3.5 Additional benefits of CO2 injection

Main objective

In this work packages several additional benefits of CO2 injection are investigated.

CO2 injection in depleted gas and oil fields

The injection of CO2 in depleted gas and oil fields could be attractive because of the additional production of hydrocarbons. This helps pressure maintenance and increases the recovery factor of such gas (EGR) or oil reservoirs (EOR) and may help offset the storage costs. The proximity of aquifers to gas and oil field offers a number of possibilities to combine CO2 storage with enhanced gas recovery. Aquifers can be used as permanent storage sites or buffer capacity depending on the balance of incoming and utilised CO2.

CO2-injection in aquifers combined with geothermal energy

A new innovative idea is to combine geothermal energy with CO2 injection. In the DAP project (Delft Aardwarmte Project) the aim is to combine CO2 with the injected geothermal water to enhance CO2 storage and reduce costs. Since CO2 will be dissolved in water early injectivity problems will be avoided. However long-term injectivity needs to be evaluated.
The aim of this task is to understand what effects the variation CO2 injection volumes will affect storage mechanism and the storage capacity of aquifers. It will also investigate how creation of buffering capacities can mitigate such effects.

CO2 buffering; seasonal storage and production

Seasonal storage:
CO2 from the Pernis refinery is currently supplied to farmers to increase the rate of growth
in greenhouses, and to soft drink producers. The amount of required CO2 depends on the weather and also on the season. For example: during summer farmers may need more additional CO2 than refinery or power plant can provide, while in wintertime they may not need any CO2.

A possible solution may be temporary storage of gas into a depleted gas field during wintertime or other underground structures, followed by reproduction during the pick demand periods. In this work package several aspects will be investigated:

CO2 tends to dissolve compositions such as water, hydrocarbons and maybe even radioactive elements. This could lead to well integrity issues (moist CO2) Reproduced CO2 may also not have enough purity for use in the various applications. Possibly the reservoir is cleaned after several cycles of injection and reproduction
A reservoir may dry out as a result of the repeated cycles of injection of dry and reproduction of wet CO2