Abstract
The subject well is a recently drilled and completed in Cambay field offshore in West coast of India. After landing the completion, two mechanical plugs were installed to nipple down BOP and nipple up X-mas tree. The plugs were installed in a 3.875" tubing hanger profile and in a 3.813" SC-TRSSSV selective profile. The problem arose while retrieving the 3.813" selective plug with 4" GS tool after installation of X-mas tree. The slickline wire snapped while doing the jarring operations resulting in fish in the well with BHA and plug slipping down below the selective profile. The plug fell inside the well and got stuck at the 4.5" × 3.5" tubing crossover joint ~20m below the SC-TRSSSV depth. The fished slickline wire along with the slickline tool-string BHA was successfully retrieved from the well, however, the plug remained stuck at the 4.5" × 3.5" tubing cross-over and could not be fished out even after several conventional approaches with slickline.
Solutions involving rig based retrieval and rig less coil tubing intervention and e-line robotic technology for retrieval of the plug were evaluated. Upon completion of a detailed feasibility study of available options, it was decided to conduct fishing of the plug with e-line based advanced robotic well intervention techniques such as eline miller, tractor and stroker. Unique milling bits were designed and customized for this operation. The milling operation involved multiple runs to target the removal of various parts of the struck lock mandrel. Upon successful milling operation, it was planned to retrieve the plug with slickline.
Initial attempts to retrieve the plug by straight pull using 33k pulling capacity Eline Stroker were unsuccessful. Subsequently, milling was attempted with a combination of E-line tractor and Miller to drill thru the plug. The milling initially started as per the plan but after 3 inches of milling the bit got stalled and was eventually stuck inside the plug. The E-line BHA had to be released from the mechanical disconnect sub above the bit. A modified 2" UPT tool with E-line tractor-stroker was run to fish out the bit and plug which resulted in the plug getting released from the stuck position and moving upwards about 10-meter from the stuck depth. Once this was accomplished, plug and bit were successfully retrieved with slickline.
The paper details the background of the stuck incident, selection methodology of fishing technique, fishing work plan and its successful execution. The paper also describes the operational difficulties encountered and the mitigation chosen while milling a plug with an electric line in the offshore environment.
