Critical Tieback Equipment Techniques for Preventing Gas Channeling during Liner Cementing in Ultrahigh Pressure Wells

Conventional tieback techniques did not take into consideration annular gas channeling during liner cementing in high pressure wells. In this paper, studies were conducted on critical techniques of tieback equipment for preventing gas channeling during liner cementing in ultrahigh pressure wells.Based on the analysis of critical techniques such as sealing elements of tieback stingers, packer types, and prevention from holding back and premature inflation of packers, reliable tieback equipment with integral tieback stinger and packer was designed, with maximum sealing pressure up to 70 MPa.Considering the structural features of the tieback equipment and key issues in on site operation, applicable operation processes and techniques were defined. Technical requirements were addressed for some vulnerable sectors such as sweeping upper cement plug, milling the tieback barrel and trial running, and more accurate buoyancy change calculation methods were put forward. This tieback equipment was successfully used in 8 high pressure wells in the Sichuan Area. Those applications demonstrated that the new tieback equipment was simple, safe, reliable, and well-performed in isolation, and it would be an effective solution in preventing annular gas channeling during liner cementing in high pressure wells.