Storage and Peak-shaving

The density of methane is approximately 1/1000 of that of petroleum. Hence, to store enough gas to have a calorific value that is equal to that of 1,000 tons of petroleum a storage capacity of 1 million cubic feet is required. Since it is very difficult to find suitable materials of construction to store the highly compressed natural gas (to reduce the volume), alternative sources of 

Porous media, generally limestone or dolomite, have a porosity of about 12—25% which is the space for storage. Permeability is the ease with which the gas or water can flow through the rock. The water that sticks to the sandstone even in the presence of natural gas is termed as interstitial or connate water. The temperature and pressure in the earth increases with depth typical temperatures in underground storage reservoirs in California and Louisiana at a depth of about 8,500-9,000 ft are 185—190°F. 

Natural gas deviates from ideal behavior at increased pressures, but the deviation decreases at higher temperatures. Compressibility factors applicable to the deviation can be predicted at given temperatures and pressures if the composition is known. Gas gravity [(molecular weight of the sample/29) x density of air] is substituted for gas composition for gases that are almost free of nonhydrocarbon components. Gas viscosity can be predicted if the temperature, pressure, and gas composition are known. Viscosity of the natural gas decreases as the temperature decreases and increases as the gas gravity decreases. 

The following major items have to be dealt with before establishing a storage reservoir  

an entire engineering design for cost estimate and construction bids 

---