Oct 19 (Reuters) - Santos Ltd STO.AX
* Qtrly sales 21.5 mmboe versus 21.3 mmboe a year ago
* 2017 production guidance 58-60 mmboe
* Qtrly production 15.0 mmboe versus 14.7 mmboe in Q2 2017
* Qtrly sales revenue $793 million versus $769 million in prior qtr
* Sales guidance upgraded to 79-82 mmboe for 2017