DUBAI, (Reuters) – Qatar Petroleum and Exxon Mobil’s planned petrochemical complex will cost about $6 billion, Qatar’s oil minister said in a speech carried by the Kuwait’s state news agency KUNA.

That was about double the initial estimated cost of the plant. The two companies gave no updated cost estimate when they announced they had signed a deal to build the complex last week.

The plant would be 51 percent owned by Qatar Petroleum and was due to start up in fourth quarter of 2015. It would include one of the largest ethylene glycol plants in the world, Attiyah said.

The complex in the industrial city of Ras Laffan includes a 1.6 million tonnes per year (tpy) steam cracker and associated units including two 650 tpy polyethylene plants and a 700 tpy ethylene glycol facilities,

Qatar is the world’s largest producer of liquefied natural gas (LNG) and Exxon is the largest foreign investor in the Gulf Arab state. Exxon has stakes in several of Qatar’s LNG projects.

In a separate report on Qatar’s state news agency QNA, an Exxon executive said the company would spend around $100 million in Qatar on reducing carbon emissions.