Troll offshore Norway reaches 20-year production mark

Offshore staff

STAVANGER, Norway – Statoil is marking the 20th anniversary since oil production started from the Troll field in the Norwegian North Sea.

To date Troll has delivered 1.56 Bbbl and NOK 460 billion ($54.05 billion) in income, with investments so far of around NOK 100 billion ($11.75 billion).

Following the award of the acreage to Norsk Hydro (later merged with Statoil) in 1979, the semisubmersible Borgny Dolphin began exploratory drilling in July that year, discovering the field four months later.

A thin oil-bearing layer stretches across the field, but is only economic to produce in two provinces in Troll West. Oil is recovered using subsea facilities with a total of 121 well slots linked to the floating production platforms Troll B and Troll C.

During planning for the development, the main challenge was to apply techniques to extract the thin oil zones without the wells producing too much gas.

All Troll’s production wells are horizontal wells, involving drilling initially down to the reservoir,1,600 m (5,249 ft) below the seabed, then up to 5,500 m (18,044 ft) horizontally into the reservoir. Most are also branch wells, with two or three horizontal sections.

To date 200 wells have been drilled around Troll B and C, and the field has been Norway’s largest oil producer for the past three years.

Statoil aims to produce 2.1 Bbbl eventually: the current recovery rate for the oil is 40%, although the longer-term target is 52%.

Produced oil is transported to Mongstad, from Troll B via the Troll Oil Pipeline, and from Troll C through the Troll Pipeline II. Associated gas is sent to Troll A.


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