The Duchesne County Sheriff's Office said the fire started about 12:10 a.m. at a rig just north of Roosevelt, operated by Frontier Drilling and owned by Devon Energy, based in Oklahoma City.
Five homes within a half mile of the rig were ordered evacuated and the evacuation was still in effect late Tuesday, The Salt Lake Tribune reported.
A Devon Energy spokesman said the company had brought in crews to cap the well and work on "regaining control of the well and [extinguishing] the fire."
The spokesman said the company would cover some short-term financial needs of those affected by the evacuation.
The cause of the fire had not been determined by Tuesday afternoon. Devon Energy had no estimate on when the evacuation order might be rescinded or how long it will take to put the fire out, the newspaper said.