Saudi Aramco’s purchase of 70% of Sabic from PIF bolsters its strategy of international expansion and downstream diversification, although it may divert focus and resources from other plans. PIF’s injection of liquidity will fund its aggressive plans.

Saudi Aramco has agreed to buy the 70% of state petchems-giant Sabic held by the PIF wealth fund for $69.1bn. In a 27 March announcement, Aramco said the acquisition would help align the “strengths and interests of two major...