Petroleum seep

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.[2]

After the arrival of Homo sapiens, humans used bitumen for construction of buildings and waterproofing of reed boats, among other uses.[3] 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.[4] 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).[5] Great quantities of it were found on the banks of the river Issus, one of the tributaries of the Euphrates.

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. Along the Tigris and Euphrates rivers, the area was littered with hundreds of pure bitumen seepages. The Mesopotamians used the bitumen for waterproofing boats and buildings. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society. In ancient Egypt, the use of bitumen was important in creating Egyptian mummies — in fact, the word mummy is derived from the Arab word mūmiyyah, which means bitumen.[3] Oil from seeps was exploited in the Roman province of Dacia, now in Romania, where it was called picula.

In East Asia these locations were known in China, where the earliest known drilled oil wells date to 347 CE or earlier.[6] The ancient records of China and Japan are said to contain many allusions to the use of natural gas for lighting and heating. Petroleum was known as burning water in Japan in the 7th century.[5] 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. In the 9th century, oil fields were exploited in the area around modern Baku, Azerbaijan. These fields were described by the Arab geographer Abu al-Hasan 'Alī al-Mas'ūdī in the 10th century, and by Marco Polo in the 13th century, who described the output of those wells as hundreds of shiploads. Distillation of petroleum was described by the Persian alchemist, Muhammad ibn Zakarīya Rāzi (Rhazes).[7] There was production of chemicals such as kerosene in the alembic (al-ambiq),[8] which was mainly used for kerosene lamps.[9] Arab and Persian chemists also distilled crude oil in order to produce flammable products for military purposes. Through Islamic Spain, distillation became available in Western Europe by the 12th century.[5] It has also been present in Romania since the 13th century, being recorded as păcură.[10]

In Europe, petroleum seeps were extensively mined near the Alsace city of Pechelbronn, where the vapor separation process was in use in 1742.[11] In Switzerland c. 1710, the Russian-born Swiss physician and Greek teacher Eyrini d'Eyrinis discovered asphaltum at Val-de-Travers, (Neuchâtel). He established a bitumen mine de la Presta there in 1719 that operated until 1986.[12][13][14][15] Oil sands here were mined from 1745 under the direction of Louis Pierre Ancillon de la Sablonnière, by special appointment of Louis XV.[16] The Pechelbronn oil field was active until 1970, and was the birthplace of companies like Antar and Schlumberger. In 1745 under the Empress Elisabeth of Russia the first oil well and refinery were built in Ukhta by Fiodor Priadunov. Through the process of distillation of the "rock oil" (petroleum) he received a kerosene-like substance, which was used in oil lamps by Russian churches and monasteries (though households still relied on candles).[17]

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.[18] A Swedish scientist, Peter Kalm, in his 1753 work Travels into North America, showed on a map the oil springs of Pennsylvania.[5]

In 1769 the Portolà expedition, a group of Spanish explorers led by Gaspar de Portolà, made the first written record of the tar pits in California. Father Juan Crespí wrote, "While crossing the basin the scouts reported having seen some geysers of tar issuing from the ground like springs; it boils up molten, and the water runs to one side and the tar to the other. The scouts reported that they had come across many of these springs and had seen large swamps of them, enough, they said, to caulk many vessels. We were not so lucky ourselves as to see these tar geysers, much though we wished it; as it was some distance out of the way we were to take, the Governor [Portola] did not want us to go past them. We christened them Los Volcanes de Brea [the Tar Volcanoes]."[19]

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.[25] 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. A secondary cause of overpressure is fluid expansion, due to changes in the volume of solid and/or fluid phases. Some examples include: aquathermal pressuring (thermal expansion), clay dehydration reactions (such as anhydrite) and mineral transformation (such as kerogen to oil/gas and excess kerogen).

There are two types of seep that can occur, depending on the degree of overpressure.[26] Capillary failure can occur in moderate overpressure conditions, resulting in widespread but low intensity seepage until the overpressure equalizes and resealing occurs. In some cases, the moderate overpressure cannot be equalized because the pores in the rock are small so the displacement pressure, the pressure required to break the seal, is very high. 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.[27]