The tie-back assembly is a special cementing tool for tieback operation.
Tieback equipment allows existing liners with a receptacle to be extended to the surface or farther up hole, and provides a high-pressure seal at the top of a cemented or uncemented liner. TIW offers variety of tieback seal nipples and tieback packers to accommodate liner top extension and remedial operations.
A. Preparation before casing
Measure and drift the casings carefully and clean all the threads.
Calculate the kelly-up of the casing (the particular part of the last casing which is above the rotary table) and arrange the casing string.
Prepare several casings, which are approximately 0.5m shorter than the others and convenient for kelly-up calibration. (The actual kelly-up is not equal to the calculated value due to measurement error and the remaining threads of the casings.)
B. Polishing the polished bore receptacle
Connect the milling shoe and trip in. Polish the inner surface of the polished bore receptacle, make sure there is no debris.
Note the depth of the milling shoe when it reaches the top of the seal assembly (judge from the changes on pressure and WOB). Then lift the drill string for 1m.
Use a drilling rate of 40～50rpm and a normal flow rate. Slowly lower the drill string. Polish the inner surface of the polished bore receptacle twice or three times. Each time polish 3～4min. During the last polishing, apply an additional load of 2～3t when the torque suddenly increases (the milling shoe reaches the top of the seal assembly) during the last polishing. Polish for another 2~3min and note the depth of the milling shoe, which is an important clue for the casing setting depth.
Circulate with high flow rate for 5min.
Trip out and check the milling shoe. If there is a circle of polished trace and the diameter is equal to the I.D. of the left thread on the seal assembly, then the milling shoe have reached the bottom of the polished bore receptacle.
With the guide shoe and circulate bore, it can stab into polished bore receptacle before cementing, more convenient than conventional cementing which pumps down cement before stabbing.
With its streamline shape, the guide shoe can stab into polished bore receptacle easily.
The Tieback Seal Assembly with three stacks of molyglass seal is designed for high-pressure and high-temperature liner tieback completions. Available in seal length is 1.2m.
Sealing capacity, MPa
Heat-proof Rating, ℃
Available Sealing Length, mm
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