3 tcf is 3 trillion cubic feet, 3 * 10**12gas in the us sells at...

3 tcf is 3 trillion cubic feet, 3 * 10**12
gas in the us sells at about $7 per 1000 cubic feet

ie 3 tcf is you could sell it all, which is highly unlikely a some of it always stays in the ground, like peanut butter in a jar.

would be worth $ 21,000,000,000.00

then of course you have to pay for wells, processing facilities, pay royalties, taxes, f*&%^ng huge bonues to the directors and you may have a few $$ left to pay 1c or 2c dividends to shareholders