Shale oil producers in the southern United States could take at least two weeks to restart the more than 2 million barrels per day (bpd) of crude output that shut down because of cold weather, as frozen pipes and power supply interruptions slow their recovery, sources said.  The winter storm that gripped Texas and much of the country over the past week forced the biggest ever weather-related shutdown in the Permian Basin, cutting 2 to 4 million bpd from nationwide oil output and hitting the roughly 5 million barrels produced each day from top shale producing state Texas especially hard. The shut in oil production represents 2% to 4% of global supply, so a slow recovery would tighten worldwide crude markets and may bolster […]