40 50 60 75 90 105 120
−43.78 −43.48 −43.27 −43.23 −43.21 −42.98 −42.17 −42.64 −42.41 −42.08 −42.81 −41.57 −42.79
−4.12 −4.02 −3.94 −3.12 −3.03 −2.93 −2.72 −2.65 −2.58 −2.47 −2.43 −2.14 −2.21
−1.48 −1.44 −1.28 −1.31 −1.24 −1.28 −1.34 −1.31 −1.28 −1.31 −1.28 −1.32 −1.34
−270.73 −267.46 −267.29 −266.82 −265.21 −265.39 −266.03 −265.42 −270.52 −266.34 −267.40 −267.21 −267.15
Acknowledgment
Table 7 Wetting improvement parameter for crude oil droplet NaOH (%)
WIP (%)
Triton X-100 (%)
WIP (%)
AF1235 (%)
WIP (%)
0.0 2.5 5.0 7.5 10.0 –
0.0 94.84 95.75 95.32 93.43 –
0.0 0.05 0.1 0.2 0.3 –
0.0 96.87 97.81 97.18 97.26 –
0.0 0.1 0.2 0.3 0.4 0.5
0.0 −524.4 −532.7 −520.3 −392.4 −373.8
1. Aqueous solutions of NaOH and Triton X-100 enhance the wetting length of crude oil droplets significantly; however, the presence of AF1235 solution reduces the wetting length gradually with polymer concentration. 2. NaOH and Triton X-100 decrease the values of droplet depth significantly due to the effect of surface-active behavior on the crude oil droplet. However, AF1235 polymer shows an insignificant influence on the droplet depth behavior. 3. The contact angle of the crude oil droplet over the limestone substrate decreases strongly in the presence of NaOH or Triton X-100. On the other hand, the presence of AF1235 polymer solution raises the experimental measurements of contact angle. 4. The presence of NaOH or Triton X-100 increases the velocity of the three-phase contact line of the crude oil droplet on the limestone substrate. Therefore, NaOH and Triton X-100 improve the spreading of crude oil droplets. 5. Both SC and WIP are improved significantly in the presence of NaOH and Triton X-100. However, AF1235 polymer causes a huge reduction for both SC and WIP. 6. The addition of 0.1% Triton X-100 enhances the spreading of 0.2% AF1235 (i.e., the lowest reported spreading behavior) significantly. WIP increases from −532.74% (polymer alone) to 95.73% when 0.1% of Triton X-100 is added.
The author is grateful for financial support from the United Arab Emirates University under Grant 03-02-711/03.
References [1] H.Y. Jennings, G.H. Newman, SPE J. (1971) 171. [2] R.L. Hoffman, J. Colloid Interface Sci. 50 (1975) 228. [3] G. Strom, M. Fredriksson, P. Stenius, B. Radoev, J. Colloid Interface Sci. 134 (1990) 107. [4] A.M. Schwarts, S.B. Tejada, J. Colloid Interface Sci. 38 (1972) 359. [5] J.G. Petrov, B.P. Radoev, Colloid Polym. Sci. 259 (1981) 753. [6] G.N. Clifton, V. Dussan, J. Fluid Mech. 118 (1982) 27. [7] T.D. Blake, J.M. Haynes, J. Colloid Interface Sci. 30 (1969) 421. [8] B.W. Cherry, C.M. Holmes, J. Colloid Interface Sci. 29 (1969) 174. [9] R.L. Hoffman, J. Colloid Interface Sci. 94 (1983) 470. [10] E. Ruckenstein, C.S. Dunn, J. Colloid Interface Sci. 59 (1977) 135. [11] V. Starov, S. Kosvintsev, M. Velarde, J. Colloid Interface Sci. 227 (2000) 185. [12] C.E. Brown, E.L. Neustadter, J. Can. Pet. Techol. 19 (3) (1980) 100. [13] G. Strom, M. Fredriksson, P. Stenius, J. Colloid Interface Sci. 134 (1990) 117. [14] W.G. Cutler, R.C. Davis (Eds.), Detergency—Theory and Test Methods, Part III, Dekker, New York, 1981. [15] E.H. Lucassen-Reynders (Ed.), Anionic Surfactants—Physical Chemistry of Surfactant Action, Dekker, New York, 1981. [16] M.J. Schick, Nonionic Surfactant, Dekker, New York, 1967. [17] M. Lewin, S.B. Sello, Handbook of Fiber Science and Technology, Vol. 2, Part B, Dekker, New York, 1984. [18] P.G. De Gennes, Rev. Mod. Phys. 57 (1985) 827. [19] N.V. Churaev, V.M. Starov, J. Colloid Interface Sci. 103 (1985) 301. [20] R.L. Kao, D.T. Wasan, A.D. Nikolov, D.A. Edwards, Colloids Surf. 34 (1988) 389. [21] J.F. Padday, in: K.L. Mittal (Ed.), Contact Angle, Wettability and Adhesion, VSP, Utrecht, 1993. [22] A. Carcoana, Applied Enhanced Oil Recovery, Prentice–Hall, Englewood Clifs, NJ, 1992. [23] R.G. Cox, J. Fluid Mech. 186 (1986) 169. [24] V. Dussan, J. Fluid Mech. 77 (1976) 665. [25] M.T. Ghannam, J. Chem. Eng. Data 47 (2002) 274.