The company behind the Horse Hill exploration site near Gatwick Airport has released details of plans to drill four more wells to produce oil for 20 years.

Horse Hill Developments Ltd said the scheme could take production to more than 500 tonnes of oil a day. If achieved, this would make Horse Hill the UK’s second largest onshore producing site on current figures.

The proposal would increase the size of the Horse Hill site by a quarter and increase to six the number of oil wells.

According to the details, available online, the site near Horley would also accommodate a well to re-inject produced water. Horse Hill production scoping request (pdf)

Added to this there would be: six surface mounted pumps, seven oil storage tanks, two fire water tanks, two produced water tanks, an enclosed ground flare, an oil heater with an exhaust stack, four gas-to-power electricity generators with acoustic enclosures, oil separators and above ground pipe and cable tracks.

The details are in a scoping request – the first stage of a planning application that would require an environmental impact assessment.

The document said the production proposals would increase the site from 2.08ha to 2.6ha by adding land immediately to the east of the existing well pad.

This is the third major application sought for the Horse Hill site. The original exploration well (HH-1) was approved in 2012 and drilled in 2014. It is currently undergoing long-term flow testing. A second application, granted in 2017, allowed Horse Hill Developments Ltd (HHDL) to drill another appraisal well (HH-2) and a sidetrack (HH-1z).

The new proposal is to produce oil from the site, drill the extra oil wells (HH-3 to HH-6) and water re-injection borehole and to develop hydrocarbon processing, storage and transport facilities.

The scoping request acknowledged that wells could be drilled at the site for more than a year. It also accepted that the impacts of construction on the existing well site could coincide with construction of the new area. The transport effects of drilling the wells could also be experienced at the same time as the transport effects of production.

The document variously estimated that the nearest homes were about 225m or 321m from the site. It accepted that the proposals would “significantly change the landscape” and give rise to “an adverse effect upon valued landscapes and the visual amenity of the area”. It also said that significant noise effects were expected from several phases of the work.

Impacts

(information from HHDL’s scoping request)

Views

HHDL said in the document:

“The duration of drilling activity followed by the placement of production facilities for 20 years has the potential to significantly change the landscape and visual baseline giving rise to an adverse effect upon valued landscapes and the visual amenity of the area.”

Lighting

Potential effects predicted from the development included light spill, glare and sky glow.

Noise

The document said:

“Each phase of development has the potential to generate noise effects upon nearby sensitive receptors”

Significant noise effects could be expected from well site modification and construction works and the drilling and well management phases, the document said.

Ground and groundwater protection

The proposed development included the use of drilling muds, cement and well development fluids, the document said. The wells would produce oil, gas and water, which may contain naturally occurring radioactive materials.

Air quality and climate change

The development would produce pollutants from electricity production from gas, flaring of gas and the use of diesel engines, the document said. HHDL said it would assess nitrogen oxides, carbon monoxide, sulphur dioxide, volatile organic compounds, particulate matter and dust.

Ecology

HHDL predicted that the impact of the scheme on the nearest sensitive wildlife was not likely to be significant because the site was already well-established. But it said it would assess the impacts on ecology, nature conservation, biodiversity and arboriculture.

Traffic

HHDL said the traffic impacts from the different phases of the work were considered “not significant”.

Socio-economic impacts

HHDL said the benefit from indigenous hydrocarbon development was considerable at “a national level”. Locally, it said the development would generate employment. The adverse effects on local tourism and other sectors would be low, it predicted.

Other impacts

The scoping report said the effects were not likely to be significant on vibration, listed buildings, loss of agricultural land, waste generation, human health, residential and recreational amenity, risk of accident or airport safeguarding.

Proposed work phases

(information from the scoping request document)

Phase 1: Well site modification and new construction work

Existing site: construction work

Duration: six weeks

Average daily HGV movements: five

Existing site: Installation of four surface conductor casings and site preparation for water re-injection well

Duration: six weeks

Average daily HGV movements: five

New site: construction of oil processing and storage area, tanker loading facilities, placement of generator sets for generating electricity from gas

Duration: 14 weeks

Average daily HGV movements: 17

Phase 2: Well drilling

Workover rig mobilisation

Duration: two days

Average daily HGV movements: 28

Initial workover operation of HH-1z and HH-2 wells

Duration: four weeks

Average daily HGV movements: seven

Workover rig demobilisation

Duration: two days

Average daily HGV movements: seven

Drilling rig mobilisation

Duration: nine days

Average daily HGV movements: 14

Drilling four new hydrocarbon production wells HH-3 to HH-6 and drilling one new produced water re-injection well

Duration: 60 weeks

Average daily HGV movements: nine

Drilling rig demobilisation

Duration: Three days

Average daily HGV movements: 29

Phase 3: Production and export of oil and electricity for 20 years

Installation of production equipment

Surface mounted pumps (one for each well)



Seven oil storage tanks (1,300 barrel capacity/tank)

Two fire water tanks

Two produced water tanks

Enclosed ground flare

Oil heater with exhaust stack

Four gas-to-power electricity generators and acoustic enclosures

Oil separators

Ancillary pumps

Above ground pipe

Cable tracks

Duration: 12 weeks

Average daily HGV movements: nine

Production

Oil will be pumped to the surface along with formation water and gas. The oil will be separated to storage tanks where it will be exported by tanker to a refinery. Formation water is re-injected. Gas is used to generate electricity for the site or for export. Flaring of gas will happen in an emergency or for maintenance purposes. Production could exceed 500 tonnes of oil per day, which would require up to 16 two-way oil tanker movements per day.

Duration: 20 years

Average daily HGV movements: 32

Well management

This could include: cleaning the pump and well; hot oil treatments to unblock restrictions; changing pumps or producing tubing; drilling a sidetrack to access a new part of the reservoir.

Work over mobilisation

Duration: two days

Average daily HGV movements: 28

Workover

Duration: two weeks

Average daily HGV movements: 14

Workover demobilisation

Duration: two days

Average daily HGV movements: seven

Sidetrack mobilisation

Duration: Nine days

Average daily HGV movements: 14

Sidetrack drilling

Duration: 15 weeks

Average daily HGV movements: seven

Sidetrack drilling demobilisation

Duration: three days

Average daily HGV movements: 29

Phase 4: Plugging, abandonment and decommissioning

Workover rig mobilisation

Duration: nine days

Average daily HGV movements: 14

Plugging and abandonment

Duration: 18 weeks

Average daily HGV movements: 10

Workover rig demobilisation and removal of surface equipment

Duration: two weeks

Average daily HGV movements: eight

Phase 5: Site restoration

Duration: five weeks

Average daily HGV movements: 17