Norway’s Equinor must drill several new wells at its much-delayed Martin Linge oil and gas field in the North Sea in order to ensure safe operations when production starts, the company said Sept. 8.

Originally scheduled for completion in 2016 under its then-operator Total, the project was taken over by Equinor in 2018 and is yet to be finished.

“Four gas wells that were drilled at Martin Linge before 2018 have well barrier deficiencies that are considered to make them inappropriate for safe production,” Equinor said.

“The wells are considered safe as they are now, but we will keep them plugged and under continuous monitoring until we have reduced the pressure in the formation by producing from other wells,” the company added.

Up to three new wells will be drilled at a cost of around 2 billion Norwegian crowns ($222 million), Equinor said.

“Total has recently been made aware of Equinor’s view that certain of the wells drilled on Martin Linge do not have the necessary barriers,” a spokesman for the French company told Reuters.

“This information is new to us and we are reviewing the matter. We have no further information to provide at this stage.”

Equinor has described the field’s main reservoir as structurally complex, characterized by high pressure and high temperatures compared to many other fields.

The company said in May it had postponed the planned startup to 2021 from 2020 previously. A new update on costs and the planned startup is due next month when the Norwegian government presents its fiscal budget for 2021.

Equinor has operated Martin Linge since March 2018 when it bought a 51% stake from Total, raising its holding to 70%. Norwegian state-owned oil firm Petoro owns the remaining 30%.

“Petoro has carried out an independent assessment of well barriers that support the operator’s view,” Equinor said.

The field, estimated to hold reserves of 256 million barrels of oil equivalents, had originally been estimated to cost 30 billion crowns to develop. The latest cost forecast released by the Norwegian government, in 2019, stood at 56.1 billion crowns.