HOUSTON – 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 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.

Now, oil majors that were slow to seize on shale are seeking further efficiencies by adapting technologies for highly automated offshore operations to shale and pursuing advances in digitalization that have reshaped industries from auto manufacturing to retail.

Chevron Corp is using drones equipped with thermal imaging to detect leaks in oil tanks and pipelines across its shale fields, avoiding traditional ground inspections and lengthy shutdowns.

Oil firms currently spend about $5.9 million to drill a new shale well, according to consultancy Rystad Energy.

“There is no amount of technology that can improve bad geology,” said Mark Papa, CEO of shale producer Centennial Resource Development Inc Anadarko Petroleum, Statoil and others are using DNA sequencing to pinpoint high potential areas, collecting DNA from microbes in oil to search for the same DNA in rock samples.