Thursday, 24 May 2012

Simple guide to Shale Gas

Very basic guide to shale gas... 
  • ·         Shale is a sedimentary rock, it is very fine grained and tightly compacted. It’s formed in marine or lagoon environments over a very long period typically 10’s of millions of years. It is formed from fine silty deposits as well as the remains of dead plankton, airborne dust etc. River delta mud often forms shale in due course. Lots of organic material is buried with the mud that forms shale; something like 95% of all organic matter that is buried by sedimentation is in mud that later forms shale. Bacteria is also buried with this organic ‘soup’ and over time convert organic matter to gas and oil: In the oil industry many shale deposits are often called “source rock” or “the kitchen”
  • ·         Most of the organics in shale “migrate up” away from the shale during the formation period as the density of this material is much lighter than the seawater that is also present in the pore spaces of the mud (just like oil and vinegar salad dressing quickly separates)
  • If the migrating organic fluid encounters an impermeable barrier such as a layer of clay, mudstone, or more shale, it becomes trapped and over time becomes an oil or gas reservoir, trapped below a “cap rock”, often in the pore spaces of sandstone. Unlike shale, sand grains create millions of tiny bridges as they are squeezed together, creating permeable sandstone that holds oil and gas in the pore spaces that are all interconnected.
  • ·         As the transformation from sedimentary mud to shale rock occurs over 1000’s of years, some remaining oil and gas remains trapped in the structure of the shale.
  • ·         Most shale has gas (or oil) trapped in tiny bubbles but unlike sandstone,  the bubbles are nor connected- the particles of mud are squeezed so tightly together the bubbles are isolated from each other , so the rock has moderate porosity- full of pores of gas, but zero  permeability- the ability of gas to flow through tiny channels in the rock.
To labour the point, Sandstone  has good porosity (lots of little bubble of oil, gas or water) and ALSO good permeability (the gaps between the grains of sand are all connected together so oil, gas or water can flow through the rock, like water through a water filter)
  • ·         Shale is formed in layers of sedimentation- it has a natural tendency to fracture horizontally along the layers. If you drill a hole into shale and pump water into the hole, it will open horizontal cracks around the bore hole.     But the water pressure has to be high enough to literally lift the entire rock sitting on top of it in order to open a crack. So the shallower the shale layer is, the easier it is to frack it horizontally along the bedding plane. As you drill into deeper layers of shale, it requires more and more pressure to create a horizontal crack. There is a certain point at which it becomes easier for a crack to ignore the bedding plane and go vertically upwards, pushing the rock to either side as the crack is propagated instead of horizontally along the weaker bedding plane..  THIS IS A VERY IMPORTANT FACTOR in shale gas development. You have to understand this point to understand the pros and cons of shale gas.
  • During fraccing, secondary fractures are created because a cold fluid is being pumped into hot rock (at 6000 ft, the temperature is about 50 centrigrade) which assists the frac process.
  • ·         When shale such as the USA Marcellus is fractured, as the water is pumped into the shale it cracks the rock horizontally because the shale is relatively shallow at (approx.) 4-6000 ft deep. If you stop pumping the water, the horizontal cracks will close up again.
  • ·         Sand is pumped with the water into the shale so that when the pumps are switched off, the cracks are held open by the sand grains. The cracks join the little bubbles of gas together (creating permeability!) allowing the gas to flow up the well.
  • ·         When the shale that is full of gas/oil is very deep in the ground such as 10,000 ft (for example), when water is pumped into it, the pump pressure is not strong enough to make horizontal cracks, instead it causes cracks to go vertical- this is the big problem with fraccing, vertical fracs are pretty useless in a normal vertical well. In deep wells, all the energy expended in fraccing the formation, only joins together areas near the well bore- further away, permeability is not created or improved. 
  • The huge game changer in the last 15 years is that horizontal wells are drilled into the shale. When fluid is pumped into the horizontal well, primary fractures are forced to radiate outward from the well bore, perpendicular to the bedding plane of the shale- from these primary fractures, millions of smaller secondary fractures travel along the weaker bedding planes of the shale vastly increasing the area of rock being fractures and making shale gas economically viable by massively increasing the productivity of the well.
(click on image to enlarge)

  • Horizontal wells are now also fracced in stages, the bottom  200’ of the well is isolated and fracced first, then the system is pulled up along the hole a few hundred feet and repeated 20-30-40 times so all the hydraulic horsepower used is focussed on a relatively small volume. 15 years ago it was common to try and fracc the whole production interval in one go, with mixed success.
  • One of the dangers of fraccing 15 years ago without doing it in stages was that all the hydraulic force would find one weak spot and create a single large fracture instead of 1000’s of small cracks. This fracture could propagate vertically 1000’s of feet without the operator being aware this was happening- it was possible to fracc vertically from the gas bearing shale all the way up to an aquifer 2-3000 feet above. However, this risk has almost been eliminated with today’s technology as the fracc job is carried out is small stages and modern computes with high resolution pressure gauges allow engineers to interpret exactly how the volume of the fracture space is growing /propagating – single vertical fractures show a markedly different pressure response to matrix fracturing and can be identified immediately- during the pumping process, allowing the job to be shut down before any environmental damage occurs. 
  • ·         Marcellus shale in the Eastern USA is perfectly placed to be too deep to contaminate surface water, but shallow enough to be fracced profitably from horizontal wells at present day economic gas production levels. (The Marcellus shale covers vast areas of the USA)
  • Shale in other regions were formed at different historical times, are at different depths. Thousands of feet of rock have been eroded above the Marcellus in America, making it easier to fracc. Often shale deposits in other parts of the world are buried much deeper and do not have the same proven properties as the Marcellus.

Wednesday, 3 August 2011

Flat Earth

Courtesy of OrkneyLad

“Try this experiment. Ask an ordinary person what Christopher
Columbus wanted to prove when he set out to reach the Orient by way of 
the Occident and what it was that the learned men of Salamanca 
stubbornly denied, trying to prevent his voyage. The reply, in most 
cases, will be that Columbus believed the earth was round, whereas the 
Salamanca sages believed it was flat and hence thought that, after 
sailing a short distance, the three caravels would plunge into the 
cosmic abyss. 
So what was the big argument all about 
in the time of Columbus? The sages of Salamanca had, in fact, made 
calculations more precise than his, and they held that the earth, while 
assuredly round, was far more vast than the Genoese navigator believed, 
and therefore it was mad for him to attempt to circumnavigate it in 
order to reach the Orient by way of the Occident. Columbus, on the 
contrary, burning with a sacred fire, good navigator but bad astronomer, 
thought the earth smaller than it was. Naturally neither he nor the 
learned men of Salamanca suspected that between Europe and Asia there 
lay another continent. And so you see how complicated life is, and how 
fragile are the boundaries between truth and error, right and wrong. 
Though they were right, the sages of Salamanca were wrong; and Columbus,
while he was wrong, pursued faithfully his error and proved to be right
—thanks to serendipity.”

The Greeks had tried hard to find out how large the 
Earth is and managed to calculate many different figures depending on 
the methods and accuracy of their work. The most famous effort was that 
of Eratosthenes, Librarian of Alexandria, who wrote a treatise On the 
Measurement of the Earth, in which he gave a figure for the Earth’s 
circumference of 250,000 stadia. Depending on how long a stadia actually
was this is the equivalent of about 23,000 miles, pretty close to the 
true figure of 24,900 miles.

At the time Eratosthenes’s result did not demand 
universal assent and was widely seen as too big. A more popular figure 
is that given by Strabo and Ptolemy, two distinguished Greek geographers
of around the first century AD who both suggested 180,000 stadia. We 
are not sure where they got their figures from but they were repeated by
the Latin writer Seneca who transmitted them to the medieval West. By 
the time that it became a live issue for Columbus, Eratosthenes’ figure 
was back in vogue and the experts were wisely urging the Italian not to 
set sail. In particular a committee set up in Salamanca examined the 
plans and rejected them on the grounds that Columbus had underestimated 
the distance he would have to travel. Their concern is easy to 
understand – imagine how much trouble Columbus would have been in if the
Americas had not been there. He could not possibly have survived the 
trip all the way to the east coast of Asia and was very lucky that some 
land intervened before he and his crew had to pay for his mistake. In 
the end, however, Queen Isabella of Spain was won over and donated the 
resources required.

It is not difficult to see how the story of Columbus
was adapted so that he became the figure of progress rather than a 
lucky man who profited from his error. According to Jeffrey Burton 
Russell here,
the invention of the flat Earth myth can be laid at the feet of 
Washington Irving, (the author of Rip Van Winkle) who included it in his
historical novel on Columbus -its theme was the victory of a lone 
believer in a spherical Earth over a united front of Bible-quoting, 
superstitious ignoramuses, convinced the Earth was flat- and the wider 
idea that everyone in the Middle Ages was deluded has been widely 
accepted ever since.

Then later authors repeated this error:

“Nineteenth-century secular thought, irritated by the 
Church’s refusal to accept the heliocentric hypothesis, attributed to 
all Christian thought (patristic and scholastic) the idea that the earth
was flat.The nineteenth-century positivist and anticlerical made a meal 
of this cliché, which, as Jeffrey Burton Russell has demonstrated, was 
strengthened during the battle the supporters of Darwinian theory joined
against every form of fundamentalism. It was a matter of demonstrating 
that, as the churches had erred about the sphericity of the earth, so 
they could err also about the origin of species.”

The myth that Christians in the Middle Ages thought the world was flat was given a massive boost by Andrew Dickson White’s weighty tome The Warfare of Science with Theology.
This book has become something of a running joke among historians of 
science and it is dutifully mentioned as a prime example of 
misinformation in the preface of most modern works on science and 
religion. The Flat Earth is discussed in chapter 2 and one can almost 
sense White’s confusion that hardly any of the sources support his 
hypothesis that Christians widely believed in it. He finds himself 
grudgingly admitting that Clement, Origen, Ambrose, Augustine, Isodore, 
Albertus Magnus and Aquinas all accepted the Earth was a globe – in 
other words none of the great doctors of the church had considered the 
matter in doubt. Although an analysis of what White actually says 
suggests he was aware that the Flat Earth was largely a myth, he 
certainly gives an impression of ignorant Christians suppressing 
rational knowledge of its real shape.

What can be stated categorically was that a Flat 
Earth was at no time ever an element of Christian doctrine and that no 
one was ever persecuted or pressurised into believing it. This is 
interesting because the Bible itself implies the Earth is flat (for 
example at Daniel 4:11) and in [Isaiah 40:22] that it is spherical. 
Clearly, belief in the complete scientific accuracy of the scriptures 
against known facts was not upheld by the early or medieval church who 
were happy to accept figurative interpretations.

Anti-clerical ‘history of science’ writers have promulgated the myth so that even today, in his book The Discoverers,
Daniel Boorstin manages to produce a totally misleading account 
(although he eventually gets Columbus right). His bias shows badly when 
he castigates Christians for thinking the world was flat when they did 
not and then praises the erudition of Chinese geographers who actually 
did believe it. The myth is so prevalent that the blurb on the back 
cover of the UK version of Umberto Eco’s Serendipities, the editor repeats the myth even though within the book itself, Eco devotes a good deal of attention to debunking it!

The doyen of historians of Medieval Science, Edward Grant, covers the issue in his 2001 book, God and Reason in the Middle Ages
where he finds all educated people in the Middle Ages were well aware 
the Earth was a sphere. Perhaps today we can at last dispense with this 
patronising belief about the Christian Middle Ages.

Monday, 27 June 2011

The Myth of Peak Oil

Peak Oil is a myth that has been around at least since the 1950’s.
Every time there is a prediction that oil will run out, there are major new discoveries of reserves, or new technologies are introduced that improve recovery from existing fields.
A recent example of  new discoveries are the pre-salt oil reserves off the coast of Brazil in 2009. These are truly vast oil reservoirs below a layer of salt that is up to  6000 ft thick in places. The salt layer absorbs seismic energy so that traditional seismic surveys cannot “see” the oil below the salt layer. This oil was discovered by the very old fashioned method of drilling a wildcat well through the salt to have a look at what was underneath. Almost the entire deepwater area off the coast of Africa, and the whole of the Mediterranean Sea has a similar layer of salt, just waiting to be drilled. The Brazilian fields will come into production in the next couple of years. In 15 years time, Brazilian oil exports will eclipse Saudi exports.
An example of new technology is the discovery of how to release gas trapped in shallow layers of shale. The gas has been known to be in place for many years, but only recent has rock fracturing technology advanced to the point that the gas can be tapped economically. This has resulted in the USA now producing more gas domestically than Saudi Arabia, and this is just the start of the shale gas revolution.
There is enough Shale gas resources in the USA to supply all their energy requirements, including transportation (LPG fuel) for 200 years at the present rate of consumption!
On top of this, recovery factors for oil have continuously increased from just being able to recover 20% of reserves back in the 1950’s to being able to recover about 55% at present- we haven’t worked it out yet, but there is no reason to suppose we cannot continue to improve recovery of known oil in place up to 80% or even more. Many North Sea platforms were due to be scrapped back in the 80’s, yet they are still economically producing oil due to enhanced recovery technology...

Wednesday, 30 March 2011

Tsunamis in the UK

I was interested to read in the MSM recently that the UK was fortunate in that it was "impossible" for us to be hit by a Tsunami like the one that recently devastated Japan.

between six to eight thousand years ago, Great Britain and the northern British Isles was inundated by a huge Tsunami which wiped out  the coast of the North Sea.

Whereas most tsunamis are caused by undersea earth quakes, some are caused by undersea "landslides".

The North Sea tsunami was caused by a huge submarine  landslide off the coast of Norway, and the area is now known geographically as the "Storegga Slide".

There were actually three major slides in the area, the first was around 50,000 years ago(BP), a second one around 22,000 BP, followed by one around 7300BP. This lasttsunami is estimated to have been between 19-25m high in the shetlands, and around 9m high along the coast of NE England.

Here is a computer simulated map of the extent of the slide, with the height of the average "run up" of the Tsunami- (as opposed to recorded peak heights due to wave focus, which were much higher in places such as river mouths etc)

T. Bugge, R. H. Belderson, N. H. Kenyon “The Storegga Slide” Philosophical Transactions of the Royal Society of London 1988

Bernhard Weiniger et al The Castastrophic Final Flooding of Doggerland by the Storegga Tsunami Documenta Praehistorica 2008


The entire global economy is built on credit. if you want to see what the world looks like with out fractional reserve banking and extensive credit, just look to North Korea.

There is no way the western world would have prospered the way it has over the last 120 years  without the humongous credit market.

Thursday, 23 December 2010

Explaining the exponential growth in Technological change

In the 1950'sThe Nobel prize winning economist Solow discovered that about 90% of all economic growth in the USA between 1909 and 1949 was directly attributable to technological invention and innovation.

There is a huge area of economic study related to this discovery and how best to finance R&D- For example, should it all be government funded or privately funded ?

Anyway, my own view is that the exponential growth of knowledge, technology and innovation is directly related to the number of human brains on the planet. As population increases, less communal brain power is dedicated to getting food, and more thinking time is dedicated to things such as how to improve a jet engine's fuel efficiency, or how to make a microprocessor smaller for example. So as population increases, the rate of change in technological innovation also increases. For this reason I am optimistic for the human race. The computing power of 9 billion brains by 2050 are sure to solve most of our pressing problems about environment, sustainable development and the improvement of the human condition.

Sunday, 28 November 2010

Gauge resolution and accuracy

If you have a thermometer with 1 degree centigrade divisions, it is reasonable to say that the thermometer has a resolution of 1c, or +/- 0.5c If the accuracy stated by the manufacturer is 0.5c, then the combined error margin is +/- 1.0c. In this case all temperatures recorded with this thermometer should be rounded up to the nearest 1c. It is impossible to measure 1.5c or 1.75c etc, even if it appears you can do so when you are looking at the thermometer. Even then, you should still remember that your observed recording is +/- 1c.
(need to expand on this at some point)