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Enhanced Oil Recovery (EOR)

When an oil field reaches the end of its normal life, the bulk of its oil (as much as two-thirds) is still left in the ground because it is too difficult or too expensive to get out. It is estimated that by recovering just 1% extra throughout the world would equate to 20-30 billion barrels of oil – oil that may have been left behind.

Steam injection makes the oil more fluid

As such, Shell’s technology is focused on squeezing out extra barrels through the use of "enhanced oil recovery" (EOR). In essence EOR is used to do two things – to reduce the viscosity of oil to ease its flow, or to literally push oil out of the pores of the rock.

To do this, Shell is using three techniques: injecting steam into reservoirs to heat and make the oil more fluid, and ease its flow; injecting gas to push oil out or to thin it, or injecting chemicals that free trapped oil. Gas injection uses gases such as natural gas, nitrogen, or carbon dioxide that expand in a reservoir to push additional oil to a production well, or other gases that dissolve in the oil to thin it and improves its flow rate.

Chemical injection involves injecting long-chained molecules into wells, which along with flushing water through, increases the pressure in the wells which helps to lift the oil. Alternatively chemicals are sometimes used to help lower the surface tension that can prevent oil droplets from moving through a reservoir.

A billion barrels more
In the 1960’s Shell used steam injection, which has proved to be one of the most successful ways of boosting oil recovery, in the large and complex Tulare reservoir of the South Belridge field in California, USA. Since then a further billion barrels of oil have been produced from this field – operated by the Aera joint venture.

In the 1970’s we pioneered the injection of naturally-produced carbon dioxide to boost oil recovery in Texas, USA. Now we are investigating ways of using carbon dioxide captured from man-made sources such as power plants to do the same job.

We continue to pioneer EOR - with Petroleum Development Oman we are working on a number of pilot projects. At Qarn Alam, steam injection assists the gravity drainage system already in place by heating the oil to reduce viscosity. At Marmul, injected chemicals are expected to boost production by around 10%. And gas injection is used at Harweel to free trapped oil. Injected oils produce a flooding effect, increasing the pressure in the well, helping to push the hydrocarbons to the surface.