The first edition of Petroleum Geoscience was published in 2004 having taken 10 years to write. This second edition was requested by the publishers in 2009 and again it has taken 10 years to update and write. During the time we took to write the first edition there were incremental changes to the petroleum industry, many of which we incorporated into the text as they happened. However, since 2004 the petroleum industry has undergone two radical changes as well as the incremental changes associated with improvements in technology.

The production of shale-oil and shale-gas (sometimes referred to as “unconventional” hydrocarbons) has changed the world in terms of the relationship between supply and demand for petroleum and in turn this has influenced global energy politics.

The production and combustion of petroleum and coal has changed the world in terms of the concentration of carbon dioxide in the atmosphere – now almost double pre-industrial levels. As a consequence our climate is changing. We must use less petroleum and mitigate the effects of that which is used if we are to maintain a habitable planet for all of humanity.

We will address both climate change and shale-oil/shale-gas in this preface but first let us reflect on some profound changes in our own employment circumstances in these past 10 years.

JG was in 2004 a director of Acorn Oil and Gas, a company he helped found. By late 2005 Acorn had been sold and a new company, Fairfield Energy formed. Fairfield inherited from Acorn the abandoned Maureen Field in the Central North Sea, a field of interest to a start-up company wishing to use Maureen for the geo-storage of carbon dioxide (carbon capture and storage, CCS) from a planned new power station on Teesside, north east England. The power plant was not built but industrial support for a new post at Durham University, the chair in Geoenergy and CCS, led JG to switch from industry to academia in 2009 and join the Earth Sciences Department at Durham University where he has since served as Head of Department, Dean of Knowledge Exchange, and Executive Director of the Durham Energy Institute.

RS was Reader in Petroleum Geology at Durham University in 2004, but also Founder and Managing Director of a small university start-up company, GeoPressure Technology. In 2005 he moved to work full-time with GeoPressure Technology located on the university Science site. Later GeoPressure Technology merged with Ikon Science and from 2010–2013 RS was the Global Director of GeoPressure & Geomechanics at Ikon Science. In 2013 RS left to set up his own consultancy and training company, but he is planning to retire from paid employment soon!

In the 16 years, since the first edition of this book was published, the USA has switched from being the world's largest importer of petroleum and derivative products to a modest exporter of petroleum liquids and liquified gas. This in turn led to a collapse in oil prices between 2014 and 2016 (and collateral fall in the value of coal) as competition for global market share led OPEC to try to regain the upper hand. The switch of the USA from importer to exporter of petroleum is also mirrored by the USA's foreign policy from expansive and global to introverted – it no longer needs to buy the petroleum produced by other countries.

The turnaround in petroleum production in the USA comes from the development of shale-gas and shale oil, principally facilitated by development of hydrofracturing along horizontal wells. Gas and oil are now produced from rocks, mainly hydrocarbon source rocks, once considered too impermeable to flow. Advances in drilling and completion technology have opened up vast areas of the USA (and Canada) for exploitation of this hard-to-produce resource. Other countries such as Argentina and China are beginning to exploit their resources too, but all are around 20 years behind the USA. Given the vast areas yet to be exploited in the USA and other countries it would seem the shale-gas and shale-oil revolution is a long way from being finished.

While much of the world still craves petroleum and other energy-dense fuels such as coal, the damage to the Earth's atmosphere from burning fossils fuels has become only too apparent. Carbon dioxide released to the atmosphere from burning coal, oil, and gas has led to a near doubling of the concentration of CO₂ in the atmosphere (now at >400 ppm) since the beginning of the industrial revolution. The increase in CO₂ and other greenhouse gases such as methane (vented and accidental leakage) is driving climate change and in particular global warming and ocean acidification. In the most recent report form the Intergovernmental Panel on Climate Change (2018) we are faced with the stark reality that humanity has little more than a decade to decarbonize its energy industry or face the irreversible consequences of increased temperatures, rising sea-levels, and significant losses of biodiversity.

And so, the largest change to occur for the petroleum industry is one of perception. To many, especially in the developed parts of the world, fossil fuels (oil, coal, and gas) are seen as bad – enemies of the environment. Greenpeace, Friends of the Earth, and other environmental lobby and projection groups have gone mainstream and in 2019 Extinction Rebellion emerged as a new force in the quest to minimize climate change. The response of many multinational oil giants as well as some of the even larger national petroleum companies has been enlightening. Business models are changing, such companies are describing themselves as “energy companies” rather than oil companies and while this may be regarded as superficial given that most expenditure still goes into finding and producing petroleum, new business streams are emerging, not least the Oil and Gas Climate Initiative (OGCI). Formed from oil majors, OGCI will begin to capture and bury carbon dioxide in industrial quantities, something that most national governments have failed to do. It seems unlikely that enough will be done to prevent major impacts from climate change – time will tell.

The problem with lessening humanity's dependence on petroleum consumption is that it has underpinned almost everything we do as a modern society. The energy density of oil and gas and the ease with which it is transported make it the energy product of choice for most applications, including transport and heating/cooling. In energy terms, petroleum is energy dense, much more so than geothermal fluids, a windy day, a lithium battery, or the sun shining upon our PV panels: it is difficult not to choose petroleum for one's energy needs. That said, and driven by real concerns about the impacts climate change will bring, carbon capture and storage, solar and geothermal energy will emerge as important energy vectors in a rapidly changing market. We have included geothermal energy and CCS sections within our new final chapter. Beyond petroleum, former petroleum geoscientists will be in demand to help realize the worth of hot water, develop storage space for CO₂, and deliver the basic materials for a cleaner world.

Wemet at AAPG London 1992 and, unknown to each other at the time, we were both facing similar problems with respect to teaching petroleum geoscience within the industry (J.G.) and academia (R.S.). The main problem was the paucity of published information on the basics of the applied science—how the geoscientist working in industry does his or her job, and with which other disciplines the geoscientist interacts. R.S. had already taken steps to remedythis with a proposal for a book on petroleum geoscience sent to Blackwell. The proposal was well received by reviewers and the then editor Simon Rallison. Simon sought an industry-based coauthor and found one in J.G. At that time, J.G. was teaching internal courses at BP to drillers, reservoir engineers, petroleum engineers, and budding geophysicists with a physics background. Simon's invitation was accepted and by early 1994 work had begun. It seemed like a good idea at the time, but the petroleum industry was changing fast, nowhere more so than in the application of geophysics, stratigraphicgeology, and reservoir modeling. The use of 3D seismic surveys was changing from being rare to commonplace, 4D time-lapse seismic was being introduced, and multi-component seismic data was also beginning to find common use. Derivativeseismic data were also coming to the fore, with the use of acoustic impedance, amplitude versus offset, and the like. The application of sequencestratigraphic principles was becoming the norm. Reservoir models were increasing in complexity manifold, and they were beginning to incorporate much more geologic information than had hitherto been possible. Along side the technological changes, there were also changes in the business as a whole. Frontier exploration was becoming less dominant, and many geoscientists were finding themselves involved in the rehabilitation of old oilfields as new geographies opened in the former Soviet Union and South America. It was tough to keep pace with these changes in respect of writing this book, but as the writing progressed it became even clearer that information on the above changes was not available in textbooks. We hope to have captured it for you! This book is written for final-year undergraduates, postgraduate M.Sc. and Ph.D. students, and non-geologic technical staff within the petroleum industry.

Producing a second edition of Petroleum Geoscience has been a long, arduous and at times thankless journey, unassisted by numerous changes in computer hardware and software since the first edition was produced. With help from Wiley we eventually managed to track down image files of the original figures but for many they were originally constructed using software that no longer exists, or at least was not accessible to us. Editing was not an option. We had to start from scratch. We thank Antony Sami and a string of earlier editors at Wiley for digging deep into archives inherited from Blackwell to find most of the original material.

Mike Bowman (long-term BP employee and now retired) was a huge help with the first edition and he was on hand to supply most of the material we needed for the new Thunder Horse case history in Chapter 4. We also need to thank senior staff at Lundin for verifying the material used in the Johan Sverdrup case history (Chapter 3) and at Tullow for the review of the information used in the Jubilee case history (Chapter 3).

The biggest thanks though go to Theresa Gluyas and Alison Swarbrick, our wives. That we have now completed the second edition is down to their support, encouragement, and at times well-directed instructions to, “get on with it,” thank you!