1. How does the CO2 quality impact on geological storage of CO2?
Oxyfuel Combustion Working Group Meeting on CO2 Quality
Cottbus, September 7
Dr. Christian Bernstone, Vattenfall Research and Development AB

2. Why is CO2 gas quality important?
All targeted CO2 streams that we aim to store contain small amounts of other components but CO2.
The CO2 quality issue can be seen as an opportunity and a risk: +
An opportunity to co-capture other main pollutants from power plant operations, and store them together with the CO2.
A concept with near-zero emissions could be created
Avoid costly and energy-demanding flue gas cleaning equipment -
A risk that components other than CO2 could have negative technical and/or HSE effects on the transport and storage system
Transporting and storing other components give no ETS credits
Too stringent requirements induce high costs for cleaning of CO2.

3. CO2 Quality vs. CCS Business Models
Business models exists for CO2-based EOR in the US.
The gas quality specs seems to be practically based rather than technically based
The available CO2 from natural CO2 fields works, with a commodity value of ~ $50/ton
Business Models for CCS will be designed based on negotiations between:
The CO2 capture operator (utilities, oil & gas companies, …)
The Transportation operator
The Storage operator
(Insurance companies)
(Third party access parties)
All stakeholders will have the exposure to risks in focus

4. CO2 Quality vs. CCS Business Models
Business models exists for CO2-based EOR in the US.
The gas quality specs seems to be practically based rather than technically based
The available CO2 from natural CO2 fields works, with a commodity value of ~ $50/ton
Business Models for CCS will be designed based on negotiations between:
The CO2 capture operator (utilities, oil & gas companies, …)
The Transportation operator
The Storage operator
(Insurance companies)
(Third party access parties)
All stakeholders will have the exposure to risks in focus

5. CO2 Quality vs. CCS Business Models
Demands on the Storage Operator:
100% Availability
If the storage site is not online then the power plant need to run at reduced load or shut-down
With no CO2 injection, the operator has no income but costs
 The impact that the CO2 quality could have on the availability will need attention in the business model
Assets of the storage operator:
The verified storage capacity of his site(s)
The injection wells at the site(s)
The safety of the site(s)

6. CO2 Quality vs. CCS Business Models
Demands on the Storage Operator:
100% Availability
If the storage site is not online then the power plant need to run at reduced load or shut-down
With no CO2 injection, the operator has no income but costs
 The impact that the CO2 quality could have on the availability will need attention in the business model
Assets of the storage operator:
The verified storage capacity of his site(s)
The injection wells at the site(s)
The safety of the site(s)

7. Impact by the gas quality on the Storage Capacity
It is the CO2 Storage Capacity of a site that is a basis for generating value of the CO2 Storage Operation
Certain component in the CO2 stream results in a reduced bulk density compared to pure CO2:
The density reduction impact on the asset of the storage site by using up more space
The reduced storage capacity may be in the range of yearly injection volumes
The maximum storage capacity is reached faster than it would be by pure CO2.
Consequence: Small volumes of other components in the CO2 stream have certain impact on the assets of the storage operator

8. CO2 Quality vs. CCS Business Models
Demands on the Storage Operator:
100% Availability
If the storage site is not online then the power plant need to run at reduced load or shut-down
With no CO2 injection, the operator has no income but costs
 The impact that the CO2 quality could have on the availability will need attention in the business model
Assets of the storage operator:
The verified storage capacity of his site(s)
The injection wells at the site(s)
The safety of the site(s)

9. Impact by the gas quality on the Injection Operation
CO2 Injection Operation
A lower bulk-density of the CO2 gas stream result in increased gas-volumes, and correspondingly an need for increased injection rate:
In general, impurities lower the phase viscosity of the fluid, and thus improve the injectivity
However, a need for an increased injection rate may require investments additional injection wells
In the Reservoir Pressure Management, it is beneficial to work with low injection rates
During operation, it is important that geochemical reactions in the near-well bore zone does not negatively reduce the injectivity

10. CO2 Quality vs. CCS Business Models
Demands on the Storage Operator:
100% Availability
If the storage site is not online then the power plant need to run at reduced load or shut-down
With no CO2 injection, the operator has no income but costs
 The impact that the CO2 quality could have on the availability will need attention in the business model
Assets of the storage operator:
The verified storage capacity of his site(s)
The injection wells at the site(s)
The safety of the site(s)

11. Impact by the gas quality on the Safety of the Site
Seal Integrity:
A literature review has not identified any studies on caprock integrity that involves other substance than CO2. The knowledge base is very limited.
Geochemical modelling initiated by Vattenfall has showed no indication of impact on the cap rocks at two candidate storage sites
With current knowledge, as long as the injection pressure is controlled within established limits, there is no geo-mechanical impact by gas mixture components on the caprock integrity.