The South Korean firm has emerged as the frontrunner for all four engineering, procurement, and construction (EPC) packages for Shaybah NGL, the sources told Reuters on condition of anonymity since the kingdom hasn't announced a winner yet.
The Shaybah project is valued at $5 billion to $6 billion and the winning bidder should be announced soon, they added.
State-run oil giant Saudi Aramco declined comment. A spokeswoman for Samsung also declined comment.
Aramco began taking bids on Shaybah last year. The project is set to begin operation in 2014 and will help meet soaring natural gas demand in the Gulf region's economic powerhouse.
It will process 2.4 billion cubic feet per day (cfd) of low-sulfur sweet gas from Saudi Arabia's southeastern Shaybah oil field, and send on 264,000 barrels-per-day (bpd) of NGLs for fractionation at an associated processing plant, known as Juaymah.
Samsung bid on four contracts including building a cogeneration plant, a gas treatment facility, an NGL recovery plant and utilities and facilities to handle gas and debottleneck Shaybah's gas-oil separation plants (GOSPs).
Aramco's gas reserves, the world's fifth-largest, stood at 275.2 trillion cubic feet (tcf) in 2009, with about half of the reserves associated to oil fields.
Domestic use of gas is rising by 5 to 6 percent per year on heavy demand for power generation and petrochemicals feedstock, raising concern over potential shortages.
Gas projects are also taking priority in the world's top oil exporter as Aramco seeks to avoid burning oil it would rather sell abroad. Saudi Arabia is looking to boost its output of raw gas to 15.5 billion cfd by 2015, from 10.2 billion cfd last year.
Shaybah is one of two gas mega-projects announced by Aramco in 2009. Among the other bidders for Shaybah are France's Technip, Italy's Saipem, and South Korea's SK Engineering and Construction, industry sources said earlier.
Aramco in January awarded construction contracts for the Kingdom's other new gas project, known as Wasit and estimated to cost $6 billion to $8 billion. SK Engineering won several of the work packages there, while Samsung will build Wasit's cogeneration plants.
Aramco already signed several earlier deals to develop Shaybah. In December, US General Electric said it had a deal worth around $500 million to expand gas-oil processing facilities at Shaybah, which could help the oil field boost production to around 1 million bpd from a current 750,000 bpd. GE said it will supply turbines and compressors.
US engineering firm KBR was tapped to carry out the front-end engineering and design of Shaybah NGL.
Aramco seeks to raise NGL production to about 1.2 million bpd in 2015 from 937,000 bpd in 2010, Chief Executive Officer Khalid Al-Falih said recently.
