American Brandon Wu carded a second round of 67 to hold a narrow lead at the halfway stage of the Puerto Rico Open, while Seamus Power and Padraig Harrington ensured that they'll be around for the weekend.

Wu fired six birdies and a solitary bogey at Grand Reserve Country Club to finish 11 under par, a shot ahead of Australia's Greg Chalmers.

"I think today went really well," Wu said. "I definitely hit a lot of good shots, kind of similar to yesterday.

"But it was kind of a grind. I missed a short putt early on in the round to make a bogey on my fourth hole.

"I kind of just had to keep my head down and play well on the back and luckily I kept having good opportunities, so I converted on those."

Chalmers added a 68 to his opening 66 to occupy second place on 10 under, with South Africa's Branden Grace and home favourite Rafael Campos a shot further back following rounds of 68 and 69 respectively.

Former Ryder Cup star Thomas Pieters is three shots off the pace after a 67, with Europe captain Harrington on two under par following a second round of 72. 

Harrington started brightly and made the turn at -2 but a double bogey on the par-5 15th wiped out those gains and he finished the round on par.

Power enjoyed a more dramatic day, with five birdies and three bogeys seeing him sign for a round of 70 and leaving him on -5 for the tournament.