Consultation opens on permit applications for Europa’s Leith Hill drilling site


Drilling site, currently occupied by Leith Hill Protection Camp

The Environment Agency is inviting comments on permit applications by Europa Oil & Gas for its exploration wellsite near Leith Hill in Surrey.

Europa has applied for environmental permits regulating mining waste, radioactive substances and the storage and handling of crude oil.

The company has said it does not need permits for industrial emissions because the volume of gas it expects to flare will be less than 10 tonnes/day. It is also not applying for a water discharge permit.

The consultation period opened today and runs until Tuesday 16 May 2017. Comments can be made online (link to consultation web page) or at Environment Agency offices at Orchard House, Endeavour Park, London Road, Addington, Kent.

The site, known as Bury Hill Wood or Holmwood, received planning permission in August 2015 for site construction, drilling, testing, abandonment and restoration, all to be completed in 18 weeks. Europa is currently negotiating with Surrey County Council over the final conditions of the planning permission.

DrillOrDrop has reviewed the permit application documents and compiled the following information from them.

Site information

Address: Holmwood Wellsite, Bury Hill Wood, Coldharbour Lane, Dorking RH5 6HN

Area: 0.79ha, including 230m access track

Location: 1.5km west of South Holmwood, 3.5km south west of Dorking in the Surrey Hills Area of Outstanding Natural Beauty (AONB), at a height of 220m

Nearest home: 530m away

Nearest Site of Special Scientific Interest: Leith Hill 0.6km

Nearest statutorily designated historic site: Anstiebury Camp 0.6km

Surrounding landscape: Mainly coniferous woodland

Utilities on site: None

Exploration licence area: PEDL143

Well information

Wellpad size: 118m by 55m

Name of well: Holmwood-1 or H-1

Type of well: Deviated borehole

True vertical depth of well: 1,450m with a contingency to 1,694m

Target formations: Portland Sandstone; Micristic Limestone within the Kimmeridge Clay; Corallian Sandstone and Great Oolite Group

Holmwood geology

Geology of the site. Source: Europa Oil & Gas

Water information

Principal aquifer: Hythe Formation in the Lower Greensand Group supplies public supply boreholes at Dorking and industrial and private domestic users. Groundwater in the Hythe formation is “very close to the site”, estimated at 25m below ground level, and supports flows to local springs

Secondary aquifer: Tunbridge Wells and Ashdown Formations (445-745m depth at the site) and Limestones in the Lulworth Formation (800m below the site)

Nearest surface water: The site is in the catchment of the Pipp Brook, 250m west of the site, which is supplied by groundwater from springs

Abstraction licences: Five groundwater and five surface water abstraction licences within 5km of the site. These include a licence held by Sutton & East Surrey Water PLC which has five boreholes for public water supply at Dorking.

Water supply to the site: By road tanker

Site operations

Wellsite construction

  • Removal of trees and existing vegetation and removal of 850m3 of top soil
  • Temporary screening bund installed on norther boundary from excavated topsoil
  • Eight geotechnical boreholes drilled to 100m to assess any soil contamination and provide information on surface geology
  • Three water quality monitoring boreholes drilled to 33m into the Hythe Formation
  • Site surfacing
    • This comprises: Lotrax geotextile layer on exposed subsoil across the compound and perimeter ditches; followed by Bentomat environmental membrane; sand; second layer of Lotrax geotextile; ending with stone (250mm or 300m) or ground matting to support weight of drilling rig and equipment
  • Well cellar: concrete chamber sunk into the ground forming a containment area for drilling the borehole.
  • Flare pit installed and surrounded by 1.5m soil bund

Well construction

Drilled in five sections, with a total length of 1,300m, south west from the wellsite to land under the village of Coldharbour. The well will reach a true vertical depth of 1,450m

  • 24” hole drilled to 50m into top of Weald Clay
  • 17 ½“ hole drilled from 50m-177m using water-based mud into Lower Cretaceous
  • 12 ¼” hole drilled 177m-700m using oil based mud into Upper Jurassic formation
  • 8 ½” hole drilled 700m-1694m into Upper Jurassic
  • 6” hole drilled 1694m-1750m into Corallian sandstone

Logging and testing

  • Geological logging: Determines which formations may contain petroleum
  • Acid wash: Five treatments using 15% solution of hydrochloric acid pumped at low pressure to clean out fractures in the formation. Volumes were estimated at 1m3/wash.
  • Acid squeeze: 15% solution of hydrochloric acid pumped at pressures below that which would fracture the formation. This results in acid being squeezed through natural fractures in the formation to increase permeability. The volume of hydrochloric acid solution was estimated 1m3 per metre of perforation.
  • Hot oiling: Hot oil is pumped into the well (but not the formation) to remove paraffin precipitates
  • Drill Stem Testing: Short test carried out during drilling to provide an initial analysis of petroleum composition and flow characteristics within the formation. It helps to decide whether there are commercially-viable quantities. Fluids produced during the test are likely to be drilling fluids, formation water, oil and gas condensate. The fluids are separated at the surface. Formation water will be tankered off the site for disposal. Oil will be taken to a refinery.
  • Flaring: Gas produced during the Drill Stem Test would be burnt in a shrouded flare in a pit measuring 12mx6m. The application said:

“Europa Oil & Gas will, if applicable, demonstrate that an enclosed flare is not suitable for their operation and there will not be a worse environmental impact as a consequence of applying the alternative [shrouded flare] technique.”

Well abandonment

If the well is not successful it will be abandoned and the site restored to former use.

Bury Hill Wood Holmwood map

Source: Europa Oil & Gas

Risks and monitoring

Water quality

A risk assessment by Envireau Water in 2015 concluded there was a minor risk to the Hythe Formation aquifer during wellsite construction and restoration. But it said

“Once the wellsite is established there is “essentially no hydrogeological risk to groundwater and surface water receptors associated with the drilling and testing phases of the proposed development”

A scheme for monitoring groundwater, also produced by Envireau Water in 2016, concluded the Sutton & East Surrey Water boreholes were not at risk from the development.

It proposed to monitor groundwater at three boreholes and surface water at two features. Baseline monitoring of ground and surface would be carried out for at least three months before the development starts, the application said.

It added:

“Whilst the introduction of hydrochloric acid to the formation is a groundwater activity, it is anticipated to be considered de-minimis by the Environment Agency, due to the low volumes proposed and once the hydrochloric acid has reacted with the formation the remaining near neutral solution is circulated back out of the well.”

Air quality

Europa said it does not plan to monitor air emissions because flaring is for a short duration and flow rates less than 10 tonnes of gas/day


The application assessed the risk of odour as “negligible”. It identified 60 homes, 0.53km-1.94km from the site, as being highly sensitive to smells from the operations.

Europa said:

“It is envisaged that the local community will not be familiar with some of the potential odours from the exploratory operations conducted at the Holmwood wellsite and therefore any odours emitted from the wellsite will be classed as offensive.”

But the company added:

“Given that all operations are temporary and that the exploratory operations, which will give rise to the highest potential for odorous emission, are also for a temporary nature the impact on the local receptors is classed as minimal.”

The application said:

“All site personnel will conduct periodic sniff testing during their shift and are to report odours perceived to be strong or odours not associated with standard wellsite operations”.

Point source sampling would be undertaken when the substance causing the odour could be determined. Residents who complained about smells may be invited to keep an “odour diary” throughout operations at the site, the company said.

Other risks

Noise and vibration from engines or vehicles: Low if management techniques were effective

Noise from flaring: Low

The following were considered low risk if management techniques and procedures were followed

  • Emissions from well, vehicles, tanks, pipework or chemicals and effluent
  • Emissions for flaring
  • Dust from vehicles
  • Run-off from the site surface
  • Litter, pests and insects
  • Plant, equipment or containment failure
  • Spills and leaks from vehicles and equipment
  • Loading and unloading or overfilling vessels
  • Wrong connections in drains and other systems
  • Poor storage of hazardous substances
  • Fire
  • Unwanted reactions
  • Vandalism
  • Waste products and filters
  • Cement
  • Engine, lubricating and equipment oils

The following risks are considered not significant

  • Overflow of site perimeter ditches: insignificant
  • Greenhouse gas emissions from site power generating, flaring, vehicles and equipment
  • Natural gas


The application identified the following wastes that would be produced by operations at the site

Hazardous waste

  • Oil-containing drilling muds: 125m3
  • Oil-containing rock cuttings:  120m3
  • Accommodation waste water and sewage: 100 tonnes/yr
  • Hazardous run-off water from site: 80 tonnes/yr
  • Natural gas: under 10 tonnes/day

Non-hazardous waste

  • Spent hydrochloric acid: 11m3
  • Waste clays and sands: 15m3
  • Well suspension brine: 25m3
  • Chloride containing drilling muds and waste: 20m3
  • Formation water: 20m3
  • Salt saturated rock cuttings: 20m3
  • Cement: 25m3


Link to permit consultation web page

Link to planning permission decision notice

DrillOrDrop key facts and timeline for Holmwood/Bury Hill Wood site

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