Hilcorp Energy Co. was hydraulically fracturing (fracking) one of its wells in the days leading up to a series of minor earthquakes that were reported in Northeast Ohio on Monday, according to the Ohio Department of Natural Resources (ODNR).

ODNR spokesman Mark Bruce said Hilcorp was stimulating at least one of six wells on a single pad at the Carbon Limestone Landfill in Poland, OH in Mahoning County, about eight miles southeast of Youngstown. The agency took a precautionary measure on Monday to halt all work at the site after the earthquakes were reported (see Shale Daily, March 11).

“We talked to Hilcorp yesterday and there are six wells on one pad, all in various stages of stimulation,” Bruce told NGI’s Shale Daily on Wednesday. “One of those wells is completed, but others are in different stages. When all this happened, they were stimulating one of those wells. I’m not exactly sure which one, but they were stimulating.”

Bruce added that an ODNR inspector recently visited the Hilcorp site, and the agency is closely watching 13 seismic monitoring stations in Mahoning and Trumbull counties. Both Hilcorp and ODNR are conducting a full review of operations at the site and poring over drilling and completion logs to determine if there’s any link between the company’s operations and the earthquakes.

Bruce said ODNR cannot yet speculate on whether the stimulation caused the earthquakes, adding that “it’s one of the facts we’ve got to use and we’ll examine other data that we gather to figure out exactly what’s going on here.”

Hilcorp, meanwhile, said Wednesday that it would likely have no further comments about the earthquakes, or its operations in the area, until ODNR completes the review.

In March 2012, months after a 4.0-magnitude earthquake rattled Youngstown (see Shale Daily, Jan. 2, 2012), ODNR released a 24-page report that strongly suggested seismic activity in the region was caused by an injection well in the city. Asked if the public could eventually expect a similar report about the cause of the area’s latest earthquakes, Bruce said he wouldn’t rule that out.

“This is going to take as long as necessary,” he said. “I know people are very interested in what caused this and we want to share what we learn.”