适用于页岩的低分子烷烃无水压裂液性能研究

页岩气等非常规油气藏在压裂改造中面临着耗水量巨大、返排废液处理困难及储层伤害严重等诸多问题,因此探索新型无水压裂技术来替代传统的水力压裂,对实现非常规油气藏的高效开发具有现实意义。利用五氧化二磷、磷酸三乙酯和混合醇合成了二烷基磷酸酯胶凝剂,将其与新型络合铁交联剂在低碳烷烃中成胶制备出低分子烷烃无水压裂液,并对其基本性能以及流变特性进行了研究。研究结果表明,在交联比为100.0:3.5和胶凝剂质量分数为1.5%的最优条件下制备的压裂液冻胶,具有良好的耐温抗剪切性和携砂性,能完全满足储层压裂施工的各项要求;交联冻胶的黏弹性、剪切稀释性能随胶凝剂质量分数的变化而变化,且具有明显的变化规律;非线性共转Jeffreys本构方程可很好地表征低分子烷烃无水压裂液的流变曲线,为其应用提供了理论依据。 

The Properties of Non-Aqueous Fracturing Fluid with Low-Molecular Alkane Suitable for Shales

During the fracturing stimulation of unconventional oil and gas reservoirs (e.g. shale gas), various challenges are encountered, including the large amount of water consumption, difficult disposal of flow-back waste fluid and formation/reservoir damage. It is meaningful to explore a new non-aqueous fracturing technology to replace the traditional hydraulic fracturing technology for development and production of unconventional oil and gas reservoirs. The dialkyl phosphate gelling agent was formed through the reaction among phosphorus pentoxide (P2O5), triethyl phosphate (TEP) and mixed alcohols, it was mixed with a modified complex iron crosslinking agent in the low-carbon alkane to produce the low-molecular alkane non-aqueous fracturing fluid. By analyzing its basic performance and rheological property,the result showed that the fracturing fluid gel was prepared by the crosslinking ratio 100.0:3.5 and gelling agent mass fraction 1.5%), which can meet the requirements of reservoir fracturing operations with good temperature resistance, shear resistance and proppant carrying capacity.The viscous elasticity and shear thinning capacity of crosslinking gel tend to vary with the mass fraction of gelling agent, with obvious regularity. The rheological curves of the low-molecular alkane fracturing fluid can be characterized by the non-linear co-rotational Jeffreys constitutive equation, which provides the theoretical basis for the new fracturing fluid.