Abstract: The application of precise managed pressure drilling technology in the Moxi-Gaoshiti and Xiachuandong areas of the Sichuan Province effectively solved such challenges as leakage and coexistence of blowout and lost circulation caused by narrow safety density window of drilling fluid.However, due to the absence of effective and safe packoffs in tripping operations and well completion, the lost circulation is serious and the well control risk is extremely high.Therefore, based on the inorganic hydraulic gel theory, dense filling theory and solidification strengthening theory, a working fluid gel plug for precise managed pressure drilling was developed by using key treatment agents.The performance evaluation results suggested that the initial flow performance and stability of the working fluid gel plug were good, the anti-drilling fluid contamination ability was strong.Further, the thickening time could be controlled within 0.5-4.0 h, and the applicable temperature was 60-150 ℃.After solidification of the gel plug, the compressive strength of gel plug achieved to 8.02 MPa, the bonding strength reached 1.39 MPa/m², the pressure bearing capacity greater than 2.69 MPa/m, and the drillability value was 1.Field application results showed that with the working fluid solidified into a plug, the gel plug could effectively seal off oil and gas, and in that way ensure safe tripping during precise managed pressure drilling.