Successful Retrieval of First Installed Velocity String – A Case Study from Middle East

Abstract

Abstract Installation of 14,200 ft of 2 3/8-in. coiled tubing (CT) as a velocity string (VS) was performed to increase the fluid production velocity and avoid a liquid loadup problem in a gas well. After the successful installation, the well produced at economic rates for few years. Because this was a pilot project to ascertain the well's deliverability with the VS installed, the operator decided to retrieve the VS. The main challenge during the VS retrieval intervention was to retrieve such a long VS that had been in a sour well (40,000-ppm CO2, 40-ppm H2S) for more than 3 years. Low carbon 90,000 psi yield strength was chosen as a material for VS to withstand corrosion and Sulphur-stress cracking. A CT tower was utilized to have the access to the work area during pipe cutting and the bottomhole assembly (BHA) removal process. The retrieval of the installed VS was executed in several stages. First, slickline was run in hole (RIH) to install the pump-through check valves at the bottom of the installed VS. Second, these check valves were inflow tested prior to CT equipment rig up. The CT unit was then rigged up on the wellhead and RIH with the VS retrieval assembly consisting of a GS pulling tool. The VS retrieval tool was latched onto the installed VS assembly, and, by applying a straight overpull, the packer that was used to hang the VS was unset. The VS was eventually pulled to surface along with the packer. The whole assembly was secured by pipe rams on blowout preventers (BOPs). After the required inflow tests on the BOP pipe rams were performed, the pressure control equipment (PCE) stack was opened and the CT was cut below the VS packer. All tools were disconnected, and a spoolable internal connector was made up to connect the retrieving CT with the VS. Eventually the VS was safely pulled to surface. When the uphole VS BHA was retrieved to the surface, the quick connection used for pressure testing was opened and CT was cut with a hydraulic cutter. Uphole packer rubbers were found to be damaged during pulling out of hole (POOH). Internal spoolable connector was made and pull tested to 1.25 times of CT hanging weight. After opening pipe/slip rams CT was successfully spooled on the reel. The retrieval of the VS was conducted in a single run with total operational time of 30 hours. The operation provided information will increase industry understanding of the use of VS in gas wells, including information about techniques, downhole tools, and procedures and risk control measures used during the retrieval of a VS from a live well.