Getting A Handle On The

Big Numbers . . .

Remember the headlines in the summer of 2015? “100 billion barrels of oil found under Gatwick!”


Well, it’s oil, so that’s good news. And 100 billion sure sounds like a big number. So we should be excited, right? But what does it actually mean? Where does it fit in? UK crude oil consumption in 2012 was 1,520,000 barrels per day. That’s about 555 million barrels per year. Like interstellar distances, or atomic scales, millions of barrels is not a quantity that most of us are readily able to visualise.


I like to think of it in terms I can understand. The town where I live, a typical UK ‘market town’, has a recreational swimming pool. The pool is 25 metres long, 1.5 metres deep, on average, and 10 metres wide, giving a volumetric capacity of 375 cubic metres. 1 cubic metre contains 6.23 barrels, so our pool could hold 2,336.25 barrels of oil. It would keep the UK running for 2 minutes and 13 seconds, or four millionths of a year. That’s not really any more accessible. Let’s apply the same principle to something a little larger.


The northern tower of the original World Trade Centre (WTC) had a floor area of 4,020 square metres, and it was 417 meters high. A tank that size would hold 10.4 million barrels. So we can say that the UK’s oil consumption can be visualised as approximately 1 WTC (North) tower per week.


For all the wrong reasons, most people are able to visualise the WTC (North) tower, and the number of weeks in a year is something that most of us are comfortable with.  Combining those two gives us a manageable handle on what 555 million barrels of oil actually represents.


It is interesting to contemplate how that quantity of oil relates to reservoir size.  Remember that the oil we can hope to recover from a reservoir using today’s technology is a maximum of 25% of the oil in place.  So we need a reservoir containing 2.2 billion barrels of oil in place to keep the UK going for a year. We know, of course, that there are no lakes of oil under the ground. Oil is contained in the inter-granular spaces of reservoir rocks. Let’s say this inter-granular space is 10% of the total material volume – it’s not so unrealistic, it keeps the maths simple and it tells us that we need a reservoir volume of 22 billion barrels, or 3.5 billion cubic meters. 

To get an idea of the size of that reservoir in real world terms, consider the following. AnTech is headquartered in Exeter, Devon, a smallish UK city covering 18 square miles, or 47 million square metres.  Whilst Devon is not renowned for its oil prospectivity, we can hypothesise a reservoir thousands of feet below Exeter’s streets. To provide enough oil to keep the UK supplied for a year, that reservoir would need to be 74.5 metres thick.


Of course the picture is never that simple in real life. A reservoir that had ‘just’ 555 million barrels recoverable would be expected to yield that total volume over a number of years, with the initial production declining to a threshold of economic viability as the total recoverable volume is approached.  The initial production rate, the shape of the decline cure and the length of the tail are strongly dependent on the reservoir characteristics and the amount of reservoir exposed by the well(s) draining it.


Similarly, while initial exploration has determined that there is 100 billion barrels of oil in place below Gatwick, the proportion of that oil that will ever be recovered, and the rate at which it is extracted is strongly dependent on the mobility of the oil in that location, and the technologies that we are allowed to use to get to it. But that is a subject for another blog post. 

Author: Richard Stevens

Published: 16th January 2017



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Wednesday 8th November 2017 at 12:21pm

The method & figures you used to describe the quantity is really impressive.Way of describing the requirement of oil on this discovery is quite impressive. It seems that it's not easy to just say that there is a discovery of 'x million' or 'z billion' oil until you haven't not sure to bring up last drop oil from it's source.

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Toni’s business focus remains the same today as it was when he founded AnTech in 1992: to lead a thriving, ambitious company that brings value to customers through engineered solutions. He is the driving force behind AnTech’s product development strategy and, more recently, the move into coiled tubing drilling services. His ability to design and innovate is reflected in the fact he is named on 17 patents. Toni has over 35 years of industry experience, starting his career with Schlumberger and serving in both field and engineering positions. He has a degree in Mechanical Engineering from Imperial College London, is a Chartered Mechanical and Electrical engineer and a Fellow of the IMechE.

As Operations Manager, Adam’s role is to deliver AnTech’s services safely and efficiently and he is committed to working with customers and service partners to ensure the promised value is realised. Before joining AnTech, Adam worked as a Drilling Engineer for BP in Aberdeen and, as Lead Engineer, demonstrated his ability to bring projects in on time and on budget without incident. Adam is Chairman of the SPE Dorset Section and previously served on the SPE Aberdeen YP Committee. Prior to that, he worked for a short period with Halliburton. Adam graduated from Imperial College London with a First Class Master’s degree in Mechanical Engineering.



Clare Miszewska-Hall is the Head of Global Sales & Marketing and leads AnTech’s business development activity, sales strategy, and the creative direction of the business. She has been instrumental in establishing AnTech's Coiled Tubing Drilling services, enabling oil companies to economically extract more value from their existing assets. Before joining AnTech, she worked in the FMCG sector in a variety of engineering and marketing roles. Clare’s expertise has been key to strengthening the AnTech brand and the launch and expansion of CTD services in the ME and USA. Clare holds a First Class degree in Mechanical Engineering from Cardiff University.



Jenny leads on the delivery of tools and support for AnTech’s Products and Services divisions, ensuring they are shipped on-time and to standard. She has been part of AnTech for over 20 years and has served in most departments, including a period as General Manager. Jenny is a Chartered Engineer with a degree in Electronic Engineering from Birmingham City University. She is a Member of the IET and IOSH qualified. Jenny devotes a significant amount of her free time to support HCPT, a charity that works with children with special needs, some of whom are terminally ill.




As Head of Business Systems, Benjamin Brooking is responsible for AnTech’s digitisation strategy. Pulling together everything from field operations through to our integrated ERP and PLM systems. Benjamin draws on his experience from his previous position as Technical Manager for the company, which included field experience and introducing new tools such as Hazardous Area equipment for various completions operations and the industry’s first North-seeking Gyro for horizontal drilling. Benjamin came to us as a Year In Industry student and then progressed within the company to Head of Engineering. He has a First-Class Master’s degree in Electronic Engineering from Exeter University and is a Chartered Engineer. 



Christopher is AnTech’s Head of Engineering, delivering the company’s new product development and program goals across both the products and services divisions. He brings a range of experience to his work from hands-on field operations, design, and program delivery having worked in a number of different areas within the business before taking up his current role. Chris has a First-Class Master’s degree in Mechanical Engineering from Exeter University and recently won The Manufacturer Top 100 'Unsung Hero' award.  


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