While production  of the easy-to-recover petroleum and natural gas declines worldwide,  several adjustments  will be made: (1) The rich countries will continue to limit their total energy consumption;  (2) the United States in particular will have to cut its primary energy consumption by a factor of two to the level of the most affluent West European countries; (3) the poor countries will be helped to produce and deploy passive  solar devices for cooking and heating, and will gain access to the clean burning,  locally produced biofuels for local transportation  and other local uses; (4) all other countries will have to limit their reliance  on coal for most of modernization;  (5) several alternative energy systems that rely on the sun will be developed  and deployed;  and (6) electricity  generation by nuclear  fission will grow as  old coal-fired power stations are decommissioned. The world will have three other environmentally unfriendly alternatives: (1) Produce massive amounts of biofuels; (2) recover, process and bum more ultra heavy oil or tar; and (3) burn more coal. For the next several decades the world will have only one environmentally acceptable option to fuel a majority of the required changes: clean natural gas. Natural gas will come from conventional deposits and, increasingly, from unconventional tight sands, shales, and coal seams.  The United States of America is endowed with the huge unconventional gas - and oil - resources. In 2009, the technically recoverable unconventional gas is energy-equivalent to producible oil in 5-10 Prudhoe Bays or 1-2 Ghawars. The Prudhoe Bay in Alaska is the largest oil field in North America. The Ghawar giant in Saudi Arabia is the largest oil field on the Earth. Major unconventional gas resources in Texas and the U.S. are discussed. Comments are made on the major technical, environmental and political difficulties of producing these resources.