Acidisation and Fracking

The government plans to allow various extreme energy extraction techniques for gas and oil across the country.

Most of the proposals coming forward for Surrey are for acidisation.

Acidisation and fracking: what’s the difference?

Acidisation and fracking – short for high-volume hydraulic fracturing – are both stimulation techniques designed to release oil or gas tightly trapped inside the pores of rocks. While fracking is used to crack open shale, acidising is used to dissolve passageways through limestone or sandstone.

In the UK, the Infrastructure Act 2015 introduced a new definition of fracking as involving the injection of more than 1,000 cubic metres of fluid per stage or more than 10,000 cubic metres in total. The type of oil exploration we see in Surrey uses lower volumes of water, so is not counted as fracking and is not subject to the fracking regulations or the moratorium on fracking.

Yet acidisation requires similar techniques to fracking, including the drilling of long horizontal laterals, and a densely-spaced pattern of wells, and has many of the same impacts.

About acidisation

Acidisation involves injecting solutions of acids along with other chemicals into wells. The objective is either to clean the well, or to create passageways through the rock along which oil or gas can flow. The industry divides acidising (or acidisation) broadly into three ‘tiers’. In increasing order of intensity:

  • an acid wash is a weak acid solution that cleans the well bore at low pressure
  • matrix acidising, injected at a pressure insufficient to fracture the rock, cleans and dissolves short pathways through the rock lying close to the wellbore
  • acid fracking is done at pressure high enough to fracture the rock, creating longer pathways.

Read more about acidisation:

Why are we concerned about acidisation?

Wells have been acidised in the Weald in decades gone by, barely regulated or monitored. What is proposed now is on a different scale.

  • It threatens industrialisation of the countryside. One company, UK Oil & Gas (UKOG), has promised ‘back-to-back drilling of production wells’ across the Weald.
  • Acidising uses much higher concentrations of chemicals than fracking. Matrix acidising and acid fracking fluids could contain up to 17 or 18% chemicals.
  • Given the repetitive nature of the process, acidising may use a lot of water.
  • With no precise definitions, scrutiny or monitoring, the industry can get away with downplaying their plans, calling everything an ‘acid wash’, or just a ‘stimulation technique’. At well-testing stage they may propose an acid wash when in truth they want to matrix acidise, in the knowledge that at production stage they will want to acidise more vigorously, at pressure.
  • Acidising brings most of the negatives of fracking: traffic, road tankers, air pollution, flares, potential water pollution via spills, leaking wells and faults, processing plants, large volumes of toxic liquid waste, stress on communities.
  • The burning of fossil fuels is causing potentially catastropic climate change. The UK government and have others have made legally-binding climate change targets. The extraction of oil will make it much harder to meet these. Rather than extracting these difficult-to-extract fossil fuels, we need to switch investment to energy efficiency and renewable technologies.

What is fracking?

The UK government imposed a moratorium on fracking in England in 2019.  It was briefly lifted in September 2022 during the short tenure of Liz Truss as Prime Minister, then reimposed in October 2022 by Prime Minister Rishi Sunak. The moratorium will remain in place unless the science “shows categorically that it can be done safely”. Scotland and Wales also have moratoria in place against hydraulic fracturing.

Fracking is a process of injecting a lot of water is mixed with sand and chemicals, at high pressure, in order to crack the shale and so allow gas and/or oil to escape.

During the fracking process carbon, toxic chemicals and possibly even radioactive material are likely to escape during and/or after drilling activities. Harmful emissions threaten our air, our groundwater, our wildlife, our children, ourselves.

The chemical mix in the fracking fluid is required for ease of drilling and to dissolve or crack the shale. It can contains many chemicals, some of which are carcinogenic and associated with cancer of the cervix, the breast, the endocrine system or the uterus.

The large quantities of water used in the process has to be brought on site – thousands of gallons per frack, usually in tankers.

After injection, the fracking fluid will pick up additional chemicals from the bedrock as it travels back to the surface. Millions of gallons of contaminated water will therefore have to be disposed of but will be initially reused for drilling and then stored in silos or in open slurry ‘lagoons’.

Types and amounts of chemicals used will vary in accordance with the geological structure of the site.

The gas makes its way to the surface via the borehole. Most of it will be captured but enough will escape to generate flaring or contribute to our carbon footprint at a time when the UK has promised to reduce it. The UK has no viable carbon capture systems in place.

Once full fracking operations are under way any one site may have up to 40 wells, all needing huge amounts of water delivered by tankers 24/7. More tankers come to carry away drilling waste or slurry, and some tankers will come to transport the liberated gas to the main grid. Such high levels of traffic will put enormous pressure on roads and the environment.

Fully operational sites will also need to feed the extracted gas into the main grid. Most sites will construct pipelines. This will involve considerable amounts of earthworks further disrupting life for people and wildlife in rural and/or urban environments. People’s concern that swathes of countryside will become industrialised are very real.

Read more about fracking:

How does the onshore oil and gas industry work?

The Oil and Gas Authority (OGA) is responsible for issuing licences to companies allowing them to explore for oil and gas.

The licences give the companies the right to explore for oil and gas in the licensed areas, but before they can do that they need planning permission too. The local planning authority (in our case Surrey County Council) has to decide whether to allow the physical works (the access roads, fencing and buildings), while the Environment Agency and Health and Safety Executive have to judge whether the proposed activities are safe for the environment and the workers.

Small companies often gain exploration rights and then raise the money from private backers to undertake exploration works. If they strike a significant resource they usually get bought out by the major global players in the minerals industry and make a lot of money (or get tax concessions to cover losses).

There are a number of small players who have licences to exploit shale gas in Lancashire and Surrey. They try to attract further investment from small investors and private energy investment companies to undertake the first stages of drilling and testing. The aim is to sell it on to a larger player.

4 Responses

  1. Gillian Hannah-Rogers says:

    Thank you for that. Very informative.

    • Maurice Eaton says:

      I think you need to get your facts right before you publish such disinformation. I have never heard of gas being transferred to the grid by tanker! Absolute Rubbish. Water is scarce in the south east, how much water do you think a Frac requires, do you seriously think that this will have any effect on domestic supplies? You complain about Cuardilla providing gas to the national grid as if this is a bad thing, would you prefer coal or nuclear. Renewable sources of energy are a great idea but what are you going to do on a cloudy and windless day? As long as we need energy, we need to produce gas or would you like to import it from the continent and just shift the problem to another country. Please read about gas production and hydraulic fracturing from more independent sources and then form your own opinion instead of accepting such a biased view as shown on this site.

      • admin says:

        Hello Maurice

        Thanks for your comment. I agree that the page above needs a bit of an update, but much of the information is still valid.

        Interesting you should ask how much water a frack (or a Frac, to use the oil industry preferred term that you have gone with) uses. According to one of our local water company managers, one fracking site uses the same amount of water in a day as the whole of Gatwick Airport, and Water UK certainly have concerns about potential conflict between residential and industrial usage ( So it seems reasonable to highlight it as a possible issue on this page.

        And “Renewable sources of energy are a great idea but what are you going to do on a cloudy and windless day?” Well, I expect we will use the energy we stored when the sun was shining and the wind was blowing. Energy storage prices are plummeting – Deutsche Bank expect the cost of lithium-ion batteries to fall by 20 to 30 percent a year – and there are a number of major storage projects getting set to launch in the UK this year (

        By the way, are you the Maurice Eaton that used to be Director of Group Operations at Northern Petroleum Plc, now with ExploreOil working on projects in Turkey, Iraq and West Africa? (Just to check the independence of your views.)

        Best wishes

        • Maurice Eaton says:

          Yes I am but that is why I suggested people should look at independent sources. I would like more renewable sources to be used but as you pointed out, energy storage is required. Large scale use of Lithium batteries are not only envirnomentally questionable but not really practical for the amount of storage required. The main problem is Peak Use” of electricity which needs either gas power stations or nuclear energy in order to handle the sudden demands. However concerning the issue of fracking, I do think that there is a lot of incorrect or misleading information that is used to support the anti-fracking crusade and I just wish that a more balanced view could be put forward. The British Government ( in marked contrast to the USA) quite rightly monitors the way in which such activities are undertaken and the engineers and geologists are just as concerned about the environment as the members of your site.

          Thank you for your reply and I appreciate the fact that you are willing to listen to a contrary view!

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