ExxonMobil Corp. subsidiary XTO Energy Inc. plans to double the capacity at its natural gas processing facility in western Pennsylvania and has filed for permits with the state Department of Environmental Protection (DEP).

According to a post from state regulators on the Pennsylvania Bulletin, XTO wants to expand its Penn Cryo facility in Butler County by 125 MMcf/d. The plant was XTO’s first completed in the Appalachian Basin in 2013 with 125 MMcf/d of processing capacity.

At the time, XTO said Butler County was vital to its Appalachian operations. It has more than 500,000 net acres under lease in Pennsylvania, where Marcellus Shale production is roughly 200 MMcf/d. The company has 46,000 net acres in Butler County.

The DEP posted the notice on the state bulletin because it plans to issue an air permit for the second processing train and must accept public comment for 30 days.

It’s unclear when XTO plans to break ground for the expansion. The plant is located in Penn Township, about 35 miles north of Pittsburgh. XTO also has an agreement with MarkWest Energy Partners LP to expand a natural gas liquids pipeline to the plant.

Despite the commodities downturn, more Appalachian producers are looking for additional processing capacity as volumes continues to increase in the basin. Last week, during its first quarter earnings conference call with financial analysts, MarkWest CEO Frank Semple said the company continues to contract with new producers (see related story).

MarkWest, the region’s largest natural gas processor, said it plans to increase its total Utica Shale capacity this year to 1.3 Bcf/d with the completion of two new plants in Ohio. In the Marcellus Shale, the company also plans to bring online an additional 31,000 b/d of fractionation capacity by the end of the year in Butler County at its Keystone Complex.