Advice provided to the Scottish Parliament Information Centre said peak production at the Laggan and Tormore fields could satisfy average demand across the whole of Scotland.
Operator Total started production at its new Shetland plant on Monday.
Highlands and Islands MSP Mike MacKenzie said it was "good news" for the country and the industry.
In total, the two new fields, which have a lifespan of 20 years, will produce about 8% of the UK's gas needs.
The Laggan and Tormore fields lie about 125km (77 miles) north west of the Shetland Islands, in an area where almost one fifth of the UK's remaining oil and gas reserves are thought to be held.
A pipeline carries the gas from the huge new Shetland Gas Plant, part of a Â£3.5bn investment by French firm Total, down to the mainland and into the national grid.
Challenging weather conditions delayed the project by more than a year and added millions to its cost, but Total said the now-operational plant would produce 90,000 barrels of oil equivalent per day.
Mr MacKenzie hailed the new facilities as good for Scotland and for the oil and gas industry, which has endured a difficult period amid plunging oil prices.
He said: "The newly constructed Shetland Gas Plant is a major economic investment and a sign of confidence in the future of our oil and gas industry.
"The scale of these new facilities is absolutely massive - with analysts confirming that these two fields will produce enough to meet 100% of Scotland's gas demand.
"That's good news for Shetland, for Scotland, and for our North Sea industry."
New gas fields off Shetland could supply 100% of Scotland's gas needs, analysts say.