MarkWest Energy Partners Announces Commencement of Mobley Processing Facility in Wetzel County, West Virginia

  MarkWest Energy Partners Announces Commencement of Mobley Processing
  Facility in Wetzel County, West Virginia

Business Wire

DENVER -- December 13, 2012

MarkWest Energy Partners (NYSE: MWE) (MarkWest) announced today the
commencement of operations of the first Mobley processing facility located in
Wetzel County, West Virginia. The 200 million cubic feet per day (MMcf/d)
plant supports the development of rich-gas from the Marcellus Shale by EQT
Corporation (NYSE: EQT), Magnum Hunter Resources Corporation (NYSE: MHR) and
other producers.

The Mobley facility is currently operating at approximately 60% utilization
and will continue to experience accelerated volume growth due to the ongoing
drilling success of MarkWest’s producer customers operating in the area.
MarkWest expects to complete construction of its second Mobley facility, a 120
MMcf/d plant, during the first quarter of 2013, and by the fourth quarter of
2013 bring online a third facility with 200 MMcf/d of processing capacity.
Once these announced projects are operational, the Mobley complex will have
approximately 520 MMcf/d of processing capacity in the significant wet-gas
fairway of northern West Virginia. The natural gas liquids (NGLs) recovered at
Mobley are being transported via MarkWest’s NGL pipeline gathering network to
the 60,000 barrels per day (Bbl/d) Houston fractionation complex in Washington
County, PA, where they are separated into valuable purity products and
marketed on behalf of producer customers.

“The initial Mobley project presented a significant challenge because of the
remote location and mountainous terrain,” said Frank Semple, Chairman,
President and Chief Executive Officer of MarkWest. “With the initial plant now
online and expansions well underway, our producer customers now have the
infrastructure needed to efficiently develop their prolific Marcellus Shale
acreage in northern West Virginia.”

MarkWest Energy Partners, L.P. 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, including the Marcellus
Shale, and is the largest natural gas processor and fractionator in the
Appalachian region.

This press release includes “forward-looking statements.” All statements other
than statements of historical facts included or incorporated herein may
constitute forward-looking statements. Actual results could vary significantly
from those expressed or implied in such statements and are subject to a number
of risks and uncertainties. Although MarkWest believes that the expectations
reflected in the forward-looking statements are reasonable, MarkWest can give
no assurance that such expectations will prove to be correct. The
forward-looking statements involve risks and uncertainties that affect
operations, financial performance, and other factors as discussed in filings
with the Securities and Exchange Commission. Among the factors that could
cause results to differ materially are those risks discussed in the periodic
reports filed with the SEC, including MarkWest’s Annual Report on Form 10-K
for the year ended December 31, 2011 and its Quarterly Reports on Form 10-Q
for the quarters ended March 31, 2012, June 30, 2012 and September 30, 2012.
You are urged to carefully review and consider the cautionary statements and
other disclosures made in those filings, specifically those under the heading
“Risk Factors.” MarkWest does not undertake any duty to update any
forward-looking statement except as required by law.


MarkWest Energy Partners, L.P.
Frank Semple, 866-858-0482
Chairman, President & CEO
Nancy Buese, 866-858-0482
Senior VP & CFO
Josh Hallenbeck, 866-858-0482
VP of Finance & Treasurer
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