Gas Penetration or Blocking Processes in Clay Cap-rock of Underground Gas Storage (UGS)

The caprock has an enormous role to prevent vertical gas flow from reservoir through sealing cap rock, especially when the gas pressure increases above the over-hydrostatic pressure. The permeability of caprock varies from 10–7 mD to 10–3 mD, Permeability decreases with the decrease of porosity and porosity decreases if the content of clay minerals increases. The caprock gas storage capacity is expressed in term of its threshold displacement pressure which is the minimum pressure required to displace water by gas from 100% water saturated caprock.

To enhance the ability of caprock or to prevent leakage of gas, it is important to keep the water saturation of the caprock at the initial state. The pressure anomaly is definitely important in underground gas storage. All the parameters like permeability, porosity, water saturation, capillary pressure and other pressure anomalies are needed to be well known, to enhance the ability or express the quality of caprock in underground gas storage. With the help of laboratory experiments different caprock core examples, we would be able to understand more about the behavior and properties of cap-rock under different circumstances, which will be presented in this presentation.