Petroleum seep

A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow. Seeps generally occur above either terrestrial or offshore petroleum accumulation structures. The hydrocarbons may escape along geological layers, or across them through fractures and fissures in the rock, or directly from an outcrop of oil-bearing rock.

Petroleum seeps are quite common in many areas of the world, and have been exploited by mankind since paleolithic times. Natural products associated with these seeps include bitumen, pitch, asphalt and tar. In locations where seeps of natural gas are sufficiently large, natural "eternal flames" often persist. The occurrence of surface petroleum was often included in location names that developed; these locations are also associated with early oil and gas exploitation as well as scientific and technological developments, which have grown into the petroleum industry.

The exploitation of bituminous rocks and natural seep deposits dates back to paleolithic times. The earliest known use of bitumen (natural asphalt) was by Neanderthals some 70,000 years ago, with bitumen adhered to ancient tools found at Neanderthal sites in Syria.

After the arrival of Homo sapiens, humans used bitumen for construction of buildings and waterproofing of reed boats, among other uses. The use of bitumen for waterproofing and as an adhesive dates at least to the fifth millennium BCE in the early Indus community of Mehrgarh where it was used to line the baskets in which they gathered crops. The material was also used as early as the third millennium BCE in statuary, mortaring brick walls, waterproofing baths and drains, in stair treads, and for shipbuilding. According to Herodotus, and confirmed by Diodorus Siculus, more than four thousand years ago natural asphalt was employed in the construction of the walls and towers of Babylon; there were oil pits near Ardericca (near Babylon), as well as a pitch spring on Zacynthus (Ionian islands, Greece). Great quantities of it were found on the banks of the river Issus, one of the tributaries of the Euphrates.

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