State oil giant Saudi Aramco has given engineering firms a fresh date to submit  bids to build Saudi Arabia's biggest gas plant, industry sources said on Saturday.

Wasit would be designed to process 2.5 billion cubic feet per day (cfd) of gas from the offshore non-associated gas fields Arabiyah and Hasbah and produce around 1.75 billion cfd of sales gas, Aramco said in a brief description of the project on its website.

The world's top oil exporter is focusing on developing its gas production to cater for rising domestic demand after it completed a massive programme last year to expand its crude oil output capacity.

Construction of the plant is split into four packages that include a gas unit, a cogeneration power plant, a sulphur recovery unit with utilities and natural gas liquids (NGL) fractionation facilities.

NGL facilities call for the processing of 240,000 bpd of ethane and NGL stream produced at Khursaniyah, Aramco said on its website.

The due date to bid for the construction of four onshore packages has been pushed to Nov. 1 from Oct. 24, the sources said. The original due date was in September.

"It is the final extension, no more extension, some bidders requested more than this period, but one week was accepted," said one source.

Wasit, along with Khursaniyah and Karan gas plants would help Saudi Arabia to process its targeted production increase of raw gas to 15.5 billion cfd by 2015 from 10.2 billion cfd.

Aramco expects overall sales gas production to exceed 13 billion cfd by 2020.

Aramco has given no cost estimate for the Wasit plant, expected to come online in 2014, but industry sources said it would cost between $6 billion and $8 billion.

Engineering and construction companies lined up to bid by Nov. 7 for the construction of offshore packages related to the plant.

Canada's SNC-Lavalin has carried out the front-end engineering and design work. – Reuters