Kevin Campbell threatened for the Baggies, stinging Jamie Ashdown's fingers with a shot from an acute angle, while Aliou Cisse drove wide for Pompey from 25 yards.
Iceland midfielder Sigurdsson was unfortunate eight minutes into the second half when his free-kick from 30 yards out came back off the post with JamieAshdown beaten.
Tyson hit the crossbar with a long-range effort in the 66th minute and McGugan curled a free-kick just wide before drawing a good save from JamieAshdown soon after.
Goalkeeper James had to replaced by JamieAshdown in the closing stages before Webber was carried away with a knee problem, leaving Pompey to finish the match with 10 men.
Meanwhile, manager Steve Cotterill told the forum he is confident that JamieAshdown will re-sign for the club before the weekend, enabling Pompey to have a senior goalkeeper for their Championship opener at Coventry City.