Operator sought to minimize ESP replacement costs

ESPs are traditionally run on jointed tubing, and rigs or heavy workover hoists are required to pull out the production string when the ESP needs replacement. The production deferment that results from waiting on rig availability and the increase in opex to replace the ESP significantly erode asset value and increase total cost of ownership; the impact is greater offshore. Other unwelcome consequences include disruption to drilling operations caused by diverting a rig, more personnel on board, and increased HSE exposure and risk. An operator working offshore West Africa sought to minimize these effects.

Rigless ESP replacement system provided alternative to a rig or hoist

The innovative ZEiTECS Shuttle rigless ESP replacement system consists of a downhole docking station and a motor connector that mates with it. The motor connector is attached to an ESP assembly, and together they constitute the retrievable ESP string. The motor connector orients and connects the ESP to the docking station. The ZEiTECS Shuttle system and ESP are initially installed in the well during a rig-supported workover. Subsequently, the ESP string can be quickly unplugged from the docking station and retrieved in a few hours using wireline, coiled tubing (CT), or sucker rods. After service or replacement, the ESP string is redeployed using the same method.

The plug-and-play design of the ESP replacement system enables any standard ESP assembly to be retrieved and redeployed without a rig or hoist. The system thus eliminates the uncertainties, inconvenience, and economic impact of using a rig. Production deferment is minimized and intervention time, cost, and risk are reduced.

Early changeout of ESP motor proved benefits of new system

For the initial rig-supported installation, the docking station was attached to the bottom of the production tubing. A third-party ESP system was preinstalled in the docking station at surface, and all checks were successful. However, when the string was lowered to the fluid level in 9 5/8-in casing, electrical integrity was lost. The ZEiTECS Shuttle system thus had an unexpectedly early opportunity to demonstrate its value. There was no need to pull out the production string; the ESP was retrieved on rods and the competitor's motor was found to have shorted.

The docking station was run “empty” to its setting depth of nearly 4,400 ft while a new motor was sourced. By eliminating the need to pull out the tubing string and suspend completion operations until a replacement motor was found, the operator saved 48–72 hours of rig time. After replacing the motor, the ESP string was reinserted, again on rods. Impressed with the ZEiTECS Shuttle system's functionality, the operator cancelled plans for a rigless replacement demonstration, deeming it unnecessary, resulting in further time savings. The customer also enjoys the long-term benefit of rigless ESP replacement capability for the rest of the well life. This was the first installation of the ZEiTECS Shuttle system in Africa and offshore.