U.S. energy firms this week added the most oil and natural gas rigs in a week since April as rising oil prices prompt more drillers to return to the wellpad.The oil and gas rig count, an early indicator of future output, rose 13 to 601 in the week to Jan. 14, its highest since April 2020, said Baker Hughes in its weekly report. The total count was up 228, or 61%, over this time last year.U.S. oil rigs rose 11 to 492 this week, their highest since April 2020, while gas rigs rose two to 109, their highest since March 2020.