They also maintained their 100 per cent record against their tenants Gretna, who again took nothing from another brave effort and appear doomed to be relegated.
Well made most of the early running and Darren Smith soon began threatening down the right flank, but the first decent chance fell to Gretna when a mistake by skipper Paul Quinn set-up Kenny Deuchar.
Although his shot was blocked by keeper Graham Smith, Brendan McGill was unlucky to clip the bar with the rebound.
Well went ahead after 25 minutes with the help of a lucky break as a Stephen Hughes drive was deflected into the path of top scorer Chris Porter, who slotted home his 12th goal of the season.
Two minutes later Ross McCormack wasted a free header from close range and from another Smith cross, Porter rippled the sidenetting as half-time approached.
There was still time for John Paul Kissock and Gavin Skelton to fire over for Gretna, while Porter ought to have scored again three minutes before the break, when he shot tamely wide after beating the offside trap.
McCormack was far more decisive two minutes into the second period as he ran on to a hopeful long ball and coolly sidefooted his tenth goal of the campaign.
Gretna looked dead and buried, but suddenly gave themselves fresh hope by pulling a goal back within three minutes. Kissock and Mickael Buscher supplied the ammunition from the left and lazy defending allowed McGill to appear unmarked at the back post for a simple tap-in.
Motherwell needed a third goal to settle any nerves and only a hesitant finish from the otherwise excellent Smith rescued Gretna after 58 minutes. It was a similar story 11 minutes later when McCormack's measured cross found Porter, who could only direct his header straight at the keeper.
Somehow, Gretna were still in the game and it required a desperate penalty-box block to keep out a late volley from substitute Nicky Deverdics.
Deverdics also shot inches wide and Deuchar had a penalty claim waved away as Motherwell wobbled, but McCormack confirmed their victory with an inch-perfect chip a minute from time.