Board Thread:Questions and Answers/@comment-84.186.189.225-20130608011330/@comment-5627887-20130608021417

Have you come across the oil as an underground pool? I've only ever come across oil on the surface (or at least, showing on the surface even though it goes down fairly deep to a large "bulb" underground). I would suggest not putting a quarry anywhere you can see oil on the surface, but if you really need to quarry that specific area, then pumping it out with an IC2 pump would work (I prefer to pump into phased transport pipes with a receiving pipe back at base), or manually picking up buckets and putting them into an Ender Tank, with another Ender Tank of the same colour code set up at your base, with the tap set to orange and connected by a waterproof pipe (cobblestone will do) to a bank of normal Tanks, which will drain anything in the Ender Tank into the normal Tanks as soon as you place liquid into the Ender Tank you have with you out in the quarry area.

Both a bit complicated I suppose but the only other option you have is to fill the oil in with sand (if you don't mind losing it).