The Fox sci-fi drama is expected to air its last episode in February 2013, with its fifth season kicking off later this month.
"[It's] a 13-hour feature film type of thing, like a saga, because I feel that's the best way to tell the end," Wyman told TVLine.
The showrunner added that the Fringe series finale will be a regular one-hour episode, but confirmed that the final three episodes "are like a three-parter".
Production on the show's final season was temporarily shut down in July so that star John Noble (Walter Bishop) could be treated for a sleep disorder.
Wyman and Fringe co-creator JJ Abrams are now developing a new futuristic cop drama with Fox, in the hope that the pilot will be picked up to series once Fringe wraps.
The final season of Fringe begins on Friday, September 28 at 9/8c on Fox. In the UK, the series airs on Sky1.