Investigation of the Formation of Fracture Intersection Geometry

Fluid flow pathways through energy-related subsurface systems depend on the connections of multiple fracture sets, both induced and pre-existing, to sustain large volumes of fluids for economic production. Few laboratory experiments have been performed to determine what controls the geometry of the voids at an intersection. Here an initial simple study is performed to examine the propagation path of an induced fracture when just a single or two voids are present. Tensile fractures were induced in additively manufactured analog rock samples (green state alumina) using a 3-point bending approach. 2D X-ray radiography was used to capture the fracture propagation path for a range of samples with different void locations and offsets from the notch. The location and size of voids had a significant effect on the induced fracture propagation path, specifically whether the fracture path would be "attracted" to a void or would it be deflected. These experiments represent just the first steps towards understanding whether an induced fracture will preferentially propagate through the void space or contact regions in a pre-existing fracture, with the ultimate goal of understanding the formation of intersection geometry.