Synthesis and Characterization of Surfactant for Retarding Acid-Rock Reaction Rate in Acid Fracturing.

Fuli Yan,Yongmin Shi,Yu Tian

doi:10.3389/fchem.2021.715009

Fuli Yan, Yongmin Shi + Show 1 more

Open Access

https://doi.org/10.3389/fchem.2021.715009

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Abstract

Acid fracturing is an effective method to develop ultra-low permeability reservoirs. However, the fast reaction rate reduces the effect of the acid fracturing and increases the near-well collapse risk. Therefore, it is necessary to retard the acid–rock reaction rate. In this work, we synthesized an acid-resistant Gemini zwitterionic viscoelastic surfactant (named VES-c), which has good performances such as temperature resistance, salt resistance, and shear resistance. Besides, a low concentration of VES-c increases the viscosity of the acid solution. The CO2 drainage method was used to measure the reaction rate between the dibasic acid and dolomite/broken core. We find that the dibasic acid containing 0.3% VES-c retards the dolomite reaction rate of 3.22 times compared with only dibasic acid. Furthermore, the dibasic acid containing 0.3% VES-c exhibits uniform distribution and is not easy to adhere to the solid surface. The VES-c also is favorable to reduce the formation of amorphous calcium carbonate. Retarding the rate of acid–rock reaction and enhancing the acidification are mainly attributed to VES-c's salt-tolerance, anti-adsorption, and the property of increasing the viscosity of the solution. Hopefully, this kind of surfactant retarding reaction rate is applied to other acid–rock reactions.

Highlights

Conventional oil fields have entered the middle and late stages of exploitation after years of development, but there are still low and difficult exploitation potentials
Erucamidopropyl dimethylamine of 42.24 g (100.1 mmol) was dissolved in 40 ml ethanol in a beaker, and the ethanol solution was poured into the flask containing the FIGURE 2 | 1H NMR of viscoelastic surfactant (VES-c)
No worm-like micelle structure was formed in the 0.3% VES-c solution, the viscosity of 0.3%VES-c dibasic acid (3% HCl+5% CH3COOH) increases due to its special molecular structure forming the layer structure with pores

Summary

INTRODUCTION

Conventional oil fields have entered the middle and late stages of exploitation after years of development, but there are still low and difficult exploitation potentials. Hydraulic fracturing fluid has been widely used, it still represents the poor stability to shear resistance and serious filtration loss. This kind of surfactant fracturing fluid shows good performance, such as shear resistance, temperature resistance, salt resistance, and harmlessness to reservoirs (Yu et al, 2019a; Chen et al, 2019). Acid fracturing is a widely used technique in both new and existing wells to increase the production in ultra-low permeability reservoirs (Rbeawi et al, 2018). To improve the cleaning efficiency of acid on reservoir interstitial materials, the polymer and viscoelastic surfactant (Afra et al, 2020) are used to increase the viscosity of the acid solution, reduce fluid loss, and prolong the distance of acid etching (Jones and Dovle, 1996). The polymers do not break gel and adhere to the surface of the rock, causing damage to the reservoir. The VES-c does not adhere to the rock surface

RESULTS AND DISCUSSION

CONCLUSION

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