Investigations and Prevention Strategies on the Fracturing Water Pollution Triggering Permeability and Production Decrease in Underground Gas Reservoirs

The fracturing water injected into the underground gas reservoirs for development purposes has polluted the reservoirs, triggering a decrease in reservoir permeability and gas production. Here, we quantitatively investigate and provide preventions for the fracturing water pollution in the underground gas reservoir. We study the effects of fracturing water pollution on reservoir permeability with core experiments. According to the core experiments, we constructed an area-divided two-phase porous flow model to study the production of the underground gas reservoir considering fracturing water pollution. The simulation results are in good agreement with the field development data. It reveals that in the early, mid-term and late development, respectively, the fracturing water pollution accounts for 88%, 80% and 45% of the decline in permeability and production of the underground gas reservoir. In terms of the prevention of fracturing water pollution, reservoirs with an initial permeability over 0.20 mD are preferably produced by natural energy rather than fracturing. Once using the fracturing water, we suggest applying the propping agent with a large particle radius to reduce the pollution from the solid solute and adding the clay stabilizer and the surfactant to the fracturing water to reduce the pollution from the water solvent.