Underground reservoirs hold oil and natural gas

A reservoir is a location where large volumes of natural gas are trapped in the subsurface of the earth. Reservoirs are made up of porous and permeable rocks that can hold significant amounts of oil and natural gas, which is confined by impermeable rock or water barriers.

What are proved reserves?

Proved reserves of natural gas are volumes of natural gas that analyses of geological and engineering data demonstrate to be recoverable under existing economic and operating conditions. Proved reserves could increase each year with additional successful exploratory wells and as more is learned about fields where current wells are producing natural gas. New technologies and increases in prices for natural gas can change previously uneconomic natural gas resources into proved reserves. Because they depend on economic factors, proved reserves shrink or grow with changes in natural gas prices and production costs. The U.S. Energy Information Administration (EIA) bases its estimates of proved reserves on an annual survey of domestic oil and natural gas well operators.

How large are U.S. proved natural gas reserves?

U.S. proved reserves of natural gas increased nearly every year since 2000. Major advances in natural gas exploration and production technologies contributed to the increases. In 2014, U.S. total natural gas proved reserves, estimated as wet gas— which includes hydrocarbon gas liquids (HGL)—set a record of nearly 389 trillion cubic feet (Tcf). The dry natural gas portion of these reserves (after removal of HGL) was 338 Tcf. Declines in natural gas prices in 2012 and 2015 contributed to reductions in proved reserves estimates in those years. At the end of 2016, total natural gas proved reserves were about 341 Tcf and dry natural gas reserves were about 322 Tcf.

What are undiscovered technically recoverable resources?

In addition to the proved natural gas reserves, large volumes of natural gas are classified as undiscovered—or unprovedtechnically recoverable resources. Undiscovered technically recoverable resources are expected to exist because the geologic settings are favorable despite the uncertainty of their specific locations. Undiscovered technically recoverable resources are also assumed to be producible over a time period using existing recovery technology. EIA estimates that as of January 1, 2015, the United States had 1,986 Tcf of unproved technically recoverable resources of dry natural gas.