U.S. drillers add oil rigs for 9th week in a row -Baker Hughes

March 17 (Reuters) - U.S. drillers added oil rigs for a ninth week in a row, extending a recovery that is expected to boost shale production by the most in six-months in April. Drillers added 14 oil rigs in the week to March 17, bringing the total count up to 631, the most since September 2015, energy services firm Baker Hughes Inc said on Friday. During the same week a year ago, there were 387 active oil rigs. That rig count increase came despite