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CoUnCIL FoR GEosCIEnCECoUnCIL FoR GEosCIEnCE CoUnCIL FoR GEosCIEnCE May 2022
May 2022 The Council for Geoscience (CGS) is the national custodian responsible for the collection, compilation and curation of all onshore and offshore geoscience data and information. The CGS aims to use this information and knowledge to develop geoscience solutions to real-world challenges in South Africa.
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The Council for Geoscience (CGS) is the national custodian responsible for the collection, compilation and curation of all onshore and offshore geoscience data and information. The CGS aims to use this information and knowledge to develop geoscience solutions to real-world challenges in South Africa. May 2022
MInERaLs anD EnERGY EnGInEERInG GEoLoGY
The Minerals and Energy theme anD GEoHaZaRDs includes integrated geoscience As the custodian of the national mapping, which is the core seismological network, the function of the CGS. This theme CGS monitors and maintains aims to attain a fundamental a geohazard inventory for understanding of South South Africa. This information
Africa’s onshore and offshore is primarily used in developing geology using an innovative effective and novel geohazard multidisciplinary approach. The mitigation solutions to promote theme encompasses fundamental safe and judicious land use. geoscience mapping, economic Modern artificial intelligence geology and geochemistry and techniques are applied in various geophysical techniques. subsidence mapping and seismic
These data are integrated hazards characterisation. towards enabling South Africa’s minerals and energy security and socioeconomic growth.
aFRICan FootPRInt anD
WoRLD CLass FaCILItIEs otHER CoLLaBoRatIons
The geoscience functions of the As the Permanent Secretariat
CGS are supported by a multi- of the Organisation of African facetted laboratory that performs Geological Surveys (OAGS), a wide range of analytical services the CGS leaves an impressive such as petrography, whole rock footprint in the African continent geochemistry, petrophysics, coal where it oversees and carries science and hydrochemistry. In out various geoscience services addition, the CGS manages a in line with global standards, geoscience museum, library, international policy and bookshop and a national core governance. In this capacity, repository, all of which are used the CGS also collaborates with by the scientific community and various academic institutions and the general public. science councils.
CGs at WoRK
• The CGS is undertaking an integrated and multidisciplinary geoscience mapping programme across South Africa. • Some recent projects under this programme include: - Multidisciplinary geoenvironmental baseline investigations in the southern Karoo into the feasibility of shale gas development. This work has uncovered previously undefined groundwater aquifers. - Regional soil geochemical sampling and detailed follow-up surveys, particularly in the Northern Cape, North West and Mpumalanga Provinces. - Geothermal energy and carbon capture and storage research, aiming to expand South Africa’s current renewable energy mix while decreasing the country’s carbon footprint. - Ground stability and geotechnical assessments for infrastructure development in the Northern Cape and Free State Provinces.
The Council for Geoscience (CGS) is the national custodian responsible for the collection, compilation and curation of all onshore and offshore geoscience data and information. The CGS aims to use this information and knowledge to develop geoscience solutions to real-world challenges in South Africa.
MInERaLs anD EnERGY EnGInEERInG GEoLoGY
The Minerals and Energy theme anD GEoHaZaRDs includes integrated geoscience As the custodian of the national mapping, which is the core seismological network, the function of the CGS. This theme CGS monitors and maintains aims to attain a fundamental a geohazard inventory for understanding of South South Africa. This information
Africa’s onshore and offshore is primarily used in developing geology using an innovative effective and novel geohazard multidisciplinary approach. The mitigation solutions to promote theme encompasses fundamental safe and judicious land use. geoscience mapping, economic Modern artificial intelligence geology and geochemistry and techniques are applied in various geophysical techniques. subsidence mapping and seismic
These data are integrated hazards characterisation. towards enabling South Africa’s minerals and energy security and socioeconomic growth.
aFRICan FootPRInt anD
WoRLD CLass FaCILItIEs otHER CoLLaBoRatIons
The geoscience functions of the As the Permanent Secretariat
CGS are supported by a multi- of the Organisation of African facetted laboratory that performs Geological Surveys (OAGS), a wide range of analytical services WatER anD EnVIRonMEnt the CGS leaves an impressive such as petrography, whole rock The CGS carries out hydrogeological studies and footprint in the African continent geochemistry, petrophysics, coal aquifer modelling. In addition, the organisation carries where it oversees and carries science and hydrochemistry. In out environmental geoscience research which aims to out various geoscience services addition, the CGS manages a provide sustainable solutions to monitor and mitigate the in line with global standards, geoscience museum, library, impact of geology and mining activities on the health of international policy and bookshop and a national core repository, all of which are used the environment and its inhabitants. governance. In this capacity, the CGS also collaborates with by the scientific community and various academic institutions and the general public. science councils.
CGs at WoRK
• The CGS is undertaking an integrated and multidisciplinary geoscience mapping programme across South Africa. • Some recent projects under this programme include: - Multidisciplinary geoenvironmental baseline investigations in the southern Karoo into the feasibility of shale gas development. This work has uncovered previously undefined groundwater aquifers. - Regional soil geochemical sampling and detailed follow-up surveys, particularly in the Northern Cape, North West and Mpumalanga Provinces. - Geothermal energy and carbon capture and storage research, aiming to expand South Africa’s current renewable energy mix while decreasing the country’s carbon footprint. - Ground stability and geotechnical assessments for infrastructure development in the Northern Cape and Free State Provinces.
MInERaLs anD EnERGY EnGInEERInG GEoLoGY
The Minerals and Energy theme anD GEoHaZaRDs includes integrated geoscience As the custodian of the national mapping, which is the core seismological network, the function of the CGS. This theme CGS monitors and maintains aims to attain a fundamental a geohazard inventory for understanding of South South Africa. This information
Africa’s onshore and offshore is primarily used in developing geology using an innovative effective and novel geohazard multidisciplinary approach. The mitigation solutions to promote theme encompasses fundamental safe and judicious land use. geoscience mapping, economic Modern artificial intelligence geology and geochemistry and techniques are applied in various geophysical techniques. subsidence mapping and seismic
These data are integrated hazards characterisation. towards enabling South Africa’s minerals and energy security and socioeconomic growth.
aFRICan FootPRInt anD
WoRLD CLass FaCILItIEs otHER CoLLaBoRatIons
The geoscience functions of the As the Permanent Secretariat
CGS are supported by a multi- of the Organisation of African facetted laboratory that performs Geological Surveys (OAGS), a wide range of analytical services the CGS leaves an impressive such as petrography, whole rock footprint in the African continent geochemistry, petrophysics, coal where it oversees and carries science and hydrochemistry. In out various geoscience services addition, the CGS manages a in line with global standards, geoscience museum, library, international policy and bookshop and a national core governance. In this capacity, repository, all of which are used the CGS also collaborates with by the scientific community and various academic institutions and the general public. science councils.
WatER anD EnVIRonMEnt
The CGS carries out hydrogeological studies and CGs at WoRK aquifer modelling. In addition, the organisation carries out environmental geoscience research which aims to provide sustainable solutions to monitor and mitigate the • The CGS is undertaking an integrated and multidisciplinary geoscience mapping programme across South Africa. impact of geology and mining activities on the health of • Some recent projects under this programme include: the environment and its inhabitants. - Multidisciplinary geoenvironmental baseline investigations in the southern Karoo into the feasibility of shale gas development. This work has uncovered previously undefined groundwater aquifers. - Regional soil geochemical sampling and detailed follow-up surveys, particularly in the Northern Cape, North West and Mpumalanga Provinces. - Geothermal energy and carbon capture and storage research, aiming to expand South Africa’s current renewable energy mix while decreasing the country’s carbon footprint. - Ground stability and geotechnical assessments for infrastructure development in the Northern Cape and Free State Provinces.
ContaCt Us
WatER anD EnVIRonMEnt
The CGS carries out hydrogeological studies and aquifer modelling. In addition, the organisation carries out environmental geoscience research which aims to provide sustainable solutions to monitor and mitigate the impact of geology and mining activities on the health of the environment and its inhabitants.
Our head office is located at: 280 Pretoria Street, Pretoria, 0184 I @CGS_RSA I I I Tel: +27 (0)12 841 1911 I Email: info@geoscience.org.za I Web: www.geoscience.org.za
ContaCt Us
Carbon Capture, Utilisation and Storage
in a South African context
Owing to its reliance on a coal-based energy supply, South Africa ranks globally as one of the high emitters of greenhouse gases. The Council for Geoscience has been commissioned by Department of Mineral Resources and Energy to pilot and prove Carbon Capture Utilisation and Storage in our country.
BY THE COUNCIL FOR GEOSCIENCE
Early research has formulated an Atlas of Geological Storage focussing on the prospectivity of deep saline aquifers and depleted oil and gas reservoirs. However, given that the major CO2 emissions point sources are located inland, primarily in Mpumalanga and Gauteng, a shift in focus to possible storage sites proximal to major point-source CO2 emitters was initiated.
As such, the Council for Geoscience has entered into agreements with the Govan Mbeki Local Municipality in Mpumalanga to establish a Carbon Capture Utilisation and Storage (CCUS) pilot injection and storage project near Leandra. It is envisaged that 10 000 to 50 000 tons of CO2 will be injected into Archaean-age (2 700-million-year-old) mafic and ultramafic formations of the Ventersdorp Supergroup at depths ranging between 1 000 and 1 700m below the surface.
Mafic volcanic rocks comprise 60% of the earth’s surface and, owing to their widespread distribution globally, are deemed viable targets for CO2 sequestration in regions where classical sedimentary storage options are limited. Mafic (commonly basalts) and ultramafic units are rich in divalent cations (eg Ca2+, Mg2+, and Fe2+) which are chemically reactive to CO2.
The addition of water, either injected with the CO2 plume, or as formational waters, results in the formation of stable, nontoxic, void-filling carbonate minerals such as calcite, magnesite, and siderite. In these conditions, geological soluble and mineral storage conditions are created significantly more rapidly than can be achieved through conventional storage options, with mineralisation occurring within a matter of years post-injection.
The current project identified potential target injection zones within mafic and ultramafic volcanic rocks of the Klipriviersberg Group which forms the base of the Ventersdorp Supergroup in the region. The core of sixteen boreholes in the area was scanned at the National Core Library of the Council for Geoscience at Donkerhoek using Intellicore hyperspectral core imaging software. The hyperspectral scanner at the library allows for high-resolution core imaging in the Red-Green-Blue (RGB), Short Wavelength Infra-Red (SWIR) and Long Wavelength Infra-Red (LWIR) bands, as well as mineral and spectral classifications.
Of the scanned boreholes, two (BH2068 and BH2188) occur within a 3km radius of the study area and were therefore selected for detailed logging and appraisal. The boreholes achieve adequate depths to intersect deep potential reservoir zones greater than 800m. For basaltic injection, however, the 800m supercritical CO2 phase barrier is not of vital importance, as evidenced by the shallow (400-800m depth) injections in the Carbfix project in Iceland.
The current study focuses primarily on basaltic reservoir/seal pairs located at depths greater than 800m. This allows for the potential injection of supercritical, dry (non-water-dissolved) CO2 (as has been achieved by Big Sky Regional Carbon Sequestration Partnership in Wallula, USA).
Schematic illustration of a possible CCUS site in Govan Mbeki Municipality.
The boreholes were logged at centimetre scale utilising RGB and mineral composition band ratios to define potential reservoir zones and associated seals. Cut-off values of 5m thickness, like those used in the Wallula project, were chosen to delineate the most prospective reservoir seal pairs. The identified pairs were subsequently logged and sampled. Reservoir zones comprised both ultramafic volcanic units, highly porphyritic lava flows, highly vesicular and amygdaloidal flow-top zones, agglomerates and flow-top breccias, whilst confining zones (cap rocks) are defined by individual massive basaltic flows, massive basalt flow interiors and entablature zones.
In line with international best practice, guidelines for CCUS site characterisation requires data on porosity, permeability, water saturation, salinity and pore pressure data to effectively define and model potential reservoir/seal pairs within specific geological strata. Analyses of these criteria are currently underway at the CGS using X-ray fluorescence, X-ray diffraction, helium porosimetry, conventional optical microscopy, scanning electron microscopy and X-ray tomography.
Resultant porosities determined for 15 potential seal and 23 reservoir units correlate well with low apparent values defined for confining zones and reservoir zones, respectively, within the Columbia River basalts of the Wallula project. Results for average envelope (bulk) density, true density and porosity are closely aligned with findings published internationally.
Geological characterisation has defined potential injection zones within porphyritic basalts, breccia zones and ultramafic volcanics developed between the depth intervals of 1 000 and 1 700m. The targeted injection reservoirs are capped by massive basalts, recognised to have low permeability. The identified sequence of stacked reservoir/seal pairs results in a world-first scientific opportunity to study the chemical reaction behaviour of CO2 within Archaean (2 700 Ma) volcanic sequences. The Council for Geoscience will continue research and development, including extensive environmental baseline monitoring, with a view to establishing the first pilot CCUS site in South Africa.
