Lourdes is a long way from Paris on a relatively slow train line. If it is a must, I would strongly recommend staying at least one night there.
The only wine growing area close enough to Paris for a day trip (Paris is fairly northerly) is Champagne. The standard daytrip destination from Paris is Rheims (pronounced Rahnce) which is a fairly large city. You could also look into the slightly smaller Epernay, or somebody on the site who knows the region better than I might be able to recommend an actual small town. If you are willing to tie yourself down to a specific arrival and departure time, you can get advance discount fares for tickets from Paris to Rheims or Lourdes online - see http://www.seat61.com/France-trains.htm for advice depending on where in the world you come from.