Oil wells
Graphic of oil well
Pouring crude oil

An oil well gets its name from traditional water wells. It is a hole that is drilled into the ground to reach a reservoir of liquid - in this case oil.

However, an oil well can be a little more complicated than a water well - especially oil wells under the sea bed.

First of all, the drill thread has to be lowered to the sea bed before it can start drilling through the cap rock.

Secondly, the well often spans out horizontally once has penetrated the reservoir. This is because the oil is held in porous rock - it is not like an underground stream. Often the oil has to be pumped out of the rock. It is only oil close to the end of well that is retreived.

Some oil reservoirs need to be pumped. In this case, there are small pumps inside the well pipes. Also, water is pumped into the well to force the crude oil mixture out. This water is pumped down injector wells while the oil is pumped out of production well.

The top end of the well is called the well head. This is where the oil is removed from the well.

The picture shows the Captain platform in the North Sea. You can see the pipes from the wells coming up underneath the platform. There are 27 wells on this platform. They fan out under the sea bed beneath the platform reaching for thousands of metres.

Five of the wells are injectors: water is pumped down them to replace the oil coming up through the other 22.

The oil comes up to the well heads on the platform. Roll over the picture to see a well head - it is the large white pipe coming up on the right (you can see a couple more in the background as well). This pipe is about 60 cm across and brings about 15,000 barrels of oil a day to the surface.

Photo of Captain platform
You can see the well pipes coming up underneath the platform. Roll over the image to see a well head.