How can surface-water samples reveal possible petroleum seepage from underground deposits?

Surface-water samples can reveal potential petroleum seepage from underground deposits through the detection of trace hydrocarbons.1

In the context of petroleum production, geologists analyze water collected from swamps, streams, or lakes to identify chemical signatures that indicate oil or gas is leaking from a subsurface petroleum trap. This geochemical technique is particularly useful in offshore exploration, where it is often employed alongside seismic profiling to locate potential petroleum accumulations.1

While natural seepage occurs when petroleum migrates through rock fissures to the surface, these geochemical methods allow researchers to identify the presence of hydrocarbons even when they are not visible to the naked eye. By measuring these minute amounts of materials, geologists can better assess the likelihood of underground deposits in a given area.213