Monthly oil, water and gas production were all up at Horse Hill in Surrey, the UK’s newest onshore production site, according to the latest official data.

The figures, from the Oil & Gas Authority, reversed three months of falling oil volumes at the site.

They show that in August 2020 Horse Hill produced 536 tonnes of oil, up 6% on July (508 tonnes) but still down on the monthly totals in the first four months from March-June 2020 (average 778 tonnes).

In barrels per day (bpd), oil production was 128 in August, up from 122 bpd in July but about half the monthly figure for April (243 bpd).

Water and gas

The level of produced water from Horse Hill reached 226.3 tonnes in August 2020, up 3% on the previous month (219.5 tonnes) but slightly below the total for June (235.7 tonnes).

The proportion of water in the total extracted in tonnes from the site was 29.7% in August. This was down slightly on July (30.2%) but remained much higher than figures in March and April when they were less than 1%. The average proportion of water for the six months from March-August was 16%.   

Usually, water production is lowest when a field begins production. The quantity and proportion usually increase as fields mature. This produced water is the largest single waste fluid stream in oil exploration and production operations.

Horse Hill has planning permission for a water reinjection well but is currently not reinjecting water. The company has said this proposed well would reduce the cost of disposing of waste water and could help to maintain reservoir pressure.

Associated or waste gas produced at Horse Hill in August rose to 20.8 tonnes, up 26% on July (16.5 tonnes), but lower than previous figures in March-June (average 23.1 tonnes).

Horse Hill waste gas is currently burned in a flare. Some other oil sites in southern England use associated gas to run an electricity generator.

Onshore production

In August 2020, UK onshore fields produced 59,874.85 tonnes of oil or 1.74% of total UK production.

The tonnage was down slightly on July (60,885 tonnes) but above the total for June (58,546 tonnes).

Of the onshore total, 84.55% in August 2020 was from the Wytch Farm oil field, which produced 50,621.61 tonnes.

Horse Hill remained the seventh highest producing field onshore in the UK in August. That month’s total was 0.89% of UK onshore production and 1.06% of Wytch Farm.

Apart from Wytch Farm, only two fields – Singleton and Welton – produced more than 1,000 tonnes in August, or more than 2% of the onshore monthly total.

Two other fields – Humbly Grove and Stockbridge – produced more than 1% of the monthly onshore total, or more than 600 tonnes in a month.