MarkWest Energy Partners Announces Sale of Marcellus Shale Gathering Assets in West Virginia to Summit Midstream Partners

  MarkWest Energy Partners Announces Sale of Marcellus Shale Gathering Assets
  in West Virginia to Summit Midstream Partners

Business Wire

DENVER -- June 5, 2013

MarkWest Energy Partners, L.P. (NYSE: MWE) (MarkWest) and Summit Midstream
Partners, LP (NYSE: SMLP) (Summit) announced today the execution of definitive
agreements whereby Summit will acquire certain gas gathering assets from
MarkWest in Doddridge County, West Virginia for $210 million in cash. Rich-gas
gathered by these assets is dedicated to MarkWest for processing at the
Sherwood complex, also located in Doddridge County, West Virginia. The
transaction is expected to close in June 2013.

The assets included in this transaction consist of over 40 miles of newly
constructed high-pressure gas gathering pipelines, certain rights-of-way
associated with the pipeline, and two compressor stations totaling over 21,000
horsepower of combined compression. The rich-gas gathering and compression
system is supported by a long-term, fee-based contract with an affiliate of
Antero Resources Corporation (Antero), anchor producer at MarkWest’s Sherwood
processing complex. Antero is a leading Marcellus Shale producer with over
312,000 net acres in the southwestern core of the play. In northern West
Virginia, Antero has 14 drilling rigs currently in operation and has access to
400 million cubic feet per day (MMcf/d) of fully dedicated cryogenic
processing capacity at the Sherwood complex. In order to support Antero’s
rapidly growing rich-gas production, MarkWest expects to install two
additional plants at the Sherwood complex by mid-2014, bringing total
processing capacity to 800 MMcf/d.

Summit’s acquisition of premier gathering infrastructure from MarkWest will
further enhance its presence as a leading growth-oriented midstream energy
company focused on developing, owning and operating strategically located
assets in North America’s growing unconventional resource basins. This
transaction represents Summit’s entry into the largest producing shale play in
the U.S. and a highly prospective growth opportunity, supported by significant
rich-gas production from Antero and potential future producers. This
acquisition further enhances Summit’s scale to execute its growth strategy and
provides greater geographic and customer diversification.

The proceeds from this transaction will provide MarkWest with additional
financial flexibility to fund growth capital investments associated with more
than 18 previously announced major midstream infrastructure projects primarily
in the Marcellus and Utica Shales. By the end of 2014, MarkWest is expected to
have over 4 billion cubic feet per day of processing capacity and 275,000
barrels per day of fractionation capacity in the heart of two of America’s
most prolific shale plays.

Jefferies LLC acted as MarkWest’s exclusive financial advisor and Barclays
Capital, Inc. acted as Summit’s exclusive financial advisor in connection with
this transaction.

“Summit is a high quality midstream operator and we are pleased to announce
the sale of our rich gas gathering system in Doddridge County,” said Frank
Semple, Chairman, President and Chief Executive Officer of MarkWest. “This
transaction provides MarkWest with ongoing financial flexibility to support
our large set of processing, fractionation and NGL transportation projects
that are currently being developed in the Marcellus and Utica Shales.”

Steve Newby, President and Chief Executive Officer of Summit, commented, “The
Sherwood asset acquisition represents Summit’s initial entry into the
Marcellus Shale, one of the largest, most active and prolific basins in North
America. We are excited about establishing a footprint in this world-class
basin and beginning a strategic relationship with MarkWest. We look forward to
working with MarkWest on this and future opportunities to expand this
relationship and complement its industry leading position in the Marcellus and

About MarkWest Energy Partners, L.P.

MarkWest Energy Partners, L.P. is a master limited partnership engaged in the
gathering, processing and transportation of natural gas; the gathering,
transportation, fractionation, storage and marketing of natural gas liquids;
and the gathering and transportation of crude oil. MarkWest has a leading
presence in many unconventional gas plays including the Marcellus Shale, Utica
Shale, Huron/Berea Shale, Haynesville Shale, Woodford Shale and Granite Wash

About Summit Midstream Partners, LP

SMLP is a growth-oriented limited partnership focused on owning and operating
midstream energy infrastructure assets that are strategically located in the
core producing areas of unconventional resource basins, primarily shale
formations, in North America. Pro forma for the Bison and Marcellus asset
acquisitions, SMLP currently provides primarily fee-based natural gas
gathering and compression services in four unconventional resource basins: (i)
the Piceance Basin, which includes the Mesaverde formation as well as the
Mancos and Niobrara shale formations in western Colorado; (ii) the Fort Worth
Basin, which includes the Barnett Shale formation in north-central Texas;
(iii) the Williston Basin, which includes the Bakken and Three Forks shale
formations in northwestern North Dakota; and (iv) the Appalachian Basin, which
includes the Marcellus Shale formation in northern West Virginia. SMLP owns
and operates approximately 747 miles of pipeline and 180,610 horsepower of
compression. SMLP is headquartered in Dallas, TX with offices in Houston, TX,
Denver, CO and Atlanta, GA.

Forward Looking Statements

MarkWest Energy Partners, L.P.:

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 (SEC). 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, 2012 and our Quarterly Report on
Form 10-Q for the quarter ended March 31, 2013. 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.

Summit Midstream Partners, LP:

This press release includes certain statements concerning expectations for the
future that are forward-looking within the meaning of the federal securities
laws. Forward-looking statements contain known and unknown risks and
uncertainties (many of which are difficult to predict and beyond management’s
control) that may cause our actual results in future periods to differ
materially from anticipated or projected results. An extensive list of
specific material risks and uncertainties affecting us is contained in our
2012 Annual Report on Form 10-K filed with the Securities and Exchange
Commission (“SEC”) on March 18, 2013 and other documents and reports filed
from time to time with the SEC. Any forward-looking statements in this press
release are made as of the date of this press release and SMLP undertakes no
obligation to update or revise any forward-looking statements to reflect new
information or events.

Photos/Multimedia Gallery Available:



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
Summit Midstream Partners, LP
Marc Stratton, 214-242-1966
Vice President and Treasurer
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