How do I clear sectors Ochre and Opal in Space Station Oblivion/Driller?

I played this game way too much when I was little. I remember eventually getting a strategy guide. Dusted the game off again, and I could remember most of it, but sectors Opal and Ochre are giving me fits. I thought there was a weak point in the force field, but I can't find it. And I have no idea where to drill in Opal at all; random drilling is getting me nowhere, and the sign tells me nothing useful.