Lessons Learned From Electrical Submersible Pumps Installed in High-Salinity and Corrosive Reservoir, TAGI Formation

Brahmi, Hichem

OnePetro 

Summary

An experience of electrical-submersible-pump (ESP) -issues troubleshooting to overcome the high-corrosion media of GSA wells is presented. Additionally, actions taken to extend the run life of pumps are explained. GSA is the company in Algeria that adopted the ESP system including all services; therefore, there was no chance to share experience with other entities in the country. Thus, it became necessary to try all available approaches during a period of 10 years to mitigate ESP failures and, eventually, production downtime.

To overcome the high salinity of >320 g/L, several actions were introduced by either of two ways--ESP equipment or well completion. Simple motors and protectors were changed to tandem to prevent water penetration inside the motor. Power cable was changed from galvanized to Monel armor for high resistance to corrosion. For well completion, single or double 1/2-in. water-dilution lines were adopted and were run along tubing and connected to tail pipe, which runs to perforations. Modification in completion metallurgy also took place, when carbon steel was replaced by Super 13Cr. Supplementary actions were taken at the surface; the pressure switch was connected with a variable-speed drive (VSD) to smoothly shut down the ESP for unforeseen surface-controlled subsurface-safety-valve (SCSSV) closures.

The adopted actions yielded considerable positive results. ESP failures that originated from the motor were reduced from four per year during 2012 to only one failure in 2016. However, salt-deposition blocs were almost prevented, and resulted in decrement in bullheading and coiled-tubing interventions by 85%, except for some wells when salt-bloc buildup was occasionally quicker and more important than water-dilution rate. Running a 1/2-in. injection line along with the tail pipe lowered ESP-shutdown frequency. Also, changing the power-cable type gave roughly good results. After running Monel armor, the number of related power-cable failures decreased, contributing to the reduction of whole failures, because related power-cable failure represented 70% of ESP failures in 2015. Considering Super 13Cr instead of carbon-steel tubing gave positive indications, and reduced sharply related tubing-integrity failure. The problem still exists, however, with very low frequency. For surface equipment, all unforeseen SCSSV closures actuated from the control panel are always accompanied by a gradual decrement of frequency and, consequently, smoother ESP shutdown.

Because our organization is the company that uses ESP with a proper sense in Algeria, this paper presents some best practices to be considered for other companies and ESP contractors that are based in the country or abroad that intend to install an ESP system in very high-salinity and corrosive fields and to adopt a lease model for downhole equipment.