* Says capital program to raise production 20 pct

* Says to sell certain midstream assets to Quicksilver Gas

* Quicksilver Gas says to offer 4 mln units

* Quicksilver Resources shrs down 1 pct after-market

Dec 10 - Oil and natural gas company Quicksilver Resources Inc (KWK.N) said it will spend $540 million under its 2010 capital program and said this is expected to increase production volumes by more than 20 percent. Also, the program will fund the company's ongoing evaluation of its high-potential exploratory acreage positions in the Horn River and Greater Green River basins, Quicksilver Resources said in a statement.

Production volumes for 2010 are expected to average in the range of 390 million to 400 million cubic feet of natural gas equivalent per day.

About $465 million of the capital program is expected to be spent in Texas, the company said.

The company also said it has agreed to sell its midstream gathering and treating assets associated with the Alliance project, in the northern portion of the Fort Worth Basin, to Quicksilver Gas Services LP (KGS.N) for about $87.1 million. Quicksilver Resources, which owns 73 percent of Quicksilver Gas, said the transaction is expected to close on or about Jan. 4, 2010.

Separately, Quicksilver Gas said it intends to offer 4 million common units and will use the proceeds to repay debt.

Shares of Quicksilver Resources were down about 1 percent at $12.88 in after-market trade, while that of Quicksilver Gas were down 6 percent at $20.95.

Shares of Quicksilver Resources closed at $12.97 and of Quicksilver Gas closed at $22.25 Thursday on the New York Stock Exchange. (Reporting by Thyagaraju Adinarayan in Bangalore; Editing by Unnikrishnan Nair)