Minerals in the petroleum industry: Barytes.
10/10/2006 As the main component in the "mud" used to keep well pressure in balance, barytes - or barium sulphate - has a heavyweight role to play in the oil and gas business.
Barytes is a naturally-occurring mineral with the chemical formula BaSO4. In nature, it usually ranges in colour from white to light yellow or brown. Like many minerals, however, this can vary widely and it is also found in red, blue or black. This substance usually occurs as massive, shapeless intrusions in ores and sedimentary rocks, or in rock faults. Its crystals range from transparent to translucent with a mother-of-pearl sheen. The commonest crystalline form takes the shape of flat plates, but prismatic variants can be found.
Barytes can also occur as collections of plates arranged rather like the petals of a flower - often dubbed "desert roses". Deposits of barytes are common in Norway and the rest of the world. However, the principal commercial reserves are not found on the Norwegian mainland. A sole licence to mine big barytes resources has been secured in Norway's far northern Svalbard islands, but it is unlikely that extraction will ever happen there. Most of the supplies for industrial purposes come from mines in north Africa. Mineral barytes is easy to recognise from its high specific gravity, which is 4.5 grams per cubic metres - making it almost twice as heavy as "ordinary" rock. This is unusual for a non-metallic mineral, and meant it was often called "heavy spar", where "spar" referred to all light minerals which split well and had a glassy sheen.
Barytes is widely used by industry in such applications as lubrication, impregnation of carbon brushes in electrical motors, a paint additive and a pigment in glass. Other uses include a filler in textiles, linoleum, rubber and wallpaper - and rat poison. Barium compounds can also be found in fireworks to produce a fine green colour. These materials have also been used as hair remover - although not always with entirely satisfactory results. In the oil industry, barytes provides the main ingredient in "mud" - the mix of chemicals used for drilling. This is because the liquid column in the well must be heavy to balance the underground pressure, and a high specific gravity comes in useful. The weight additive represents 80-90 per cent of total chemical consumption in drilling, and barytes accordingly accounts for the bulk of the compounds which can be discharged to the sea.
The mineral is harmless in itself, but it is often found in combination with lead and zinc, and these heavy metals could be a pollution problem if they leak out. Although lead and zinc are not regarded as readily absorbed by the ecosystem, the aim is to find barytes deposits with a low content of these metals. Barytes mud might pose a problem for marine animals - deep sea corals - which live by filtration. This has led to greater attention being paid to its role in mud, and research is under way to find alternative weight minerals. The barium atom absorbs high-energy radiation, and thereby impenetrable by X-rays and the like.
So it is often used as a concrete additive in nuclear power stations or the contrast medium in stomach and intestine imaging.
Although barium sulphate is basically extremely toxic, it is also one of the least soluble of minerals. This means it does not dissolve in water or the stomach, rendering it harmless