State refiners Aramco, Adnoc and KNPC are seeking access to overseas fuels markets and integration with petchems. But, with global downstream investment rising, they are not alone.

State-owned petroleum firms in Saudi Arabia, Abu Dhabi and Kuwait are part of a global oil push further downstream, in a bid to squeeze more value out of their crude oil resources. In particular, Aramco has already invested in export refineries and Adnoc and KNPC are following suit.

The three firms are also...