More than anyone knows!
In the 1970s and early 1980s, oil companies drilled 16 wells on and around the Destin Dome, in federal waters off the Florida Panhandle; none were successful. Then from 1987 to 1995 Chevron made commercial gas discoveries on the Destin Dome 25 miles (40 km) off the coast. The discovery extended the Norphlet productive trend, which is highly productive in Alabama state waters in Mobile Bay. However, the state of Florida objected to plans to produce the deposits, and in May 2002, the US government agreed to buy back 7 leases from Chevron, Conoco, and Murphy Oil for $115 million.
Natural Gas Hydrates have long been known to exist in sediments beneath the Gulf of Mexico. In May 2009 the US Geological Survey announced the discovery of thick natural gas hydrate deposits beneath the Gulf of Mexico that are recoverable by current technology. To date, natural gas from hydrates has not been produced from the Gulf of Mexico.
Under the destine dome filed plan, Chevron would drill 12-21 wells to establish production, estimated at 300-450 million cubic feet of natural gas per day, from just one "reserve". That is about 150 BILLION Cubic feet per year from one spot and the oil and gas guys always lowball. The LA Gulf was supposed to run dry decades ago, but new technology always allow many times what is initially speculated.
http://www.mlwebdesign.com/lampl_herbert2/_Upload/publication/doc/12.pdf (map on page 13). The National Petroleum Council estimated
that as much as 24 Tcf of natural gas is currently off
limits in the eastern Gulf planning area off Florida (see Figure
None of this shows the new discoveries South of the Keys. And under the dry land.
The truth is nobody knows how much there really is except there is a hell of a lot, a hell of a lot.