Abstract
The fracture propagation process using polymer-based fracturing fluids is commonly applied to increase the productivity of producing wells, especially in tight gas formations. During the fracturing operation a layer of concentrated polymer (filter cake) forms on the fracture faces, which limits the loss of fluid to the formation. However, during the production phase, the partially broken filter cake and remaining residues damage the fracture conductivity. The fracture cleanup process is complex and may suffer from the presence of a yield stress, non-Newtonian fluid in place, non-Darcy flow effects in both the fracture and matrix, crushed proppant, embedded proppant and formation spalling as well as both mechanical and hydraulic damage to the matrix near the fracture face. A previously published fast and robust single well model was applied to study the important parameters involved during the fracture cleanup process. This 3-phase, 2-D model is capable of modeling multiple parameters separately. However, the simulator code which was employed did not address the modeling of non-Darcy flow or the rock stress effects on permeability, but focused on the yield stress effects of the fracturing fluid. The simulator proved very useful for assessing the significance of reservoir capillary pressure, fracturing fluid viscosity and yield stress, formation damage, and fracture conductivity on low permeability gas reservoir production with permeabilities from 0.005 to 5 mD. These trends may not carry over to nanodarcy reservoirs, such as the gas shales. The three phases included gas, water and fracturing fluid.
