India’s Shubhankar Sharma carded four-under-67 in the second round with five birdies and a lone bogey and lying at T40.
Guerrier played some tremendous iron shots and putt well to make seven birdies and just two bogeys in blustery morning conditions at Dom Pedro Victoria Golf Course in the second round of Portugal Masters, setting a testing clubhouse target of 14 under par.
The afternoon starters could not get anywhere near Guerrier’s total, handing him the largest 36 hole lead of the 2020 European Tour season so far.
Sihwan Kim was Guerrier’s closest challenger on nine under after he reeled off five birdies in his last six holes to post a 66 on Friday.
Antoine Rozner, Wilco Nienaber, Scott Vincent, Adrien Saddier, Adrian Meronk, Martin Simonsen, Matthew Jordan, Marcus Armitage and first round leader Liam Johnston were another two shots further back in the huge tie for third.
Guerrier came into the week sitting 125th in the Race to Dubai Rankings Presented by Rolex, having spent the 2020 season working his way back from an injury that only allowed him to play three times in 2019.
He made an outstanding start to this week’s tournament on Thursday, notching nine birdies and no bogeys to begin his second round a single shot behind overnight leader Johnston.
Guerrier made his first bogey of the week at the opening hole on Friday morning but bounced back straight away, firing birdies at the second, third and fifth to take over at the top of the leaderboard.
A second bogey arrived at the sixth before Guerrier got up and down for a par on the tricky seventh, stylishly holing his 30 foot putt to remain tied for the lead.
The 35-year-old left long birdie putts short on the eighth and ninth greens but was able to tap in for par on both occasions to keep the bogeys off the card.
After sending his tee shot into the rough on the tenth, Guerrier displayed exceptional distance control with his approach as he lifted his ball to tap-in range for a birdie.
He then increased his lead to two shots with another birdie on the 11th from within five feet as the wind got up.
Guerrier was lucky to avoid the water with his tee shot at the 12th but ended up in the very thick stuff on the bank.
After chopping out onto the fairway, he found more rough over by the green with his third shot but did extremely well to get up and down for a valuable par.
Guerrier continued to make chances but had to settle for pars on the 13th and 14th before taking advantage of the 15th to get to 13 under.
He made a birdie at the par five 17th for the second day in succession before closing his second round with a par.
Guerrier said: “I’m feeling great. It looks easy but it’s not.
“After shooting nine under it’s always tough to make a good score so I’m really happy to have played good.
“I just try to hit it on the fairways and hit the greens after. I’m feeling good on the greens so I think it’s a bit easier when you are confident around the green.
“In Valderrama it was really tough so that was more about fighting spirit. After the injury you try to get a good level and find your mark on your game under pressure so it’s perfect for me to play on the weekend.”
Kim reached the turn in 33 after sandwiching the only bogey of his front nine between gains at the second and fourth, and making another birdie at the tricky seventh.
He did not make a single par on the back nine, cancelling out bogeys on the tenth, 12th and 16th with birdies at the 11th, 13th, 14th, 15th, 17th and 18th to cut Guerrier’s lead to five shots.
Kim said: “Julien is a very good player and obviously he’s the only one on top just now. I’ll try my best to keep up.
“I know Sunday is supposed to be really windy and anything can happen there. I’ll try to make up as much ground as possible tomorrow and just go for it on Sunday.
“I need to stay patient. Some spots around the green are so thick, I just need to take my shots more towards the middle of the green and just putt like I’ve been putting and I’ll be good to go.”
Two players made a hole-in-one on Friday afternoon, with Northern Ireland’s Jonathan Caldwell firing his ace from 210 yards on the sixth and France’s Mathieu Fenasse holing his tee shot from 151 yards with an eight iron on the short eighth.
