【摘要】 为了定量预测粗糙裂缝内支撑剂覆盖率,开展不同工况下粗糙裂缝内支撑剂覆盖率的试验研究。基于自主设计的粗糙裂缝试验装置,通过控制变量方法进行不同壁面粗糙度、泵注排量、支撑剂质量分数、压裂液黏度等条件下的输砂试验,定性揭示不同施工参数对支撑剂在粗糙裂缝中输送的影响规律,并基于试验结果提出粗糙裂缝内支撑剂覆盖率计算模型。结果表明:以分形维数(变差函数)为主的裂缝壁面粗糙度定量描述方法能够解释支撑剂在粗糙裂缝内运移沉降过程;支撑剂在粗糙裂缝内的运移、沉降和充填行为与光滑裂缝内有较大差异;不同的裂缝壁面粗糙度能导致支撑剂运移、沉降和充填方式的差异;粗糙裂缝输砂需要足够高的压裂液黏度及泵注排量才能保证支撑剂的有效流动;支撑剂质量分数越大需要与之匹配的流体黏度、携砂液排量越大;基于试验结果建立的粗糙裂缝内支撑剂相对覆盖率预测模型,能够实现对不同粗糙裂缝内不同施工参数组合下支撑剂覆盖范围的预测。更多还原

【Abstract】 A series of experiments were conducted to quantify the proppant filling ratio in rough fractures under different operating conditions using a self-designed rough-fracture experimental set-up. The effects of wall surface roughness, proppant mass fraction, fracturing fluid viscosity and fracture width on sand transport were investigated. Based on the experimental results, a new empirical model was proposed to predict the areal coverage of the proppants in rough fractures, and the roughness of the fracture walls was correlated into the model using the variation-function-based fractal dimension parameter. The experimental results show that, due to the rough nature of the fracture surfaces, the proppant transport behavior in rough fractures is very different from that in smooth fractures. In rough fractures, high fracturing-fluid viscosity and pumping rate are needed to ensure an effective migration of proppants, and the greater of the proppant mass fraction, the higher of fluid viscosity and pumping rate are required. The newly established model can effectively predict the areal coverage of proppant in rough fractures under different operating conditions.更多还原