 US crude production has already peaked, according to one of the countrys leading shale executives, as producers battered by the price crash shun new output growth and start trying to become profitable. Matt Gallagher, chief executive of Parsley Energy, one of Texass biggest independent oil producers, said the record output level struck earlier this year would be the high-water mark. I dont think Ill see 13m barrels a day again in my lifetime, the 37-year-old Mr Gallagher told the Financial Times. 