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 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 the liquids-rich areas of the Marcellus Shale. The Utica Segment develops integrated gathering, processing, fractionation, and NGL marketing solutions. The Southwest segment gather, process, treat, fractionate and transport off-gas, as well as natural gas and natural gas liquids in East Texas, Southeast Oklahoma, Western Oklahoma, Gulf Coast and several smaller systems in the Southwest. The Northeast segment processes and fractionates natural gas in the Appalachian Basin, with integrated processing, fractionation, storage and marketing operations.