基于Pickering乳液的页岩气藏水力压裂液构筑及作用机理

There are two key problems to be solved in hydraulic fracturing stimulation for shale gas reservoirs in China, such as the effective support of hydraulic fractures and the maintenance of long term conductivity.This project stems from the capacity of solid particles in Pickering emulsion can stabilize the fractures or concentrate together within fractures,which results in achieving high conductivity.The Pickering emulsion fracturing fluid system has been put forward, which is suitable for shale gas reservoir hydraulic fracturing. In this fluid system, solid particles are able to enter the fractures or micro-fractures together with emulsion.Focused on the material preparation of Pickering emulsion solid particles for shale gas reservoir hydraulic fracturing,the physical and chemical effects between Pickering emulsion and shale minerals,the mechanism of post-frac shale gas production increase and other problems, a lot of research have been carried out. The research includes the fabrication of Pickering emulsion system, the mechanism of stabilizing or propping up the fractures, the physical simulation of hydraulic fracturing, and the optimization of fracture system. Some experimental investigation and explanation are applied to the method of building up the Pickering emulsion suitable for the shale gas fracturing and the mechanism of stabilizing fractures and provide the high efficiency conductivity channel.The built-up and optimized Pickering emulsion hydraulic fracture system will omit the process of proppants transportation, simplify the fracturing technology and significantly increase the initial and ultimate production capacity.The Pickering emulsion hydraulic fracture system will be used to establish a new method to inject proppant within fractures and a new method to stabilize fractures for the shale gas development in China.

目前我国页岩气藏水力压裂改造需要解决裂缝有效支撑和维持裂缝长期导流能力两大主要问题，源于Pickering乳液内含固相颗粒能稳定裂缝或能在裂缝内聚集形成无限导流能力通道,提出构筑适合页岩气藏水力压裂的Pickering乳液压裂液体系。围绕稳定Pickering乳液的固相颗粒材料研制、乳液与页岩矿物间的物理化学作用、压裂后页岩气藏产能增加机理等科学问题，开展Pickering乳液构筑、稳定或支撑裂缝机理、水力压裂物理模拟、压裂体系优化等内容研究，实验探究与阐释适用于页岩气藏水力压裂的Pickering乳液的构筑方法、稳定裂缝与提供有效裂缝导流能力的机理。Pickering乳液水力压裂技术省略输送支撑剂环节，研究成果将大大简化水力压裂工艺，大幅度提高页岩气产能，为我国页岩气藏水力压裂创建一种注入支撑剂和稳定裂缝的新方法。

现如今，页岩储层的增产依赖于压裂液的更新及优化来实现收益的增长； 然而，由于滑溜水压裂液的砂承载能力有限，支撑剂不能深入到裂缝或微裂缝深处，致使压裂效果较差。为了解决这个问题，本项目组研制微米或纳米颗粒稳定的Pickering乳液，期望Pickering乳液作为压裂液，且在造缝过程中固相颗粒能支撑裂缝或稳定微裂缝。. 生物柴油、水和微米或纳米颗粒用来制备Pickering乳液。本项目研究了乳液的滤失性、稳定性、流变性、造缝能力和固体颗粒在裂缝中运移与堆积行为等。本项目设计了将可视化注入装置与显微镜连接的监测方法，来记录Pickering乳液的详细迁移现象。同时，采用扫描电镜、岩心驱替设备和水力压裂模型，研究了Pickering乳液中纳米及微米粒子的稳定和支撑裂缝作用机理。优选了适用于体系的添加剂，研发了一个完整的性能优良的Pickering乳液体系。. 通过上述研究方法，优选出纳米级二氧化硅颗粒与微米级硫酸钡颗粒作为配制Pickering乳液的固相颗粒，最佳固相颗粒质量分数为2%~3%，最佳油水比为4:6。通过可视化注入实验，发现Pickering乳液在注入裂缝后与页岩接触发生破坏，其所含的固相颗粒释放出来，吸附到壁面上，且经过水驱后仍有明显的吸附现象。页岩裂缝注入实验结果表明：Pickering乳液中的固相颗粒有良好的支撑裂缝的作用，颗粒在裂缝中会发生局部堆积，可以阻止裂缝的闭合，形成无限导流能力的通道。基于室内评价的水力压裂模拟实验，Pickering乳液压裂液与滑溜水压裂液相比，具有抑制页岩膨胀、滤失量低、造缝数量多等特性。为了得到更完善的体系，对添加剂进行了优选与评价，最终得出添加剂为0.08%的助排剂（FY-F501）和0.08%的降滤失剂（CMC，分子量1200万）。. 这项工作的价值在于创造Pickering乳液作为页岩储层的新型压裂液，可以穿透整个裂缝和复杂网络。它能扩大裂缝的有效面积，进而取代了传统的支撑剂泵送。这些成果将带来巨大的经济效益。