This paper investigates experimentally proppant flow and transport through intersected slots at angles representing interaction between pre-existing and new fractures. Proppant is small granular material, placed in hydraulic fractures during geothermal and hydrocarbon reservoir stimulations for permeability increase. This study investigates proppant flow and transport through plexiglas slots enhanced with image analysis for tracking particle motions and quantifying slurry velocity field. Coupled effects of fracture intersection angle and fluid viscosity have not yet been fully understood. This paper focuses on intermediate fracture angles, which have been identified from studies where hydraulic and pre-existing fractures intersect. Although higher fluid viscosity dominantly enhances proppant flow and transport efficiency through the intersection, sharper fracture intersection angles decrease proppant flow and transport and increase the dune angle. Higher fluid dynamic viscosity increases the quantity and size of proppant clusters. Lower fracture intersection angle causes particle clusters more inclined to the right. For both fractures, the shapes are rounded and elongated and the distances of particle clusters are moderately separated.
This paper investigates the proppant flow and transport efficiency through an intersection of pre-existing and hydraulic fractures. Proppant is widely used in oil, gas and geothermal industry for increasing the reservoir permeability and improving production. Laboratory investigations of proppant flow and transport have been conducted over past decades. Majority of studies relied on simple planar fractures, thus experiments of complex fractures are relatively rare. Dayan et al. (2009) did the first experiment in complex fractures and found that proppant will not flow into secondary fractures if the flow rate and the particle bed in primary fracture are too low. Sahai (2012) observed that gravity plays an important role in proppant falling into the secondary fracture. Furthermore, the proppant volumetric concentration plays smaller role in proppant flow and transport than the fluid flow rate. Sahai et al. (2014) additionally found that the proppant size affects the proppant travel efficiency. Li et al. (2016) studied the effect of angles in Y-shaped intersection, where two of the fractures in the same plane are called primary fractures. The dune height in secondary fracture decreases as the intersection angle between primary and secondary fractures increases from 30° to 90°. Tong and Mohanty (2016) confirmed Li et al. (2016) results for the intersection angles beyond 90°. Viscosity plays a dominant role in proppant transport at secondary fractures closer to the injection point, while gravity plays an important role in proppant transport at secondary fractures further away (Wen et al., 2016). Alotaibi and Miskimins (2015) studied the effect of particle surface roughness and found that angular sands transport better than rounded sands. Kesireddy (2017) confirmed that the fluid flow rate controls transport behavior in secondary fractures and found that the proppant dune height in secondary fracture increases dramatically as fracture width in primary fracture increases. Pan et al. (2018) observed that the fluid flow rate decides proppant transport behavior in secondary fractures and that the dune length in secondary fracture is inversely proportional to the intersection angle.
