The chemical firm has agreed to pay BP up to $250 million (£199.5m) for the business, with half up-front and half coming over the next seven years.
It is considered a strategic UK asset and delivers almost 40% of the UK’s North Sea oil and gas.
Around 20% of the oil that passes down the pipeline feeds the INEOS refinery and provides 80% of Scotland’s fuel.
Once the acquisition is completed, INEOS will also own and operate the Kinneil terminal, a gas processing plant, the Dalmeny terminal, various sites in Aberdeen, the Forties Unity Platform and other associated infrastructure.
INEOS CEO Jim Ratcliffe said: “We have a strong track record of acquiring non-core assets and improving their efficiency and reliability, securing long term employment and investment.
“I am delighted that we can now bring this integrated system back under single ownership in INEOS.”