Using gas to lift oil
On the Norne field in the Norwegian Sea, Statoil has adopted a new method of gas lift for subsea wells tied back to seabed templates.
The free gas from the upper part of the reservoir is mixed with the oil in the well. The oil thereby weighs less and is easier to produce.
This is the first time Statoil has used the method on subsea wells on the Norwegian continental shelf, reports Erling Rostad, manager of drilling and well operations at Norne.
The oil on the Norne field is produced from a production ship that is tied back to templates on the seabed. A valve that controls the desired amount of gas is hydraulically operated from the ship. Sea depth is 380 metres, and flexible risers convey the well flow to the ship.
It has taken about four months to prepare and plan the work. The Borgland Dolphin drilling rig has spent 16 days in preparing well B4-BH for gas lift production.