Equinor started production from Troll Phase 3 Stage 2 on 22 August, bringing eight new subsea wells online in the North Sea several months ahead of schedule and below the NOK 12.3 billion estimate. The wells accelerate recovery of 55 billion cu m of gas from the Troll West reservoir, routed through the 30-year-old Troll A platform to the Kollsnes processing plant in western Norway. Partners on the project are TotalEnergies, ConocoPhillips and Petoro.
Deliverability is not the same thing as pressure
This is the distinction that makes Troll interesting for anyone who works on rotating equipment. Eight new wells add deliverability — more paths for gas to reach the platform. What they cannot do is restore reservoir pressure. A gas field produces by pressure difference, and that difference narrows every year the field runs.
Kollsnes needs its gas delivered at a fixed inlet pressure. The reservoir supplies less and less pressure over time. The gap between the two is closed by compression, and closing that gap is why compression capacity has been added to Troll A across its operating life. Every extension of a mature gas field is, underneath the headline, a decision about how much more compression the host can carry.
Three consequences worth noting
Falling suction pressure raises compression ratio per stage. That drives discharge temperature up, pushes machines toward surge at low flow, and puts anti-surge control and recycle valves squarely on the critical path for availability.
Liquids do not disappear because the stream is called gas. Condensate knockout, condensate export pumping, and glycol regeneration and circulation at Kollsnes all scale with throughput. The glycol circulation pumps on a gas plant are unglamorous, and they are also the machines most likely to constrain a debottleneck.
Ageing hosts constrain new projects more than new reservoirs do. Troll A is 30 years old. Deck space, power availability and structural capacity set the ceiling on what can be added, which is why brownfield gas projects so often resolve into an argument about weight and footprint rather than about geology.
Delivering eight wells early and under budget on a platform of that age is a real execution achievement, and the European gas supply case for it is obvious. The engineering case is quieter: the field's remaining life is a function of how much pressure the machines can put back.
