Cuadrilla web Q & A dismisses fears about sour gas at Fylde fracking site

PNR 171208 gv2 CR

Laura Hughes (left), Cuadrilla’s Commercial Director, at the Preston New Road shale gas site near Blackpool. Photo: Still from video produced for Cuadrilla Resources

The fracking company, Cuadrilla, has dismissed fears that shale gas in the Fylde area of Lancashire would contain large amounts of hydrogen sulphide, a hazardous gas associated with the smell of rotten eggs.

Concerns were raised earlier this month in a report by the geologist Robin Grayson on the website Researchgate.

He said there was a culture of secrecy about hydrogen sulphide (H2S) in gas in the Fylde and there were proven examples in the shales in Lancashire.

Mr Grayson said gas with high levels of H2S, known as sour gas, was also produced from shales under the seabed off Lancashire, Merseyside and North Wales and then treated at Rampside and Point of Ayr.

He said drilling for sour gas was dangerous and local communities should have been informed by companies and regulators. He said:

“All drilling should cease immediately on grounds of public safety and the need for Parliament and enforcement agencies to investigate the large mountain of evidence.”

But in a live webcast this afternoon, Cuadrilla’s commercial director, Laura Hughes, said there was no sour gas at Preston New Road:

“That has been found in reservoirs offshore in the east Irish Sea and across the globe.

“There’s no indication that we have hydrogen sulphide, there’s no indication that we have sour gas here in the Bowland Shale. That’s both in this well and the data that we’ve got from historic wells.

“So there’s no sour gas here.”

The 50-minute webcast, the third organised by Cuadrilla from its Preston New Road shale gas site, was watched by about 80 people at any one time.

Ms Hughes said Cuadrilla expected gas to be released from the Preston New Road wells in the middle of 2018 after the company finished drilling two horizontal wells.

She said a vertical pilot well had almost reached the target depth, more than 2km below the surface. The company had collected core samples of rock, which would be analysed on the site and in specialist laboratories.

“Drilling is going very well. We are getting the information we need.”

The webcast heard there were currently about 30 people on site, split between Cuadrilla employees and contractors, working on the well and on testing the samples.

pnr 171208 core samples lab CR

Core samples taken from the Preston New Road site near Blackpool. Photo: Still from video for Cuadrilla Resources

pnr 171208 gas bubbles from sample CR

Gas bubbles coming from a core samples taken from the Preston New Road site near Blackpool. Photo: Still from video for Cuadrilla Resources

Ms Hughes said the company would be looking at how fractures created by the fracking process would spread through the shale rock. She said the rock properties would vary throughout the shale layers. The company was looking for the sweet spots, she said.

“Which layer will see horizontal drilling will be decided by mechanical qualities of the rock and quality of the gas in the formation.”

“It’s all about the geology.”

Ms Hughes said Cuadrilla planned to drill horizontally for about 1km from the Preston New Road wellhead westwards towards Blackpool.

She described horizontal drilling as “perfectly safe” and said “there will be no interaction with local properties.”

The well at a depth of 2km would have a diameter of 6 inches, she said.

pnr 171208 bent pipes 2 CR

Drill pipes with a slight bend to be used to create the horizontal well. Photo: Still from video for Cuadrilla Resources

pnr 171208 drill bits CR

Drill bits at Preston New Road shale gas site. Photo: Still from video for Cuadrilla Resources

PNR 171208 electronics CR

Pipes with equipment to record information about depth and location of horizontal drilling which is then sent back to the surface as a series of pulses. Photo: Still from video for Cuadrilla Resources


Ms Hughes didn’t indicate how many wells might be drilled from Preston New Road but she said:

“The idea is that you would have one location that you would be drawing gas from a wider area of the sub surface so it lessens the surface impact.”

PNR 171208 blow out preventer 2 CR

Blowout preventer at Preston New Road shale gas site. Photo: Still from video for Cuadrilla Resources

pnr 171208 blow out preventer 1 CR

Blowout preventer at Preston New Road shale gas site. Photo: Still from video for Cuadrilla Resources

42 replies »

  1. I would also like to add that the Douglas Oilfield (hosted in Permo-Triassic) has compartments with oil/gas contacts that are microbially altered. These would be horizontal at the time of formation but are now tilted, demonstrating that groundwater containg microbes accessed the oil in that field during the Neogene (possibly Miocene). Nothing to do with the Bowland Shales. Also the surface H2S seeps which occur in the drinking water catchment of NW England (and cause no problems to fisheries or drinking water quality) are caused by ground water circulation introducing microbes into the shallow geology. Again – nothing to do with Bowland Shale buried far below modern or even Neogene groundwater penetration.

      • Sherwulfe, go dig in the sand on Blackpool Beach, Clevelys, or St Annes, Morecambe or Lytham. When you get to the dark layer, only a few centimetres down, sniff it. That is the layer, with H2S, that is due to sulphur reducing microbes. I suppose all the beaches should be evacuated if we followed your scaremongering reasoning – which of course we should not!

        • I’m sure Dr Nick, Robin Grayson would be a better expert to discuss the shortcomings of H2S and shale gas with you.

          In the meantime, we are poised before the storm. The hounds are ready to be released; the law companies are chomping at the bit; it will be the best thing since PPI. The claims will make INEOS’ paltry claims for breach of injunction look like a prize in a church raffle.

          Make no mistake, the residents are not the ‘poor’ that inhabited the first shale areas in the US, these are educated, reasonably well off and feisty humans who have already spent money investigating the anticipated effects, and are waiting; no gagging orders here….. what a shame it came to this.

          I hope the drilling companies and their investors have deep pockets and have a contingency plan for the ALL STOP when the bungling governance run for the door.

          ‘only a few centimetres down, sniff it. That is the layer, with H2S, that is due to sulphur reducing microbes. ‘

          The toxic hydrogen sulfide is a waste product of sulfate-reducing microorganisms. Clearly the levels a few cms under Blackpool beach are not sufficient to cause a closure of the beach; so not clear on your point.

          • What is hydrogen sulphide?

            Hydrogen sulfide is the chemical compound with the formula H2S. It is a colorless gas with the characteristic foul odor of rotten eggs. It is very poisonous, corrosive, and flammable. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.

            In 2011 it was reported that increased concentration of H2S, possibly due to oil field practices, was observed in the Bakken formation crude and presented challenges such as “health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements”.

            Biocide compounds are often added to water to inhibit the microbial activity of sulfate-reducing microorganisms. Because biocides are intended to kill living organisms, many biocidal products pose significant risk to human health and welfare. Great care is required when handling biocides and appropriate protective clothing and equipment should be used. The use of biocides can also have significant adverse effects on the natural environment.

            Disposal of used or unwanted biocides must be undertaken carefully to avoid serious and potentially long-lasting damage to the environment.

            ‘Sour crude oil will have greater than 0.5% sulfur and some of this will be in the form of hydrogen sulfide. Sour crude also contains more carbon dioxide. Most sulfur in crude is actually bonded to carbon atoms, nevertheless, high quantities of hydrogen sulfide in sour crude can pose serious health problems or even be fatal.

            Hydrogen sulfide is famous for its “rotten egg” smell, which is only noticed at low concentrations. At moderate concentrations, hydrogen sulfide can cause respiratory and nerve damage. At high concentrations, it is instantly fatal. Exposure to high levels of hydrogen sulfide is thought to be in part responsible for Gulf War Syndrome, which is characterized by chronic fatigue, headaches, dizziness, memory problems, serious breathing problems, and even birth defects. Hydrogen sulfide is so much of a risk that sour crude has to be stabilized via removal of hydrogen sulfide before it can be transported by oil tankers.

            Members of the public should be informed at all times of any potential risk, so they can make informed decisions.

          • How can anything possibly advance with latter-day luddites [edited by moderator] around? Ignore expert advice, follow the ignorant emotional mob. [edited by moderator] – never created anything other than misery.

            • Stan; You should only advance that which is good, not that which is bad……..
              ‘Ignore expert advice’ is what are governance does well. There is no such thing as an ignorant emotional mob. By its very nature ‘an emotional’ mob will have something passionate to get fired up about, passion is fueled by outrage, outrage by finding out the truth and realising those who should be accountable are passing the buck. Think about it.

    • You mention Douglas. What is the source rock for that oil / gas? It wouldn’t be the Bowland Shale by chance…. The fields in that area were full of H2S.

  2. Any ‘experts’ out there to explain the categoric denial from Cuadrilla that there’s no Hydrogen Sulphide in the all of the Bowland Shale or maybe that they need to qualify it to ‘the bit of the Bowland Shale we have sampled’. Also maybe advise the ‘senior geoscientist’ of Cuadrilla to improve the videos on to make them at least a little convincing? I stopped studying earth sciences at degree level but this sort of stuff is just a joke.

    More seriously, can anyone tell me how the gas coming back up the well is captured and analysed as they drill down now. So when the used mud comes up the well, I assume the accompanying gas is captured any analysed. All you well engineers out there …. is it done … is the data available as a FOI … or is it commercially confidential …

    • Every drilling operation I’ve worked on had an independent gas monitoring system in addition to the rig’s system, usually the mud logging unit. As this is a development well and Cuadrilla are drilling mainly for information then I would expect this to be a pretty advanced unit (ie full bells and whistles). Also I’ve not seen any pictures suggesting Sabre, Draeger or any of the other H2S specialists are on site.

  3. Richard
    There is an explanation back in DOD. Look up the report for 24th Oct 2017 relating to Burning throat, nausea etc at Kirby Misperton.
    Scroll down the comments to a reply to Phil P by a injuneer dated Oct 25th 2017 08.27.
    There is a reply followed by some further discussion.
    It covers how monitoring is done, but how it is reported will no doubt attract further discussion.

    • Thanks for that hewes62.

      I’m not that mechanically minded, but I get the gist. I suppose ideally they should have a vacuum degasser then, but as with all these presentations and videos from Cuadrilla nothing is definitive or detailed. Else presumably gas escapes, all a bit too much like a dangerous open system then to me without a degasser…

      Also, I notice there’s no categoric statement there’s no H2S coming out of the well, just that there’s none in the Bowland Shale and that at the 4 or 5 locations they’ve drilled. No gas here? No, not where SHE is, when SHE said it! I suspect that’s why its worded like it is rather than stating ‘We have not monitored any H2S whilst we have drilled!’ as would be typically what you’d state, if you weren’t hiding something

      Yes so maybe H2S in the Collywood or Millstone, capped by the Manchester Marl. Of course the nice simple Cuad video omits the Collywood and infers the Manchester Marl is nice and thick, not laterally variable in thickness as typical with a landscape unconformity – hopefully not faulted due to associated bed drying and slumping properties over the unconformity – the usual indeterministic geological stuff …

      Hmmm maybe its best not to visit the site anymore. I was only going to stop going when they started fracking, but perhaps its wiser to stay away when they’re drilling as well.

      Will the blowout preventer be several stages or is it just a one mechanism device – They’ll be dual redundancy, multiple power sources, duplexed sensors. I just see one big junk of metal – is that it? Enough power and duplexed mechanisms to stop a hefty blow out from encountering a big gas pocket as they drill through a cap rock?

      • Richard

        Unfortunately injuneer is not posting now. He has lots of experience of onshore drilling.

        But here goes, in brief…

        The mud de gasser just cleans up the mud and pops it back down the well. There is not a lot of gas coming off the mud, as it is it’s job to keep any gas, oil or whatever you come across down the well.

        What comes up in the mud is of gripping interest to the mud loggers, so they know, and, if there was high H2S in the mud the drillers would smell it. It is in the interests of those working on the site to know.

        Should you run across unexpected pockets of pressure, then the pressure in the well ( the weight of mud ) is less than the formation pressure and gas or fluids enter the well. This is called a kick.

        Petrowiki has a good section on how kicks are detected.

        The well is shut in, and they work out how much they need to increase the weight of the mud to bring it all back into balance ( kill the well).

        Petrowiki has a section …. Variables affecting kill procedures .. which gives information on how that decision is managed.

        Then they get going again

        If that fails, then the well is shut in.
        Re blow out preventers .. see Wikipedia, which has a good description of what they are and do.

        BOPs are designed to cope with blow outs, and have levels of redundancy built in. They need to be maintained and tested, of course.

      • The blow out preventer is actually a secondary line of defence in well control. The primary method of well control is the mud, or more specifically the correctly weighted mud.
        The appropriate mud density is chosen to provide a column of dense fluid to balance the weight of any incoming fluid. As well as removing cuttings and cooling the bit, It’s job is to be dense enough to hold back the surrounding rock plus any influx without being so heavy as to fracture the formation and flow out into the surrounding rock.

        If a fluid, such as gas, water or oil does have sufficient pressure to flow into the well, then it’s displacement of the drilling mud is detected at surface in the mud logging unit or by the drill crew. The volume of the circulating mud system is known to tight tolerance so a gain or loss in that volume is visible on the pit level sensors and in the rate of flow of mud out of the hole.

        As for H2S monitoring, there is continuous sampling system which samples the gas level in the mud immediately it reaches surface. The mud logging unit has a set of gas evaluation tools which include a chromatograph, giving methane to pentane breakdowns, a separate unit which gives a total hydrocarbon equivalent to methane, and as seen in the PNR video, a rather unusual carbon isotope detector. The total gas and chromatograph are standard tools in most mud logging units.

        H2S is also continuously measured. The alarms are usually set at 2ppm for a low alarm, and 5ppm for high. It’s not unusual to drill in the North Sea with 1 or 2 ppm in the background. Importantly these are measurements of the contents of the exiting mud, not the atmosphere around the rig. Gas and H2S are held in the mud as far as the shakers, so detected levels will be far higher in the mud than the atmosphere. There will be hydrocarbon and H2S sensors around the rig which measure the atmosphere, but these are treated as secondary line of detection after the mud gas sensors. Body worn sensors would be issued if there was an elevated risk of H2S. At no point should crew be able smell H2S before it is detected in the mud.

        There is no cap rock as such with a shale reservoir. The gas forms in situ in its source rock without migration to a reservoir of permeable rock which would need a cap rock in a conventional reservoir.
        Hope that helps.

        • Yes, thanks Martin. Interesting stuff and it all seems safe based on that information.

          But on the last point of the cap rock – my suggestion is that every time Cuadrilla drill through the Manchester Marl, they have the potential to hit conventional gas that is held in the underlying Collyhurst/Millstone grit. This gas could have originated from the Bowland Shake and risen up to be capped. So its not the shale reserve but a conventional gas pocket.

          Also,Cuadrilla don’t really help themselves when they make absurd oversimplifications of the geology.

          Click to access Smythe%20slideshow%20-%20Environmental%20risks%20from%20fracking%20in%20the%20Fylde%20Nov2014.pdf

          is a bit more representative of the geology they should be drawing.

          And to not explain the problems they have – bent pipes coming out of the well, when they first drilled. People do notice!

          • Well Richard, I think you might have a rather movies-based idea of what drilling into gas bearing zones would be like ! Its rather more prosaic than ‘pressurised gas pockets” in real life. If youre drillng in a formation in the UK, the pressures are generally known, either from direct measurement in other wells or from estimations based on seismic survey data or regional studies. Theres already a producing gas well in the Collyhurst at Elswick. It’s poor permeability sandstone was hydraulically fractured in 1993 so its pressures should be known exactly unless there are sealing faults between there and PNR in which case a reasonable estimate can be made.The poor permeability, found also in other wells, would also reduce any threat of problems.If you have to fracture it to produce from it, its unlikely to allow a lot of gas to flow out by accident. You’ll probably just see the total gas come up to a few percent as you grind up an 8 1/2″ wide cylinder of rock.

            There are times when a formation can have an unexpectedly high pressure but generally these are allowed for in a safety factor of mud weight. The planning that goes into this stuff is very long winded before a well is drilled, as there are safety and cost ramifications of getting it wrong. The presence of gas though, doesnt actually equate to uncontrollable formation pressure and rig-based flaming catastrophe.

            As I said, during drilling, the well is monitored for signs of gas and unexpected pressure as a routine. If there is an unexpected gain to the circulating mud system which might indicate higher than anticipated pressure, everything stops, the well is observed, then if the gain continues, the BOP can be closed and the well monitored. The BOP is a big valve, probably rated to 5 or 10 thousand psi. This gain to the system is called a ‘kick’ and is something rig crews train for and are tested on, repeatedly.
            But theyre drilling in a well known area there and pressures can be pretty accurately predicted. To give you an idea of how often it happens in bog standard UK drilling, I’ve maybe seen 4 or 5 such kicks in 30 years offshore, sometimes only water coming in, and never once seen a blowout.

            As for Cuadrilla’s ‘oversimplification’ of geology, I’m sure they have enough data to work from. Financially, the better their interpretation of the surrounding geology, the more likely they are to have a successful well. Its in their interests to have a correct model. Smythe says the EA and Cuadrilla are all wrong in their interpretations. Thats an opinion. Cuadrilla and the EA have a different opinion. But the interpretations will be tested when the well is drilled, cored and wireline logging completed. And the BGS will get confidential copies of all their data and physical samples from the well.

            • Thanks again Martin. Sure, I have little knowledge of gas reservoirs.

              But you do highlight the Cuadrilla discrepancies, the Collyhurst is not presented in their video, yet historically they have declared it to be important – the fracked well at Elswick. Not high volume, high pressure but fracked nonetheless. Why not show it? Isn’t it important? Isn’t the Collyhurst thicker than the Manchester Marl? Perhaps you haven’t seen their video on the geology?

              And their opinions – is it at coincide that they are now only drilling 1km west rather than the 2km they originally stated. Maybe it’s because they have been alerted to the ‘wakepark’ fault Smythe picked up? And the way they originally erroneously depict the local fault at PNR not continuing up to the Manchester Marl boundary. It’s also in their interests to present an interpretation to allow them to frack when the geology suggests it may not be safe.

            • I’m guessing the change from 2km or 1km was a reduction in the length of the sidetrack length?. While its easy to leap to a conclusion of some conspiracy or coverup, by far the most common reason for that is financial, and I’ve seen that several times offshore.
              This is an exploration well, not a producer and is drilled to prove economic value to further drilling. The horizontal section, with its directional gear, coring, LWD tools and people is the most expensive part of the well other than the mobilisation of kit. So its very common for the finance department to ask a geology department “can you answer the question being asked by this well by only drilling half the originally planned horizontal leg?”. If the answer is “yes, we’ll have enough shale to fracture to demonstrate economic viability”, then thats what would happen. It may be that they have got some late interpretation on seismic, but finances is by far the most likely.

              Not sure what the thinking is with the Collyhurst. If the well is not thought to penetrate it then it wouldnt be included in the section shown in the video or they may be lumping it in as part of the Manchester Marls, but it would perhaps have been better to say that. From a quick look on google, there seems to be 160m of Collyhurst initially epected before the well was drilled. I did look at the video of the large canvas schematic of the well and I’m not sure what the thinking was there but I agree its confusing and leaves room for the conspiracy theorists.

              But the EA are professional people, and seem confident of the planned well. The points Smythe brought up were addressed by them and the EA dont agree (see Appendix 8 of the PNR/Lancashire documents). Whilst I realise that Smythe tells you what you may want to hear, its entirely possible that he may not be correct, as can be seen even below the line of this story in the discussion of H2S, where there can be disagreement between people with respectable CVs in the subject.

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 )

Google photo

You are commenting using your Google 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