Concern over oil well in village

Oil companies and their PR people frequently tell us that acidising oil wells is no big deal because water well drillers do it all the time. This is the song Angus are singing at the end of your article.

But it is not true that water wells are frequently acidised, and anyway, acidising an oil well is hugely more risky.

If, rarely, water wells are acidised, no chemicals are used other than hydrochloric acid - in contrast with the numerous chemicals used in oil wells. Acidising in water wells is not done at pressure. So the chemicals are truly confined to the area of the well itself, and truly intended for cleaning purposes.

Water wells are drilled into a clean aquifer. What flows back from an acidised water well is a diluted version of what went in - very dilute hydrochloric acid - but nevertheless workers have to wear appropriate protective gear and follow strict health and safety rules.

Oil and gas wells, by contrast, are drilled into dirty, hydrocarbon-bearing rocks, typically also a very salty environment. Numerous other chemicals are used in addition to hydrochloric acid, for example biocides, solvents, corrosion inhibitors, iron inhibitors…

While an oil or gas company may in the first instance ‘acid wash’ their well and its immediate vicinity, exerting no pressure other than that supplied by gravity, at test stage they are likely to increase the pressure, and at production stage they are likely to acid frack at much greater pressure.

What flows back from an acidised or fracked oil or gas well includes reaction products of injected chemicals and the formation rocks, remnants of the injected chemicals, and substances released or leached out from the formation, including salts (perhaps five times the salinity of seawater), hydrocarbons, heavy metals and possibly Naturally Occurring Radioactive Materials (NORMs).

In a letter to government officials in 2012 Cuadrilla said they would have to frack if the Balcombe well site were to be viable.

Kathryn McWhirter

London Road, Balcombe