This follows the discovery last week of a hairline crack in a section of pipe at Red Moss near Netherley, just south of Aberdeen, during a routine inspection.
INEOS mobilized a repair and oil spill response team last Wednesday following reports of a small amount of oil seepage, with measures subsequently applied to contain the leak.
No oil has been detected entering the environment, the company stresses, and the pipe is under continuous surveillance.
The pipeline pressure was reduced to allow a fuller assessment of the situation. However, the crack has subsequently extended.
The Incident Management Team has decided that a controlled shutdown of the pipeline is the safest way to proceed, allowing a suitable repair method to be implemented based on the latest inspection data.
INEOS completed acquisition of the FPS in October from BP. The 23-mi (37-km) trunkline system transports oil and gas from 85 North Sea facilities to the UK mainland, with average throughput in 2016 of 445,000 b/d of oil and around 3,500 metric tons/d (3,858 tons/d) of gas.