Well candidate screening and post-installation performance evaluation for CSSI on critical-rate gas wells — scaling from a 5-well pilot to 55 asset-wide installations, achieving a combined production gain of up to 2.5 MMscfd.
As gas is produced from a depletion drive reservoir, available energy to transport produced fluid to surface declines. Flow rates reduce and liquids accumulate in the wellbore, creating additional hydrostatic backpressure on the reservoir. This phenomenon — known as gas well load-up — eventually balances the available reservoir energy completely and causes the well to die.
The common practice is to cycle such a well: flow until it dies, shut in until pressure builds, flow again. CSSI breaks this cycle by restoring continuous production through chemical foaming rather than mechanical intervention.
The key factor for the success of CSSI is well candidate selection. The procedure developed for this asset covers three sequential screening steps:
Wells with depletion, weak water drive, or medium water drive reservoirs are the preferred candidates. Physical installation and surfactant injection operations were executed by the service company; the engineering scope covered candidate identification, ranking, and post-installation performance surveillance.
Surfactant selection was based on technical and economic evaluation — foam height, half-time, compatibility with surface facilities and environment, with tendering to select minimum price meeting technical standards. The optimum injection rate was determined by trial and error per well; the average injection rate across all existing installations reached 23 gallons per day.
Monitoring includes tracking pump discharge pressure and well performance for capillary string plugging (typically caused when the well is shut in and injection stops). A minimum injection rate is maintained even during temporary shut-ins to prevent plugging.
Following the 5-well pilot validation, the technology was expanded across all fields of the asset. An example well (B-30 in the Badak Field area) demonstrated sustained, relatively stable production in the 0.8 to 1.0 MMscfd range after CSSI installation — compared to fully cyclic (on-off) production that preceded it.