Natural gas production, already at new highs thanks to shale gas, is expected to grow 44 percent in the U.S. between 2011 and 2040. (See Natural Gas Nation: EIA Sees U.S. Future Shaped by Fracking.)Now countries around the world, including China, the United Kingdom and South Africa, are eyeing shale development as the potential key to unlock a similar windfall of homegrown energy.