Wolverhampton Wanderers have signed five current and former Eagles players so far.
Wolves were bought by Chinese conglomerate Fosun International in July, and have utilised their new owners' contacts to sign three players from the Primeira Liga champions, as well as another two who used to play for the Eagles.
However, despite their business so far, Thelwell has revealed there is no official agreement between the two clubs - although that is not to say their relationship won't develop in future.
"It’s a good fit for us," he said, as quoted by the Express & Star. "Fosun have got a strong relationship with Gestifute (the agency founded by Jorge Mendes) and Gestifute have got a strong relationship with Benfica.
"We plan to spend a bit of time there in the future and have a look at their working model. Their core values and principles are not too dissimilar to ours."
Joao Teixeira, who spent last season on loan to Vitoria Guimaraes, Helder Costa (Monaco) and Ola John (Reading), have each swapped the Estadio da Luz for Molineux in search of games, and according to Thelwell they may not be the last to do so.
"It’s an opportunity to identify and recruit young players that perhaps can’t get a chance at Benfica but could get a chance here," he added.
"It’s something we’ll look to build on in the coming months and years. It's a very informal cooperation at the moment. It would be wrong for us not to take advantage of that resource, that support, that relationship.
"Who knows if it'll develop into something - we're not that far down the line on it just yet. But there's certainly an opportunity to spend some time over there, talk to their sporting director and their ownership and look at how they do things."
Club-record signing Ivan Cavaleiro, who rose through the Eagles' ranks, and full-back Silvio, who spent the past three campaigns in Lisbon, have also arrived at Molineux from Monaco and Atletico Madrid respectively.