It said the hotly anticipated feat came on October 27, following final commissioning of the field systems.
Amjad Bseisu, EnQuest chief executive, told investor that full production would start in early 2016 once additional wells have been opened up.
"We are pleased to confirm first oil from Alma/Galia. A further summary will be provided in EnQuest's next operations update,” Bseisu added.
A total of seven production wells will be tied into the EnQuest Producer floating production storage and offloading (FPSO) vessel, which can process 57,000 barrels per day and hold up to 625,000 barrels.
The field, located nearly 250 miles from Aberdeen, has 34mln barrels of proved and probable reserves.
EnQuest shares were up 0.5p, 1.8%, trading at 28.5p each.