Defending champion Andy Sullivan had 10 birdies in a 10-under round of 61 to take a share of the lead after two rounds of the Portugal Masters on Friday.
The English golfer, who won last year's event by a record nine shots, pulled level with overnight leader Marc Warren.
"It only takes a couple of putts to go in and you start seeing it go in all the time," Sullivan said. "Last year, I was aggressive the whole way around, and I've got to be aggressive again."
The Scottish player Warren had seven birdies and one bogey in a round of 65 to stay with Sullivan on 14-under overall.
Irish veteran Padraig Harrington — who posted 63 on the day — and Swede Jens Fahrbring (64) are one stroke behind.
American David Lipsky is another shot back.