Shell Experience with Plunger Assisted Intermittent gasLift (PAIL)
Charlie Moncur
Shell International EP
Jim Hall - Presenter
Abstract
Intermittent gaslift has not found much favour as an artificial lift technique in Shell Operating Companies. Shell has trialed and tested intermittent gaslift installations since 1962 in a number of its operating units. Success with intermittent lift has been limited due to the poor capabilities of the surface control units, hardware and the additional operational workload, which these systems generated. Intermittent gaslift was seen as an art rather than a science and placed in the “too difficult box”.
A specific intermittent lift technique PAIL (Plunger Assist Intermittent Lift) was developed and used in a Shell operating company over the last 2 decades. A total of 10 wells have been produced on PAIL with varying degrees of success. Despite the poor performance a number of wells have remained in production, for some 14 years, with PAIL systems. These wells have produced significant cumulative volumes of oil.
The latest trial with Parkburn Well Management Systems Ltd. control units has proved very encouraging. The control system was retrofitted to two existing PAIL installations. These control units proved significantly superior to those previously installed. The viability of PAIL as an artificial lift technique has significantly improved.
Production increases and reduction in gaslift was achieved on both wells. The control unit catered for automatic kick-off of the well, production logging and automatic optimisation of the well cycle to deliver maximum production at optimum cycle frequency. The control unit developed can also orchestrate multiple wells and prevent synchronisation of the production cycles. Bean back to a lower rate is also possible with automatic adjustment of slug size and gaslift injection requirement per cycle.
As reservoir pressure and well productivity decline, continuous gaslifted wells can be converted to beam pumps. The conversion and subsequent maintenance of these wells can be expensive in terms of life cycle cost. There is an argument to support continuing production under a gaslift regime (PAIL). With application of PWMS Ltd. systems a viable alternative to beam pumping is available. Production range is from a few barrels per day up to the level where continuous gaslift is viable is possible.