Operations have begun at MarkWest Energy Partners’ Sherwood I gas processing plant and the initial phase of its high-pressure gas gathering system in Harrison and Doddridge counties, WV, to serve the Marcellus production of Antero Resources.

Earlier this year MarkWest struck an agreement with Antero to expand the Doddridge and Harrison counties’ gathering facilities to support the company’s growing gas output (see Shale Daily, May 7).

The 200 MMcf/d facility is the first phase of its planned processing capacity at the Sherwood complex. MarkWest is constructing the 200 MMcf/d Sherwood II facility, which is expected to be in service during the second quarter of 2013.

MarkWest and Antero have entered into agreements for the potential development of a third processing facility at the same site, Sherwood III, to support additional rich gas production. A third facility would bring total processing to 600 MMcf/d at Sherwood, which is near the center of Antero’s rich gas production in northern West Virginia.

The complex’s associated volumes would be gathered by MarkWest, Antero and other providers. MarkWest and Antero estimate that future capacity at Sherwood could exceed 1 Bcf/d with continued development by Antero.

Antero has more than 200,000 net acres of rich gas leasehold in northern West Virginia. The company is flowing about 90 MMcf/d through Sherwood I from a portion of its 104 horizontal Marcellus wells, which are producing more than 400 MMcf/d. Antero said it plans to “significantly increase” Sherwood I throughput over the next several months.

Natural gas liquids (NGL) recovered at Sherwood would be delivered via MarkWest’s NGL pipeline network, which also connects MarkWest’s Mobley and Majorsville complexes to its Houston fractionation and marketing complex.