Performance Evaluation and Field Application of a Novel Water Lock Reducing Flushing Fluid NDF-1

In the Ordos Basin, water lock is common in low-permeability oil and gas bearing sandstone reservoirs, and it has serious effect on oil and gas reservoir producing degree and decreases the recovery rate. After analysis was performed on the factors influencing water lock effect, a novel water lock reducing flushing fluid NDF-1 was prepared with a water lock removal agent, inhibitor, anti-water lock surfactant and high-temperature corrosion inhibitor, so as to reduce water locking degree. After its performance evaluation was completed, the flushing fluid NDF-1 was field tested in Well CBx-c in the Ordos Basin. According to the performance evaluation, the oil/water interfacial tension dropped below 20 mN/m and the average rock wetting angle increased from 21.6° to 78.6°. The corrosion rate dropped by 89.9% and 84.7%(compared with fresh water) respectively after the downhole string samples were soaked in NDF-1 for 6 hours and 24 hours. After the core contaminated by drilling fluids and completion fluids was cleaned out by NDF-1, its permeability recovered to 182.14%. Field tests demonstrated that the gas production of Well CBx-c increased to 185.7% after it was cleaned out by NDF-1. In summary, the waterlock reducing flushing fluid NDF-1 could effectively efficiently the water lock effect in low-permeability reservoirs and increase the production rate of oil and gas wells.