Royal Dutch/Shell and Total have signed a $2bn deal to develop the country's huge gas reserves in the vast south-eastern Empty Quarter desert.

Saudi Arabia, the world's largest oil exporter, is also thought to have the fourth largest reserves of natural gas in the world.

The two companies will work in a consortium with Saudi state oil firm Aramco to explore, develop and produce the gas.

Shell will have 40% of the project while Total and Aramco will have 30% each.

However, the investment is a mere token compared with the originally planned $US20 billion deal which collapsed earlier this year when the sides could not agree terms.