HOUSTON - Noble Energy Inc has put North Sea assets up for sale that some Wall Street analysts value at up to $650 million.

Scotia Waterous has been hired by Houston-based Noble to broker the deal for the oil and gas company's interest in four North Sea oil fields, four United Kingdom Southern Gas Basin fields and a field offshore the Netherlands.

The properties, which have a crude oil output greater than 90 percent, are projected to produce 13,700 barrels of oil equivalent per day by the end of 2009, Scotia Waterous said in documents on its website. Bids are due on Oct. 21.

The asset sale also includes Noble's interest in a floating production storage offloading vessel, the bank said.

The North Sea is a non-core asset for Noble with less upside potential than their core portfolio of assets, energy research firm Simmons & Co International, said in a research note. Accordingly, monetizing this asset and directing the capital towards Noble's $2 billion in upcoming developments makes sense.

U.S.-based analysts had pegged the value of Noble's assets in the region at between $600 to $650 million.

A representative for Noble was not immediately available to comment on the sale.

Shares of Noble were up 0.5 percent to $66.43 in early afternoon trading Monday on the New York Stock Exchange. (Reporting by Anna Driver in Houston; Editing by Tim Dobbyn)