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Artificial Lift Techbook 2018

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EPmag.com | July 2018 | 41 ARTIFICIAL LIFT: CASE STUDIES Baker Hughes, a GE company (BHGE) developed its TransCoil rigless-deployed ESP system to improve installation while removing rig-related challenges. Designed in collaboration with a national oil com- pany, TransCoil takes the rig out of the installation equation, with an aim of helping operators to bring wells on production faster while lowering overall lifting costs. The system includes an inverted ESP with the motor above the pump and connected to the high- strength, corrosion-resistant power cable. The system is installed through the existing completion via coiled tubing (CT). This design improves ESP installation and oper- ational life in several ways. Placing the motor on top eliminates the motor lead extension, which is the area with the highest potential for electrical failure in conventional ESP systems. The new configuration prevents migration of water through the seal to the motor, increasing reliability and extending runlife. The power cable is encapsulated in the CT string, which protects the cable during installation and helps ensure long service life in extreme production envi- ronments. Fully isolating the cable from well fluids also eliminates cable elastomer expansion during changes in pressure cycles. Resolving common problems By removing the need for a rig to install and retrieve ESP systems, the TransCoil system eliminates the lost time and deferred production associated with waiting for a rig. The system can be deployed and retrieved under live well conditions, which means that the tubing and completion assemblies do not have to be retrieved to install a new ESP. In addition, the time involved in killing the well and the associ- ated risks are eliminated, and the potential costs of dealing with wet-connect failures are avoided. Taken together, these improvements help cut ESP instal- lation times by 50% compared to a conventional rig-deployed system. Unlike wireline-deployed ESPs, the new system can be installed through a deviation in the wellbore. This capability allows operators to land the ESP closer to the producing zone for greater reservoir pressure drawdown and reserves recovery. The ESP can be reliably installed later in the life of the well, thus eliminating the need to install the system when a well is first drilled when it could then sit idle for months or years. The new system is designed to eliminate most common failure points. For example, approximately 30% of all ESP failures are due to electrical compo- nents, and of these, 46% are associated with the motor lead extension or cable. But by connecting the motor directly to the power cable, the TransCoil system eliminates the failure-prone, in-well "wet connection" for improved system reliability. And rather than relying on typically available CT sizes and metallurgies, the power cable can be fabri- cated from metallurgies that are specifically geared for well requirements. Premium metallurgy options can withstand H 2 S saturation levels as high as 15% to significantly extend ESP operational life in harsh- environment fields. With an outer diameter that is approximately 40% smaller than current 2- 3 / 8 -in. CT cables, the new cable is significantly lighter and reduces tubing pressures. The cable design also extends the ESP operating range to 12,000 ft and beyond, depending on operational loads, exceeding capabilities of other CT-deployed ESP systems. The fully retrievable ESP system is different from other CT solutions in that it can be re-used for multi- ple workovers. Bending fatigue testing demonstrates that the system withstands up to 180 trips in and out of the well. The system can be installed in 4½-in. to 9-in. casing in wells with flow rates up to 20,000 bbl/d. In mature offshore fields, where high intervention costs can limit the application of ESPs, the system can be deployed through the existing 4½-in. tubing. Dealing with unplanned workovers With rig schedules typically established a year in advance, entering an unplanned ESP workover into the rig plan is a logistical challenge. This can lead to long lead times to get a rig on location to retrieve and install ESP systems, resulting in downtimes of three to six months or longer. But because of its ease and speed of deployment in a growing number of field trials, the new rigless-deployed unit allows operators to get production back online quickly at increased rates. The first TransCoil system was installed in Decem- ber 2016 in a well in the Middle East that had been waiting a year for a rig to replace an ESP system that experienced an electrical failure. Rig-based work to replace the completion and install a vertical electri- cal penetrator system was completed ahead of the rigless operations. A BHGE CT team helped plan the operation, delivered a surface unit to the well site and worked with artificial lift engineers to install the system. The well was brought back into production after one year of downtime, producing at a rate of 8,000 bbl/d. The planned rig schedule was not interrupted,

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