UPDATE 1-MarkWest commences 4.7 mln units offering; shares fall

* Says to use proceeds to fund capex, repay debt * Shares down 6 pct in trading after the bell

Aug 12 (Reuters) - Oil and gas processor MarkWest Energy Partners LP (MWE.N) said it commenced a public offering of 4.7 million common units, sending its shares down 6 percent.

MarkWest intends to use net proceeds from the offering to partially fund its ongoing capital expenditure program and to pay down borrowings under its revolving credit facility, the company said in a statement.

The company also said that an entity controlled by a director of its general partner is selling an additional 300,000 secondary common units. The company will not receive any proceeds from this sale.

The offering is yet another attempt by MarkWest to raise money this year as it seeks to repay debt and fund its capital program. [ID:nBNG451254]

Other oil and natural gas companies like McMoRan Exploration Co (MMR.N), Whiting Petroleum Corp (WLL.N) and Stone Energy Corp (SGY.N) have also been tapping equity markets to raise money as commodity price environment remained weak.

Shares of MarkWest fell 6 percent to $20.70 in trading after the bell. They closed at $21.99 Wednesday on the New York Stock Exchange.

For the alerts, please double click [ID:nWNBB4656] (Reporting by Arup Roychoudhury in Bangalore; Editing by Pradeep Kurup) (arup.roychoudhury@thomsonreuters.com; within U.S. +1 646 223 8780; outside U.S. +91 80 4135 5800; Reuters Messaging: arup.roychoudhury.reuters.com@reuters.net))