Negative BHA LL with DNO

Kjøttkake (35/10-13) – Production section

What happened:

KOP set on ACST tool above 9 5/8” casing cut at ~1192 m to 1051 m (47 m inside 20” casing – shoe at 1098 m). Drilled out cement inside 20” and cleaned out rathole. Attempted to kick off at 1108 m and drilled down to 1140 m without positive indications of successful kick off. Survey and cuttings samples indicating 17 ½” hole following mainbore hole. Time drilled according to SLB from 1140 m to 1155 m. No successful kick off.

What was planned:

Kick off with 17 ½” RSS below 20” shoe from original 12 ¼” mainbore hole.

What was learned:

There is the possibility that 17 ½” bit did not have enough support from cement plug to allow it to push off from mainbore. Due to the KOP only being 12 ¼”, it is raised awareness that the plug might collapse when 17 ½” bit tries to bite into formation when attempting to kick off – thus leading the 17 ½” bit to follow 12 ¼” wellbore.

The decision to time drill was made partly due to SLB onshore recommendation and not having the backup 17 ½” bent housing motor BHA on the rig ready to go. SLB’s D&M onshore team advised to follow their recommendation, ie. to time drill with the RSS to achieve kick off.

No one from SLB could demonstrate a track record of kicking off with bigger OD bit that original borehole size. This could have been discussed in greater detail during planning phase, which will be a key takeaway from this operation.

Based on no progress in attempt to time drill to kick off, the decision was made to POOH and RIH with 17 ½” bent housing motor.

There is an opportunity to drill out the 12 ¼” hole down to 9 5/8” cut depth with a 17 ½” bit in order to set a 17 ½” KOP to kick off from later. This would allow kicking off in same OD hole as the bit, which is the conventional procedure for kicking off in open hole.

What actions are required:

Discuss lessons learned and apply best way for future applications.

Gather experience from SLB on successful and unsuccessful attempts on kicking off with bigger OD bit than mainbore hole size.

Potential options (assuming Kjøttkake hole sizes):
1. Plan to drill out mainbore with same OD bit that is planned to kick off with. In this case drill out the 12 ¼” mainbore hole with a 17 ½” bit prior to setting KOP.
2. Initiate kickoff with 12 ¼” bit. POOH and RIH with 17 ½” bit making it easier for 17 ½” bit to kick off.
3. Initiate kick off with a 12 ¼” bit with a 17 ½” hole opener and drill to section TD.
4. Commit to running 17 ½” bent housing motor BHA first attempt, perform kick off and POOH to run 17 ½” RSS (Kjøttkake required RSS to be used for hole cleaning purpose (rpm) – and high directional requirement (G&G)).
5. Run 17 ½” RSS (as was done on Kjøttkake initially). After drilling down to 1140 m and unsuccessfully kicking off, instead of time drilling, be brave and put high WOB and rpm in attempt to force bit to bite into new formation. Essentially this is the opposite of what the purpose of time drilling was.