Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2012

Organization and Basis of Presentation

Organization and Basis of Presentation

1. Organization and Basis of Presentation

        MarkWest Energy Partners, L.P. ("MarkWest Energy Partners") was formed in January 2002 as a Delaware limited partnership. MarkWest Energy Partners and its subsidiaries (collectively, the "Partnership") are 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. We have 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. The Partnership's principal executive office is located in Denver, Colorado.

        The Partnership's consolidated financial statements include all majority- owned or majority-controlled subsidiaries. In addition, MarkWest Utica EMG and MarkWest Pioneer, VIEs for which the Partnership has been determined to be the primary beneficiary, are included in the consolidated financial statements (see Note 4). For non-wholly-owned subsidiaries, the interests owned by third parties have been recorded as Non-controlling interest in consolidated subsidiaries in the accompanying Consolidated Balance Sheets. Intercompany investments, accounts and transactions have been eliminated. The Partnership's investment in Centrahoma in which the Partnership exercises significant influence but does not control and is not the primary beneficiary, is accounted for using the equity method. The accompanying consolidated financial statements of the Partnership have been prepared in accordance with GAAP.