MarkWest Energy Partners, a Denver-based midstream company, has announced plans to expand its rich-gas processing capacity in the Marcellus shale.

The company said it will add two new new cryogenic processing plants at its Sherwood complex in Doddridge County, West Virginia and its Mobley Complex in Wetzel County, West Virginia.

At its Sherwood complex, MarkWest will build a new processing plant that will produce an additional 200 million cubic feet per day (MMcf/d), bringing the total capacity of the complex to 1.2 billion cubic feet (Bcf/d) by the second quarter of 2015. It is being constructed at the request of Antero Resources Corp. and is anchored by a long-term, fee-based contract.

MarkWest is also adding a 200 MMcf/d processing plant at the Mobley Complex, which will increase total processing capacity at that site to 920 MMcf/d. It is being built at the request of EQT Corp.

The compay has 17 major processing and fractionation projects currently under development in the Marcellus and Utica shales and expects to complete 11 of these projects in 2014, which would bring total Northeast processing and fractionation capacity to 4 Bcf/d and 250,000 barrels per day, respectively.

“We are very excited to continue developing critical midstream infrastructure on behalf of Antero and EQT,” said MarkWest President and CEO Frank Semple. “The ongoing success of our producer customers is truly impressive and our Sherwood and Mobley complexes are two of our premier assets in the rich-gas areas of the Marcellus Shale.”