Negative Planning LL with Wellesley

Serin (35/12-7) – P&A

What happened:

Equipment sent out did not include specialized eq for cut and pulling 30″ and 20″ casing in case the 20″ came free. Tools sent out for this (unplanned) operation meant 27″ OD grapple would not engage 30″ conductor (1.5″ wall thickness) with the stop ring landed out on the top of the LP housing. Had to modify stop ring to allow to pass inside LP housing and stop at the bottom, allowing 27″ OD grapple to enter 30″. Rest of BHA below had to be reconfigured on the rig with difficult fishnecks/required use of rig tongs, including using a 12 ¼” bit entered into the 13 3/8″ to give some stabilisation at the bottom of the BHA (no 12 ¼” stabilisers on board).  Lengths of tools available on board dictated second cut was 80cm deeper than first, meaning 20″ had to be cut a second time at 384.90m. A ring of 20″ was cut, fished with the knives and dropped on the seabed before a new attempt was made to cut the 30″. Further attempts to recut the 30″ firstly with the same (back-up) tool already in the hole, secondly with same tool with new knives, finally with original tool with best set of knives available, all failed. First two attempts used 12 ¼” bit in 13 3/8″ for stabilization, third attempt used 17 ¼” sleeve stabilizer in 1.33m 20″ stub left in well. Weatherford equipment mobilized used a cutter with 26″ stabilizer immediately below which cut the casing without problems in 4 hours. With hindsight, probably the case that attempts to centralise below the cutter with the 12 14″ bit and the 17 ¼” stabilizer did not work and allowed eccentric/offset “wobbling” cutting. Both relied on the integrity of the original 13 3/8″ cement job to keep the casing string and hence the stabilization concentric with the 30″ cut.

What was planned:

Cut & Pull 20″ x 30″

What was learned:

A planned contingency BHA is required for cutting 30″ if 18 ¾” HP housing comes free, but planned so that second cut is SHALLOWER than first, AND with centralization inside the 27″ ID of the 30″ conductor

What actions are required:

Recommend to include contingency eq in load out in case 20″ is coming loose during cutting of 20″x30″ ; stop plate, 30″ spear, cutting BHA modified for cutting 30″.