UK Oil & Gas has said one of its wells at Horse Hill in Surrey is being tested to find out whether recent work has successfully increased oil flows.

The operation, which began on 1 October 2020, reperforated the Portland section of Horse Hill-1 (HH-1). A new production tubing string was inserted and the downhole pump was placed at a deeper level.

DrillOrDrop reported earlier this week that the rig had left the Horse Hill site.

In a statement this afternoon, UK Oil & Gas (UKOG) said HH-1 had now been shut in for a long-term pressure build up test.

It gave no details of the duration of the test but said it would:

“provide data necessary to understand whether the Portland reperforation programme has achieved the desired optimisation of well inflow performance”.

Official production data has suggested that Horse Hill has not yet lived up to the expectations behind its early nickname, the Gatwick Gusher.

The figures show that production in tonnes and barrels per day (bpd) have fallen consistently between April 2020 and July 2020.

In July 2020, the most recent figures available, Horse Hill produced 121 bpd or 508 tonnes.

UKOG said the HH-1 intervention was “part of normal oil well optimisation”.

It said well operations could result in considerable periods where there was no production. Monthly or annual production figures may “not fully reflect the long-term flow rates of the well”, the company said.

It added:

“During 6-month period to the end September 2020, approximately 28,060 bbls of oil were produced over approximately 135 operating days.”

Official data for August 2020 is due to be released on 1 December 2020 and September 2020 on 1 January 2021.

UKOG also said it was normal to change the placement of the downhole pump if flow characteristics changed. This could because of factors such as the break-out of solution gas and increased water cut, the company said.

The proportion of production water at Horse Hill has increased since April. In July 2020, the official data indicated that water was 30% of the total production in tonnes.

The company statement added:

“It is also normal that individual conventional oil well production declines over time.”

The first full month of official production at Horse Hill was April 2020.

The UKOG share price dropped after the announcement but recovered and closed up slightly at 0.15p.

Updated on 5/11/2020 to correct closing share price.