The London-listed firm's shares rose as much as four per cent to 76.17p per share in early morning trading, giving it a market capitalisation of around £365m.
Tom Durrant, chief executive of Premier, said: "We are pleased to have completed the acquisition of the UK North Sea assets from E.On which strengthens Premier's position in the UK North Sea, adding high quality assets at a compelling valuation of only $1.6 barrels of oil equivalent."
"The acquired assets have had a strong start to 2016, performing ahead of expectation, adding immediate cash generative production of more than 17,000 barrels of oil equivalent per day and provide future opportunities to enable us to deliver value for our shareholders."
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An overwhelming majority of the company's shareholders gave a thumbs up to the deal earlier this week, paving the way for Premier to snap up the assets located in the central North Sea, west of Shetlands and the southern Gas Basin.
The price of oil has fallen from more than $110 in the middle of 2014 to around $40 today — piling pressure onto producers in the ageing oil and gas basis.
Premier previously said the deal would lead to "significant" production and cashflow increases this year and in 2017.