Propped Fracture Conductivity Evolution During Reservoir Drawdown

This paper investigates propped fracture conductivity evolution as a function of proppant loading concentration under elevated stress as an analog to reservoir drawdown. In particular, we explore the relative impacts and interactions between proppant crushing, embedment, compaction and particle rearrangement and their impacts on fluid transport. Proppant of realistic concentrations is sandwiched between split core-plugs of Marcellus shale that accommodates embedment and rigid steel that excludes it. Fracture’s conductivity decreases by up to 95% as effective stress is increased by 50 MPa (7000 psi), broadly independent of whether the fracture walls are rigid or deformable. The stress-sensitivity of conductivity is generally muted with increasing proppant loading concentration. Low proppant concentrations return higher permeability at low effective stresses but lower permeability at high effective stress. This suggests the dominant role of proppant interior compaction and rearrangement over proppant crushing and embedment for higher proppant concentrations, as more displacement degrees of freedom are added to the system and provide accommodation for proppant redistributions. Extended effective stress holding times and proppant “aging” exert little impact on transient changes in fracture conductivity.