The Troll oil and gas field in the North Sea chalked up a new milestone last week when the Troll B installation surpassed 500 million barrels of oil produced.
"The climaxes are coming rapidly on Troll these days," says Johan Kristian Mikkelsen, manager of Hydro's Troll business unit. "On April 23, Troll B had produced 500 million barrels of oil since its production start on September 19, 1995 - averaging an astonishing 208,000 barrels per day (bpd)."
Troll's total oil reserves are currently estimated to be about 1,350 million barrels, out of which 45 percent have been produced.
The 500 million barrel mark was reached just two weeks after a new production record was set at 444,000 barrels per day (bpd) from Troll B and C, underlining Troll's position as the definitively largest oil producing field in Norway.
"Troll's achievements are even more amazing when you look at the history of the field," says Mikkelsen. "In the 1980s, Troll was only considered a gas field" and "production from the thin yet enormous oil zone on the field was deemed uneconomical."
This picture radically changed because of Hydro's sustained efforts to develop well technology capable of tapping the thin oil layers, he points out.
Three key technological elements made oil recovery on Troll highly economical:
- Long, accurately drilled horizontal wells used to "trench" the reservoir. The total horizontal distance in one well has increased from 500 meters in 1990 to 7500 meters today.
- Branched wells that create two or more horizontal sections in one hole, enhancing production in each well and significantly reducing costs and enabling production from previously uneconomical areas. To date, Hydro has completed 15 multi-branched wells out of 85 drilled.
- The inflow control in the horizontal sections of the well, which allows oil to be produced along the entire horizontal plane - thus enhancing both production and recovery.