How are oil seeps and natural gas seeps used in petroleum exploration?

Historically, oil and natural gas seeps were the primary indicators used to locate underground petroleum deposits, as they provided direct evidence of hydrocarbons reaching the surface. For example, the first oil well drilled by Edwin L. Drake in 1859 was situated near a known surface seepage of crude oil.1

In modern petroleum engineering, the utility of these seeps is limited. While crude oil may appear as tarlike deposits or thin films on water, natural gas seeps are often invisible and require specialized instruments to detect concentrations in the air or seawater. Crucially, these geochemical surface methods are not applicable to the vast majority of petroleum reservoirs, which do not exhibit surface leakage.2

Today, exploration relies on more sophisticated, integrated techniques—such as seismic surveys, geochemistry, and gravity or magnetic field analysis—to identify subsurface features like salt domes, faults, and folds that are favorable for trapping oil and gas, even when no surface indications exist.213