Dec 23 U.S. energy companies added oil rigs for an eighth week in a row, extending a seven-month drilling recovery as crude prices remained near a 17-month high. Drillers added 13 oil rigs in the week to Dec. 23, bringing the total count up to 523, the most since December 2015, but still below the 538 rigs seen a year ago, energy services firm Baker Hughes Inc said on Friday.