* Gazprom losing domestic market share
* Novatek's shares up 3.3 percent (Combines previous stories, adds detail, quote)
MOSCOW Dec 5 (Reuters) - Novatek, Russia's second-largest natural gas producer, has reached a deal to deliver 27 billion cubic metres of gas, worth up to almost $4 billion, to Mosenergo in 2013-2015, the electricity generator said.
Novatek and top Russian oil company Rosneft have recently been taking domestic market share from Gazprom , Russia's largest gas producer and the major supplier to Mosenergo.
The deal, approved by Novatek's board, will be discussed at an extraordinary general meeting of shareholders (EGM) on Jan. 9, 2013, Novatek said on Wednesday. Mosenergo valued it at up to 121 billion roubles ($3.9 billion).
Novatek's shares rose 3.3 percent on the news, outperforming the broader Moscow stock market, which was up 1.75 percent as of 1325 GMT.
Novatek said the deal would facilitate closer access to end-consumers.
"The contract will allow Novatek to considerably reduce the present volume of natural gas sold to wholesale gas traders in relation to the company's overall natural gas sales volumes mix," it said.
Mosenergo supplies power to the Moscow area, covering 60 percent of its electricity needs with 15 plants.
($1 = 30.8495 Russian roubles) (Reporting by Vladimir Soldatkin; additional reporting by Nastya Lyrchikova; Editing by Jason Bush and Jane Baird)