̽��ֱ�� of Cambridge - oil

What makes a sand dune sing?

sc604 — Fri, 04 Nov 2016 08:50:28 +0000

For Marco Polo, the desert could be a spooky place, filled with evil spirits. Writing in the 13th century, he described the famous singing sands, which “at times fill the air with the sounds of all kinds of musical instruments, and also of drums and the clash of arms.” But the low, loud rumbles coming from the dunes were not the work of spirits. They were the work of physics.

As grains of sand slide down the side of certain dunes, they create vibrations that can be heard for miles around. ̽��ֱ��sand avalanches trigger the dune’s natural resonance, but only when conditions are just right. It can’t be too humid, and the grains of sand need to be just the right size and contain silica. Only then will an avalanche cause the dunes to start singing.

An avalanche, whether it’s made of sand or snow, is an example of a granular flow, when solid particles flow like liquids, colliding, bouncing around, interacting, separating and coming back together again. Granular flow processes can be found everywhere from the world’s highest mountains to your morning bowl of cereal.

Dr Nathalie Vriend, a Royal Society Dorothy Hodgkin Research Fellow in the Department of Applied Mathematics and Theoretical Physics, is a specialist in granular flows. Her PhD research at the California Institute of Technology unravelled some of the physics at work in the same singing sands that mystified Marco Polo. At Cambridge, her research focuses both on sand dunes and on avalanches, and how to quantify their behaviour, which can have practical applications in industries including pharmaceuticals, oil and gas. Vriend’s work relies as much upon laboratory experiments and fieldwork as it does on mathematical models.

“An avalanche can behave as a solid, liquid or gas, depending on various factors, which is what makes them so difficult to model mathematically,” says Vriend. “For me, modelling their behaviour starts with observation, which I then incorporate into a model – it’s nature where I get my inspiration from. That, and curiosity – I see something and I want to try to explain it.

“Since there are particles which collide and interact in a granular flow, there is a certain degree of randomness to the process, so how do you incorporate that into a model? You try to translate what you’re seeing into a physical description, and then you perform numerical or theoretical simulations to see if the behaviour you get from the models is the same as you observe in nature.”

Despite their somewhat chaotic nature, avalanches and other types of granular flows share some distinct patterns. Owing to a phenomenon known as segregation, larger particles tend to rise to the top in an avalanche, whereas smaller particles sink to the bottom, falling into the gaps between the larger particles. A similar phenomenon can be seen in your breakfast cereal: the smaller, tastier bits always seem to end up at the bottom of the bowl. Larger grains are also pushed to the side and the front, forcing the flow of the avalanche into channels.

Similar processes are at work in sand dunes. As wind blows across a dune, there is segregation of the individual grains of sand, as well as small avalanches taking place on the granular scale. But for a sand dune that is 40 m high, there are also processes taking place on the macro scale. ̽��ֱ��entire dune itself can move and race across the desert floor. Small dunes migrate faster than large dunes, as if playing a “catch me if you can game”.

A cross section of a typical sand dune would reveal a slope on one side of a ridge, and a sharp drop on the other. As the wind blows across the dune, it pushes grains of sand up the slope, where they gather in a heap. When the heap gets too big, it becomes unstable and tumbles over the other side, causing an avalanche, eventually coming to a stop. This process happens again and again, causing layers to form within the dune. “A sand dune may look like a monolithic mass of sand, but there are multiple layers and structures within it,” says Vriend.

How does this understanding of the anatomy and movement of a sand dune translate into practical applications? Understanding granular flows can be useful in the pharmaceutical industry, where two different active ingredients may need to be mixed properly before a pill is made. Granular flows are also highly relevant to the oil and gas exploration process, and with this in mind Vriend is working with Schlumberger, the oilfield services company.

Sand dunes are major sources of noise in seismic surveys for oil and gas in deserts, which are conducted to probe the location and size of underground oil and gas reserves. ̽��ֱ��surveys use an acoustic pulse from a source and carefully placed receivers at different points to listen to the signal that is received, which can then be used to calculate what is hidden underground. ̽��ֱ��problem encountered by surveyors is that the sand dunes are composed of loose sand and therefore have a much lower wave velocity than the rocky desert floor, and as a result they act as traps of wave energy: the energy keeps reverberating and creates a source of noise in the post-processing of the seismic surveys. As part of a secondment at Schlumberger, one of Vriend’s PhD students is performing numerical simulations to understand the origin and features of this noise.

Another industrial problem that Vriend’s group is currently working on is the phenomenon of ‘honking’ grain silos. As grains are let out of the bottom of a silo, the friction of the pellets on the walls of the silo makes a distinctive ‘honking’ sound. Annoying for the neighbours perhaps, but hardly dangerous. However, when the vibrations get loud enough, it can cause a resonance within the silo, leading to structural failure or collapse. Vriend’s students are attempting to understand what affects the way that silos honk, which could someday be used to minimise noise, or even to prevent collapse.

̽��ֱ��phenomenon behind honking silos on a busy farm is similar to that which causes massive desert sand dunes to sing, although one could be perceived as an annoyance while the other is considered captivating. For Vriend, however, it’s the real-world observations and the opportunity to spend time in nature that motivate her.

She explains: “What I love about my research, whether it’s looking at silos or avalanches, is that you can observe it, see it, feel it, touch it.”

Inset images: Avalanche Zinal, credit: dahu1. Slip face GPR, credit Matthew Arran.

When solids flow like liquids they can make sand dunes sing, and they can also result in a potentially deadly avalanche. Cambridge researchers are studying the physics behind both of these phenomena, which could have applications in industries such as pharmaceuticals, oil and gas.

A sand dune may look like a monolithic mass of sand, but there are multiple layers and structures within it

Nathalie Vriend

̽��ֱ��District

Sand dune

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Bacteria in the world’s oceans produce millions of tonnes of hydrocarbons each year

sc604 — Mon, 05 Oct 2015 19:00:00 +0000

An international team of researchers, led by the ̽��ֱ�� of Cambridge, has estimated the amount of hydrocarbons – the primary ingredient in crude oil – that are produced by a massive population of photosynthetic marine microbes, called cyanobacteria. These organisms in turn support another population of bacteria that ‘feed’ on these compounds.

In the study, conducted in collaboration with researchers from the ̽��ֱ�� of Warwick and MIT, and published today (5 October) in the journal Proceedings of the National Academy of Sciences of the USA, the scientists measured the amount of hydrocarbons in a range of laboratory-grown cyanobacteria and used the data to estimate the amount produced in the oceans.

Although each individual cell contains minuscule quantities of hydrocarbons, the researchers estimated that the amount produced by two of the most abundant cyanobacteria in the world – Prochlorococcus and Synechococcus – is more than two million tonnes in the ocean at any one time. This indicates that these two groups alone produce between 300 and 800 million tonnes of hydrocarbons per year, yet the concentration at any time in unpolluted areas of the oceans is tiny, thanks to other bacteria that break down the hydrocarbons as they are produced.

“Hydrocarbons are ubiquitous in the oceans, even in areas with minimal crude oil pollution, but what hadn’t been recognised until now is the likely quantity produced continually by living oceanic organisms,” said Professor Christopher Howe from Cambridge’s Department of Biochemistry, the paper’s senior author. “Based on our laboratory studies, we believe that at least two groups of cyanobacteria are responsible for the production of massive amounts of hydrocarbons, and this supports other bacteria that break down the hydrocarbons as they are produced.”

̽��ֱ��scientists argue that the cyanobacteria are key players in an important biogeochemical cycle, which they refer to as the short-term hydrocarbon cycle. ̽��ֱ��study suggests that the amount of hydrocarbons produced by cyanobacteria dwarfs the amount of crude oil released into the seas by natural seepage or accidental oil spills.

However, the hydrocarbons produced by cyanobacteria are continually broken down by other bacteria, keeping the overall concentrations low. When an event such as an oil spill occurs, hydrocarbon-degrading bacteria are known to spring into action, with their numbers rapidly expanding, fuelled by the sudden local increase in their primary source of energy.

̽��ֱ��researchers caution that their results do not in any way diminish the enormous harm caused by oil spills. Although some microorganisms are known to break down hydrocarbons in oil spills, they cannot repair the damage done to marine life, seabirds and coastal ecosystems.

“Oil spills cause widespread damage, but some parts of the marine environment recover faster than others,” said Dr David Lea-Smith, a postdoctoral researcher in the Department of Biochemistry, and the paper’s lead author. “This cycle is like an insurance policy – the hydrocarbon-producing and hydrocarbon-degrading bacteria exist in equilibrium with each other, and the latter multiply if and when an oil spill happens. However, these bacteria cannot reverse the damage to ecosystems which oil spills cause.”

̽��ֱ��researchers stress the need to test if their findings are supported by direct measurements on cyanobacteria growing in the oceans. They are also interested in the possibility of harnessing the hydrocarbon production potential of cyanobacteria industrially as a possible source of fuel in the future, although such work is at a very early stage.

Reference:
Lea-Smith, D. et. al. “Contribution of cyanobacterial alkane production to the ocean hydrocarbon cycle.” PNAS (2015). DOI: 10.1073/pnas.1507274112

Scientists have calculated that millions of tonnes of hydrocarbons are produced annually by photosynthetic bacteria in the world’s oceans.

This cycle is like an insurance policy – the hydrocarbon-producing and hydrocarbon-degrading bacteria exist in equilibrium with each other

David Lea-Smith

Image courtesy SeaWiFS Project

Global chlorophyll

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Benefits by the barrel

bjb42 — Sat, 09 Apr 2011 08:00:21 +0000

Being an oil-rich country is not a curse, but the volatility of oil income can prevent a country from capitalising on its assets, according to a new series of studies by economists including Gates alumnus Kamiar Mohaddes [2005].

̽��ֱ��study, Does oil abundance harm growth?, published in the journal Applied Economics Letters, argues that previous assumptions that oil abundance is a curse were based on methodologies which failed to take into account cross-country differences and dependencies arising from global shocks, such as changes in technology and the price of oil.

Kamiar says: “ ̽��ֱ��idea that oil and resource abundant countries are cursed, the so-called ‘resource curse paradox’, has been around for some time and is based largely on the experiences of countries in Africa and the Middle East. But if you have a certain level of income and suddenly you discover billions of dollars worth of oil that will last you for decades, why should you be made worse off?”

̽��ֱ��researchers studied data from the World Bank over the period 1980 to 2006 for 53 countries, covering 85% of world GDP and 81% of world proven oil reserves. They found that oil abundance positively affected both short-term growth and long-term income levels.

̽��ֱ��researchers from the ̽��ֱ�� of Cambridge's Faculty of Economics also have a grant from the Economic Research Forum (ERF) to investigate the impact of commodity price volatility on economic growth. Using data on 118 countries over the period 1970-2007, they discovered that it is the volatility in commodity prices, rather than abundance per se, that drives the resource curse paradox. These results are to be published as an ERF working paper entitled Commodity price volatility and the sources of growth.

̽��ֱ��research suggests the importance of diversifying exports away from a handful of primary commodities to technology intense goods. It also suggests that resource abundant countries could manage the volatility better by investing oil revenues in sovereign wealth funds to use at a later date.

“This volatility channel of impact has been overlooked in the literature despite the fact that countries specialising in the export of just a few primary products are usually exposed to substantial commodity price uncertainty and macroeconomic instability,” says Kamiar. “What we hope is that policymakers will use this research to put more emphasis on better management of resource income volatility to create a more stable macroeconomic framework.”

Kamiar's PhD in Economics was funded by a Gates scholarship.

Countries rich in oil have long been associated with the "resource-curse paradox" - a principle which states they will suffer, rather than benefit, in the long run. Not so, new research by a Cambridge Gates scholar suggests.

We hope that policy-makers will use this research to put more emphasis on better management of resource income volatility.

Kamiar Mohaddes

Clinton Steeds from Flickr

Oklahoma Sunset Oil Well

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

‘Elephant hunting’ with less risk

lw355 — Sat, 01 Aug 2009 15:30:21 +0000

Increasingly, companies such as BP are exploring for oil in very deep waters along the edges of the continents. Drilling beneath the seabed through rocks down to depths of 4 km and in water depths of nearly 3 km is both risky and costly. Scientists at the Bullard Laboratories in the Department of Earth Sciences are helping to reduce the uncertainty of finding oil in these hostile environments by developing an understanding of the structure and evolution of the Earth’s tectonic plates.

Dr Nicky White leads a project funded by BP that studies the prime focus of deep-sea oil exploration: submerged continental margins at the edges of ocean basins. It is in these regions that the thinning of the tectonic plate over many millions of years has generated rock layers and structures that have favoured oil formation and trapping. Over time, organic-rich rocks produce oil, which is expelled upwards, where it fills the pore spaces of a reservoir rock and is trapped in place by overlying impermeable rocks. For oil generation, it is crucial that the organic-rich rocks have been subjected to suitable temperatures for the right amount of time (thermal maturation) and it is here that Dr White’s group is providing invaluable new understanding.

̽��ֱ��laboratory’s track record of active involvement with BP reaches back to Professor Dan McKenzie, whose fundamental work on plate tectonics in the 1970s and 1980s helped BP undergo a major refocus on exploring sedimentary basins around the world. Within 10 years, BP’s search for giant oil fields in frontier areas – known in the industry as ‘elephant hunting’ – resulted in a string of exploration successes in places such as the Gulf of Mexico, Angola, Egypt, Russia and Azerbaijan.

Dr White’s work continues this pioneering geophysical research, generating sophisticated numerical models of sub-surface conditions. Working with BP has been key to the research, as Dr White explained: ‘A quantitative understanding of thermal maturation is only possible with access to terabytes of high-quality seismic data. BP acquires amazing sub-surface images that we then interpret and model.’

With billions of dollars at stake, reducing uncertainties in oil exploration will help BP to continue their century-long success in exploration and production, bringing new reserves on stream to compensate for depleting global inventories.

For more information, please contact Dr Nicky White (nwhite@esc.cam.ac.uk).

Cambridge scientists are helping to improve the chances of success of oil exploration in some of the Earth’s most hostile frontiers.

Ross Hartley

Acoustic image

Energy giant BP looks to its engagement with universities like Cambridge to help stay connected to cutting-edge research in science and technology.

‘As head of BP’s research and technology portfolio, my job is to ensure that BP has the technology it needs to contribute to the world’s future energy demands,’ said David Eyton, BP Group Head of Research & Technology and Executive Sponsor for Cambridge. ‘As part of this, we work closely with a handful of excellent academic centres like Cambridge to keep us plugged into the fast-changing world of science and technology.’

BP’s relationship with the ̽��ֱ��, which stretches back through the past century, was recently formalised by the signing of a Memorandum of Understanding (MoU). ‘ ̽��ֱ��MoU,’ David Eyton explained, ‘embraces all of our current interactions with Cambridge at a strategic level – from research activities, through policy development and training, to recruitment – as well as laying the groundwork for mutual support and development so that the relationship can fulfil its greatest potential.’ These interactions are being overseen by Andy Leonard in his role as BP’s Vice-President for Cambridge.

Valuing research

BP’s annual spend for 2009 across the ̽��ֱ�� is £3.6 million, of which approximately £1 million is funding technical research and the remainder is principally funding endowments and scholarships.

̽��ֱ��company’s main channels of engagement are the BP Institute for Multiphase Flow, established in 2000 with a £22 million endowment from BP, and Judge Business School through the Centre for India and Global Business and the Cambridge Centre for Energy Studies. BP has also had long and fruitful collaborations elsewhere in the ̽��ֱ��, especially with the Bullard Laboratories within the Department of Earth Sciences.

Several areas of applied research activities in Cambridge have brought world-class expertise to bear on practical issues that have reaped immediate benefits for BP, from exploration through to fuels and lubricants. But BP also views fundamental research as strategically important: ‘Although fundamental research can take years from invention to commercialisation, it also has the potential to yield something truly significant,’ said Eyton. ‘ ̽��ֱ�� ̽��ֱ�� has a fabulous track record of creating important knowledge and that is one of the reasons we are investing in Cambridge. As a business, we have to stay competitive and invest in areas that we believe will benefit our shareholders.’

Recruiting the best

Recruitment is very much part of the strategic relationship with Cambridge. ‘ ̽��ֱ��people we recruit today could have a profound impact on the company over many decades,’ explained Andy Leonard, ‘so we need to ensure that the highest quality students are exposed to the range of employment opportunities within BP.’ Also of importance, partly from a recruiting perspective, is the large number of scholarship programmes BP runs for research students, mainly in collaboration with the Cambridge Commonwealth and Overseas Trusts. This year, BP has made job offers to 20 graduates and 17 interns in Cambridge, as well as partially funding 49 research scholarships.

Recognising opportunities

‘ ̽��ֱ��key to success in strategic relationships is to create situations where there is genuine mutuality,’ said Eyton. ‘We want the relationship with Cambridge to achieve its greatest potential and to progress the strategic aims of the ̽��ֱ�� and BP.’ ̽��ֱ��company is also keen to support the strengthening of links between universities such as Cambridge, the Massachusetts Institute of Technology (MIT) and Tsinghua ̽��ֱ�� in Beijing, predominantly with regard to finding new forms of low carbon energy and moving towards a more sustainable energy landscape in the world.

‘I am a big believer in investing in places like Cambridge that have a proven record of success,’ explained Eyton. ‘I also think that we have even more to discover in terms of opportunities for productive interactions. I’m delighted to say that we are on this journey.’

For more information about BP, please visit www.bp.com/

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

BP Institute for Multiphase Flow

lw355 — Sat, 01 Aug 2009 15:10:59 +0000

Endowed by a £22 million donation from BP, the BP Institute for Multiphase Flow (BPI) was created in 2000 with the explicit intent of hosting research teams from five departments within the ̽��ֱ��: Applied Maths and Theoretical Physics, Chemical Engineering, Chemistry, Earth Sciences and Engineering.

Today, a multidisciplinary team of almost 40 academics and students is working to understand how gases and fluids move. Multiphase flow is an area of great interest to BP as it underpins all parts of its business: from enhancing oil recovery to delivering it to customers, and from refining hydrocarbons to investing in a low carbon future.

For the BPI, engagement with BP enriches research in a very practical sense, as Professor Andy Woods, Director, explained: ‘Our close working relationship with BP gives us in-depth exposure to technical challenges in the industry as well as unparalleled access to field data that would be impossible for us to collect. This means that we can frame research directions that are fundamentally interesting to us as academics and can also solve problems that are of relevance to the industry.’

Currently, a large pan-Institute project is analysing the interactions between fluids and solids in oil fields to understand the physical chemistry that controls how much oil can be recovered as a function of the salinity of the water used to pump it from the well. Other projects vary from analysing the molecular basis of how lubricants work to understanding how volcanoes erupt, and from addressing questions about the long-term storage of CO₂ in redundant oil wells to determining how you can control heat transfer in buildings through natural convection. This latter research theme led in 2006 to the spin-out company E-Stack, which was set up to commercialise a low energy ventilation system that uses natural convection to keep the interior temperature of buildings buffered from exterior changes.

Professor Woods sees the link between basic research and industrial applications as key to research at BPI. ‘We determine our own research programme and our prime interest is in answering fundamental questions about flow. But we’re also looking at how this impacts on ‘real world’ applications because this in turn informs a whole new set of fundamental questions and, if we’re lucky, the development of unforeseen applications.’

For more information, please contact Professor Andy Woods (andy@bpi.cam.ac.uk) or visit www.bpi.cam.ac.uk/

Understanding flow – whether it’s of oil, air, lubricants, lava, seawater or CO2 – lies at the heart of Cambridge’s BP Institute.

Our prime interest is in answering fundamental questions about flow. But we’re also looking at how this impacts on ‘real world’ applications because this in turn informs a whole new set of fundamental questions and, if we’re lucky, the development of unforeseen applications.

Professor Andy Woods

̽��ֱ�� of Cambridge

BP Institute

Energy giant BP looks to its engagement with universities like Cambridge to help stay connected to cutting-edge research in science and technology.

Valuing research

Recruiting the best

Recognising opportunities

For more information about BP, please visit www.bp.com/

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes