Majors still control three quarter of output; even after $10 bln of deals, private equity still plays only modest role.
French oil major Total has overtaken rival Royal Dutch Shell to become the second-largest producer in the North Sea with its acquisition of Maersk's Norwegian and UK producing assets.
The $7.45 billion deal by Total was welcomed by the market, with analysts saying it helped the French company rebalance its portfolio by adding assets in developed countries after going for projects in riskier places such as Iran and Russia.
The deal boosts the share of eight global oil majors in the North Sea - Statoil, Total, Shell, Exxon Mobil, Conoco
, ENI, BP and Chevron - to back above three quarters of total output.
Several oil majors have been actively looking to divest fields in the North Sea - one of the most mature global oil provinces where future developments will be complicated by high decommissioning costs of old infrastructure.
Some assets have been bought by private equity firms which have expanded significantly in the region, with companies such as Chrysaor
and Siccar acquiring fields from Shell, Austria's OMV and France's Engie.
But despite around $10 billion worth of deals in the North Sea over the past two years, private equity firms remain fairly small players with their total share still below 10 percent.
On Tuesday, UBS analysts upgraded Total to "Buy" from "Neutral" after the Maersk deal, saying Total bought the assets at an average price of $7.3 per barrel of oil resources, implying a long-term Brent price of $62 per barrel.
"In the context of a global asset market dominated by U.S. unconventional and Canadian oil sands transactions this year, a conventional offshore deal stands out as an anomaly," UBS said.
It said that opportunities for inorganic growth in the North Sea were beginning to diminish because EU utilities have fully divested of the upstream sector while oil majors have also largely sold out their non-core portfolios.
"The sale of another North Sea focused portfolio that was on the market, combined with Total's clear commitment to the basin, emphasises that competition for assets could remain high in spite of depressed oil prices
," UBS said.
Reporting by Dmitry Zhdannikov