暂堵颗粒在水力裂缝中的封堵行为特征

Plugging behaviors of temporary plugging particles in hydraulic fractures

采用可视化水力裂缝内暂堵实验装置,开展了不同携带液排量、黏度条件下,不同粒径、不同浓度的暂堵颗粒在水力裂缝中的封堵实验,分析了暂堵颗粒在水力裂缝中的封堵行为特征。研究结果表明:(1)携带黏度越大、排量越大,封堵层形成难度越大;暂堵颗粒粒径越大、浓度越大,封堵层形成难度越小。(2)当粒径缝宽比(暂堵颗粒粒径与裂缝宽度的比值)为0.45时,封堵层的形成主要受暂堵颗粒质量浓度、携带液黏度控制,暂堵颗粒质量浓度小于20 kg/m^(3)或携带液黏度大于3 mPa·s时难以形成稳定的封堵层;当粒径缝宽比为0.60时,封堵层的形成主要受暂堵颗粒质量浓度控制,暂堵颗粒浓质量度小于10 kg/m^(3)时难以形成稳定的封堵层;当粒径缝宽比为0.75时,封堵层形成与否基本不受其他参数的影响,实验条件范围内均能形成稳定的封堵层。(3)封堵层的形成过程包括2个阶段和4种模式,影响封堵层形成模式的主控因素为粒径缝宽比、携带液排量、携带液黏度。

Using the visualized experimental device of temporary plugging in hydraulic fractures,the plugging behaviors of temporary plugging particles with different sizes and concentrations in hydraulic fractures were experimentally analyzed under the conditions of different carrier fluid displacements and viscosities.The results show that the greater the carrier fluid viscosity and displacement,the more difficult it is to form a plugging layer,and that the larger the size and concentration of the temporary plugging particle,the less difficult it is to form a plugging layer.When the ratio of particle size to fracture width is 0.45,the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle and the viscosity of the carrier fluid,and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 20 kg/m^(3)or the viscosity of the carrier fluid is greater than 3 mPa·s.When the ratio of particle size to fracture width is 0.60,the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle,and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 10 kg/m^(3).When the ratio of particle size to fracture width is 0.75,the formation of the plugging layer is basically not affected by other parameters,and a stable plugging layer can form within the experimental conditions.The formation process of plugging layer includes two stages and four modes.The main controlling factors affecting the formation mode are the ratio of particle size to fracture width,carrier fluid displacement and carrier fluid viscosity.