Poor proppant transport in slickwater is an industry challenge in the hydraulic fracturing of unconventional reservoirs. Part of this challenge is the difficulty in estimating the settled proppant dune height inside induced fractures. An experimental study was conducted and used to develop lab-based correlations that can predict slickwater proppant dune height as a function of certain key parameters.

A slot flow apparatus was designed and used to conduct more than 70 experiments to obtain the data necessary for the correlation development. The designed fracture slot has a rough surface and is 23.25 inches high and 0.2 inch wide. White sand was tested over a wide range of field representative values for slurry velocity and proppant size and concentration.

Power law correlations were developed for slickwater proppant dune height based on slurry velocity, proppant size, and concentration. The slurry velocity refers to the initially slurry velocity before proppant starts to settle inside the induced fracture. The overall correlation was developed by experimentally studying the effect of each parameter on the dune height and then combining them all in one correlation based on their respective relationships. The developed correlation covers proppant sizes ranging from 100 to 20/40 mesh and concentrations ranging from 0.25 to 2.80 ppg. The developed correlation showed high prediction accuracy relative to obtained lab data with an average error value of less than 0.6% relative to lab data. The developed correlation was further evaluated for its accuracy relative to lab data and the previously published correlation by Wang et al. (2003).

The developed correlation is the first of its type to be based on experimental data while using rough surface slot walls. Roughness is proven to have a considerable effect on proppant settling which makes this correlation more representative for field applications. Also, compared to the well-known correlation by Wang et al. (2003), this correlation covers a wider range of proppant sizes, concentrations, and slurry velocities.

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