British Sign Language Glossaries of Curriculum Terms

BSL Environmental Science Glossary - Tertiary oil recovery definition

Definition: Primary and secondary oil recovery both use pressure to bring oil to the surface. Sometimes the oil beneath the surface is thick/viscose and won't readily flow to the surface - in these instances there are a number of different methods that can be used to make the oil less vicious to allow it to then flow to the surface.

One way is to use bacteria with modified DNA and pass this down the well shaft and into the oil deposit. The bacteria eats away at the surrounding rock freeing up the oil and making it more fluid. At the same time the bacteria absorb O₂ and release CO₂ which builds pressure and helps drive the oil to the surface.

Another method is the use of steam which involves heating surrounding underground water to the point where the buildup of steam not only heats the oil deposit but adds pressure that then drives the oil to the surface. In this instance the water can be heated by solar panels at the surface. Chemicals can also be used that make the oil less viscous so that it flows more readily. These are all examples of tertiary oil recovery and in this way approximately 60% of the oil can be brought to the surface.