In 1958, Cabot completed its first underground storage pool or depleted gas reservoir. This is done by reversing the flow of natural gas back into a well while restoring it to its original internal pressure. In doing so, the newly-repurposed wells able to store the same amount of natural gas that they originally produced when first drilled. Thanks to the constant maintenance and inspection of these depleted gas reservoirs, the original wells are still being used today.
Natural Gas Storage Then and Now
In 1958 when this article was published, America’s demand for natural gas was at a historical high due to the increase in usage from World War II. This was coupled with the growth of demand for natural gas that rises every winter as people begin to heat their homes. To keep up with this demand, Cabot began converting newly emptied wells into depleted gas reservoirs. These reservoirs were often located near where the energy being held would be consumed.
Today, these same wells are still being used. They are regularly inspected for possible gas leakage. In addition, because of the structural properties of the underground area, the gas is able to stay contained. A few features that gas companies have to consider when picking an area for exploration is the porousness and permeability of the rocks. Porousness is desired in depleted reservoirs because it means that natural gas is able to fill all the tiny spaces in the rock. The more porous the material, the more gas can be stored. Permeability is the property of rocks to allow a gas or a liquid to go through it. The need for permeability is why a reservoir must be restored to its original amount of internal pressure for natural gas to be stored in it. While the needs for and uses of natural gas have grown and changed since the 50’s, the basic principles behind underground storage remains the same.
New Types of Storage
Today, natural gas storage has progressed to include the storage in underground salt caverns, aquifer reservoirs, liquefied natural gas (LNG) storage tanks and more. Natural gas is unable to permeate through the large amounts of salt found in quarries. This means that these salt formations are exceedingly good at making sure that there are no gas leaks underground. Aquifers, or underground water reservoirs, are a less popular form of storage because of their relatively high cost to maintain and explore. LNG storage tanks are unique because they do not reside underground. These tanks are advantageous because they store natural gas in liquid form rather than gas. This saves on the amount of space needed for safe storage. Because they don’t require gas withdrawal from underground, they can be used to easily transport gas to where it needs to go.
In short, today there are many different options for safe natural gas storage. While Cabot has changed in many ways since the 50’s, the usage of depleted gas reservoirs has stayed the same. By taking advantage of our preexisting wells and retooling them for storage use instead of abandoning them when they are empty, we make effective use of our resources. Geographic closures are a non-permeable part of the rock formation that closes or “caps off” an underground storage area. These are consistently found in depleted gas reservoirs. This, plus the location of wells and depleted reservoirs near big consumption points make depleted well reservoirs a useful and convenient storage method for us.