CO2 storage capacity estimates for South Africa: The

uncertainties and way forward

J.H.A. Viljoen, M. Cloete, F.D.J. Stapelberg and N. Hicks

• Scale of assessment• Availability of data• Quality of data• Assumptions that have to be made in the

calculation of capacity estimates• Storage Efficiency Factor • Injectivity and Containment• Non-geological factors

Uncertainties

Scale of assessment (CO2CRC, 2008)

Availability and quality of data

• Public domain• Published articles/books• Petroleum Agency SA (off-shore)• Council for Geoscience (onshore)

(CO2CRC 2008)

Data Confidence Indicator (after US DOE, 2007)

• Scale of assessment• Availability of data• Quality of data• Assumptions that have to be made in the

calculation of capacity estimates• Storage Efficiency Factor • Injectivity and Containment• Non-geological factors

Uncertainties

Assumptions that have to be made to calculate storage capacities

CO2 STORAGE CAPACITY ESTIMATION FORMULAE

Deep saline reservoir: MCO2 = A hg φtot ρ E

Symbols:

MCO2 = Mass estimate of CO2 storabilityA = Geographical area of formation

hg = Gross thickness of formation

φtot = Average porosity of formation

ρ = CO2 density at storage pressure and temperatureE = Storage efficiency factor

Borehole SequenceDepth to potential

reservoirs (m)

Nett Sandstone

(m)

Porosity(%)

Permeability

D-A1

9At1 – 13At1 1 051 – 1 225 39 19 – 26 Good

6A 1 596 – 1 717 30 8 - 13 Poor - Fair

1At1 – 5At1 2 202 – 2 232 19 10 Ave. 10 mD

D-B1

5A 1 170 – 1 242 24 25 Good

5A 1 486 – 1 535 28 20 – 24 Fair – Good

1At1 – 5At1 1 805 – 1 830 17 12 – 19 Fair

1At1 – 5At1 1 864 – 1 893 29 23 Good

D-C1DCII – 1At1 1 782 – 1 806 21 6 – 9 Poor

DCII – 1At1 1 818 – 1 828 10 23 Fair

D-D113A 1 503 – 1 547 35 25 Good

9At1 – 13At1 1 606 – 1 670 24 20 – 25 Good

E-B1

13A 1 075 – 1 120 27 25 – 26 Good

6A 1 164 – 1 270 82 25 – 26 Good

5A 1 347 – 1 376 29 23 - 24 Good

Average ~ 80 ~ 20

Storage Efficiency factor (that part of the total pore volume that can practically be filled by CO2)

• Atlas: 10%

• Currently: 1 – 4%• Even < 1%

Containment and Injectivity

• Size of Reservoir/Porosity (Volume)

• Cap rock, trap, faults (Containment)

• Permeability/Pressure regime (Injectivity)

Non-geological factors

• Source/sink matching• Transport • Detail Land-use

Way forward(parallel to the CCS Roadmap of the SACCCS)

• Assessment and evaluation of all potential basins and sub-basins as identified in the Atlas (existing unpublished data – Petroleum Agency SA)

• Sub-basins must be assessed and rank• Identify gaps in the existing data• Pre-competitive Prospecting (acquire new and additional) data if

needed• Effective/practical storage capacity assessment of suitable

basins/sub-basins if possible• Promotion and licensing Areas with low hydrocarbon prospects (source rocks) but

with good reservoirs and cap rocks; hydrocarbon depleted areas• Prospecting and verification (site selection)• This process must start as soon as possible

Carbon Capture and Storage Acreage Release The Offshore Petroleum and Greenhouse Gas Storage Act 2006, which came into force on 21

November 2008, provides for a system of access and property rights for the geological storage of greenhouse gas in offshore waters under Commonwealth jurisdiction. As the first step in the

process of providing these access and property rights, the Minister for Resources and Energy release ten offshore areas for the exploration of greenhouse gas storage areas. These release

areas are located in the following basins:Gippsland Basin 

Torquay Sub-basinOtway Basin

Vlaming Sub-basinPetrel Sub-basin

The document, Guidance Notes for Applicants sets out information for prospective applicantsPlease note the varied closing dates for applications for GHG assessment permits:Friday 30 September 2011 for release areas GIPP-01, GIPP-02 and GIPP-03; and

Friday 30 March 2012 for the remainder of the release areas (TORQ-01, TORQ-02, OTWY-01, VLAM-01, VLAM-02, PTRL-01 and PTRL-02)

In all other respects the original conditions for application and assessment accompanying the April 2009 Gazettal remain the same.

Well data and geophysical data are provided for release areas.

Summary

• It should be understand that the Atlas is a Country Scale Assessment of South Africa's geological storage potential of CO2.

• There are still uncertainties/gaps in the storage potential/capacity estimates of South Africa’s basins.

• Basins identified as potential CO2 storage sites should be investigated further up to a point that private investors have a better understanding of the risks involved so that they can make investment decisions.

• If the S.A. Government is seriously about CCS, resources should be made available to achieve this.

Thank you