The deal, worth almost $2.7bn (£2bn), includes assets that produced approximately 72,000 barrels of oil equivalent (boe) per day last year.
Chrysaor, which is backed by Harbour Energy-managed EIG Partners, claims that the acquisition will make it one of the largest oil and gas producers in the UK North Sea.
The purchase will add three material assets to its portfolio, including Britannia and J-Block - two new operated hubs in the UK Central North Sea - along with an interest in the Clair Field area located in the “highly prospective” West of Shetlands region.
ConocoPhillips UK assets contain in excess of 280 million boe proved and probable oil and gas reserves.
Chrysaor will fund the purchase using existing cash resources and an “upsized” $3bn debt facility.
The transaction is expected to complete in late 2019, subject to regulatory approval.
Phil Kirk, chief executive at Chrysaor, said: “This significant acquisition reflects our continuing belief that the UK North Sea has material future potential for oil and gas production.
“These assets complement our existing operations and, with operating costs at less than $15 per barrel across the enlarged group, our portfolio delivers high margins and significant positive cash flow.”
He added that the business is seeking to extend its portfolio further through the acquisition of additional interests and acreage.
Linda Z Cook, chairman of Chrysaor, said that the outcome of the deal is “a reinvigorated oil and gas sector”.