Cosco said the pad has a total of five permitted wells, but Antero hasn't drilled them all yet.
The explosion is the latest of several high-profile incidents for Antero in West Virginia.
Last August, three workers at the company's Cottrill No. 3 well in Harrison County were injured when methane from several hundred feet below ground ignited and triggered a fire on the drilling rig floor.
The DEP cited Antero for failure to maintain well control at the pad near Sycamore.
Two months before that, a drilling operation in the Sardis area of Harrison county hit an aquifer and inadvertently re-pressurized a handful of old water wells. That created a backyard geyser at least 10 feet high and several smaller gushers, but no one was injured.
Schopp said at the time that workers had been drilling an initial well hole with just fresh water and air when the bit became stuck. Rather than turn the air flow off, the crew left it on as they tried to withdraw the drill.
That effectively charged up the aquifer, and the trapped air sought an escape. The crew was still thousands of feet away from oil and gas deposits.