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Sarah Clark

Part of STEM Ambassador Week

Hello! My name is Sarah, I am a process engineer, and my job is to design and operate the oil and gas platforms offshore to take oil and gas from the seafloor and turn it in to products that we use every day.

Before I talk about the details of my day job, I wanted to talk about school!

I was rubbish at maths and science, and every subject, when I was in primary school and early high school. I really struggled to understand what I was doing, but I wanted to be better. My dad would help me a lot, and would sit with me to coach me through my homework. He gave me really good advise that when doing a calculation to write down everything I know at one side of the paper, and everything I don’t know at the other side of the paper; sometimes this gave some inspiration about that formula I was going to use if I was really struggling! The other piece of advice he gave me was to write every step down. A lot of the time, the final answer only has a couple of marks, and you get more marks from the working, even if you make a mistake! Strategically, this made a lot more sense to get most of the marks, and actually, I often got the right answer because I would realise my mistakes. This approach, plus ensuring I did my homework, and a little bit more each day, meant I moved from the bottom classes in 2nd year high school to the top classes within 6 months, and I was able to stay there, continue improving, and doing Highers’ and Advanced Highers’ in 5th and 6th year. As I had pretty good grades, especially in maths, physics and chemistry, I decided to do chemical engineering at university.

Back to my day job! There are a lot of people involved in making products from oil and gas, and I am just one of the pieces of that puzzle. How it works is first we build a platform, like the one below, to receive the fluids produced from drilling.

Clair Ridge Platform
Figure 1: Clair Ridge Platform (source:

These fluids contain: oil & gas, which we want, and also lot of other components that we don’t want like water, sand, sulphur dioxide and others; so, we need to treat the fluids so we can send them onshore safely for refining and make in to useable products.

The fluids go through lots of processes, and each platform is slightly different, but typically they will be separated in a huge vessel called a separator. Gas, because it’s light, will separate quickly and leave via the top of the vessel. Oil and water will flow to the bottom. These two liquids will separate out over a certain amount of time because they have different densities, which makes them weigh differently. Water is heavier, so it sinks to the bottom and oil floats to the top and is skimmed over a weir (like a wall) to another part of the vessel to leave.

Separator Internals
Figure 2: Separator Internals (Source:


If you put cold water and cooking oil in a bottle with the lid on, give it a good shake and then leave it alone for a couple of hours, you’ll see they will separate. Water will drop to the bottom, because it’s heavy (heavier density) and oil will sit on top of the oil because it’s lighter (lighter density). Make sure the lid is on tight before you shake this! But we know that it’s not as simple as that, right? We know there will still be some liquid in the gas, some water in the oil, and some oil in the water, this is what we called entrainment, so what do we do?

Normally there are lots more types of separation before we can export the oil and gas to onshore. The additional types of separation could be another separator (like above), or other machinery like hydrocyclones (which spins the liquid really fast to separate oil, water and solids) or produced water treatment to make the water really pure (so the liquid might go through something like a giant sponge or sieve), or a gas dehydrator (where the gas will be passed through a vessel like a hairdryer taking all the moisture away).

My job is to make sure all the machinery is designed and operated in a way that we can make the oil and gas as pure as possible offshore, before we transport it to onshore. Once the oil and gas are ready, we export it onshore to a refinery, via huge pipeline. Lots of platforms will use the same pipework and same refinery, so that’s why the pipeline needs to be really big, to take all the gas and oil at the same time.

The whole process can take many hours and we are constantly producing, so we need to think of safety and the environment. Lots of teams, including process engineers, therefore work together to make sure what we are doing offshore is safe, to protect the workforce and protect the environment, both the air and the sea and all the sea life.

So, what do you think we use oil and gas for every single day?

Some examples I have listed below:

  • Oil for cars & planes
  • Heating our homes and offices
  • Cooking at home and restaurants
  • Making electricity
  • Plastics
  • Fertilisers and pesticides for our gardens and fruit/veg
  • Curtains
  • Jumpers
  • Soap
  • Deodorant
  • Lipstick
  • Footballs

This list is not exhausted, there are literally thousands of items that we used every single day that is made from oil and gas!

Any Questions?

I hope you have found my journey in to engineering to be interesting, if you have any questions please write to the Science Centre and I’ll be happy to answer them!

Sarah Clark
Photograph of Sarah Clark on an Offshore Platform
Sarah Clark
Sarah Clark
Process Engineer, Offshore Industry

This page is part of the STEM Ambassador Week information.

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