MarkWest Energy Partners, L.P. (NYSE: MWE) (“MarkWest”) (the “Partnership”) announced today the completion of the 200 million cubic feet per day (MMcf/d) Buffalo Creek cryogenic gas processing plant and associated high pressure trunk line in the Granite Wash. The Buffalo Creek facility is supported by long-term fee-based agreements with Chesapeake Energy Corporation (NYSE: CHK) (“Chesapeake”). As part of the gas processing agreement with MarkWest, Chesapeake dedicated approximately 130,000 acres throughout the Anadarko Basin. The completion of the Buffalo Creek plant increases the Partnership’s total processing capacity in the Anadarko Basin to 435 MMcf/d at two major complexes. The 200 MMcf/d Buffalo Creek facility and the 235 MMcf/d Arapahoe processing complex in Western Oklahoma are connected through the Partnership’s extensive rich-gas gathering system, which provides 575 MMcf/d of gathering throughput capacity and tremendous flexibility and reliability. MarkWest’s infrastructure also provides producers with multiple residue gas outlets and access to natural gas liquids takeaway pipelines to Mt. Belvieu and Conway. MarkWest anticipates volumes at the new plant to ramp quickly as Chesapeake has approximately 100 MMcf/d of existing production that the Partnership has begun to process. Chesapeake has an active drilling program throughout the area and MarkWest will continue supporting their development plans. “The completion of the Buffalo Creek plant is critical to our ongoing support of Chesapeake’s successful development of their Granite Wash acreage,” stated Frank Semple, Chairman, President, and Chief Executive Officer of MarkWest. “This new 200 million cubic feet per day processing plant and the associated gathering and compression facilities will further expand MarkWest’s significant midstream presence in the Texas Panhandle and Western Oklahoma.” MarkWest Energy Partners, L.P. is a master limited partnership engaged in the gathering, processing and transportation of natural gas; the gathering, transportation, fractionation, storage and marketing of natural gas liquids; and the gathering and transportation of crude oil. MarkWest has a leading presence in many unconventional gas plays including the Marcellus Shale, Utica Shale, Huron/Berea Shale, Haynesville Shale, Woodford Shale and Granite Wash formation.