Royal Dutch Shell Plc (NYSE: RDS.A) announced two divestments Jan. 31 worth $4.7 billion including selling a chunk of its North Sea assets to private-equity backed Chrysaor Holdings Ltd. which will now become a top three oil and gas producer in Britain.

The deals bring Shell's disposals to $12.5 billion since mid-2015 as it aims for $30 billion in deals by 2018.

Shell is reducing debt accrued through its $54 billion acquisition of BG Group last year.

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Shell agreed to sell a mixture of new and late-life North Sea oil and gas assets, accounting for more than half of Shell's U.K. North Sea production, to Chrysaor for up to $3.8 billion.

"[The deal is] providing a springboard for Chrysaor to bring new investment and growth into the basin," said Shell Upstream Director Andy Brown.

The deal is expected to complete in the second half of the year and will make Chrysaor Britain's leading independent E&P.

Chrysaor is backed by EIG and Noble Group Ltd. investment firm Harbour Energy Ltd. BMO Capital Markets Ltd. advised the company, while Bank of America Merrill Lynch advised Shell.

Major oil companies such as Shell and BP Plc (NYSE: BP) are withdrawing from the mature North Sea basin to instead focus on higher-profit areas like Brazil or the Gulf of Mexico.

"We do have six or eight wells we would be looking to sanction that the vendor was probably not looking to sanction," Phil Kirk, CEO of Chrysaor, told journalists.

The package includes Shell's interests in Buzzard, north of Aberdeen, a relatively new field that feeds into the global Brent oil benchmark, as well as a 10% stake in the BP-operated Schiehallion oil field.

Other fields include Beryl, Bressay, Elgin-Franklin, J-Block, the Greater Armada cluster, Everest, Lomond and Erskine, the companies said.

Shell agreed to cover $1 billion of the assets' total $3.9 billion decommissioning costs, an often contentious issue between buyers and sellers of assets in mature areas.

Around 400 Shell staff are expected to transfer to Chrysaor on completion of the deal.

Shell also announced the sale of a stake in Thailand's Bongkot gas field to Kuwait Foreign Petroleum Exploration Co. for $900 million.

"[These deals] will help Shell move past peak-gearing and contribute to deleveraging," said RBC Capital Markets analyst Biraj Borkhataria, who rates Shell's stock as 'outperform'.

Shell's London-listed shares were up 0.3% at 3:10 a.m. CT (9:10 GMT) Jan. 31.