Abstract
Electric Submersible Pumps (ESPs) are conventionally rig-deployed via production tubing, with clamped-on power cable. The long wait and installation times incur high operating expenses, with large surface and carbon footprints. Riglessly-deployed, permanent ESP systems address the above limitations, but challenges include safe deployment of the large, heavy high-power cable and ESP to the required setting depths. This paper discusses a solution using commercial Coiled Tubing unit with modified injector head grippers.
A wireline-style, stranded armor power cable design offers the best compromise for flexibility, and long-term operational reliability inside a well. Cable damage by Coiled Tubing Injector head during deployment, however, can be a showstopper. A Finite Element Analysis (FEA), followed by multiple gripper designs and lab tests led to the optimum gripper architecture. The target Injector head was then fitted with one gripper set. Dynamic and static tests were performed with the ESP power cable. Correct gripper pressures, maximum safe loads and operating risks were determined for field operations. Crew training procedures were updated to address the critical deployment challenge.
After installation and retrieval from the test well, the cable was inspected for damage. The maximum static pull test cable sample was stripped down to the individual conductors and thoroughly inspected for external and internal mechanical and electrical damage. Besides the intentional gripper slippage surface wear, no internal damage or cable mechanical integrity compromise were observed. The decision was made to proceed with full-field trial using operational settings recorded during the tests. A complete set of operational instructions and guidelines was also established for the upcoming ESP field trial.
The novel gripper design and rigorous testing proved that stranded armor cables can be safely conveyed using Coiled Tubing Injector heads. Thus, saving significant cost and time that would have been spent developing fit-for-purpose cable deployment winch units and reels.
