Underground reservoirs hold oil and natural gas
A natural gas reservoir is a location where large volumes of natural gas are trapped in the subsurface of the earth. These reservoirs are composed of porous and permeable rocks that can hold significant amounts of natural gas 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 wholesale (spot) 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, such as horizontal drilling and hydraulic fracturing in shale, sandstone, carbonate, and other tight geologic formations, contributed to increases in natural gas production and reserves.
According to U.S. Crude Oil and Natural Gas Proved Reserves, Year-end 2019, as of December 31, 2019, U.S. total natural gas proved reserves—estimated as wet gas—which includes hydrocarbon gas liquids (HGL)—totaled about 494.9 trillion cubic feet (Tcf). This is the second-highest natural gas reserves total after the record high of 504.5 Tcf at year-end 2018. The year-to-year decrease of about 2% was the first decrease in total U.S. natural gas proved reserves since 2015. The dry natural gas portion of these reserves (after removal of HGL) is about 465.4 Tcf, a decrease of about 3% from the 479.4 Tcf of dry gas reserves in 2018.
What are undiscovered technically recoverable resources?
In addition to the proved natural gas reserves, large volumes of natural gas are classified as undiscovered—or unproved—technically recoverable resources (TRR). Undiscovered TRR are expected to exist because the geologic settings are favorable despite the uncertainty of their specific locations. Undiscovered TRR are also assumed to be producible over a time period using existing recovery technology. EIA estimates in the Annual Energy Outlook 2021 that as of January 1, 2019, the United States had about 2,867 trillion cubic feet (Tcf) of TRR of dry natural gas.
Last updated: February 12, 2021