Proppant Transport Behavior in Inclined Versus Vertical Hydraulic Fractures: An Experimental Study

Abstract Understanding proppant transport in complex fracture systems plays an essential role in determining propped fracture area, fracture conductivity, and their impact on well productivity and economics. Despite extensive, historical work that has studied proppant transport in vertical fractures, very limited investigation exists regarding proppant transport appraisal in inclined hydraulic fractures. This study provides a better understanding of proppant distribution in inclined hydraulic fractures. Proppant transport is governed by several factors such as varying of slurry velocity, fracture geometry, proppant size, and proppant concentration. The main purpose of this experimental study is to evaluate the proppant settling and transport and to determine fracture propped area as a function of the key proppant transport factors in different inclined fracture geometry. Low viscosity fracture fluid (slickwater) was used with different particle sizes: 20/40, 40/70, 100- mesh ceramic proppant. To mimic slurry transport in hydraulic fracturing treatments, a 2 ft. × 2 ft. fracture slot model was constructed with gap of 0.25 in. representing the fracture width. Orientation of the fracture model can be adjusted from vertical to inclined positions. Four injection points perpendicular to the wellbore were used to simulate injection through multiple perforations, in addition to single point injection scenarios. Equilibrium dune height (EDL) is expressed in three regions (near the wellbore, in the center of the fracture, and at the fracture tip) for created fractures. Variations in EDL as a function of the number of perforations that contributed during proppant transport are compared for both vertical and inclined fractures. Experimental results show that both fracture inclination and number of contributing perforations impact EDL and propped fracture area. Inclination of fractures can have significant impact on proppant transport due to the friction or contact force, which comes from the fracture wall. This friction impacts settling velocity of the proppant and impacts the proppant distribution efficiency inside the fracture. Increasing fracture inclination angle increases fracture propped area. Finally, this work observed that number and perforations and their position play an important role in proppant transport, particularly in inclined fractures.