RIYADH, (Reuters) – Saudi Arabia is stepping up exploration to boost its natural gas reserves by around 40 percent in the next 10 years as it prepares to meet rising domestic demand, Oil Minister Ali al-Naimi said on Wednesday.

“We are planning to add in the next 10 years 100 trillion cubic feet to our current reserves of gas,” Naimi told a conference on economic development in Riyadh.

The kingdom holds the world’s fourth largest natural gas reserves at 252 trillion cubic feet, Naimi said.

Saudi Arabia faces increasing demand for natural gas from its rapidly growing population and new petrochemical and industrial projects.

Domestic gas sales were expected to rise by 40 percent through 2012 from the current level of around 7 billion cubic feet per day, Naimi said.

The kingdom plans to drill 186 exploration wells for gas and 332 development wells by 2012, Naimi said. That was higher than a figure of around 70 gas exploration wells given by an Aramco executive last November.

Gas output from the offshore Karan gas field will start in 2012, Naimi said, a year later than previously planned. He gave no reason for the delay.

Karan is a $3 billion development that will yield domestic gas sales of 770 million cubic feet per day, Naimi said.

The kingdom has opened its gas fields to international firms to help meet demand growth. The upstream oil sector of the world’s largest crude exporter is off limits to foreign investors.

Four consortia of European, Russian and Chinese firms were awarded gas exploration blocs in the Empty Quarter in 2003 and 2004.