通道压裂支撑剂运移规律试验

Experiment on proppant placement for channel fracturing

基于通道压裂的特点,设计具有粗糙裂缝壁面、不同角度分支缝组合并考虑地层滤失、缝宽可变的大型支撑剂运移模拟装置。利用大型支撑剂运移模拟装置分别对直缝和直缝与分支缝组合两种情况下施工排量、支撑剂粒径、压裂液黏度、纤维比例等因素对支撑剂铺置的影响进行试验研究。结果表明:压裂液黏度显著影响支撑剂团块在裂缝长度方向上的分布;纤维比例的增加能够增加团块的数量,团块中支撑剂的含量和纤维与支撑剂的比例有关;适当增大排量有利于通道之间的相互连通;支撑剂质量浓度对支撑剂团块在裂缝高度方向上的分布影响较大;随着支撑剂粒径的增加其与纤维结合形成团块的能力越差;分支缝通道率明显低于主缝,结合分支缝的分流作用影响,其对试验变量的敏感性要低于主缝;随着分支缝角度的增加,纤维越容易在裂缝入口处滞留堵塞,堵塞分支缝入口。

Based on the characteristics of channel fracturing,a large scale experimental set-up for proppant transport study was built,in which rough fracture wall surface and fracture branchs in different angles were simulated,and the fluid loss into the formation and variable fracture widths were also considered.In the experiments,the effects of fracturing fluid volume,proppant particle size,fluid viscosity,fiber to proppant ratio in the fracturing fluid on the proppant placement were studied.The influence of straight fractures and branch fractures and their combinations were also investigated.The experimental results show that the viscosity of the fracturing fluid significantly affects the distribution of proppants in the fracture channels.Higher fiber concentration can increase the number of proppant clusters in the fracture,and the proppant content in the briquettes is closed related to the ratio of fiber to proppant.Higher fracturing fluid volume and better proppant displacement are beneficial to the mutual communication between the fracture channels.Proppant concentration has a great influence on the distribution of the proppant clusters in the direction of the fracture height but the ability to form proppant agglomerates with fibers as the proppant particle size increasing becomes poor.The flow conductivity of the branched channels is smaller than channels with one single and main fracture due to the branching effect of flow.As the angle of the branched fractures increa-ses,the fibers can be readily accumulated at the fracture entrance to form a blockage.