Quantitative testing method of solid-liquid two-phase for unconventional fracturing proppant transport

In unconventional reservoir slickwater fracturing, a large flow rate of slickwater with proppant is injected into the fracture network to create a complex solid-liquid two-phase flow. To obtain the flow pattern, quantitative testing methods must be explored based on conventional proppant transport laydown qualitative observation experiments. Optical visualization of the flow field was achieved by improving the structure of the flat plate fracture experimental unit, followed by particle image data acquisition of the fracturing fluid-proppant twophase flow field using laser particle image velocimetry on the constructed experimental setup. The image acquisition parameters were optimized based on the proppant particle exposure characteristics, and a method was developed to enhance the proppant-tracer particle image for separation. Based on particle center detection, a model for proppant particle velocity calculation was established based on quasi-rigidity theory, and the validity of the model was verified using an artificial flow field. According to the experimental test and calculation results of the two-phase flow field with different proppant particle sizes, types, and different flow regimes, such as turbulent and laminar flow, the designed device and the established quantitative test and calculation method of the solid-liquid two-phase flow field can better adapt to the testing problem of the proppant transport velocity field in unconventional fracturing, and aid further quantitative studies of the proppant transport law.