Once the CO2 has been captured and transported it reaches the storage site in a condition similar to a liquid state, characterised by high density as compared to gaseous CO2. In order to keep it at this high density, the storage needs to be in a deep geological formation (at a depth of more than 800 metres) with suitable characteristics (highly porous and permeable rock called “storage rock”, covered in turn by “cap rock” preventing leakage towards the surface and guaranteeing its sequestration, as the storage rock absorbs the liquid CO2 in its pores).

Cortesy of ZEP

Types of storage

The most significant geological sites by abundance and capacity to store CO2 are:

  • Deep saline aquifers: porous and permeable sedimentary rock containing salt water, structurally isolated and not usable as a water resource
  • Oil and gas fields: depleted or in the process of depletion, well known from their record of exploration and extraction and with access through existing facilities
  • Deep coal seams: coal absorbs gases in its surface pores and fissures. The aim is to utilise the high volume of pores in unmineable coal seams, combining CO2 storage with recovery of the methane contained in such seams..

If you would like more detailed information on CO2 storage please consult the Spanish CO2 Platform paper “Almacenamiento de CO2: tecnologías, oportunidades y expectativas”.

Planta de inyección en suelos de CO2, PSICO2. Cortesía de Ciuden
Research Plant for CO2 Injection in Soils, PISCO2

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