Research and application on environmental friendly and reservoir protection workover fluid

In order to decrease the pollution of reservoir caused by workover fluid, enhance the production recovery rate after repairing operation, short the period of yield recovery and protect the surrounding environment, an environmental friendly and reservoir protection workover fluid has been studied through optimizing and combination the adhesives, filtration reducing agents, inhibitors, cleanup additives and stabilizers. Lab performance evaluation of the novel fluid was conducted, and the results illustrate that the density of the solid-free repairing fluid range from 1.00 to 1.25 g/cm3; API filter loss could be maintained at less than 15 mL per 30 minutes; The decrement is greater than 90%; interfacial tension is lower than 3 mN/m and permeability recovery rate of experimental core is bigger than 90% and nontoxic. The field application results show that this new technique could effectively protect the oil and gas layers from polluting and enhance the output recovery effect after the repairing treatment.