Course objectives: Upon completing the course, the student will be able to explain the mechanisms of gas dissolution in oil and water; assess the storage capacities of underground storage facilities for natural gas, carbon dioxide, thermal energy, hydrogen and compressed air; discuss the problem of permeability of isolating rocks and design simulation models of injecting gases and energy into the storage geosystem.

Course content:

• Types of fluids that can be stored underground;
• Activities related to individual methods of energy storage, conversions of energy units, efficiency / effectiveness / cost-effectiveness of each method;
• Underground gas storage - divisions of underground gas storage (aquifers, depleted gas reservoirs, depleted oil reservoirs);
• Gas dissolution in oil and water - problems of gas injection into the aquifer zone;
• Ternary systems H₂O-NaCl-CO₂ - special types of phase diagrams of non-hydrocarbon mixtures;
• Gas storage - calculation of the well pressure drop, pressure drop depending on the injection and the pressure profile in the near-wellbore zone;
• Calculation of the influence of reservoir properties and present fluids (hydrocarbons, aquifer) on gas injection and prediction of reservoir and production system behavior during frequent gas withdrawal and injection;
• Estimates of changes in the mobility of injected or withdrawn gas;
• Estimates of energy expended on gas injection;
• Volumetric estimates of storage capacity in old hydrocarbon reservoirs;
• Analytical calculation of natural gas injection into an depleted gas reservoir;
• Simulation assessment of natural gas storage in deep saline aquifer and comparison with storage in depleted hydrocarbon (gas) reservoir;
• Determining the working volume, deliverability and injectivity of underground gas storage (UGS) site;
• Determining the function of cyclic withdrawal or injection of media (natural gas, compressed air, hydrogen);
• Project / seminar assignments: assessment of storage potential (1) thermal energy storage, (2) CO₂ storage, (3) hydrogen and compressed gas storage, (4) natural gas storage, simulation example of gas injection into a reservoir (comparison with analytical prediction).

Learning outcomes at the level of the course:

• Predict the behaviour of the reservoir and the production system during the gas injection and withdrawal cycle;
• Make a simulation natural gas injection model into the reservoir, and CO₂ storage model into depleted reservoirs and into aquifers;
• Determine the possibilities of wind energy storage in underground energy storage facilities;
• Determine the possibilities of storing hydrogen underground;
• Determine the optimal size and concept of the cushion gas;
• Optimize the underground storage system by the ratio of injection and withdrawal speed and water cut;
• Determine safety of the assessments based on technical, economic and geological parameters.