MarkWest Energy Partners, L.P. (MarkWest) 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 (NGLs), and the gathering and transportation of crude oil. The Company operates in four segments: Marcellus, Utica, Northeast and Southwest. The Marcellus segment provides integrated natural gas midstream services in southwestern Pennsylvania and northern West Virginia. The Company's MarkWest Utica EMG provides gathering, processing, fractionation and marketing services. The Northeast segment assets include the Kenova, Boldman, Cobb, Kermit and Langley natural gas processing complexes, an NGL pipeline and the Siloam fractionation facility. The Company owns a system that consists of natural gas gathering pipelines, centralized compressor stations, two natural gas processing complexes and two NGL pipelines.