The origin of spilled crude oil or refined product is commonly difficult to determine because they can be displaced from their point of origin by groundwater or ocean currents and many potential sources may be nearby, e.g. natural seeps, pipelines, tankers, and production platforms. Likewise, exploration is complicated by the fact that oil tends to migrate from fine-grained, organic-rich source rock to coarser-grained reservoir rocks. Because both short- and long-distance migration of petroleum can occur and several potential source rocks are generally available in a given basin, the source for many oils remains problematic.

Areas of concentrated petroleum occurrence can be predicted using mapping methods that integrate geology, geophysics, and geochemistry (Demaison, 1984). Biomarkers are a powerful component in this petroleum exploration approach. Combined with other exploration tools, biomarker geochemistry significantly reduces the risk associated with exploration for petroleum.