UPDATE 1-Chevron-led Kazakh oil venture TCO's output slips in Jan-Sept

ALMATY, Nov 20 (Reuters) - Output at Chevron-led Tengizchevroil (TCO), Kazakhstan's largest oil producer, fell by 1.5 percent year-on-year in the January-September period to 19.8 million tonnes (158 million barrels), the company said on Thursday.