Imaging and fluid flow measurements of reservoir cap rock and ceramic analogues

The study of reservoir seal formation characteristics is vital to the success of carbon sequestration projects. The unique properties of these formations allows for the safe long-term storage of carbon dioxide. These intrinsic properties also give rise to numerous experiment complexities outside of the realm of traditional core characterization techniques. Samples were obtained to represent the main classes of cap rocks; shales from both a quarry in the UK and a Spanish carbon storage pilot site, anhydrite from UK extraction mines, and a evaporite sample from a reservoir located in the Middle East. An apparatus has been constructed capable of measuring the permeability and capillary threshold pressure of reservoir cap rocks. The pressure decay technique was used to measure the permeability relationship of clay-rich and evaporite samples with varying applied stresses was measured. Unique trends are observed for each geologic sample exhibiting minimums in permeability. The initial reduction of permeability as effective pressure was increased was due compaction and the subsequent increase at high stresses was due to the opening of micro-fractures. The capillary threshold pressures of each sample were determined using three different techniques. A novel technique takes advantage of the pressure decay permeability measurements technique in quantifying extremely small fluid volumes during initial sample drainage. Capillary threshold pressures were shown to also be dependant on applied system stress. The capillary threshold pressure was observed to decrease dramatically following the increase in permeability with further increasing effective pressure. Imaging capabilities were also explored, ranging from core scale to nanometre scale techniques. Computerized micro-tomography was used in plug sample evaluation, and in the observation of fractured system behaviour under varying stress. Scanning electron microscopy paired with focused ion beam milling was used to extract the 3D pore space of the ceramic allowing for permeability estimates from numerical simulations.Open Acces