Non-invasive measurement of proppant pack deformation

•We use XRCT and digital image correlation to monitor proppant pack deformation.•The approach provides a non-invasive method to track sub-fracture-scale movement.•Proppant movement was studied in a core of Marcellus shale loaded to 10,000 psi.•The analysis captured a failure event in the proppant pack.•The event coincided with the appearance of vortex-like grain motions.

In this paper, we describe a method to non-invasively study the movement of proppant packs at the sub-fracture scale by applying three-dimensional digital image correlation techniques to X-ray tomography data. Proppant movement is tracked in a fractured core of Marcellus shale placed under a series of increasing confining pressures up to 10,000 psi. The analysis reveals the sudden failure of a region of the proppant pack, accompanied by the large-scale rearrangement of grains across the entire fracture surface. The failure of the pack coincides with the appearance of vortex-like grain motions similar to features observed in biaxial compression of two dimensional granular assemblies