pH值对适于页岩气储层的SDBS压裂液性能的影响研究

Research on the Influence of pH on the Performance of SDBS Fracturing Fluid Suitable for Shale Gas Reservoir

摘要:

在低渗、低孔隙率页岩气储层压裂改造过程中，压裂液体系的pH值直接影响地层中的造缝、稳缝效果。pH值对阴离子表面活性剂压裂液的粘度、表面张力和页岩膨胀抑制性影响很大。通过改变阴离子表面活性剂的浓度，测定了在不同pH值条件下压裂液体系基本性能的变化。研究表明：SDBS压裂液体系的粘度随着pH值的增加先增大后减小，在pH值=9时达到最大；体系在pH值=5时降低体系表面张力的能力最好；页岩的膨胀量随着pH值的增大逐渐增大，在pH=7时膨胀量最大，且随着pH值的进一步增大，页岩膨胀量先减小后增大，在pH值=9时膨胀量最小；当体系的pH值一定时，SDBS在临界胶束浓度状态能够最大程度抑制页岩的膨胀。从化学微观角度上分析了pH值对SDBS压裂液性能的影响，有利于SDBS压裂液体系配方优化。

关键词:SDBS压裂液;pH值;粘度;表面张力;膨胀抑制性;页岩气

Abstract:

In the fracturing treatment process of shale gas reservoir with low permeability and low porosity, pH value of fracturing fluid system directly affects the formation and stability effects of fracturing, it also affects the anionic surfactant fracturing fluid a lot in viscosity, surface tension and shale swelling inhibitory. In this paper, by changing the concentration of the anionic surfactant, basic performance changes of fracturing fluid system in different pH conditions are measured. The experiment results indicate that the SDBS viscosity of SDBS fracturing fluid system increases with pH increase first, then decreases, and reaches the maximum when pH is 9. The best ability to reduce surface tension of the system is with pH 5. The expansion volume of the shale increases gradually with the increase of pH, and reaches the largest when pH is 7; along with the further increase of pH value, shale expansion decreases first and then increases, the expansion capacity is the smallest when pH is 9. When the pH value is invariable, SDBS can inhibit the shale expansion most in the state of critical micelle concentration. In this paper, the effect of pH value on the performance of SDBS fracturing fluid is analyzed from the chemical micro point of view, which is beneficial to the optimization of SDBS fracturing fluid system formula.

Key words:SDBS fracturing fluid; pH value; viscosity; surface tension; expansion inhibition; shale gas