Shale Gas and Fracking (eBook)

The Science Behind the Controversy

Michael Stephenson (Autor)

eBook Download: PDF | EPUB

2015 | 1. Auflage
170 Seiten
Elsevier Science (Verlag)
978-0-12-801762-3 (ISBN)

Infos

Shale Gas and Fracking: The Science Behind the Controversy explains the relevant geological principles before examining the peer-reviewed evidence and presenting it through a simple and compelling illustrated narrative. Each chapter focuses on a particular controversy, such contamination of well water with gas from fracking, and follows a similar format: starting with the principles; then detailing peer-reviewed case studies for earthquakes, radioactivity, and climate change; and concluding with a judgment of the general risks involved.

Shale Gas and Fracking: The Science Behind the Controversy provides readers with the unbiased information they need to make informed decisions on the controversial issue of fracking.

• Presents a clear and unbiased view of the pros and cons of fracking in Europe and the US, through a simple and compelling narrative from an informed publicly-funded scientist
• Includes full-colour diagrams, photographs, and maps to present information clearly and simply
• Focuses on peer-reviewed, documented examples, particularly of earthquakes and groundwater contamination due to fracking

Mike Stephenson is an expert on Energy and Climate Change and has a unique mixture of modern climate/energy science and policy experience in 'deep time' climate change, and coal/petroleum geology. He has published two books on related subjects and over 80 peer-reviewed papers. His recently published book Shale gas and fracking: the science behind the controversy (Elsevier) won an 'honourable mention' at the Association of American Publishers PROSE awards in Washington DC on 4th February 2016. He is also Editor-in-Chief of the Elsevier Journal Review of Palaeobotany and Palynology. In addition, as Chief Scientist of the British Geological Survey Mike Stephenson has represented UK science interests in energy, as well as providing extensive advice to the UK Government. For example, in October 2013 he was shale gas and carbon capture and storage (CCS) advisor to Sir Mark Walport, Chief UK Government Scientific Advisor, on a fact-finding mission to Texas and Alberta. He gave verbal evidence to the UK House of Lords Select Committee on Economic Affairs inquiry into shale gas on 15 Oct 2013.

Inhalt

Front Cover 1
Copyright 5
DEDICATION 6
CONTENTS 8
PREFACE 10
ACKNOWLEDGEMENTS 12
CHAPTER 1 - 
14 
THE GAME CHANGER 15
THE FLIP SIDE 29
BACK TO THE FACTS? 33
BIBLIOGRAPHY 34
Chapter 2 - Shale, Shale Everywhere 36
HOW SHALE FORMS 37
WORKING OUT HOW MUCH GAS THERE IS 47
RESOURCE AND RESERVE 56
NORTH AMERICA 60
IT ALL SEEMS SO SIMPLE 67
BIBLIOGRAPHY 67
Chapter 3 - To Frack or Not to Frack? 70
FRACKING IN ACTION 73
HOW DO ENGINEERS KNOW WHERE THE FRACTURES GO? 79
SWEET SPOTS 81
BIBLIOGRAPHY 85
Chapter 4 - Gas in Our Water? 86
FRACKING AND GROUNDWATER 88
THE MYSTERY OF THE FLAMING TAP 94
SO IS IT SAFE OR NOT? 99
BIBLIOGRAPHY 100
Chapter 5 - Did the Earth Move? 102
FAULTS AND EARTHQUAKES 105
WATER DISPOSAL AND EARTHQUAKES 109
WHAT IS THE RISK? 110
BIBLIOGRAPHY 110
Chapter 6 - The Shale Gas Factory 112
WHAT DOES IT MEAN FOR ME? 115
NUISANCE OR REAL DANGER? 121
BIBLIOGRAPHY 122
Chapter 7 - Shale Gas and Climate 124
SO SHOULD SHALE GAS BE LEFT IN THE GROUND? 130
DOES SHALE GAS HAVE A PLACE IN MODERN ENERGY? 135
BIBLIOGRAPHY 136
Chapter 8 - Keeping Watch 138
WHO OWNS THE GAS? 141
SOCIAL LICENCE 143
MONITORING FOR CHANGE 146
IMPROVING THE QUALITY OF THE DEBATE 149
BIBLIOGRAPHY 151
Chapter 9 - The Science behind the Controversy 154
THE VALUE OF APPLIED SCIENCE 157
GLOSSARY 160
INDEX 164

Textauszug

Chapter 2

Shale, Shale Everywhere

A few decades ago you would have been hard-pressed to find a geologist that specialised in shale. This grey or black, fine grained sedimentary rock was considered rather boring because to the unaided eye one type of shale looks much like another. But shale has now taken on a new fascination. This is not just because shale is at the heart of a new rush for gas; it’s also because shale conceals many things because it’s so fine grained. In it are the remains of ancient forests and seas of algae. The fine layers – that look like the pages of a book – tell stories of ancient environmental change. The organic matter – the organic mush – that makes it dark in colour is probably one of the largest stores of ancient decayed once-living material on Earth. Just some of this organic mush is responsible for the gas that’s produced by fracking. In this chapter I’ll look at the formation of the shale itself, how the organic mush got in there, and how we can work out how much gas shale can produce. Then I’ll explain why some places have a lot of shale gas while others have less.

Keywords

Barnett; Carbon; Fracking; Marcellus; Reserve; Resource; Shale; Source rock; Unconventional

Contents

How Shale Forms 24

Working Out How Much Gas There Is 34

Resource and Reserve 43

North America 47

Barnett Shale 47

Marcellus Shale 47

Eagle Ford Shale 50

Haynesville Shale 52

Fayetteville Shale 53

Muskwa (Horn River) Shale and Montney Shale in Canada 54

It All Seems So Simple 54

Bibliography 54

I’ll start with the disconcerting fact that a lot of geologists don’t even like the word ‘shale’ – because it has never been strictly defined. A geologist interested in sedimentary rocks – the kind of rocks deposited at the bottom of seas, lakes or in river valleys – would probably prefer the term ‘fissile mudrock’. This technical term is a bit obscure but it does convey some of what shale is. It’s made of very small particles – like in mud for example – and you can split it into flat pieces.

Both of these characters – the small particles and the fine layering – are inherited from the way shale forms and they strongly influence the way it generates shale gas.

How Shale Forms

If you did any geology at school it’s likely that you studied the rock cycle (Fig. 2.1). This is a simple representation of the way that all rocks are connected. Igneous rocks from volcanoes are weathered and eroded and their broken up remains get transported by rivers and landslides to seas and lakes where the pieces are deposited. The layers of deposits are called sediments. These get buried deeper and deeper under more sediment that keeps arriving and then they turn into harder more compact versions of themselves called sedimentary rocks. Sometimes if they’re buried very deep they turn into metamorphic rock because of deep Earth heat and pressure. Deep rocks can get melted and included in deep magma and find their way back out onto the Earth’s surface as lava, or can just be revealed by long periods of erosion. So the whole thing goes in a cycle.

Figure 2.1 The rock cycle. From the Geological Society of London’s Website. http://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3445.html.

To understand shale we have to see a little further into the formation of sediments. Those that are made of fragments of earlier rocks are either made of big fragments (they are coarse grained) or fine fragments (fine grained).

The fine-grained sedimentary rocks tend to be deposited far away from their sources – far from the land or mountains that they originally came from. This is a simple principle – that smaller particles can be transported by rivers further from their source than can larger particles – because they are lighter. So shale tends to be formed under deep seas and lakes a long way from the land (though there are exceptions).

There’s a chemical aspect to the formation of shale also. In fact the original fragments of rock that are carried in rivers to the deep sea and lakes undergo quite a lot of degradation on the way. The minerals that make up the fragments are attacked and transformed into other minerals, usually clay minerals. These are complex but very stable, in other words they aren’t likely to degrade any more. They can sit on the sea bed for a long time without changing, and then get buried under sediments that are always being fed in by rivers. So big piles of fine-grained mud collect, made up of a lot of stable clay minerals. This slowly hardens into shale. Over very long periods really huge thicknesses (several miles) of shale can accumulate.

What gives shale its fine layers? If you look closely at it, the layers are really fine laminations. These allow the shale to split, rather like the grain in wood. The laminations are very thin though. The photograph taken with a microscope (Fig. 2.2) shows a view that is less than 1 mm across so the individual layers of dark brown, light brown and light grey are only around a tenth of a millimetre thick. When you split shale with a knife or a finger nail you’re spitting between these layers.

The shale has these laminations for a couple of reasons. Perhaps the most important is that the clay minerals that make up some of its bulk are naturally flat in shape or ‘platey’ as they are sometimes called. These tiny mineral fragments are lying flat on top of each other in the shale, piled up like minute coins. The other constituents of the shale – the remains of once-living material like plants and algae and particles of sand and silt – are also squashed in the layers, mainly because of the weight of sediments that begin to accumulate above them. It’s this squashing from above that squeezes the shale into a laminated, layered texture a bit like the pages of an old book (Fig. 2.3).

As you might expect from the wide extent of the places where it is first deposited in oceans and in large lakes, shale is a very common sedimentary rock (Fig. 2.4), much more common than the coarser grained sedimentary rocks like sandstone that are deposited nearer to the sediment source. In fact shale is the most common, making up 35% of rocks at the Earth’s surface. So shale isn’t rare or unusual. It’s ability to generate gas (or oil) has also been known for a very long time, in fact for most oil and gas geologists shale is what’s known as a source rock. But more of that later.

Figure 2.2 Layers or laminations in shale. The sideways span of the photo is about 1 mm. This is relatively young Palaeocene shale around 55 million years old deposited in the ancient North Sea. Photo M. Stephenson.

Figure 2.3 Layers of dark grey shale on a typically rainy day in the English Pennine hills. This shale outcrops in the Pennines but is present to the east and west in the deep subsurface where it is prospective for shale gas. Photo M Stephenson.

Figure 2.4 The occurrence of shale at the Earth’s surface. Data from Pettijohn (1975).

Perhaps the most interesting part of the shale is the organic material it contains. Up to now I’ve been calling it mush which is clearly not a technical term but is quite appropriate. Alongside all the clay minerals and rock fragments in those ancient rivers, lakes and seas, there were a lot of small bits of once-living material – from trees, shrubs, fungi, algae, even insects and other land and sea animals. This mush gets dumped with the clay minerals and rock fragments and is completely mixed up with it. The very dark brown and black material in the microscope photograph in Fig. 2.2 is mostly organic material. Because it’s very broken up and decayed, it’s difficult to see precisely where the organic material has come from but careful study can help.

One of the ways we can study the organic material is to isolate it by dissolving the clay minerals, silt and sand particles from the rock so that only the organic material remains. This can be done by treating shale samples with hydrofluoric acid. After a few weeks all the rock apart from the organic material is dissolved. If you take the organic material that’s left (it’s usually about 1% or 2% of the weight of the rock) and spread it onto a microscope slide, it looks as shown in the microscope photo in Fig. 2.5. This picture which spans about half a millimetre, shows some of the particles that make up the organic matter.

The particles are very small and not immediately recognisable. However with careful observation it’s possible to see that the elongated black particles are tiny fragments of ancient wood – in this case around 330 million years old! A scanning electron microscope can show some of the ancient structures of the wood and even help to identify the kinds of tree that produced the wood. The circular yellow-brown objects (like the one with the red arrow) are tree spores, perhaps spores from the same tree that produced the wood. These are less than a twentieth of a millimetre in diameter. There are other spores in...

Produkt-Details

• Erscheint lt. Verlag: 2.2.2015
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geologie
• Themenwelt: Technik ► Bauwesen
• ISBN-10: 0-12-801762-7 / 0128017627
• ISBN-13: 978-0-12-801762-3 / 9780128017623