I recently bought a 2006 DTS that was left in-progress for a water pump replacement by a previous owner. The intake manifold has been removed, and I can see a pool of what appears to be oil in the "V" that is normally hidden by the intake manifold. I have attached an image; this was taken after I had already sucked out some of the liquid with a turkey baster. Is there a common problem that causes this oil pool?

Image of the pool of liquid underneath the intake manifold.
Let me know if there is anything any of you know!