Development and Field Test of High-Temperature Gel Valve

There are well completion challenges in Nanpu buried-hill fracture reservoirs due to the coexistence of the risk of loss of circulation and blow out combined with formation temperatures over 150℃. To solve the problems, the formula for twice-crosslinking gel valves were developed. In the design, a structural gel was developed to meet operational demands.In the first crosslinking step the gel possesses high strength and quick formation speed.In the second crosslinking step involved insuring proper operations in the isolated borehole section. RM2100 HTHP online gel detector was used to monitor the formation of gel valves. Results showed that viscosity of the gel system could be maintained over 1 000 mPa·s. In the secondary crosslinking step,gel formation started at 150 min with ultimate viscosity above 12,000 mPa·s. Simulated boreholes were used to determine pressurebearing/load capacitywhich could reach over 2 MPa/100m.In addtion, the gel at 150℃ maintained a satisfactory viscosity for 72 h. Gel-breaking could be done through flushing by using drill bits. Successful application in Well NP23-P2016 indicated effective isolation of hydrocarbons to minimize losses and to provide reliable well-control conditions for deployment of tie-back tailpipes. Research results showed that the high-temperature gel valves could provide satisfactory solutions to challenges in well control encountered during well completion in Nanpu buried-hill reservoirs.