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- Improving well performance and integrity
Case studies



Key info

  • Region: UK North Sea
  • Customer: Premier Oil
  • Field: Brenda
  • Well Type: Subsea


Case benefits

Retrofit Gas lift design to avoid a costly workover. Prior to intervention there was no production. Without the design work carried out by PTC petroleum engineers, straddles could have been set at the incorrect depth.


Key capabilities

  • Gas lift for wells without side pocket mandrels or mandrels set at incorrect depths.


Typical applications

  • Retrofit gas lift to increase oil production
  • Retrofit gas lift for gas well dewatering
  • Retrofit annulus to tubing bleed off

GoLift for Premier Oil

Retrievable Gas Lift Straddle
Retrievable Gas Lift Straddle
GoLift Straddle
GoLift Straddle
GoLift Straddle
GoLift Straddle
GoLift Straddle

Retrofit Gas Lift System for Premier Oil's Brenda D3

An existing subsea gas lifted oil well in the Central North Sea stopped producing. The existing third

party gas-lift system was comprised of 2 x IPO unloading valves and an operating valve. Due to an error in

the gas lift design continuous gas injection could only be achieved via the uppermost IPO unloading

valve. The uppermost IPO unloading valve eventually failed and it was no longer possible to inject lift gas

into the well, stopping production. PTC designed, built and installed a retrofit (straddle based) system

using an intervention vessel. The intervention operation was completed as planned and the well was

successfully brought back online .



Existing subsea well Brenda D3 (block15/25b)

  • 3 x gas-lift mandrels in 5-½" tubing in 9-⅝" casing

  • 2 x IPO unloading valves, 1 x operating valve

  • Mandrels set too deep for well conditions and existing Gas Lift Valves (GLVs) could not be pulled.


Well historically lifting from uppermost (IPO unloading) valve only

  • Deeper valves unused
  • Uppermost IPO unloading valve failed, as it was not designed for constant injection (3rd party, non-PTC valve)
  • Gas injection not possible


Well unable to flow without gas lift and as a result production stopped.



PTC performed a gas lift design for D3 and discovered that only one unloading valve and one operating valve would be required over the life of field. Holes were punched in the tubing at the PTC specified depths. Interwell straddles packers were used in conjunction with PTC’s GoLiftTM straddle and GLVs.



The intervention operation took approximately 7 days. PTC was provided production data after restart on 29th of November which showed that the well was now averaging 1685stb/d. The well is still successfully producing today. It was estimated that the costs for the entire intervention operation, including all equipment, personnel and the intervention vessel was recovered after 68 days of production.