Synthesis and Interface Activity of a Series of Dicarboxylic Cationic Surfactants and a Structure–Efficiency Relationship Study

Preparation of Multifunctional Surfactants Derived from Sodium Dodecylbenzene Sulfonate and Their Use in Oil-Field Chemistry

Four products were obtained from sodium dodecylbenzene sulfonate (SDBS) and formaldehyde (40% solution) using a simple reaction. The products were characterized by TGA, IR, UV and MS to confirm the major chemicals in each sample. The new products could reduce the interfacial tension between oil and water in the experimental temperature range further compared to SDBS. The emulsion ability was also enhanced by SDBS-1 to SDBS-4. The oil-displacement efficiencies of SDBS-1 to SDBS-4 were obviously higher than that of SDBS, and the oil-displacement efficiency of SDBS-2 was the best, with an efficiency of 25%. The experimental results all indicate that these products have an excellent ability to reduce oil-water interfacial tension and that they can be used in the oil and petrochemical industry for oil production and have certain practical uses.

Use of Betaine-Based Gel and Its Potential Application in Enhanced Oil Recovery

In this paper, a betaine-based gel containing 2.0% erucamide propyl betaine (EAPB), 0.5% oleic acid amide propyl betaine (OAPB), and 0.1% KCl was prepared for use as a fracturing fluid. The performance evaluation showed that KCl may improve the temperature resistance and increase the viscosity of the optimized fracturing fluid. At 80 °C, the apparent viscosity of the viscoelastic surfactant (VES)-based fracturing fluid was approximately 50 mPa·s. Furthermore, the gel had high shear resistance, good viscosity stability, and high sand-carrying performance. After being sheared at 170 s−1 for 60 min, the reduction in viscosity was 13.6%. The viscosity of the gel was relatively stable at room temperature (27 °C) for one week. In a suspension containing 10% sand (particle size < 0.45 mm, density = 2.75 g cm−3), the settling velocity of proppant particles was 1.15 cm h−1. In addition, we detected that the critical micelle concentration of this gel was approximately 0.042 wt%. The viscosity could be reduced to <5 mPa·s at 60 °C within 1 h when 6.0% crude oil was present, and oil displacement experiments showed that the broken fracturing fluid can enhance the oil displacement rate up to 14.5%. This work may facilitate research on fracturing fluids and oil recovery.

Research of a Surfactant Gel with Potential Application in Oilfield

In this study, a viscoelastic surfactant gel was composed using erucoylamine propyl betaine and other additives. The formulation of this viscoelastic surfactant gel solution was determined as: erucamide propyl betaine:oleic acid amide propyl betaine:octadecyl hydroxyl sulfonate betaine = 1.7%:1.36%:0.01%. Then the performance of viscoelastic surfactant gel fluid was evaluated. The results showed that the viscoelastic surfactant gel has good temperature resistance and salt resistance. At 50°C, the apparent viscosity reaches the maximum value, 37 mPa · s, and it displays high shear resistance under the shear rate of 170 s–1, with the viscosity retention of 83.3%. Kerosene (1%) can completely break the gel within 2 h, which can convert the gel into a surfactant solution soon. Also the gel shows high emulsion ability, which can benefit the oil displacement in oilfield. Finally this gel can enhance the oil displacement rate as high as 28%.

The Effect of Halide Counter Ions and Methanol on the Foaming Behavior of Cationic Surfactants and a Mechanism Study

In this work, four quaternary ammonium cationic surfactants including cetyltrimethyl ammonium fluoride (CTAF), cetyltrimethyl ammonium chloride (CTAC), cetyltrimethyl ammonium bromide (CTAB) and cetyltrimethyl ammonium iodide (CTAI) were investigated to study the effect of halide anions on the surface activity and foaming performance. The result showed that CTAF had superior surface activity, which could reduce the surface tension of water to 33.15 mN/m at a low CMC (critical micelle formation concentration) of 1.65 mmol/L. Based on the calculation of Amin (the minimum occupied area per surfactant molecule), we assumed that this higher surface activity was related to the small ionic radius of the fluorine ion (F–). The foamability and foam stability of CTAF has great advantages over other surfactants studied. On this basis, the factors affecting the formation and stabilization of the CTAF foam were investigated. The results showed that foam formation benefited from high temperatures and low methanol concentration, while high salinity was beneficial for foam stability. When CTAF at a concentration of 0.2% was used as a foaming agent, foaming was excellent at a methanol concentration of 10%, a salinity of 22 ⨯ 104 mg/L, and a temperature of 90°C. With this study, uncertainties that existed in the literature regarding the effect of anion on surface activity and foam performance were explained and the effect of temperature, methanol and salinity on foam generation and stabilization was understood.

Preparation and the Foaming Activity Study of Hydroxymethyl Cetyltrimethyl Ammonium Chloride

In this paper, hydroxymethyl cetyltrimethyl ammonium chloride (HM-CTAC) was prepared from cetyltrimethyl ammonium chloride (CTAC) and formaldehyde with different molar ratios (1:1 to 1: 4). The effects of reaction conditions (molar ratio) on surface properties were studied, including surface tension, foaming ability, high temperature resistance, methanol resistance and salt resistance. The results show that the minimum surface tension of HM-CTAC is lower than that of CTAC, and HM-CTAC (1:1) has the lowest surface tension of 31.89 mN · m–1. The foam volume of HM-CTAC with different molar ratios is higher than that of CTAC, and HM-CTAC (1:4) has a high foam volume of 435 mL. Compared to CTAC, the HM-CTAC under different reaction conditions has higher temperature resistance. At the methanol content of 10 wt.%, the initial foam volume of HM-CTAC is higher than that of CTAC, and the initial foam volume of HM-CTAC (1:2) is the highest with a volume of 21.5 mL. Among all the surfactants prepared under different reaction conditions, HM-CTAC (1:3) has the highest salt resistance with a relatively stable change in foam volume under different salt contents.

Synthesis and Properties of Octadecyl Trimethyl Ammonium Polyacrylic Surfactants

In order to expand the application range of surfactants, octadecyl trimethyl ammonium chloride (OTAC) and polyacrylic acid (PAA) were used as raw materials to synthesize octadecyl trimethyl ammonium polyacrylic (OTAP). The molar ratios of OTAC to polyacrylic acid monomer were 1:1, 1:2 and 1:3. The synthesized compounds were named as OTAP-1, OTAP-2, OTAP-3. The obtained research results show that the best foaming ability was achieved with OTAP-1, and the best foam stability with OTAP-2. When the concentration was 2.0 g/L, the order of the emulsifying ability was: OTAP-1 > OTAP-2 > OTAP-3; when the concentration was 4.0 g/L, the emulsifying ability order was OTAP-2 > OTAP-3 > OTAP-1. OTAP-1 had a corrosion inhibition capacity of up to 85.11 %, and OTAP-2 and OTAP-3 had a sustained release rate of 81.06 % and 72.82 %, respectively. OTAP-3 had a good effect on scale inhibition, and the scale inhibition rate was 65.01 %.