The Origins of Low-Fracture Conductivity in Soft Shale Formations: An Experimental Study

Sufficient fracture conductivity must be sustained in fracture networks created by massive slickwater fracturing to continue the exploitation of ultralow-permeability shale formations. However, unrealistic conductivity values obtained under ideal laboratory conditions are generally utilized for fracture designs. In this study, we outlined an experimental program to measure the conductivity of different possible fracture patterns in the fracture network, such as standard smooth fractures and shear fractures, with varying amounts of proppant and placement patterns. The results show that low-conductivity fractures are likely to form in a soft shale. The high roughness and shear displacement of fracture surfaces improve conductivity. However, the crushing degree of the surface asperities is high for soft shale, which reduces the self-supporting capability of the fracture. The conductivity values under ideal proppant-placement conditions are overestimated substantially.