Following the temporary plugging of the well with snubbing operations in end 2013 the Deutag T207 (350t) drilling rig was used to permanently abandon the existing salt cavern.
To place the final abandonment plug the inside of the well was successfully dressed down to depth. Following this operations attempts were made to retrieve the 11-3/4” casing completely; after retrieval of the upper half of the casing, it was however found be severely stuck. To complete the abandonment a section was then milled in the 11-3/4”casing, after which a cement plug was placed.
Throughout this phase of the project, the operating torque was high. This was caused by the S-shape profile of the well, combined with the high friction water-based milling fluid, which was required for hole cleaning with metal cuttings. Detailed BHA modeling for side loads and resulting torque and drag was therefore used actively with good results in order to optimize the milling operations.