We are planning to carry out a cased hole sidetrack which entails setting a Whipstock using the Trackmaster Assembly with Fastrack mill. The following are the challenges we foresee.
I will appreciate your response in anticipation.
Thanks for the feedback Tinuade. It is good to find out what has happened good or bad and in your case, it seems very good.
My biggest concern about milling a window through un-cemented casing is not the casing coupling but the centralizers. Milling through a coupling is not something you would do knowingly but as the rest of the group have intimated it can be done it just takes a little longer some times. The problems can occur when you try to mill certain types of centralizers and stop collars. Its true you can mill through pretty much any centralizer and stop collar when it´s held rigidly in place with cement but when its free to mover that´s when the risk increases.
Thanks all for the response.
The following operations were executed.
The operations went as (or better than) planned without any NPT.
* A number of wells have been successfully sidetracked through uncemented casing without problems (the fact only known due to the lack of cement traces in the returns). However, it was considered that the risk of sidetracking through possibly uncemented casing and potentially through a casing collar was one too far. Had it been known that the casing was cemented at that point, the risk of milling the coupling would have been taken. On each occassion the required FIT was achieved without the need for a cement squeeze.
** Previous experiences of milling the rathole have been unsuccessful due to very slow penetration rates, to the extent that dedicated dual water melon mill BHA runs were planned. In this case the second run was not necessary with the original sidetracking watermelon mill came out of hole within the limits.
Tinuade, to your questions there are many other questions you need to share the answers to.
Is this a straightforward sidetrack or a multilateral you are carrying out?
What size, weight and grade of casing and range of casing joints are in the hole?
What size hole was the casing run into and what type and how many centralisers are attached to each joint?
What is the hole angle you will be setting the whipstock at?
What orientation do you plan to cut the window at?
You ask if anyone has milled a window with no cement, from this are we to assume you do not have any cement?
Are there any signs of pressure in your B annulus?