Experimental research on synergistic drag reduction of cationic surfactant and nonionic polymer

When the OTAC/NaSal con-centration reaches polymer saturation point of 1200 ppm, thedrag reduction rate of the mixed solution reaches the max-imum value of 14.09% and the drag reduction

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Petroleum Science and Technology

ISSN: (Print) (Online) Journal homepage: www.tandfonline.com/journals/lpet20 Experimental research on synergistic dragreduction of cationic surfactant and nonionicpolymer

Jiaqiang Jing, Ying Yuan, Ran Yin, Peiyu Jing & Xianfeng LiuTo cite this article: Jiaqiang Jing, Ying Yuan, Ran Yin, Peiyu Jing & Xianfeng Liu

(2023) Experimental research on synergistic drag reduction of cationic surfactantand nonionic polymer, Petroleum Science and Technology, 41:1, 45-63, DOI:10.1080/10916466.2022.2029884

To link to this article: https://doi.org/10.1080/10916466.2022.2029884

Published online: 13 Apr 2022.

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The coupling of surfactant and polymer can weaken theirshortcomings, improve drag reduction rate, and enhance thestability of drag reduction This paper takes the cationic sur-factant octadecyl trimethyl ammonium chloride and the non-ionic polymer polyethylene oxide as the research objects, anduses the coaxial cylinder system of Anton Paar MCR102 tostudy the synergistic drag reduction of cationic surfactant andnonionic polymer The experimental results show that cationicsurfactants and nonionic polymers has obvious synergisticdrag reduction Compared with 800 ppm OTAC/NaSal solutionor 40 ppm PEO solution, the drag reduction increases by61.49% and 19.78%, respectively Moreover, the drag reduc-tion rate of the mixed solureduc-tion is not monotonically increasingwith the surfactant concentration When the OTAC/NaSal con-centration reaches polymer saturation point of 1200 ppm, thedrag reduction rate of the mixed solution reaches the max-imum value of 14.09% and the drag reduction rate increasesby 34.15%; when the concentration of OTAC/NaSal is less than1200 ppm, the drag reduction rate increases with the increaseof the concentration of cationic surfactant; however, when theconcentration of OTAC/NaSal is greater than 1200 ppm, thedrag reduction rate is basically stable In addition, the shearresistance of the mixed solution is significantly enhanced.

cationic surfactant; coaxialcylinder; injection pipeline;nonionic polymer;synergistic drag reduction

1 Introduction

With the oilfield development entering the middle and late stages, the water injection pipeline is often difficult to meet the water injection demand due to insufficient design output (Jing et al 2019) Hence, for water injection oilfield, how to effectively reduce the frictional resistance and increase the transportation amount of the water injection pipeline are the technical problems that need to be solved urgently At present, the main methods of drag reduction include: riblet drag reduction (Ao, Wang, and Zhu 2021), LEBU (Large-Eddy Break Up) devices drag reduction

CONTACTYing Yuan201811000100@stu.swpu.edu.cnCollege of Petroleum Engineering, SouthwestPetroleum University, Chengdu, Sichuan 610500, China.

ß 2022 Taylor & Francis Group, LLC

(Cheng et al 2017), surface coating drag reduction (Taghvaei et al 2017), wall oscillation drag reduction (Skote, Mishra, and Wu 2019), additive drag reduction (Chai et al 2019), etc The additive drag reduction technology is widely used in the field of flow drag reduction because of its low dosage, wide source, simple operation and high drag reduction efficiency In gen-eral, drag reducers can be divided into polymers, surfactants, fibers, micro bubbles and smooth coatings (Mohsenipour and Pal 2013) Polymers and surfactants are the most commonly used drag reducers in industrial pro-duction, such as oil production (Lucas et al 2009), district heating and cooling (Jing et al 2021), sewage system (Liu, Wang, and Wei 2018), and firefighting (Chai et al 2019) However, each of them has certain advan-tages and disadvanadvan-tages Polymers can exhibit surprising drag reduction effect at a relatively low concentrations, but they are prone to degradation under high temperature or high shear, resulting in drag reduction failure And this degradation is permanent and irreversible Surfactants have good light, heat and mechanical stability, and their degradation is reversible, while, they become effectively only when the concentration above the crit-ical micelle concentration (CMC).

In recent years, related studies have shown that the coupling of surfac-tant and polymer can weaken the shortcomings of the both, improve the drag reduction rate, and enhance the stability of drag reduction Mohsenipour and Pal (2013) explored the role of surfactants in the mech-anical degradation of polymers, and found that adding anionic sodium dodecyl sulfate (SDS) to the nonionic polyacrylamide (PAM) solution will slow down the mechanical degradation and enhance its drag reduction Liu, Wang, and Wei (2018) studied the drag reduction of a mixed solution of nonionic polymer polyacrylamide (PAM) and cationic surfactant cetyl trimethyl ammonium chloride (CTAC), and found that the drag reduction of the mixture was greatly improved compared to a single drag reducer Chai et al (2019) studied the synergistic drag reduction of the mixed solu-tion of anionic surfactant sodium dodecyl sulfate (SDS) and different charge of polymer polyacrylamide (PAM), and found that the best drag reduction combination was anionic PAM and SDS It was also observed that the addition of SDS to the cationic PAM solution will lead to the flow resistance increases.

Until now, there are many studies on the drag reduction performance of pure surfactant or pure polymer, but the study on the synergistic drag reduction of the surfactant and polymer is less, and the mechanism of syn-ergistic drag reduction is not yet clear In this paper, the cationic surfac-tants octadecyl trimethyl ammonium chloride (OTAC) and nonionic polymer polyethylene oxide (PEO) are taken as the research object, and the coaxial cylinder system of the rotational rheometer is used to study the

establishing the microstructure prediction model of the mixed solution.

2 Experimental

2.1 Material

The cationic surfactant used in the experiment is octadecyl trimethyl ammonium chloride (OTAC), the nonionic polymer is polyethylene oxide (PEO) Sodium salicylate (NaSal) is used as the counterion in combination with a cationic surfactant (to enhance the stability of the micelle structure and reduce the critical micelle concentration of the surfactant solution) (Liu, Wang, and Wei 2018) All the above materials are shown in Table 1 And the experimental water is distilled water.

2.2 Sample preparation

Surfactant solution preparation: dissolve the OTAC and NaSal powders with desired concentration in 500 ml distilled water and stir with the mag-netic stirrer at 500 rpm for 30 min (the molar ration of OTAC to NaSal is 1:1), then keep stationary for 12 h to eliminate internal air bubbles and obtain a homogeneous surfactant solution Polymer solution preparation: sprinkle evenly the PEO powders with desired concentration on the 500 ml distilled water surface, and stir with the magnetic stirrer at 500 rpm for 12 h, then keep stationary for 12 h to obtain a homogeneous polymer solu-tion (Chai et al 2019) Surfactant-polymer solution preparation: mix the OTAC/NaSal solution and PEO solution in the beaker, stir with the mag-netic stirrer at 500 rpm for 2 h and keep stationary for 12 h to get homoge-neous mixture It should be noted that the experimental solution should be prepared within 24 h before the experiment In addition, the concentration range of surfactant, polymer and mixed solution are all presented in Table 2.

2.3 Experimental apparatus

At present, the instruments for measuring turbulent drag reduction mainly include pipe flow system, capillary rheometer and rotational rheometer The pipe flow system has disadvantages of complicated experimental device and long time-consuming The capillary rheometer has a large measure-ment error due to the limited measuremeasure-ment distance of the capillary However, the rotational rheometer can overcome the above-mentioned defects and obtain high precision experimental results in a shorter time Therefore, the coaxial cylinder system of commercial rotational rheometer Anton Paar MCR102 (speed range: 0 3000 rpm) is used for the turbulent drag reduction test in this paper Figure 1 is the geometric structure of the coaxial cylinder system, and the geometric parameters are shown in Table 3.

2.4 Data process

This paper uses the drag reduction rate (DR) to evaluate the drag reduction effect, and the DR is defined as Eq (1).

The relevant calculation equations for the evaluation of the drag reduc-tion rate is shown in Eqs (2)–(9) (Pereira and Soares2012).

Table 2.Concentration range of surfactant, polymer and compound system.

First of all, we conduct preliminary tests to ensure the accuracy and stabil-ity of test equipment and verify the effect of different flow regimes on drag reduction, and the experimental results are shown inFigures 2 and 3.

Figure 2(a) is the viscosity versus rotor speed of rotation curve of water at 25C, and Figure 2(b)is the fanning friction factor versus rotor speed of rotation curve of water at 25C In the region of laminar flow, the viscosity of water verifies the accuracy of the test equipment In addition, the two test curves can overlap well, which further verifies the stability of the test equipment.

As shown in Figure 3, there are two critical Taylor number value Ta I is 1700 and the corresponding Re is 140, Ta II is 11219 and the correspond-ing Re is 362 When the Ta< Ta I, the flow is laminar; when the Ta I<Ta < Ta II, the flow is unstable laminar; when the Ta > Ta II, the flow is turbulence Moreover, drag reduction can be only observed in the flow of

Figure 1.Geometric structure of the coaxial cylinder system.

Table 3.Geometric parameters of coaxial cylinder system.

Coaxial cylinder systemRa(m)Ri(m)L(m)CC2713.3270 10314.4675 10340.0200 103

turbulence This result is consistent with the research results of Pereira and Soares (2012), the drag reduction is not related to laminar instability such as Taylor vortices, and is only significant in the flow of fully turbulent 3.2 Surfactant drag reduction

3.2.1 Concentration effect

The drag reduction of surfactants is greatly affected by its concentration As the concentration increases, the microstructure of micelle in the solu-tion changes continuously When the changing microstructure acts on the macroscopic flow, there will be different drag reduction phenomena This paper tests the drag reduction of different concentrations of OTAC/NaSal solution, and the experimental results are shown in Figure 4.

It can be seen that there is not a single linear relationship between the drag reduction rate (DR) of OTAC/NaSal solution and its concentration As the concentration increases, the DR of OTAC/NaSal solution first increases and then decreases When the concentration is 200 ppm, there is

Figure 2.Experimental results of distilled water (T ¼ 25˚C).

Figure 3.Fanning friction factor in the coaxial cylizder system.

almost no drag reduction effect This is because the concentration does not reach the critical micelle concentration (CMC), only monomeric surfactants exist in the solution (Popova et al 2018) With the increase of concentra-tion, rod-like and thread-like micelles begin to form, and the solution grad-ually show more and more significant drag reduction effect (Wang et al 2011) At the concentration of 1400 ppm, the DR reaches the peak However, when the concentration exceeds 1400 ppm, the DR begins to decrease This is because the micelle structure in the solution has been saturated Increasing concentration only increases viscosity of the solution, resulting in a decrease in DR.

3.2.2 Rotor speed effect

With the increase of rotor speed, the micelle structure in the solution con-tinuously aggregates and ruptures under shearing, and the drag reduction rate changes accordingly This paper tests the drag reduction of OTAC/ NaSal solution at different rotor speeds, and the experimental results are shown in Figure 5.

As shown in Figure 5, when the rotor speed is low and the flow in the coaxial cylinder is laminar, the fanning friction factor of OTAC/NaSal solu-tion is greater than that of water, and the drag reducsolu-tion rate is negative When the flow in the coaxial cylinder reaches turbulence with the increases of rotor speed, the fanning friction factor of OTAC/NaSal solution is smaller than that of water, and the drag reduction effect is gradually signifi-cant The rotor speed at which the drag reduction occurs is defined as the first critical rotor speed However, the drag reduction rate does not increase infinitely with the increase of rotor speed When the drag reduction rate reaches the peak, and then continues to increase the rotor speed, the drag

Figure 4.Drag reduction rate versus OTAC/NaSal concentration at different rotor speeds.

reduction rate begins to decline This is because with the increase of rotor speed, the micelle structure in the solution is destroyed under strong shear-ing, resulting in the decrease of drag reduction rate (Wang et al 2011) The rotor speed at which the drag reduction rate begins to decrease is defined as the second critical rotor speed Moreover, it also can be seen that with the increase of concentration, the second critical speed gradually increases, such as the second critical rotor speed of 200 ppm is 796 rpm, 600 ppm is 1780 rpm, and 1000 ppm is 2270 rpm, which means that the drag reduction stability is enhanced The reason is that with the increaser of concentration, the micelle structure in the solution is more stable and the shear resistance increases.

3.3 Polymer drag reduction3.3.1 Onset of drag reduction

Drag reduction can be only observed in the flow of turbulence The point at which the drag reduction phenomenon starts to occur during the flow is called the onset of drag reduction As shown in Figure 6, the onset of drag reduction of PEO solutions with different concentrations are different, which is consistent with the research results of Pereira and Soares (2012) When the PEO concentration is 10–200 pm, the rotor speed corresponding to the onset of drag reduction increases slowly with the increase of concen-tration in the range of 551–612 rpm However, when the PEO concentra-tion exceeds 200 ppm, the rotor speed corresponding to the onset of drag reduction increases greatly, for example, the rotor speed corresponding to the onset of drag reduction of PEO solution with concentration of 250 ppm is 2630 rpm, and that of 300 ppm is 2790 rpm This phenomenon is closely related to the increase of solution viscosity (Sreenivasan and White2000).

Figure 5.(a) Fanning friction factor versus rotor speed and (b) Drag reduction rate versus rotorspeed with different OTAC/NaSal concentrations.

3.3.2 Concentration effect

Figure 7 shows the effect of polymer concentration on drag reduction It can be seen that PEO solution reaches the maximum drag reduction rate of 11.93% at 50 ppm, and the corresponding fanning friction factor is 0.0034; when the PEO concentration is less than 50 ppm, the drag reduction rate increases with the increase of PEO concentration, while the fanning friction factor is opposite; when the PEO concentration is greater than 50 ppm, as the PEO concentration increases, the fanning friction factor begins to recover and the drag reduction rate decreases.

The reason for the above phenomenon is that PEO is nonionic polymer When it is dissolved in water, the polymer molecules are mainly subjected to hydrophobic association With the increase of polymer concentration, the polymer molecular chain changed intramolecular association to inter-molecular association, and the inter-molecular chain gradually extended and intertwined to form aggregates (Cao et al 2008) These aggregates can effectively inhibit the occurrence of turbulence Therefore, the drag

Figure 6.Onset of drag reduction of PEO solution with different concentrations.

Figure 7.(a) Fanning friction factor versus PEO concentration and (b) Drag reduction rate ver-sus PEO concentration at different rotor speeds.