OREANDA-NEWS. MarkWest unitholders voted today to approve the acquisition by Marathon's MPLX midstream partnership, giving the Marathon subsidiary access to the largest network of pipelines and gas processing facilities in the Marcellus shale.

Marathon twice raised its offer for the Denver-based partnership after some unitholders complained the terms of the original deal were unfavorable to MarkWest investors. Marathon's MPLX will pay $6.20 per unit for MarkWest, or roughly $1.28bn in total.

MarkWest's merger with MPLX will give Marathon access to MarkWest's liquids pipelines and gas processing facilities throughout the Marcellus and Utica regions, providing potential NGL blendstocks to its midcontinent refineries and access to the LPG export terminal in Marcus Hook, Pennsylvania, via MarkWest's Mariner East pipeline.

The merger comes as MarkWest and other midstream operators face lower commodity prices that make investment in major capital projects more difficult. So far this year, US propane prices fell roughly 13pc amid record inventory levels as production outpaces both demand and exports.

MarkWest chief executive Frank Semple rebuffed the idea of a broader transaction at a February dinner in Denver set up by Marathon Petroleum chief executive Gary Heminger. Heminger brought it up again a month later amid ongoing discussions on potential joint ventures, and by the end of March, the two executives were discussing the rough outline of a deal with the blessing of MarkWest's board.

The board decided by the end of April that it made more sense to go it alone, and talk on a purchase faded away. But an unidentified natural gas company approached MarkWest at the end of May, rekindling talks. By the end of June, facing weak commodity prices, the MarkWest board was deciding that it would be "increasingly difficult" to increase distributions and finance projects.

Roughly 80pc of units voted in favor of the merger agreement.