Abstract (300 words)
During the completion phase of an unconventional well in the United Arab Emirates (UAE), an electric-cable-equipped coiled tubing (ECE-CT) had to be cut and dropped in hole while performing a plug-and-perf campaign. The CT service provider and tool manufacturer jointly redesigned a specific fishing tool for a flat-shaped collapsed CT pipe, which allowed the latching of the U-shaped collapsed ECE-CT pipe and its safe recovery.
The fish and potential solutions were analyzed by the engineering teams from operator, CT service provider, and tool manufacturer. Because of the U-shape of the fish, the existing techniques of conventional overshot for rounded profiles and flat overshot for flat-shaped profiles could not be applied. The U-shape of the fish was replicated and used to create the overshot entry guide. The prototype was manufactured and tested at surface to ensure the profile was getting inside. The tool-string included an indexing tool to allow controlled rotation, which was key to the success of that fishing operation.
Upon completion of the last perforating stage in a 10-stage completion in the well, the ECE-CT pipe accidentally parted and then collapsed when it was being retrieved to surface. The CT operator activated the pipe/slips ram, but a leak was observed. The 2-in. CT pipe was cut and dropped by activating the shear/seal ram, thus leaving 8,360-ft of CT pipe in the well.
A lead-impression-block (LIB) run to identify the fish profile found the U-shape fish at a depth of 6,686-ft. The electric cable did not cover the top of the fish, thus reducing the risk of the retrieval operation. Despite several attempts made with the available fishing tools for rounded profiles, even when latching was achieved, the fish was lost. Inspection of the overshot after it reached surface showed the presence of broken slips due to uneven load transmission.
After analysis of both the top of fish and available fishing tools, a hybrid rounded/flat overshot was designed to allow the U-shaped CT pipe to get inside the overshot and the traveling slip to latch onto the collapsed body, allowing higher contact area and resulting in the proper latch and retrieval of the collapsed ECE-CT pipe.
Because a suitable overshot was not available, the operation required designing, producing, and implementing a customized hybrid semi-rounded/flat overshot for U-shaped profiles, as well as the development of a new methodology, to successfully latch and recover the pipe. The availability of a tools manufacturer inside the country allowed a fast response, it only took 7-days to design, manufacture, and test the tool prototype, thus limiting the time the well remained idle.
