| Massive hydraulic fracturing operations conducted in shale reservoirs create extensive fracture networks to enhance recovery of hydrocarbons from low permeability shale reservoirs. Fluid invasion into the shale matrix is identified as one of the possible mechanisms leading to low fracturing fluid recovery after the fracturing operations. Studying the mechanisms of liquid imbibition into shale matrix is essential for understanding the fate of non-recovered fracturing fluid that can eventually lead to better utilization of water resources by reducing cost and environmental impact.;This study aims to investigate effects of base fluid type (aqueous vs. oleic phase), polymer enhanced viscosity, salinity and surfactants in aqueous solutions on the imbibition rate in actual shale samples. The shale samples were collected from Fort Simpson, Muskwa and Otter Park formations, all belong to greater Horn River Basin. The samples were characterised by measuring porosity, wettability (through contact angle measurements), mineralogy (through XRD analysis), TOC, and interpreting wire line log data.;We find that imbibition rate of aqueous phase is higher than that of oleic phase. Moreover, we find that imbibition rates of KCl brine, surfactants and viscous polymer solutions are lower than that of fresh water. We find that dimensionless time used to model spontaneous imbibition in conventional rocks requires specific adjustments for application in shales. Based on applied upscaling method, it was found that spontaneous imbibition can cause significant water loss at the field scale during shut-in period after hydraulic fracturing. |
