"A fundamental change in the natural gas supply base," the result of shale gas development, has led to an equally fundamental change in the electric power supply base, said Michael Rutkowski, managing director for energy at Navigant Consulting. The extent to which natural gas has claimed market share from coal became further evident July 9 when Patriot Coal Corp. filed for bankruptcy, reportedly the first U.S. coal producer to seek court protection since gas prices began to fall. The company and nearly 100 affiliates were part of a Chapter 11 filing in the U.S. bankruptcy court in Manhattan.