Forum:What was the G-Man's motivation to have Shepherd kill the Gene Worm in Opposing Force?

The G-Man helped Shepherd when the room as over flowing with acid, but soon after prevented him from escaping Black Mesa by closing the doors to the Osprey about to take off. His only reason for doing this would be to have Shepherd stay in Black Mesa so the Gene Worm would be killed. But why would the Gene Worm go through all that trouble just to see the death of the Gene Worm?