Systematic investigation of the effects of mixed cationic/anionic surfactants on the interfacial tension of a water/model oil system and their application to enhance crude oil recovery

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In our previous report, the mixed cationic/anionic surfactant system consisting of N‐dodecyl‐N‐methylpyrrolidinium bromide (L12) and sodium dodecyl sulfate (SDS) showed good interfacial tension (IFT) reduction of water/model oil (Vtoluene:V n‐decane = 1:1). In the present study, the effects of divalent salts (MgCl2 or CaCl2) on the interfacial activity were systematically evaluated. The additional Mg2+ ions greatly reduced the IFT to an ultralow value, whereas Ca2+ ions caused the generation of the precipitates and resulted in increased IFT values. The precipitates disappeared in binary divalent salt solutions, and the IFT values remained at a low level. Based on the valence, polarizability, and hydrated radius of the ions, we proposed a model to explain the abnormal changes. The effects of NaCl and temperature were investigated to further verify our proposed mechanism. Moreover, the additional divalent salts obviously enhanced the stability of L12/SDS stabilized emulsions.

Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…Chemicals N-dodecyl-N-methylpyrrolidinium bromide (L12) was synthesized according to our previous report (Jia et al, 2017a).…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effects of Divalent Salts on the Interfacial Activity of the Mixed Surfactants at the Water/Model Oil Interface

Jia

Han

et al. 2019

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Salt‐Induced Constructions of Gemini‐like Surfactants at the Interface and Their Effects on the Interfacial Tension of a Water/Model Oil System

Jia

Huang

et al. 2018

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It is an urgent issue to enhance oil recovery for unconventional reservoirs with high salinity. Focused on this topic, salt addition is a powerful tool to motivate the surfactant assembly at the water/oil interface and improve the interfacial activity. We used a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic salt dicarboxylic acid sodium (CnDNa) to construct gemini-like surfactants at the interface and evaluated their ability to reduce the interfacial tension (IFT) between model oil (toluene and n-decane, v:v = 1:1) and water. Interestingly, the fabrication of a (CTAB) 2 /C4DNa gemini-like surfactant was hardly achieved at the fresh water/model oil interface, but accomplished at the brine/model oil interface. At a high NaCl concentration (100,000 mg L −1 ), the IFT value is reduced to 10 −3 mN m −1 order of magnitude, which is generally desired in practical applications. The control experiments displacing the surfactant type and the spacer length further confirmed the NaCl effects on the interfacial assembly.

Investigation of Interfacial Tension Reduction, Wettability Alteration, and Oil Recovery Using a New Non‐ionic Oil‐Based Surfactant from Gemini Surfactants Family Coupled with Low‐Salinity Water: Experimental Study on Oil‐Wet Carbonate Rock

Dabiri

Honarvar

2020

Low‐salinity surfactant (LSS) flooding is a combined enhanced oil recovery (EOR) technique that increases oil recovery (OR) by altering the rock surface wettability and reducing oil–water interfacial tension (IFT). In this study, optimum concentrations of several types of salt in distilled water were obtained on the basis of IFT experiments for the preparation of low‐salinity water (LSW). Then, a new oil‐based natural surfactant (Gemini surfactant, GS) was combined with LSW to investigate their effects on IFT, wettability, and OR. Experimental results showed that LSW is capable of reducing IFT and contact angle, but the synergy of GS and the active ions Mg2+, Ca2+, and SO42− in LSW was more effective on IFT reduction and wettability alteration. The combination of 1000 ppm MgSO4 and 3000 ppm GS led to a decrease in contact angle from 134.82° to 36.98° (oil‐wet to water‐wet). Based on core flooding tests, LSW injection can increase OR up to 71.46% (for LSW with 1000 ppm MgSO4), while the combination of GS and LSW, as LSS flooding, can improve OR up to 84.23% (for LSS with 1000 ppm MgSO4 and 3000 ppm GS). Therefore GS has great potential to be used as a surfactant for EOR.