Experiment on proppant placement for channel fracturing

Key words:  channel fracturing  fibers  visual simulation  flow conductivity

Abstract:

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 increases, the fibers can be readily accumulated at the fracture entrance to form a blockage.