Fault seal analysis for geological carbon dioxide storage in the Pletmos Basin, offshore South Africa

Sedimentary basins are considered to be potential carbon sinks and could provide a significant solution to decarbonising the global economy. In the highly faulted Pletmos Basin located offshore South Africa, there is potential for CO ₂ storage that draws attention to analysing the behaviour of faults as seals or pathways for CO ₂ migration. Faults were examined based on 3D seismic imagery using shale volume (V _shale) logs from well data. We employed well juxtaposition analysis using triangle-type diagrams and Shale Gouge Ratio (SGR) algorithms to predict their sealing potential. The sealing classification was based on results from SGR calculations. SGR between 0 and 0.2 represented “not sealing,” 0.2–0.4 represented “moderately sealing” and 0.5–1.0 represented “highly sealing.” From the seal classification, faults F-2, F-3, F-7 and the Superior Fault were moderately sealing faults, and fault F-11’s SGR (0.5) with limited sand-sand juxtapositions was classified as highly sealing. The SGR for the respective faults exceeded the 0.2 threshold, indicating their potential to act as seals for CO ₂ migration. The findings are expected to provide valuable knowledge that could enhance the overall understanding of the feasibility of geological CO ₂ storage in South Africa.