One of the operations that is essential for a successful and cost effective coiled tubing sidetrack is the casing exit. Currently, two coiled tubing casing exit methods exist dependent on completion configuration; through non-restricted monobore completions and "thru-tubing" casing exits.
The monobore completion or liner is exited by setting a packer and orientated whipstock then running a traditional starting mill and window mill.
The thru-tubing whipstock, which typically is run through a 4–1/2" completion and set in 7" casing / liner, utilizes a hinged mechanism which cams into place in the casing. A new generation of mills is used to cut the window.
This paper will discuss specific equipment, procedures and applications employed in a number of case history wells located in Alaska and in the North Sea.