A multi-physics integrated framework for evaluating propped fracture width in unconventional reservoirs

Numerical simulation of hydraulic fracturing in horizontal shale gas and oil wells remains challenging, specifically leading to difficulties in modeling fracture width variations under proppant support. To address this, we present an integrated computational framework that explicitly accounts for proppantinduced reaction forces on fracture surfaces, which are coupled with fracture width through a robust iterative algorithm. The model synergistically combines a phase-field model for fracture propagation, a fluid flow model for proppant transport, and a fracture closure model. Validation against analytical solutions demonstrates that the predicted fracture length and width are in excellent agreement with theoretical expectations. The simulated proppant settling also agrees well with experimental observations. Numerical results demonstrate that the distribution of propped fracture width shows a significant difference compared to the distribution of fracture width before proppant settling. Additionally, we found that the propped fracture width is sensitive to slurry properties, such as injection rate, fluid viscosity, and proppant concentration, alongside the mechanical strength of the proppant. Crucially, proppant strength plays a significant role in sustaining fracture width during closure, which in turn has a substantial impact on long-term productivity. The presented model provides a new tool for fracturing design to enhance the conductivity of the hydraulic fractures.