HOUSTON, Nov 28 (Reuters) - Shale oil engineer Oscar Portillo spends his days drilling as many as five wells at once - without ever setting foot on a rig.

Part of a team working to cut the cost of drilling a new shale well by a third, Portillo works from a Royal Dutch Shell Plc office in suburban Houston, his eyes darting among 13 monitors flashing data on speed, temperature and other metrics as he helps control rigs more than 500 miles (805 km) away in the Permian Basin, the largest U.S. oilfield.

For the last decade, smaller oil companies have led the way in shale technology, slashing costs by as much as half with breakthroughs such as horizontal drilling and hydraulic fracking that turned the United States into the world's fastest-growing energy exporter.