Royal Dutch Shell and Qatar Petroleum will jointly study building a major petrochemicals plant in the Ras Laffan industrial city in Qatar, Shell said on Tuesday.

"The scope under consideration would include a mono-ethylene glycol plant of up to 1.5 million tons per annum...to yield over 2 million tons of finished products," Shell said in a statement.

Exxon Mobil Corp had been in talks with the Gulf Arab state to build the plant, which was estimated to be worth $6 billion. Industry sources said they believed the U.S. company has pulled out, but chief executive Rex Tillerson last week denied that and told reporters that the company was waiting for Qatar to make its decision.

ExxonMobil and France's Total, also in talks with Qatar on the same project, were not immediately available for comment.

Shell said the memorandum was signed between Qatar's Energy Minister Abdulla bin Hamad Al-Attiyah and Peter Voser, chief executive of Shell.
The company did not give a value for the project.

"This new project will combine Shell's experience and technology with the ambition of the State of Qatar to create further value from its natural gas resources," Voser said.

The small Arab country has recently reached its long-term goal to export 77 million tons of liquified natural gas (LNG), making it the largest exporter in the world.

Qatar is also involved in another project with Shell, where it will ramp up supplies of middle distillates through its $19 billion Pearl gas-to-liquids (GTL) project with the company.