Petroleum Science (2019) 16:318–327 https://doi.org/10.1007/s12182-018-0260-z (0123456789().,-volV)(0123456789().,- volV) ORIGINAL PAPER Novel application of PEG/SDS interaction as a wettability modifier of hydrophobic carbonate surfaces 1 2 3 2 Nasim Heydari • Mahdi Asgari • Narjes Shojai Kaveh • Zahra Fakhroueian Received: 24 April 2018 / Published online: 10 October 2018 Ó The Author(s) 2018 Abstract Wettability alteration of carbonate reservoirs from oil-wet to water-wet is an important method to increase the efficiency of oil recovery. Interaction between surfactants and polymers can enhance the effectiveness of surfactants in EOR applica- tions. In this study, the interaction of polyethylene glycol (PEG) with an ionic surfactant, sodium dodecyl sulphate (SDS), is evaluated on an oil-wet carbonate rock surface by using contact angle measurements. The results reveal that wettability alteration of carbonate rocks is achieved through PEG/SDS interaction on the rock surface above a critical aggregation concentration (CAC). The behaviour of PEG/SDS aqueous solutions is evaluated using surface and interfacial tension measurements. Furthermore, the effect of PEG and SDS concentrations and impact of electrolyte addition on PEG/SDS interaction are investigated. It is shown that electrolyte (NaCl) can effectively decrease the CAC values and accordingly initiate the wettability alteration of rocks. Moreover, in a constant SDS concentration, the addition of NaCl leads to a reduction in the contact angle, which can also be obtained by increasing the aging time, temperature and pre-adsorption of PEG on the rock surface. Keywords Sodium dodecyl sulphate (SDS) Á Polyethylene glycol (PEG) Á Wettability alteration Á Contact angle Á Critical aggregation concentration Á Carbonate surface 1 Introduction 2000, 2003; Zhang et al. 2006). These molecules may act as ‘‘anchors’’ for the other polar molecules adsorbing onto The recovery of oil in naturally fractured carbonate reser- the surface mostly by hydrophobic and dipole/dipole voirs is low in general and can be improved significantly by interaction in a co-operative process. Unless the injected the alteration of the wettability of carbonates from oil-wet water contains surface-active wettability-modifying conditions to water-wet conditions (Jarrahian et al. 2012; chemicals, no spontaneous imbibition of water can take Karimi et al. 2012; Nazari Moghaddam et al. 2015). It has place under these conditions due to a negative capillary been found that fatty acids and carboxylates from the crude pressure (Standnes and Austad 2003). oil are strongly adsorbed onto the carbonate minerals and For this purpose, chemicals such as surfactants have make the surface more oil-wet (Gomari et al. 2006; Jar- been widely considered before (Babadagli and Boluk 2005; rahian et al. 2012; Salehi 2009; Standnes and Austad Golabi et al. 2012; Hirasaki and Zhang 2004; Jarrahian et al. 2012; Kumar et al. 2016; Salehi 2009; Standnes and Austad 2000, 2003). Surfactant molecules contain at least Edited by Yan-Hua Sun one hydrophilic and one hydrophobic group; therefore, they can lower the interfacial tensions and alter wetting & Nasim Heydari [email protected] properties. SDS is one of the most popular surfactants. Due to the presence of the sulphate group, this surfactant is 1 School of Chemical Engineering, Iran University of Science sensitive to temperature (Chegenizadeh et al. 2016). Thus, and Technology, Tehran, Iran SDS performance is more effective in reservoirs with lower 2 School of Chemical Engineering, College of Engineering, temperature. For instance, in China 13 field cases have University of Tehran, Tehran, Iran been studied with the highest reservoir temperature of 3 Department of Geoscience and Engineering, Delft University 86 °C (Olajire 2014). It has been confirmed that an anionic of Technology, Delft, The Netherlands 123 Petroleum Science (2019) 16:318–327 319 surfactant such as SDS cannot change the wetting condi- (Osterloh and Jante Jr 1992). In addition, the polymer tions towards strongly water-wet (Jarrahian et al. 2012; interaction with surfactant can decrease the alkalinity in Salehi 2009; Standnes and Austad 2000). As an anionic ASP flooding in order to reduce the scaling problems of the surfactant, SDS adsorption to the rock surface, through rock minerals. hydrophobic interaction between its tail (hydrophobic part) Polymers are susceptible to mechanical degradation at and the adsorbed acid molecule on the surface, changes the high temperatures, and this occurs at lower temperatures in wettability of rock to neutral-wet condition. Among non- the case of high salinities, and this characteristic puts ionic, cationic and anionic surfactants, the ability of certain restrictions to their use in high-temperature reser- modifying the wetting properties to more water-wet voirs. PEG has been mentioned as being water soluble, salt decreases in the order: cationic [ non-ionic [ anionic tolerant and in some cases, thermo-responsive. Thus, the (Jarrahian et al. 2012; Standnes and Austad 2000). The use of PEG in the preparation of surface-active polymers cationic monomers interact with negatively charged has recently experienced a great interest (Raffa et al. 2016). adsorbed materials, mostly carboxylic groups, by electro- Osterloh and Jante Jr (1992) used a high salinity brine of static forces and desorb them from the rock surface by 190,000 mg/L TDS, to verify whether the PEG addition forming an ion pair (Gupta and Mohanty 2008; Jarrahian can improve the cost-effectiveness of surfactant/polymer et al. 2012; Kumar et al. 2016; Salehi 2009; Standnes and flooding. da Silva et al. (2004) studied the effect of tem- Austad 2000). Pillai et al. (2018) investigated the ability of perature in the SDS/PEG interaction within the range of a series of synthetized ionic liquids to alter the wettability 15–65 °C and observed that temperature variations are not of an oil-wet quartz surface. Wettability alteration was so significant as to influence the intensity of the interaction achieved by ion-pair formation through the interaction of PEG with SDS. In order to determine the cloud-point between the positively charged head groups of the ionic curve of the solutions of PEG in t-butyl acetate and in liquid and the carboxylic acid groups from crude oil (Pillai water, Saeki et al. (1976) examined the thermal degrada- et al. 2018). Adsorption of non-ionic surfactant on the rock tion of PEG. They confirmed that no thermal degradation surface through the polarization of p electrons and ion was observed for a solution of PEG in water in the range of exchange releases stearic acid from the surface. The acid is 40–240 °C. then adsorbed on the surface as a new layer through Jones (1967) showed that by changing SDS concentra- hydrophobic interaction between its non-polar part and the tion, the surface tension behaviour falls into three distinct tail of the adsorbed surfactants (Jarrahian et al. 2012). regions with two transition points. The first one is the point In addition, Dutkiewicz and Jakubowska (2002) have at which binding of surfactant aggregation to the polymer studied the influence of the type and concentration of chain starts and often known as critical aggregation con- electrolytes on the values of the critical micelle concen- centration (CAC). The second transition point is the critical tration (CMC) and the degree of electrolytic micelle dis- micelle concentration (CMC). Between CAC and CMC, sociation of aqueous solutions of SDS. They found that surface tension plots go through a plateau till all binding electrolyte cations cause a decrease in the CMC in the sites on the polymer chain are occupied and then start to ? ? ? 2? order: Na \ NH4 \ K \ Mg , and that the anions fall again; this point is referred to as the polymer saturation enhance the degree of electrolytic micelle dissociation in point (PSP). It is confirmed that the surface tension at CAC - - - the order: F [ ClO4 [ Cl . NaCl has the minimum is dependent on polymer concentration (Dey et al. 2015; effect on the electrolytic micelle dissociation of SDS Jones 1967); however, the surfactant concentration at this solution. point is independent of polymer concentration (Dai and Surface activity of the surfactants can be increased by Tam 2001; Jones 1967; Moroi et al. 1977). It is worthwhile surfactant/polymer interaction, resulting in a reduction in to mention that in several studies a minimum point was interfacial tension between the oil and the injected fluid observed in the surface tension isotherm due to the pres- and also wettability alteration by formation of a multilayer ence of dodecanol as an impurity in the SDS used (Dey (Karimi et al. 2012). Water-soluble polymers often interact et al. 2015; Lin et al. 1999; Umlong and Ismail 2007). with surfactants in aqueous solutions, and due to the It has been known that the driving force of the polymer– importance of applications of such mixtures, there is a surfactant complex formation is the interaction between great interest in a better understanding of the nature of the anionic head groups of the surfactant aggregation and the interaction and the behaviour of polymer/surfactant mix- ethylene oxide group of polymer (de Alvarenga et al. tures in the solution as well as at the interfaces (Penfold 2004), and both hydrophobic and electrostatic interactions et al. 2006; Purcell et al. 1998). For this purpose, poly- are playing a role in the formation of the polymer–sur- ethylene glycol (PEG) and sodium dodecyl sulphate (SDS) factant complex (Dey et al. 2015). The well-known struc- are the most studied systems. Using PEG reduces the ture for these complexes is the necklace model, in which chromatographic separation of surfactant components the SDS aggregations are bound to the polymer chain like 123 320 Petroleum Science (2019) 16:318–327 pearls of a collar (de Alvarenga et al. 2004; da Silva et al. (SDS), with a purity of 90%, and polyethylene glycol 2004; Jiang and Han 2000).