Former Saint Omer winner Nilsson is 89th on The Race to Dubai and knows his chances of reaching the Dubai World Championship could hinge on his final round showing.
“It's a big week for me,” he said. “I'm trying to get into the Top 60, so I hope for another good day but you never know.”
Sweden's Peter Hanson and Denmark's Thomas Björn are just two shots off the lead on 16 under, Hanson carding a superb 64 and Björn - seeking his fourth win of the season - returning a 66.
Hanson, a member of the victorious Ryder Cup Team at The Celtic Manor Resort last year, said: "I wasn't really thinking about a 64 but I got off to a good start and managed to keep a bit of momentum into the back nine.
"I've been struggling a bit with every part of my game this season, it has not been consistent but I've been working hard on that the least few weeks.
"I'm just outside top 15 on the Race to Dubai and would love to get into that. I'm also 51st on the world rankings and it would be nice to move up there as well."
South African Hennie Otto was among those on 14 under after producing a brilliant 63.
Otto carded seven birdies and an eagle to complete his round two hours before overnight leader Simon Khan was due to tee off.
The 35 year old made the cut with nothing to spare on five under after rounds of 72 and 67.
"I got it to six under yesterday with three holes to go and then I double-bogeyed the seventh," Otto said.
"I had five under par in my head to be the number for the cut and I chipped and putted on the eighth for par but then managed to birdie nine to get in right on the mark.
"With the early time and fresh greens, I really wanted to have a go. I played well last week but made 18 pars in a row in the first round.
"Yesterday I also played well but didn't make the putts, but I knew it was going to happen sooner rather than later for me."