垂直裂缝内液体二氧化碳携砂性能的数值模拟

Numerical Simluation on Proppant Transport of Liquid Carbon Dioxide in Vertical Fracture

二氧化碳干法压裂以液态二氧化碳为压裂液,相较于传统的水力压裂,具有无水相、无残渣、低伤害、增加地层能量等优势,因此应用前景广阔。液体二氧化碳的密度和黏度很小,其携砂能力的大小成为决定压裂成败的关键因素。建立垂直裂缝模型,基于计算流体力学方法建立了液体二氧化碳流体和支撑剂的两相流动规律,并利用有限体积法进行数值模拟研究。结果表明:液体二氧化碳流体的携砂能力要弱于滑溜水。支撑剂在液体二氧化碳流体和滑溜水中的分布特征相似;通过降低支撑剂密度、减小支撑剂粒径和砂比或提高泵注排量可以提高液体二氧化碳流体对支撑剂的携带作用。研究结果可为液体二氧化碳压裂工艺参数设计提供依据。

As the fracturing fluid of carbon dioxide dioxide dry fracturing,lquid carbon dioxide has the advantage of no water phase presented, no residue,low damage and large formation energy enhancement compared with conventional hydraulic fracturing, enables this stimulation metliod have broad application prosjects. Due to its lower density and viscosity, the capacity of proppant transport is concerned. Based on the vertical fracture model, the two phaseflowmathematical model of liquid carbon dioxide and proppant was established and numerical simulation was con-ducted using finite volume method. The simulation showed that proppant transport capacity of liquwas less effective than water. The distribution characteristics of proppant in liquid carbon dioxide was similar to thefeatures in water. Moreover, reducing the density of proppant, the grain size of proppant and sand ratio respectivelyor increasing the injection rate can enhance the proppant transport capacity of liquid carbon dioxide. This study provide the basis for liquid carbon dioxide fracturing treatment design.