Gas Storage

Gas storage has become a necessary and vital part of the gas delivery system to the ultimate user.  It permits a steady supply of gas to serve a widely fluctuating demand and meet the peaks demands of winter.    The natural gas simply is injected into underground storage reservoirs when market demand falls below the supply available from the pipeline and it is withdrawn from the storage environment when the demand exceeds the supply. 

Generally, there are three primary objectives in designing and operating storage reservoirs:

1. Verification of inventory (knowing the storage capacity for gas as a function of pressure and time). 
2. Retention against migration (strong need for monitoring system to verify where the gas resides and ensure that losses are not occurring. 
3. Assurance of deliverability (ability to develop and maintain a certain gas delivery rate.  Water interference can force wells to lose their deliverability)

Epic has strong expertise in the areas of modeling all types of gas reservoirs (tight gas, naturally fractured, strong water drive, etc.)  It is extremely useful to history match the primary depletion period of a gas reservoir for reservoir pressure, well flowing bottom-hole pressures, gas production, and water production, before modeling the gas storage cycle period. History matching the primary depletion period allows one to get a good handle on important parameters such as permeability, original volumes and place, initial pressure, and current pressure. Trapped gas saturation becomes a key parameter when gas is displacing water and entering the aquifer zone during the gas injection cycle.  During the production cycle, a certain percentage of this gas will be trapped by the water phase and will become immobile.  In addition, history matching can also provide insight into gas losses which can occur through surface equipment, cementing imperfections in the wellbore or gas diffusion into the water phase.

Gas storage reservoir

History matching primary production provides more confidence in deliverability during demand periods