A new compounded clean fracturing system based on Gemini surfactant

This paper is aimed at building up a new compounded clean fracturing system of low damage. After cationic Gemini surfactant was synthesized, a new compounded clean fracturing system based on Gemini surfactant was developed by combining nonionic surfactant with organic salt additive. Then, its performance was evaluated in laboratory. It is shown that after this fracturing system is sheared at 170 s^-1 under 120 ℃ for 90 min, it is better in temperature and shear resistance and its viscosity is still kept at about 90 mPa·s. Its elasticity is still higher in the case of lower viscosity, so it can satisfy the demand of proppant carrying. After this fracturing system is set under the air temperature for 90 d, its viscosity is nearly constant, indicating good stability. Its viscosity is lower than 5.0 mPa·s after gel breaking for 20 min by kerosene and formation water. And it is indicated that the gel breaking of this fracturing system is fast and thorough. The interfacial tension of gel breakers is 0.416 mN/m and 0.605 mN/m, respectively, which are favorable for the back flow of fracturing gel breaker. After gel breaking by kerosene and formation water, their damage ratios to natural cores are 8.71%and 12.02%, respectively, presenting the characteristic of low damage. This new type of compounded clean fracturing system based on Gemini surfactant is applied on site in Well CZ-22. It is shown that after the fracturing, the daily oil production of Well CZ-22 is four times that of its neighboring unfractured well (Well CZ-21). It is demonstrated that the fracturing stimulation effect of this fracturing fluid system is remarkable.