MarkWest Energy Partners, L.P. | 14,694 followers on LinkedIn. MarkWest Energy Partners, L.P. (MarkWest) is a master limited partnership engaged in the gathering, transportation, and processing of natural gas; the transportation, fractionation, marketing, and storage of natural gas liquids; and the gathering and transportation of crude oil. MarkWest has extensive natural gas gathering, processing, and transmission operations in the southwest, Gulf Coast, and northeast regions of the United States.