Royal Dutch Shell and Saudi Aramco announced plans to break up Motiva Enterprises in a deal that ends a partnership of nearly two decades and hands control of the biggest US refinery to the Saudi state oil giant.

News that the two energy companies will divide assets in their oil refining and marketing joint venture had been expected by many as they navigated an often-frayed relationship where their respective interests sometimes diverged.

An early sign of a pending breakup emerged last summer when Motiva announced plans to set up its own oil products trading operation separate from Shell. The desk started up in January.

The divorce also comes as the Saudi government considers selling shares in the world’s largest oil firm.

Abdulrahman Al Wuhaib, senior vice president of downstream at Saudi Aramco, said in a statement that the joint venture formed in 1998 served the partners’ downstream business objectives "very well for many years."

"It is now time for the partners to pursue their independent downstream goals," he said.

A US spokesman for The Hague-based Royal Dutch Shell said the breakup and split of Motiva’s assets were consistent with Shell’s plans to simplify its global portfolio.

Motiva’s three refineries in the US Gulf Coast region have a combined capacity of over 1.1 million barrels per day (mbpd), located within a 195-km radius of one another. The marketing operations support a network of about 8,300 Shell-branded gasoline stations in the Eastern and Southern US.

The partners said that under the terms of a non-binding letter of intent, Aramco would take over the Port Arthur, Texas, refinery and retain 26 distribution terminals as well as the Motiva name.

It will also have an exclusive license to use the Shell brand for gasoline and diesel sales in Texas, the majority of the Mississippi Valley, the Southeast and Mid-Atlantic markets, it said.

Shell will solely own the Louisiana refineries in Convent and Norco, where it also operates a chemicals plant, as well as Shell-branded gasoline stations in Florida, Louisiana and the Northeastern region.