Online Journal for E&P Geoscientists

Padmanabhan, Eswaran ^*1
(1) Geoscience and Petroleum Engineering, Universiti Teknologi Petronas, Tronoh, Malaysia.

Current concern revolves around the adoption of appropriate criteria to adequately characterize basins for safe and long-term sequestration of CO2. Six sedimentary basins from around the world were chosen for this study.

The Bakken Formation of the Williston Basin (US and Canada) shows variations in geographical extend, thickness, lithology and petrophysical properties in the members. The North Alpine Foreland Basin (Germany) shows similar complexities in addition to the presence of two megasequences that coarsen upwards. The Ridge Basin (California) exhibits rapid lateral facies changes such that fluviatile sandstones and conglomerates pass directly into lacustrine shales and siltstones. The Niger Delta Basin (West Africa) comprises growth fault traps, stratigraphic traps related to paleochannel fills, regional sand pinch outs and truncation. The reservoir properties are heavily dependent on sand/shale ratios and sealing potentials. A complicated sequence of sedimentation can also be seen in the Taranaki Basin (New Zealand) from the Cretaceous onwards. The Tertiary Sabah Basin (Malaysia) comprises growth faults that has produced strong lateral lithological and facies changes at many stratigraphic levels. This has resulted in complex trap geometries and complicated sand/shale ratios.

The existing criteria used for ranking of sedimentary basins for CO2 sequestration is qualitative, suffers from a few weaknesses and is insufficient. The criterion on tectonic setting requires a stability analysis of the setting. General classification of the geothermal conditions on a basin-scale is not suitable for CO2 sequestration purposes as results show that the influence of heterogeneity on heat flow characteristics can be diversified. Reservoir rock heterogeneity needs to be incorporated as an additional criterion. This criterion impacts the overall ranking of these basins and enhances the confidence in the resilience of long-term CO2 sequestration. In addition to this, fabric stability appears to be a very important criterion in determining the overall efficiency of sedimentary basins to sequester CO2 efficiently.

Long-term CO2 sequestration could be achieved with a higher degree of resilience with the adoption of appropriate criteria.