State of the art review of CO2 Storage Site Selection and Characterisation Methods

 
1. INTRODUCTION
 
2. GEOLOGICAL CHARACTERISATION OF THE SITE
 
3. FLOW MODELLING
 
4 REACTIVE FLOW MODELLING
 
5. COUPLED GEOMECHANICAL AND FLOW MODELLING
 
6. ENVIRONMENTAL IMPACT AND RISK ASSESSMENT
 
7. ECONOMIC ANALYSIS
 
8. PUBLIC PERCEPTION AND ACCEPTANCE
 
9. CONCLUSIONS AND RECOMMENDATIONS
 
 
2.1 Site screening criteria
 
2.2 Storage capacity estimation methods
 
2.3 Safety of CO2 storage in saline aquifers
 
2.4 CO2 storage site ranking criteria
 
2.5 Conclusions
 
 
» 2.1.1 Saline aquifer
 
2.1.2 Hydrocarbon fields
 
2.1.3 Coal beds
 
 

2.1.1 Saline aquifer

Tab. 2-1 presents the criteria proposed in the CO2STORE Best Practice Manual (Chadwick et al., 2006) for screening saline aquifer Formations and Structures suitable for demo or large scale industrial projects.

Tab. 2-1: Criteria proposed in the CO2STORE projects (Chadwick et al., 2006).

Positive indicators

Cautionary indicators

Storage capacity

Total storage capacity

Total capacity of reservoir estimated to be much larger than the total amount produced from the CO2 source

Total capacity of reservoir estimated to be similar to or less than the total amount proceed from the CO2 source

Reservoir properties

Depth

> 1000 m, < 2500 m

< 800 m, > 2500 m

Reservoir thickness (net)

> 50 m

< 20 m

Porosity

> 20 %

< 10 %

Permeability

> 300 mD

< 10 - 100 mD

Salinity

> 100 gl-1

< 30gl-1

Caprock properties

Lateral continuity

Unfaulted

Lateral variations, fullting

Thickness

> 100 m

< 20 m

Capillary entry pressure

Capillary entry pressure much greater than buoyancy force of maximum predicted CO2 column height

Capillary entry pressure similar to buoyancy force of maximum predicted CO2 column height

Obviously, it is essential to acquire geological data sufficient to evaluate the formations and structures (Fig. 2-1) against these key geological and reservoir criteria.

  • The upper depth of the reservoir corresponds to the minimum pressure and temperature at which CO2 is found in dense, less mobile phase - so called supercritical phase. The lower depth is less accurately defined, depending on reservoir parameters, which usually deteriorate at this level, sometimes deeper.
  • Reservoir parameters - thickness (net), porosity and permeability define reservoir performance and feasibility of its use. Higher values indicate a better reservoir. In principle, sandstone rather than carbonate Reservoirs are preferred.
  • High salinity value is an indication that no contact of the reservoir and potable aquifers occurs.
  • The quality and integrity of caprock preventing leakage from the reservoir is no less important than reservoir properties. The greater the thickness of continuous impermeable formation (e.g. shale), the better the caprock integrity is. Faults parting the entire caprock are in general a negative indicator, although a fault can be either a migration path or a barrier. Multiple caprock formations are recommended, provided they have sufficient thickness. The capillary entry pressure is also an important caprock parameter. This parameter informs the additional pressure build-up caused by injected CO2, especially on the top of a structural closure (see Fig. 2-2).

E. Fig 2-1

Fig. 2-1: Methods for storing CO2 in deep underground Geological formations (after IPCC, 2005 & CO2CRC).

E. Fig 2-2

Fig. 2-2: Buoyancy forces acting on the crest of the structural closure (after the CO2STORE manual - Chadwick et al., 2006).