They can run live flare inspections, chimney inspections, structural inspections, thermal inspections, and emergency inspections. All done using a simple remote control. Because drones can fly, they can gather more data than the average human being who is limited by his physical inability to hover over the earth.
Gas utilities are also using drones for the purpose of assessing damages caused due to natural disasters. For instance, if rains or floods damage a pipeline then drones are sent to inspect the state of the pipeline and take detailed images of it.