A decade ago, natural gas was heralded as the fuel of the future. In shale fields across the country, hydraulic fracturing uncorked a lucrative new source of supply. Energy giants like Exxon Mobil and Chevron snapped up smaller companies to get in on the action, and investors poured billions of dollars into export terminals to ship gas to China and Europe. The boom has given way to a bust. A glut of cheap natural gas is wreaking havoc on the energy industry, and companies are shutting down drilling rigs, filing for bankruptcy protection and slashing the value of shale fields they had acquired in recent years. Chevron, the country’s second-largest oil and gas giant after Exxon, said on Tuesday that it would write down $10 billion to $11 billion in assets , mostly shale gas holdings in Appalachia and a planned liquefied natural gas […]