Reutilization of Fracturing Flowback Fluids in Surfactant Flooding for Enhanced Oil Recovery

摘要

The reutilization of fracturing flowback fluids (which are primarily composed of viscoelastic surfactants) in surfactant flooding was investigated with the aim of making the surfactant flooding process more efficient and cost-effective. The dynamic and equilibrium interfacial tensions and the effects of salinity and temperature on interfacial tension were studied. The oil/water interfacial tension was lowered to 10(-3) mN/m due to 0.004-0.008 wt % viscoelastic surfactant in the flowback fluids. The fracturing flowback fluids were found to be suitable for reservoirs, with a salinity ranging from 0 to 110000 mg/L and temperatures ranging from 50 to 90 degrees C. In the solid/liquid system, the saturated adsorption capacity and dynamic retention capacity were 8.09 mg/g and 2.29 mg/g, respectively. A series of sandpack core-flooding tests were conducted under the reservoir condition to investigate the effects of concentration and the slug size of chemicals on oil recovery. The results showed that the oil recovery value was highest with a surfactant concentration of 0.006 wt %. The oil recovery improved with slug sizes. The optimal chemical slug size in this study was maintained between 0.7 and 0.9 pore volumes (PV) for the efficient reutilization of fracturing flowback fluids. This investigation established that the simulated flowback fluids recovered from fracturing treatment using viscoelastic surfactants can be reused for surfactant flooding with probable environmental and economic benefits.