Petrophysical and petrographic characterisation of the reservoirs in Niger delta for carbon capture and storage

The unprecedented levels of carbon dioxide in the atmosphere are linked to the rising average temperatures that the world is experiencing. Carbon sequestration in geological formations is one of the key strategies to combat climate change. However, it is essential to characterise these geological formations to assess the potential success of environmentally friendly carbon sequestration. Controlling carbon sequestration and its migration within porous sandstones is largely dependent on the textural and geometrical characteristics of the pore networks, including tortuosity, connectivity, pore size distribution, and pore shape. Microstructural analysis of the reservoirs helps reduce risks and uncertainties associated with carbon storage by enhancing our understanding of the reservoir’s quality. This study focuses on the petrophysical and petrographic characterisation of reservoirs in the Niger Delta, using an X-ray diffractometer, scanning electron microscope, and synchrotron radiation. Quartz, clays, and feldspar were identified, with quartz being the most abundant. Na, Al, Mg, Si, and Fe were observed, confirming the XRD mineralogical results. The formations’ rough surface morphology suggested that there was a large surface area available for storing and capturing carbon. The synchrotron radiation, with its high-resolution capabilities, revealed the internal structure of the formations. Reconstruction of CT images, a non-destructive method, assessed the porosity, accounting for both connected (permeable) and unconnected (closed) voids. The pore volume of the samples was determined using Fiji software (ImageJ). The BV/TV ratio averaged 0.6, inferring good structural integrity. Overall, the petrophysical and petrographic characteristics of the Niger Delta formations suggest that they are favourable for carbon sequestration.