GEL DAMAGE REMEDIATION BY EVAPORATIVE MECHANISMS: A LABORATORY INVESTIGATION

Polymeric gels are widely used in hydraulic fracturing operations to produce natural gas from tight sands. The recovery of injected gel is often poor and large quantities are left behind, which can cause a loss in gas productivity due to a reduction in the fracture conductivity. In this paper, we present a novel study of remediation of gel damage from proppant packs by dry gas injection. We experimentally investigated removal of polymeric fracturing fluid gels from proppant packs and their impact on recovery of gas flowrate at constant pressure drawdown conditions. The gel removal process takes place in two steps, the first being a viscous displacement process which is followed by the evaporative process. Due to the high viscosity, gel removal by simple displacement is ineffective and only 20‑25% of the gel is removed at high drawdown pressures and only 1 % of the undamaged flow rate is recovered. However, when dry gas is injected, the entire water content in the gel is completely removed. Results from experiments conducted with sandpacks and fracture packs show that about 30% of the undamaged flow rate is recovered by dry gas injection. Dry gas injection is effective in removing water content of the gel from sandpack and fracture pack. Hence the residual gel saturation is lowered, leading to greater gas relative permeability and gas flowrate. A compositional model is developed to predict the rate of removal of water from gel and the rate of recovery of gas in damaged laboratory scale fracture and sandpacks. The model results show a good comparison with the experimental data and therefore can be used to predict field scale performance of dry gas injection operations. Thus field scale gel blockage due to unbroken polymer may be remediated, by a simple dry gas injection process.