Scotland’s First Minister Nicola Sturgeon has said she will not support new North Sea fields, including the now stalled Cambo development off Shetland.
But Mr Ewing said “we need all the oil and gas production we can get for the short and the medium term”.
Speaking to ITV Border’s Representing Border programme on Wednesday, the MSP for Inverness and Nairn said: “The transition [period] will last for decades.
“Not two or three years, five or 10 years, but we will still require oil and gas for a much longer period.
“Every day household products, drugs in the NHS, anaesthetics, we require hydrocarbons for all of these things, let’s not forget that.
“It’s not possible just to produce oil and gas for anaesthetics and abandon it for everything else, the industry doesn’t work like that.”
Asked if Ms Sturgeon had made a mistake by bringing the Greens into her government, Mr Ewing said that is a question that should be directed at the First Minister.
He added: “I can’t say that I’m a great enthusiast for the policies of the Green Party that do seem to me to be somewhat extreme.
“Particularly policy of sacrificing the people in our oil and gas industry. I think they are amongst the best in the world.
“They do a great job. They keep the lights on, they keep the heating on in our homes. That’s valuable.
“We should be praising and thanking them, not saying that they should get their P45s tomorrow.”
Scottish Greens co-leader Patrick Harvie responded on Twitter: “Predictably, not so much as a single mention of the word climate. We already have far more fossil fuel than we can afford to burn if we want a chance of surviving the crisis their use has caused.”
And Green MSP Mark Ruskell said Mr Ewing’s analysis “ignores the climate crisis”.
He said: “It ignores that an over reliance on oil and gas allowed Putin to amass power in the first place, and critically, it ignores that an independent Scotland would lead Europe’s renewables revolution creating thousands of jobs and opportunities for energy exports to Europe.
“The transition away from oil and gas will take time, but expanding reserves now will only lock us into long term dependency on oil and gas for decades to come.
“That would be irresponsible for our climate and our energy security.”
In response to the interview, Scottish Conservative shadow cabinet secretary for Net Zero, Energy and Transport Liam Kerr said: “It should be a wake-up call for Nicola Sturgeon when her own former energy minister breaks ranks to criticise her stance on Scotland’s oil and gas industry.
“Fergus Ewing has thrown up in lights that the SNP Government is abandoning Scotland’s oil and gas industry because of the extremist Greens.
“Nicola Sturgeon must stop appeasing the Greens and back the North Sea oil and gas industry to secure our energy supply, protect jobs, and keep energy bills down.”