垂直裂缝内液体二氧化碳携砂规律研究

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。

Numerical Simulation of Proppant Transport of Liquid Carbon Dioxide in Vertical fracture of Carbon Dioxide Dry Fracturing

The unique property of liquid carbon dioxide has the advantage of preventing the clay from swelling and avoiding water lock effect compared with conventional fracturing. Due to its lower density and viscosity, the capacity of proppant transport is concerned. The two phase flow of liquid carbon dioxide and proppant during liquid carbon dioxide fracturing was analyzed using computational fluid dynamics simulation. The simulation showed that proppant transport capacity of liquid carbon dioxide is less effective than slick water. Moreover, reducing the density of proppant, the grain size of proppant and sand ratio respectively or increasing the injection rate can enhance the proppant transport capacity of liquid carbon dioxide. This study can provide the basis for liquid carbon dioxide fracturing treatment design.