Synthesis of two chiral surfactants by a simple method and the surface activity evaluation

Study of a high efficient composite foam drainage surfactant for gas production

The foam drainage technique for gas production has the disadvantage of requiring a large amount of surfactant and having low resistance to salt and oil. In this study, a new surfactant mixture (composite surfactant) of lauramidopropyl betaine (LAB-35), α-olefin sulfonate (AOST), sodium alkyl sulfonate (SASE) and cetyltrimethylammonium bromide (CTAB) was tested and its foaming properties were investigated in detail. The foaming properties were determined using high-speed measurements and the Ross-Miles method. The results show that the foaming volume of the composite surfactant can reach 563 mL, indicating that the foaming behaviour of the composite surfactant is more effective than that of the individual surfactants used for the mixture. In addition, the results show that the composite surfactant has a resistance to salt, methanol and condensate oil that most foam drainage agents do not have. However, the stability of the composite surfactant gradually decreases with increasing temperature and concentration. The surface tension was measured and the critical micelle concentration of the composite surfactant is 0.023 g/L.

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.

Study of the Surfactant Transport Law Based on an Improved Adsorption Model with an Artificial Seismic Wave

To explore the law and mechanism of enhanced surfactant flooding with a low-frequency artificial seismic wave, for single-phase fluids in porous media, a heterogeneous two-stage adsorption model for a surfactant with a low-frequency artificial seismic wave is introduced into the surfactant transport equation of a single-phase fluid. With this model, the surfactant fluid transport model in porous media with an artificial seismic wave is obtained. The model is solved using the C-N difference and chasing method. The migration law of the surfactant is simulated and quantitatively analyzed for different vibration accelerations, injection slug sizes, displacement speeds, and reservoir parameters with the action of low-frequency artificial seismic waves. The results show that artificial seismic waves can increase the effective range of the surfactants and reduce the number of chemical agents through reduced adsorption. Low-frequency vibration with the same surfactant injection rate can increase the effective range by a factor greater than one. For the same effective action distance, the dose of chemical agents can be reduced by more than 60%, and the optimal acceleration and the injection slug size are 0.3 m/s² and 0.4 PV, respectively. With the increase of the injection rate, the effect of low-frequency vibration on the diffusion and transport of the surfactant decreases. A low-frequency wave combined surfactant has a better effect on the low permeability reservoirs. The research results provide important support for further understanding of the low-frequency artificial seismic wave composite surfactant flooding law and the optimization of the field parameters.

Corrosion Inhibition Coating Based on the Self-Assembled Polydopamine Films and Its Anti-Corrosion Properties

Metal corrosion is becoming increasingly serious in oil and gas production, and one way to solve this problem is to modify the metal surface. Thus, a corrosion inhibition coating on the N80 steel was constructed via the self-polymerization and assembling of the dopamine. The optimum reaction condition of polydopamine films was determined by the corrosion rate assessment of the films coated N80 steel, which was the reaction at 60 °C and 5 g/L dopamine in the Tris-HCl buffer solution (pH = 8.5) for 1 h. The spectral results confirmed the existence of the polydopamine coating on the surface of N80 steel, and high stability of the coating in the oil well produced water was observed. The anti-corrosion performance of the polydopamine-coated N80 steel confirmed that high temperature accelerated the anti-corrosion effect of the coating, and the corrosion rate of N80 plate in 90 °C oil well produced water was 0.0591 mm·a⁻¹, lower than the standard value. The corrosion rates of the polydopamine coated N80, A3 and J55 plates at 90 °C were 0.0541 mm·a⁻¹, 0.0498 mm·a⁻¹ and 0.0455 mm·a⁻¹, respectively. No significant effects of the categories of corrosive medium and steel plate on the performance of the coating were observed.

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%.

Achieving the Super Gas-Wetting Alteration by Functionalized Nano-Silica for Improving Fluid Flowing Capacity in Gas Condensate Reservoirs

It is well-known that the production of gas-condensate reservoirs is significantly affected by the liquid condensation near the wellbore region. Gas-wetting alteration can be one of the most effective approaches to alleviate condensate accumulation and improve liquid distribution. However, gas well deliverability is still limited because the wettability of cores is altered only from liquid-wetting to intermediate gas-wetting by using traditional chemical stimulation. To solve this bottleneck problem, herein, we developed a fluorine-functionalized nanosilica to achieve super gas-wetting alteration, increasing the contact angles of water and n-hexadecane on the treated core surface from 23 and 0° to 157 and 145°, respectively. The surface free energy reduces rapidly from 67.97 to 0.23 mN/m. The super gas-wetting adsorption layer on the core surface formed by functionalized nanosilica not only increases the surface roughness but also reduces the surface free energy. The core flooding confirms that the required pressure for displacement is apparently reduced. Meanwhile, the core permeability can be dramatically restored after the super gas-wetting alteration. The microscopic visualization is employed to further understand the impact of fluorine-functionalized nanosilica on the fluid flow behavior and mechanism in porous media. The oil saturation in the micromodel decreases sharply from 48.75 to 7.84%, eliminating the "water locking effect" and "Jiamin effect", which indicates that the added functional nanosilica effectively improves fluid flow capacity and may contribute to production in the gas condensate reservoirs. In addition, this work reveals the fluid flow behavior and mechanism in the reservoir in detail, which will expand the better application of this material to many oilfields and other mining engineering systems.