Egdon plans “small-scale fracking” instead of acidisation at Wressle oil site

Wressle oil site. Photo: Used with the owner’s consent

The operator of the Wressle oil site near Scunthorpe has confirmed it no longer plans to use acidisation to improve production.

Egdon Resources will now use a technique described by regulators as “small-scale hydraulic fracturing activity” as the first option to stimulate oil flows.

For the past six years, Egdon Resources had said it intended to inject dilute hydrofluoric acid into the well.

Acidisation would, the company previously said, dissolve fine particles that had blocked the pores in the oil-bearing Ashover Grit sandstone reservoir, known as skin problems.

But Egdon has now abandoned the process because it may reduce the effectiveness of proppant squeeze, an alternative form of stimulation planned at Wressle.

Proppant squeeze injects a slurry of gelled liquid and proppants under pressure to open fractures in the surrounding rock formation. It was previously a second option if acidisation did not work and was highly controversial with opponents of onshore oil production.

Egdon told local representatives recently:

“ongoing evaluation has indicated that the proposed acidisation process may adversely impact the proppant squeeze operation. Given this, we can now advise that we are not now undertaking the acidisation operation as part of the work to enable production at Wressle.”

Asked why the company had changed its mind, a spokesperson told DrillOrDrop today:

“There is a low risk of the mud acid deconsolidating some of the sandstone close to the perforations which could impact the effectiveness of the proppant squeeze – it has therefore been concluded that the proppant squeeze alone would be the most effective treatment to deal with the skin issue in the Ashover Grit whilst simplifying operations.”

The spokesperson said:

“As part of our detailed pre-operational planning we review all planned activity with our contractors and the proposed change to our operations came to light during early summer as part of this process.”

DrillOrDrop asked Egdon whether it intended to use acid at any stage of production. The spokesperson replied:

“No. Acids are not now intended to be used as part of the operations.”

Egdon is the second onshore company to state publicly it will not use acid to stimulate wells. In March 2019, UK Oil & Gas plc said it would not use acidisation in the Weald Basin in southern England because it said the process could “have a significantly detrimental effect on the ability of oil and gas to flow into the well”.

Cross-section of site during workover of the Wressle well. Source: Egdon Resources planning application to North Lincolnshire Council

Opponents of Egdon’s operation at Wressle criticised the use of hydrofluoric acid, which is highly corrosive. They were particularly concerned about the risk of contamination to ground and surface water.

They were also alarmed at the prospect of proppant squeeze, now Egdon’s first option.

They have criticised proppant squeeze as “fracking by stealth” because it uses hydraulic fracturing techniques, while avoiding fracking regulations in the Infrastructure Act. It is not covered by the current moratorium on fracking in England.

The Environment Agency described the proposed operation at Wressle as “a small-scale hydraulic fracturing activity”.

Egdon said proppant squeeze was a “standard enhancement technique”. It planned to inject 150m3 of slurry in the operation at Wressle. This is 15% of the 1,000m3 per stage used to define associated hydraulic fracturing in the Infrastructure Act.

The process needs a hydraulic fracture plan (HFP), to be approved by the Oil & Gas Authority and the Environment Agency. But HFPs for operations with lower volumes require less information than those using larger volumes.

Egdon told DrillOrDrop it still planned to carry out a single proppant squeeze operation at Wressle. It said the volume and composition of the fluid would also remain the same, despite the decision not to use acidisation.

The environmental permit for Wressle said the hydraulic fracturing fluid to be used in the proppant squeeze was mainly a slurry of water, friction reducer and proppant (ceramic beads).

According to the permit, the treatment would comprise 20-30 tonnes of ceramic beads and 80m3-120m3 of gelled liquid. The operation would be carried out at a depth of 1,500m-1,700m.

The slurry would be injected at a surface pressure of 9,000psi, above formation fracture pressure, for 1-2 hours. The slurry would be forced 40m sideways into the formation and 20m above and below perforations in the wellbore. An estimated 50%-70% of proppant fluid would be retained within the formation, the permit said.

If the proppant squeeze does not sufficiently improve oil flow, Egdon said it would continue with its plan to drill a sidetrack of the main wellbore.


Elizabeth Williams, of Frack Free Lincolnshire, welcomed the decision not to use acidisation at Wressle:

“People feel a sense of relief that “hydrofluoric acid squeeze”   is no longer intended at Wressle-1.   For the last five years campaigners have raised urgent concerns about acidisation in all its forms.  And to its credit the EA did listen (to some extent).”

But she said:

“There remains the element of considerable hazard that “proppant squeeze”  at 9000psi will be delivered down a deviated “S well”.  This is not a simple vertical operation and complex processes and procedures will be carried out directly beneath the town of Broughton.   How can any critical incident or accident in the wellbore be responded to?   We do not think that local Fire and Rescue Services are fully aware of the extent of this well stimulation.  Has proppant squeeze previously been delivered this way onshore UK – with full regulatory scrutiny?

Ms Williams also asked questioned the acceptability of hydrocarbon exploration in the light of climate change science.

“We urge planners and policy-makers to make radical choices and move away from fossil fuel.   We urge the Oil and Gas Industry to cut its losses and stop contributing to global ecological disaster.”   

Updated 29/9/2020 to include reference and link to UK Oil & Gas plc not using acidisation and on 4/10/2020 to include reaction from Frack Free Lincolnshire

21 replies »

  1. Matt Hancock ‘comfortable’ with government breaking international law in ‘limited and specific way’, reports the Independent of Johnson’s plan to renege on his treaty obligations. Egdon’s ‘Small-scale fracking’ plans for Wressle are similarly ‘limited and specific’. This government certainly proceeds by stealth hoping thus to detoxify its blatant and amoral disregard for its promises, actions which further lower its international standing and the respect it considers it commands. And yet the Minister tells us that fracking is over in the UK. Do we believe this? Beware Tory Ministers, even bearing gifts.

    • iaith2017

      Good way to express your disgust at the present gov while involving Wressle frack plans.

      I am not sure that they are limited and specific (as opposed to broad ranging and rather vague?) in the context of one well, but needs must when the devil drives eh!

      What promises do you refer to re this small scale frack, that the present gov has disregarded?

      Mr Kwarteng, tells us (in the context of the fracking moratorium) that the battle has been won.

      Should we spin his words to suggest he meant something else?

  2. Just rechecked the pressure of this naughty little frack. 9,000 psi. Pounds pre so inch Convert to tons per sq U.K. inch 90 psi would be around 0.7 tons. 900 psi. 7 tons And 9000. 70 tons per square inch I had underestimated by using US conversions. I think the concept of 70 tons psi U.K. values would come across scary. This is Extreme Energy Extraction. We want to know also the chemicals they will use. Could you imagine a pin hole sized leak in a joint, valve or crack or up the outside of the pipe with that pressure applied? Also will it be 9000psi above geological pressure and if so what is that figure?

    Stay Safe. The virus hasn’t gone away. It hasn’t changed.


    • Hi Tim

      Thanks for your comment.

      I didn’t follow how you arrived at your figure. According to Google, 1 (imperial) ton is 2240 pounds.
      So, by my reckoning, 9000 pounds per square inch would be 9000/2240 or just over 4 tons psi.

      • Paul you can’t follow Tim’s comment because there is a clear lack of understanding of the process which is surprising after all this time but typical anti and maths not a strong point?

    • Tim

      You got me thinking there. Near my feet, when driving, there is diesel fuel being compressed to 29000 psi, or more than three times that which will be used at wressle. And there they are not injecting diesel!

      This is extreme energy in action, inches from my feet. Can you imagine the consequence of a pin hole leak in a joint, valve or crack? How many diesel cars have exploded? How many people are killed each day by such events? What is the government not telling us?

      This and other governments certainly proceeds by stealth hoping thus to detoxify their blatant and amoral disregard for the good people of the UK by allowing such danger to exist. Its not even mentioned in the car handbook (danger of death from high pressure fuel lines). I expect it was banned by the government.

      Was it Gordon (Lab Scottish) who set is on this path of destruction, getting us to drive such dangerous vehicles, when we were all happy with 100psi petrol injections systems? Those down low self serving gov ministers have a lot to answer for eh.

      But then no one told us that in both cases there is also an explosion right there, by our feet! I bet gov advisors would not have driven to Durham or wherever it was they went to self isolate had they known that the dangers of driving there exceeded the dangers of getting it or spreading it? Diesel Injection stuff Petrol injection stuff

      • Seems that is okay if you are an anti driving a diesel, hewes62!

        And, of course, it has been declared on DoD that if they are German diesels they produce low emissions.

        Oh, just noticed the guy from Audi is in Court. Wonder what the charge is?

        • Martin. Indeed. Better in simpler days when petrol was just sucked into the engine. No risk there i guess as its below atmospheric pressure.
          Dull days on DoD recently, but now conservative MPs are against HPHV fracking we will never see a red wall again? Will Wresstle ( one well so far and as good as vertical) cause Preaton Road type protests? Interesting times ( as interesting as China Coronavirus stats i guess).

          • Yes, the Covid stats are fascinating!

            Countries that are renowned for producing stats out of thin air are now being quoted by both BBC and Sky as gospel. All very illuminating. Seems that all the reporters who swarm over every piece of info still can’t be bothered to relate it to the wider picture, and then they pontificate about confusion. A lot easier to create confusion than to clarify, and creates a much longer news cycle as a result.

            I do note hydrogen zones starting up. Won’t be long until the hydrogen source is explored. Must admit I like the concept, but suspect to make it really expand something like fusion would need to go hand in hand. Will see how that goes, but I have a sneaking suspicion that may be a better long term option than a glorified milk float.

            • The biggest hurdle to replacing Natural gas with Hydrogen is cost.

              A recent European Hydrogen Strategy paper put the current Natural gas price at around €22/MWh and green Hydrogen around €150/MWh. They hope that the cost of renewable electricity and electrolyzers reduce enough to bring green Hydrogen prices in at around €30/MWh by 2050.

    • Tim any thoughts on why wellhead equipment and Blow out preventers are rated at 5,000 or 10,000 or 15,000 psi? And tested to 150% of rating? And please do not include the word scary. A pin hole leak initiates the ESD system and the operation shuts down.

  3. So, the proppant squeeze is to proceed, the acidisation no longer thought necessary, or desirable. One would think that one treatment dropped would be cause for delight amongst the antis.

    Nope. If they won the lottery, they would whinge about it not being the previous week.

    9000psi-scary? Nope. Wonder what the “green” geo thermal energy fracturing in Cornwall uses? That’s much harder rock, so could be very high. Wonder how much psi needed to blow apart much of the Lizard to enable construction of the Swansea Lagoon at somewhere near (not that near) economic sense? Green psi obviously less of an issue!

    Oh, my imagination is running riot!

    • Try and stay relevant. The point is that government’s decision to drop fracking in the UK is suspect. Nothing to do with pros or antis whoever they may be.

    • United Downs Geothermal have stopped work and apologised for causing seismic activity, whilst conducting tests on the well today.

        • Thank you hewes62, I’ve been following the project with great interest.

          What I have found fascinating is the lack of concern from some quarters regarding the fact that there are no regulations to try and control any seismic activity generated. This is despite enhanced geothermal projects having a far worse track record than oil or gas fracking.

          There is also the issue of chemical use. Due to the geology, all the planned geothermal projects in Cornwall need to use Hydrofluoric acid to clean the well. This has not been an issue for them, yet it’s mere mention at Wressle has raised all manner of doom.

  4. Well, 1720, you have posted many times before, so others will know already “whoever they may be”. Are you suggesting your posts are not read?

    No, that is YOUR point. Not all about you. Tim made HIS own point. I was merely explaining that high psi is not such an issue that imagination needs to be utilised to cause panic. High psi are used in many industries. Quite routine. I quite like high psi being utilised by the fire brigade to save lives, or others who help within disaster relief. Neither am I too bothered with the same regarding the tests in Cornwall that have been authorised. I would be concerned about high psi’s being used around St. Keverne, as they have quite clearly said NO, and surely the greenies would not like to drive a coach and horses through local planning-AGAIN? (Ref, the again, check what happens to build a Tesla factory in Germany. Ignore the trees and the sand lizards.)

    Governments are a temporary state,1720, so every decision by Government is suspect in respect of whether it will continue. I really can’t see the current moratorium is any different to any other matter. You could make the same point about driving on the left/ capital punishment etc. etc. I know antis live off creating a grievance, but in the way you try and do it in this instance could be done for ALL of this government’s decisions, or any other government for that matter. Yet, you suggest staying relevant!

  5. Silly me, I was rather working on the assumption that Tim and I were making the same point in different ways. If I’m right, then you are missing the point and my irrelevance charge remains. If not, then I of course am missing the point.

    “Whoever they may be”. Sorry again, I find it difficult to divide that proportion of the human race that disagrees with me in my omniscience into simple condescending categories like ‘antis’and ‘greenies‘.

    “Governments are a temporary state”. True. Sorry however that you can’t see any difference between on the one hand fossil fuel extraction and capital punishment, and on the other hand, driving on the left. No principles involved then which might just make it difficult for a government to completely change direction.

  6. A government changes direction if and when the electorate force them to do so, 1720. Nothing to do with me or you-or, maybe a very little bit, or a lot more if we were the Robinson Crusoe and Man Friday electorate. .

    Goodness we could (no) have a Lib Dem government that hasn’t completely changed direction over Brexit! Or, a Labour government that hasn’t completely changed direction regarding the Jewish community! Well, no hope unless they did, a small hope if they do-so, they will.

    You seem very confused still between reality and fantasy. Please tell me about ONE UK government that in reality has not changed principles to get into government, or shortly afterwards.. There are even those who do so just to get a small piece of the action-Lib Dems and student fees come to mind.

    There I go again, living within the real world where high psi cutters are used to extract antis from their chains, but high psi is an issue to antis! But, I am okay with that because it is the real world and I do not panic about the real world as thinking about it clarifies things. I do find the fantasy world a little more uncomfortable as thinking is removed so avoid it myself, but do take an interest in those who don’t.

  7. How times and attitudes change, it doesn’t seem that long ago when the antis were dismissing evidence produced by another company as part of their HPHV fracking application bid, as not being similar or relevant to the hydraulic fracking debate.

    The evidence produced was that a fracking operation at 8,500psi with 73 m3 of water/Kerosene emulsion and 11 tons of sand proppant, had been carried out previously on an adjacent well. This is not a million miles away from the 9,000psi, 80-120 m3 of gelled liquid and 20 tons of ceramic proppant, planned by Egdon.

    UK values used for fluid pressure are psi (pounds per square inch) or bar (metric unit). See vehicle tyre pressure information, central heating system pressure information etc. if proof is required.

    If scaremongering was the aim, converting to the correct SI unit (pascal) would have been the correct direction to take.

    The 9,000 psi or 621 bar will be the surface pressure recorded at the pump. As a rule of thumb, equipment is usually designed and chosen to be able to withstand at least 1.5 times the stated operational pressure.

    Once on site and installed, the equipment and well casings are subjected to a hydraulic pressure test in excess of the planned procedure pressure, to check for and eliminate any possible leaks before the actual procedure commences.

  8. Great that they’ve finally decided not to use highly toxic chemicals. Note that the reason given is that it might hinder the proppant squeeze. Not because they’re considering the concerns of local people or the dangers of working with highly hazardous substances. If it turns out, however, that it might be useful to do so, no doubt it’ll be back on the menu.

Add a comment

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s