Study On Cleanup Additive And Evaluation Method For Fracturing

The cleanup additive for fracturing is composed of surfactant.Fluorinated surfactants have good resistance to temperature and could reduce surface tension,but its cost is high and it would cause some extend pollution to the environment.In this paper,sodium bisulfite,epichlorohydrin,dodecyl tertiary amine and isopropanol are used as raw materials to synthesize SQHT surfactants,and then compounded with low surface and interfacial tension surfactants for fracturing with SY-3 cleanup additive.Through the research on the drainage mechanism and the operational characteristics of cleanup additive,its surface tension,interfacial tension,stability,wetting angle with lipophilic,hydrophilic glass flakes,and the compatibility with fracturing fluid,drainage performance and core damage were comprehensively evaluated.(1)The optimal synthesis conditions of SQHT surfactant are:solvent(isopropanol and water)ratio 3:1,reaction temperature 90℃,reaction time 4h,yield reached more than 97%.At regular temperature,the critical micelle concentration(CMC)of the SQHT surfactant aqueous solution is about 0.1%by mass,and the surface tension corresponding to the CMC point is 29.8mN/m.When the concentration is greater than or equal to 0.3%,the interfacial tension reaches the order of magnitude of 10-2.This indicates that the surfactant has a lower critical micelle concentration,and also has lower surface tension and interfacial tension.In the salt resistance test,as the salinity of Na+,K+,Mg2+,and Ca2+increased,when the concentration reached 100000 ppm,the change rate of surface tension was around 10%,showing good salt resistance.At the same temperature,as the concentration increases,the water drainage rate of the SQHT surfactant aqueous solution decreases,and the water drainage rate at 120 minutes was less than 40%.(2)The critical micelle concentration(CMC)of the SY-3 cleanup additive aqueous solution was about 0.1%by mass,the surface tension corresponding to the CMC point was 22.8mN/m,and when the concentration was greater than 0.05%,the interfacial tension with kerosene is Reached the order of 10-2,with a constant temperature of 60℃ for 6h,the surface tension change≤0.5mN/m,and the interfacial tension changed less than 0.12mN/m.The surface and interfacial tension after compounding are lower than those before compounding and are in line with industry standards.When the concentration of SY-3 cleanup additive solution was 0.2%,the temperature was 60℃,70℃ and 80℃ respectively,the surface contact angles were 69.7°,65.3° and 62.8° respectively,and the contact angles on the surface of the hydrophilic glass sheet were 69.5°,63.9° and 62.5° respectively,it showed weak hydrophilicity,which is conducive to the backflow of the fracturing fluid.After comparing the blank control group with five groups with different concentrations of cleanup additive,it illustrates that the influence rate of the viscosity of the base fluid and the jelly fluid was much less than 15%,and could effectively reduce the surface and interfacial tension of the gel breaker fluid.It shows that the compatibility of SY-3 cleanup additive and fracturing fluid is good;when the concentration of cleanup additive was 0,the average discharge efficiency was 48.74%.After adding different concentrations of cleanup additive,the drainage efficiency was greater than 87%,and the drainage rate was more than 79%,indicating that SY-3 cleanup additive has good drainage effect.When the concentration of cleanup additive is 0,the core injury rate of fracturing fluid was 16.7%,and the core injury rate of fracturing fluid with different concentrations of cleanup additive was between 15.8%and 16.9%.The maximum was about 5%,so the addition of SY-3 cleanup additive to the fracturing fluid has very little effect on the core damage.(3)Through the tests of various performances of SY-3 cleanup additive with different concentrations at the optimal ratio,considering various evaluation results of performance and economically reasonable factors,the optimal ratio of SY-3 cleanup additive for fracturing was finally determined as the ratio was silicone:BDE(B:D:E=1:1:2)=1:4,and the concentration was 0.1%.