The Nitty Gritty
We thought it pertinent to consider what's been happening
recently regarding the shale gas exploration at Cuadrilla's Preston New Road wellpad.
Amongst those who follow matters closely there is speculation that fracking operations might have stopped.
In this article we'll look at some of the underlying reasons why that might be the case, and at two aspects of the exploration that we think are related.
These are both about the geological conditions that exist in the area in which Cuadrilla are, (or were), fracking.
The first is about what they expected to find from their seismic surveys.
And the second is mostly about the sand they use to keep the fractured rock open - to make the gas come out.
Finally we've an excellent review of the earthquakes so far (and their implications) prepared by local expert Mike Hill, before we add our own view of where we seem
to be now.
We begin with In the Grit - the Geology for the drillpath and particularly at the Millstone Grit layer which seemed to have changed between 2017 and
Next we look at some of the Earthquake Troubles we've been having of late, before asking What's happening to fracking now?
To understand that, and the conditions and forces that created our geology, we have a simple Geological Primer before asking
How we get the Gas out?
Then we look at the Sand that's used to prop the fractures open - and the mechanical properties of various types of sand.
Next we look at What might have gone wrong at the Preston new Road site, before considering local expert Mike Hill's excellent
Review of local earthquakes, before giving Our own take on all of this.
IN THE GRIT
In July 2017, before they started the actual fracking at Preston New Road, Cuadrilla prepared a detailed 'Pre Drilling Fracking Plan'.
We're going to be using excerpts from it in this article, but anyone wanting full chapter and verse can follow this link to
download the full pre drilling fracking plan from Cuadrilla's
website or from here from our own website.
As you'd expect, its a detailed and technical document, but the bit we're most interested in is to do with the geology through which they expected to be drilling.
On Appendix 2 Page 4 there's a
diagram headed 'Seismic Cross Section' which is a very deep vertical slice through the earth showing the layers of various rock there
This section was produced as it says, from a Seismic Survey which allows you to estimate the type of rocks that are present, roughly how thick each of the layers are, and
how deep each of them is below the earth's surface at various points.
As you can see, under the superficial deposits (probably what we might call soil) there were thought to be five types of rock above the two layers of shale, and the
planned drilling path at that time is shown in red.
The blue lines and writing on this picture are our own. We've added it to highlight the place where Cuadrilla expected to drill through a layer of rock known as 'Millstone
Grit' before reaching the shale rock below.
Readers can also see three 'faults' shown on the section
We think these are places where the forces of nature have set up tensions at some time in the past, and where the layers of rock have moved and 'slipped' out of what
once was an alignment with each other.
Readers should also note at this point that in the whole of the section, the layer of 'Upper Bowland Shale' (into which Cuadrilla planned to drill horizontally) never
reaches the creamy yellow layer of 'Collyhurst Sandstone'
So far so good.
Then, almost a year later, in June 2018, a revised fracking plan was produced.
This time, on page 18 of Appendix 2
there's a similar diagram. This one is headed "Sub Surface Information v Geological Cross Section PNR1"
Once again we're using an extract, but our readers can follow this link to
download the full revised plan from Cuadrilla's website, or get it
here from our own website
And once again, there are 5 layers of rock being shown.
But this time, the planned drilling / fracking path (shown on this section in black, with the fracturing area in orange) doesn't go through the Millstone Grit at all,
it goes straight through the Collyhurst Sandstone into the Upper Bowland Shale.
We can also see that on this section, the Upper Bowland Shale is now shown as having a large direct interface with the creamy yellow Collyhurst Sandstone layer.
It looks to be that the Millstone Grit layer has been moved or shortened, and the area of Upper Bowland Shale has increased in size.
And as a small aside at this point, readers might also like to note that 'Fault-1' is now shown as having a series of lateral lines which are being drilled through as
well as a longer 'main' fault line from the section published a year earlier.
We were not at all sure what was going on here, but we can't help thinking it could be significant that Cuadrilla's drilling path appears to go straight through some of
these fault lines.
We do know that Cuadrilla's starting point on the surface has not moved significantly, so their starting point must be the same
Surely it couldn't be that layers of rock under the ground can move as far as these seem to have been shown to have moved without anyone noticing.
Discounting that option, we were left with the possibility that either Cuadrilla's first seismic survey was incorrect, and it has been replaced by a more accurate one done a
Or perhaps this one was after more after core sample drilling and the like had taken place.
Or perhaps it was that Cuadrilla had changed the angle at which they were going to drill, so as to avoid the need to drill
through the Millstone Grit rock (which we're guessing might be harder than the shale rock).
So, to try and get a better handle on what's going on, we tried to do an overlay of the two sections to see the differences.
Now, at this point we need to issue a 'health warning' for the next bit of this article.
The two illustrations we had are not exactly the same size and we had to shrink one of them a bit to make them both the same size.
So we can't claim absolute accuracy on the comparison, but we found it interesting, and we thought what we'd done was worth showing to our readers.
As with the other graphics,
readers can click on the one on the left to open a bigger version of it in a new browser window.
From what we can see, the drilling paths are broadly similar, except the later version shows the (black) drill line going deeper (and into the Lower Bowland Shale)
than the (red) one from the section shown a year earlier.
The red line (from the previous year) was also shown as going deeper into the underlying 'Hodder
The fault lines seem to be more or less in the same places on both sections.
What seems to us to have happened is that in the second (2018) section, the extent of the Millstone Grit has changed, as has the position and thickness of the Upper
Bowland Shale layer.
We don't understand exactly why this has changed between the two sections, but perhaps the 2018 results are more accurate.
But what we do worry about is that if the nitty gritty of two survey results within a year of each other can show such a big difference in where the rock layers and
formations are, how can we be sure that the other details - including the natural fault lines - are also shown accurately in any of the sections we've seen up to date?
And if these features are not where Cuadrilla think they are, how can we be sure that the fracking process that started on 15 October 2018 isn't going to interfere with
these fault lines?
Might it perhaps trigger something like earthquake at Preese Hall - which was caused by fracking, and which resulted in an existing geological fault line changing again and
causing a much bigger earthquake than the 49 or so smaller ones that went before it.
We also understand that the Preese Hall earthquake deformed the metal casing of the wellbore sealed inside its cement layer, and that caused the exploration to be abandoned on that site.
We find the uncertainty created by these seismic surveys very worrying.
From what we understand at present, it looks as though the actual fracking of the well at Cuadrilla's Preston New Road site might be in trouble.
And it sounds like it's all to do with the sand (which we'll get to shortly).
The problem is that the fracking process is setting off earthquakes, and we've seen 36 of them since it started.
Some have been very small, but all are officially classed as 'earthquakes' and have been recorded on the monitoring equipment set up for that purpose.
The bigger earthquakes (those producing a tremor of more than 0.5 on the Richter scale) have triggered a requirement for Cuadrilla to shut down their fracking
operation for a mandatory18 hours of frack-free assessment - to see if any more arise in that time. If not, fracking operations can continue.
To date, the biggest event has been an earthquake of 1.1 on the Richter scale.
The one that deformed the casing and caused the Preese Hall site to be abandoned in 2011 had a measurement of 2.3, and that one was preceded by 50 smaller earthquakes.
Seismic scales are based on a logarithmic measurement. This means a reading of 2 not just twice as strong as a reading of 1, it is actually TEN TIMES STRONGER than a reading of 1.
After the Preece Hall event, a temporary moratorium was put in place by the Government.
But in December 2013, Cuadrilla held an event at Pipers Heights Caravan Park where
seismic engineer Huw Clarke explained that the company was installing 80 geophone detectors that would become a 'Traffic Light' safety system which would ensure no
recurrence of the Preece Hall incident
That arrangement - introduced and implemented by Cuadrilla themselves - led to the creation of today's much more formalised safety Traffic Light system with triggers for
various seismic event levels.
So it was a bit of a surprise to us when, so quickly after the 1.1 magnitude earthquake, Cuadrilla called for the trigger levels to be eased.
They called on the government to relax the operating rules that have forced them to halt work several times already.
Cuadrilla’s chief executive told 'The Times' newspaper that the company wanted the limit raised to a magnitude of 2 - which, it said, would still be far stricter than
rules in the US, where fracking has caused a boom in oil and gas production.
Adding to the pressure on the UK Government, he also said Cuadrilla might abandon plans to test the flow of gas from Preston New Road site because as they stand at present,
the rules have prevented it from fracking effectively.
Government Minister Claire Perry - who is already beleaguered by Members of Parliament and the public in areas of the UK where shale gas exploration is taking place, and
(in the midst of anger from all sides over Brexit) must be mindful that the national Labour Party has promised to ban fracking in the UK if they are elected - took a strong
line against these entreaties from Cuadrilla.
She told the 'Financial Times' she was
“not considering weakening the monitoring controls on seismicity”.
And she told The Times that the current restrictions were entirely appropriate during the initial testing phase, but that the government would need to review the limits if
the industry got to an operational state, adding
"It would be a very foolish politician who would do things that would be considered to be relaxing regulatory standards when we are trying to reassure people
This is likely to cause real trouble for Cuadrilla, whose parent company (A J Lucas) - supported by other major shareholders including 'Centrica' - have been bankrolling
significant parts of Cuadrilla's operations so far.
But Lucas has seen its share price tumble from over £1 around five years ago, to just under 30 pence today.
We suspect if it can't show that gas will soon start flowing, Lucas and others might want to cut their losses with Cuadrilla.
SO WHAT'S HAPPENING TO FRACKING NOW
Well, it looks as though Cuadrilla have ceased or drastically cut back their operations at Preston New Road, at least for the moment.
A press release from Frack Free Lancashire this week said
'Since 2 November, almost three weeks ago, Cuadrilla appears to have stopped fracking at the site.
....It has been suggested that, as well as the earthquakes, Cuadrilla is facing problems ranging from further issues with their "impermeable" membrane to
problems with their well bore. This uncertainty has led to local MP Mark Menzies requesting an independent investigation into well integrity at the site.
As the coiled tubing has been removed from its tower it is also suggested that Cuadrilla may have abandoned their first well without having been able to
inject sufficient fluid or proppant to achieve a commercially acceptable flow of gas....'
Local expert Mike Hill is of a similar opinion (see later).
So what's going on here?
A Geological Primer
Well, to understand the process, we need to begin with a simple geology primer.
Shale rock is 'sedimentary' rock - meaning it was originally laid down as fine mineral deposits (think mud) typically in slow moving water.
Over years, it was laid down in thin deposits (think periodic flooding) and had organic matter (maybe plant material when not flooded) incorporated into it.
As more and more layers of silt and clay built up, the pressure of the weight above increased and compressed this fine mineral and organic deposits into a much smaller space
and they became a type of mudstone rock.
Furthermore, the natural warmth that's always present lower down in the earth caused the decomposing organic material to convert to molecules of natural oils and natural
Because of their fine particle size, clays and silts pack together much more tightly and become more solid than, say, sandy soils (as any gardener knows).
But because the particles and organic matter were often laid down in what became lots of shallow layers, this makes some shale rocks 'fissile' - meaning you can split
it along their sedimentary layers.
You can see this sort of process at its beginning if you walk out on the marsh from Lytham. The River Ribble has already dropped the heavier particles of gravel and sand
in its faster flowing waters upstream of Preston.
So when the river reaches Freckleton and Lytham it widens out, and its rate of flow slows. This causes the more sluggish flow to start to deposit the silt and finally the very fine particles of clay that it
has been carrying in suspension. Today, we see these forming into saltmarsh and eventually a delta.
Add a few million years and that saltmarsh will be deep under the surface of the earth as mudstone and shale rocks.
So How Do We Get The Gas Out?
Well, because the shale rocks are very dense, the molecules of gas and oil are trapped in tiny pore-spaces that are not nearly so interconnected as may be found in other rocks.
Think about the ease with which water would drain through a tea-chest full of ping-pong balls and a tea-chest full of mud.
The shale rock is like the mud, but dried, compressed, and hardened.
But it was discovered that if you pump liquid under extreme pressure into the shale, it can cause the shale to fracture and increase its permeability.
The increased permeability and the pressure created by the injection process forces some of the trapped gas molecules out of the shale.
This Is Where The Sand Comes In
From a commercial exploitation perspective, the process is considerably improved if the fractures can be 'propped open' by mixing sand particles into the fluid.
So another sort of grit - or more accurately - sand, is used to prop open the rock fractures and allow the gas molecules to flow out.
But it's not just any old sand.
There are some sands (Like the 'Zone 2 Concreting Sand' that used to come from the Hoveringham's quarry near Scorton) where - if you look with a magnifying lens - the
particle sizes range from grit down to dust.
Put some of that in a funnel and pour a glass of water onto it and the water flows through as you would expect. Pour a second glass, and none will go through.
That's because all the fine particles have been washed and settled into the spaces between the bigger grains by the first glass of water, and it has become blocked solid.
So that type of sand is good for making dense concrete but useless to improve drainage.
The opposite of this is to have a single particle sized sand with far greater (and more un-blockable) pore spaces.
These are very expensive because they have to be treated, sieved, and graded to more or less a particular
single grain size.
Such sands will be terrific draining devices and are used in the 'sand-slitting' technology deployed on expensive sports areas such as high grade football pitches.
The large, interlinked, pore spaces in single particle sized sand are also excellent for allowing gas from shale rock to flow out.
However, for propping open fractured shale rock to let the gas out, the sand must also be physically very strong and able to withstand vast pressures.
Typically, fracking uses high-purity quartz sand that has very round grains and is a very durable crush-resistant form of sand.
So there you have it. Drill down, crack the shale rock with fluid under pressure, then pump fluid mixed with single particle sized quartz sand into the cracks, and increase
When the pressure reaches breaking point, the fractures suddenly occur, and the water - and millions and millions of rounded sand grains - are swept into the fractures by
the rush of water under pressure as it fills up the new fractures.
When you turn off the enormous pumps, and the pressure reduces, the fractures 'deflate' a bit, causing the gas to flow out and back up to the wellhead, but the sand
grains hold the fractures open for this flow carry on for some time - or at least they should.
And when the gas flow stops or becomes commercially unviable, you can do another fracking operation to push the fracking fluid and sand further into extended fractures in
the shale rock.
So What's Gone Wrong At Preston New Road?
Well, from what we can understand (Cuadrilla are - unusually - being a bit tight-lipped about it), the first issue seems to be that pumping the fluid in to crack the
shale rock is producing very small earthquakes which are noted and recorded, but they are below the threshold at which fracking has to be halted.
But when they try to include the sand, (maybe using a greater pressure), it's producing earthquakes above the 0.5 limit.
This means Cuadrilla have to suspend fracking
operations for 18 hours each time this happens.
Cuadrilla's Mr Egan told The Times that so far it had only been able to inject less than half the volume of sand it needed to hold the fractures open, and they wanted the
'pause' limit raised from 0.5 to a magnitude of 2.
According to Mike Hill - and we've no reason to doubt his maths (which are way better than ours) - to raise the safety limit for fracking from 0.5 to 2 (i.e.
increase of 1.5) would not mean the power of the quake is 3 times more as you might expect (3 x 0.5 = 1.5).
It is 32 times greater in power (10' .5 ) and the energy released would be some 178 times more.
The Times quoted Mr Egan as saying
“We are not getting effective fractures. We are not getting enough sand into the grounds to get a good test.
We may not want to flow test it because it’s not a totally indicative representation of what this shale rock could do if tested with sensible [earthquake]
And he told the Financial Times
"It certainly looks like it would be - I can’t say impossible - but I could say very difficult to make this a commercial venture if you had to continue
operating within a 0.5 red line,”
He also told The Times he was concerned that flow testing based on the inadequate fractures to date would generate a false negative which could turn off investors, adding
"We may decide it’s better to pause and await the outcome of a review of the traffic light system.
"It’s possible if we are constrained to operate in a 0.5 traffic light system it’s not commercially viable."
A REVIEW OF FYLDE'S RECENT EARTHQUAKES
We're very fortunate in this area. We have our own local expert - Mike Hill.
For those that don't know him, he has consulted/advised/given evidence to: The Dept. of Energy and Climate Change (U.K. Gov.), The European Commission Joint Research Council
, Office for Unconventional Gas and Oil, the local councils (FBC, WBC, LCC), The Royal Society, the UK Regulators (HSE, EA), NGOs (FoE, COOP, RAFF, EKAF, REAF, FFF), the
British Geological Survey, The Churches in Lancashire Group and the industry. He has spoken at numerous conferences, Q&A Panels, public meetings, professional bodies and in the
We've heard him, and we think he's ALWAYS worth listening to.
We're fortunate because he has just published a
short paper called 'Review and analysis of the earthquakes caused by fracking the Fylde: Why should the safety limit not be
We recommend readers to follow this link and download a copy of Mr Hill's Paper to read in full.
In essence it's a review of the earthquakes caused by fracking in Fylde.
It asks the questions: What Happened? How did we get here? and Where are we going?
It also addresses why we should keep the 0.5 limit and asks 'What's the problem with the regulators'
One of the things Mr Hill is best at is taking a complex problem and distilling it into clear and simple terms, and as ever, we think he does this really well in this report.
His conclusion is that Government should not allow the increase from magnitude 0.5 to magnitude 2 before fracking is paused or stopped.
OUR OWN TAKE ON ALL OF THIS
We attended the very first meeting organised to consider shale gas exploration in Fylde, and we reported it in 'Gas
Exploration' on 9 January 2011.
We have gradually moved from being ambivalent, to being opposed to the plan to extract shale gas.
That's not so much an in-principle or environmentally based decision, but more a hardening of a view that has been caused by Government's unreasonable willingness to bend,
twist and change established laws and rules that used to apply to all, so as to create a favourable climate specifically for the establishment of a fracking industry in England.
We had two turning points in this progress. One was the talk given in St Annes by Canadian scientist Jessica Ernst (Jessica Ernst v Canada) in 2013 where we could simply not
believe that a civilised and democratic government like Canada could have sanctioned - let alone driven - the implementation of fracking to the clear detriment of its citizens,
and treated them as terrorists when they made serious and justified complaints.
The second was when David Cameron and George Osborne led their party to change the law on the ancient rights that people in England had enjoyed for centuries about ownership
of surface land extending in a cone to the centre of the earth. Giving permission to drill under people's land without first needing to reach an agreeable compensatory
arrangement or to have the terms settled by a court which became convinced of the need to override the property right, was a step too far for us.
In practical terms, we don't support the imposition of fracking wellpads on Fylde's countryside any more than we would support open cast mining, and we recognise that
democracy at all levels up to the County Council opposed these developments in the locations that were proposed
Government then overrode those decisions because they wanted the gas and revenue from it.
We've watched people in Fylde grow increasingly hostile to these plans and, at times we have wondered in amazement how thick a skin you must need to be so hated an industry
yet still impose yourself on an unwilling community that wants none of you.
Even Cuadrilla's sticks of rock have failed to sweeten the people's palate toward fracking.
The self-evident community disapproval has led to - and is still leading to - the Government taking the blame for what is happening here.
Although at present we expect no 'democratic earthquakes' in the
short term, that sense of growing anger and blame cannot but have electoral consequences for the Government in the longer term.
Perhaps that thought will steel Minister Claire Perry's resolve to continue to recognise - as she has already said:
"It would be a very foolish politician who would do things that would be considered to be relaxing regulatory standards when we are trying to reassure people
And if that position remains the case, and Cuadrilla dare not continue with the fracking for fear of creating another larger earthquake that could cause (or - according to
some opinions - might even already have caused) damage to its existing wellbore, and or triggering even larger movement in an existing fault line in the natural geology, then
fracking at Preston New Road might become a dead duck.
That site would then become the latest in a decreasingly successful line of well sites that didn't work out well for Cuadrilla.
And if that happens, and Cuadrilla's backers and investors were to decide to cut and run, then we might yet see the process of democracy win out.
And if it does, we will not be shedding a tear.
Dated: 24 November 2018