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 natural terrestrial or underwater petroleum accumulation structures (e.g., sandstones, siltstones, limestones, dolomites).
[5] 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.
[6] 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.
In ancient times, bitumen was primarily a Mesopotamian commodity used by the Sumerians and Babylonians, although it was also found in the Levant and Persia.
In East Asia these locations were known in China, where the earliest known drilled oil wells date to 347 CE or earlier.
[7] In his book Dream Pool Essays written in 1088, the polymathic scientist and statesman Shen Kuo of the Song dynasty coined the word 石油 (Shíyóu, literally "rock oil") for petroleum, which remains the term used in contemporary Chinese.
In southwest Asia the first streets of 8th century Baghdad were paved with tar, derived from natural seep fields in the region.
[11] Arab and Persian chemists also distilled crude oil in order to produce flammable products for military purposes.
[12] In Europe, petroleum seeps were extensively mined near the Alsace city of Pechelbronn, where the vapor separation process was in use in 1742.
[13] In Switzerland c. 1710, the Russian-born Swiss physician and Greek teacher Eyrini d'Eyrinis discovered asphaltum at Val-de-Travers, (Neuchâtel).
[19] The earliest mention of petroleum seeps in the Americas occurs in Sir Walter Raleigh's account of the Pitch Lake on Trinidad in 1595.
Thirty-seven years later, the account of a visit of a Franciscan, Joseph de la Roche d'Allion, to the oil springs of New York was published in Sagard's Histoire du Canada.
In North America, the early European fur traders found Canadian First Nations using bitumen from the vast Athabasca oil sands to waterproof their birch bark canoes.
[20] A Swedish scientist, Peter Kalm, in his 1753 work Travels into North America, showed on a map the oil springs of Pennsylvania.
Romania is the first country in the world to have its crude oil output officially recorded in international statistics, namely 275 tonnes.
Other sources of oil initially associated with petroleum seeps were discovered in Peru's Zorritos District in 1863, in the Dutch East Indies on Sumatra in 1885, in Persia at Masjed Soleiman in 1908, as well as in Venezuela, Mexico, and the province of Alberta, Canada.
A petroleum seep occurs as a result of the seal above the reservoir being breached, causing tertiary migration of hydrocarbons towards the surface under the influence of the associated buoyancy force.
The most common cause of overpressure is the rapid loading of fine-grained sediments preventing water from escaping fast enough to equalise the pressure of the overburden.
[28] If burial stops or slows, then excess pressure can equalize at a rate that is dependent on the permeability of the overlying and adjacent rocks.
If the overpressure continues to increase to the point that it overcomes the rock's minimum stress and its tensile strength before overcoming the displacement pressure, then the rock will fracture, causing local and high intensity seepage until the pressure equalizes and the fractures close.
