Hi,

1. Hydrocarbon shows; (a) Gas Chromatography - Look for high methane concentration.
(b) Oil stains on cuttings - Characterized by florescence of some sort.
Both of these will show up on a mud log. Also lookout for any kick information, like gas kicks (gas) and liquid kicks (oil).

2. Look for segregation/contacts; neutron-density will show the biggest cross-over in gas, then smaller cross-over in oil, then overlie each other in 100% water.

Markus