Bloomberg has reported that BP‘s newly appointed chief executive, Meg O’Neill has ordered a strategic review of its upstream assets in the basin. A full divestment could raise approximately £2 billion ($2.7 billion).
That BP, the company that discovered the North Sea’s largest oil field, could be considering selling all or part of its UK offshore operations, would have been almost unimaginable a generation ago.
No final decision has been made, and BP stated only that it has “a strong North Sea portfolio with significant untapped potential, supported by a highly skilled workforce”.
Yet the direction of travel is unmistakable. The company already holds $27 billion in debt and is targeting $20 billion in divestments by the end of 2027. It has been shrinking its North Sea presence for more than a decade, offloading the Shearwater field, the Magnus platform, and the iconic Forties Pipeline System. What remains, principally a 45% stake in the Clair field, the largest producing asset on the UK Continental Shelf, now sits under review.
One trigger is the UK government’s Energy Profits Levy, a windfall tax originally introduced in 2022 and extended by the Labour government to March 2030. The surcharge pushes the effective tax rate on North Sea profits to 78% – one of the highest rates anywhere in the world for upstream oil and gas – and BP’s own tax report has described it as creating “significant uncertainty for the UK’s oil and gas industry”. With only around 10% of BP’s global earnings derived from the UK, the case for maintaining a heavily taxed, maturing asset base becomes difficult to defend against shareholders demanding capital reallocation.
The Original Seven Sisters
To understand the scale of what is being lost, it is necessary to go back to the beginning – not just of North Sea exploration, but of the global oil order that shaped the twentieth century.
The term “Seven Sisters” was coined by Enrico Mattei, the Italian industrialist and founder of ENI, as a sardonic description of the cartel of Western oil corporations that dominated the global petroleum industry from the 1940s through the 1970s. Together, these seven companies controlled approximately 85% of the world’s oil reserves at their peak. They were, in essence, the architects of the modern world’s energy infrastructure, and in many cases, of the geopolitics that surrounded it.
The original seven were:
- Standard Oil of New Jersey (Esso) – later merged with Mobil to form ExxonMobil
- Standard Oil of New York (Socony/Mobil) – the other half of that merger
- Standard Oil of California (SoCal) – now Chevron
- Gulf Oil – absorbed by Chevron in 1985
- Texaco – acquired by Chevron in 2001
- Anglo-Persian Oil Company (AIOC) – evolved through Anglo-Iranian into British Petroleum, now BP
- Royal Dutch Shell – the only European company still operating under a recognisably similar identity today
Most traced their origins to John D. Rockefeller’s Standard Oil empire, broken up by US antitrust action in 1911. Shell and BP were the European counterparts. Together, they jointly owned vast concession rights across Iran, Iraq, Saudi Arabia, and the Persian Gulf – even co-owning the Iraq Petroleum Company – in arrangements that effectively made them sovereign actors in all but name.
By the 1990s, industry consolidation had reduced the Sisters to four surviving descendants in any recognisable form: ExxonMobil, Chevron, BP, and Shell. They remain major players by any conventional measure – ExxonMobil posted 2024 revenues of $339.25 billion, Shell $284.31 billion, Chevron $193.41 billion, and BP $189.19 billion. But the age of their unchallenged dominance was already over.
The North Sea Gold Rush: 1964–1980s
Against this backdrop of global oil power, the UK government issued its first North Sea exploration licences in 1964. The Seven Sisters and their affiliates dominated the initial rush. BP’s discovery of the Forties Field in 1970 cemented its status as the most iconic North Sea operator. Shell ran major fields across the northern and central basin for decades. ExxonMobil operated extensively through its Esso UK subsidiary. Chevron was active through its Gulf Oil lineage, while Conoco (later ConocoPhillips) was a significant early licence holder in both oil and gas.
The supporting cast was equally distinguished: Amoco held early licences on key southern North Sea gas fields before being absorbed by BP in 1998; Mobil was an active player from early licensing rounds before its eventual merger with Exxon; ARCO (Atlantic Richfield) held important central North Sea licences before being acquired by BP; and Phillips Petroleum was among the very first to drill, discovering the Hewett gas field as early as July 1969.
For two decades, this was effectively an Anglo-American lake – governed by private, listed companies, mostly with roots in the old Rockefeller empire or the British imperial oil tradition, and operating within a broadly stable Western political framework.
The Middle Era and the Shifting Tide: 1980s–2010s
The picture began to change as North Sea production matured. Output peaked in the late 1990s and has been in structural decline since. The 2014–2016 oil price crash accelerated the departure of the majors. Unable to justify the high operating costs of ageing North Sea infrastructure against falling commodity prices, the Anglo-American giants began selling.
New arrivals filled the gap. The most significant was Equinor – formerly Statoil – the Norwegian state-owned energy company, which became a major UK North Sea operator, running fields including Mariner, Buzzard, and the vast Rosebank field, holding close to 500 million barrels of oil and gas, the UK’s largest undeveloped oilfield. TotalEnergies (then Total) had long been a licence holder across the basin. BG Group built significant gas positions in the southern North Sea before Shell acquired it in 2016. Mid-sized independents like Tullow Oil also took on exploration licences.
Private equity began its own advance. In 2010, just 8% of North Sea production was accounted for by private companies. By 2020, that figure had risen to approximately 30%. The old order was quietly dissolving — not in a single dramatic event, but through thousands of asset-by-asset transactions.
The Rise of the New Seven Sisters
While the North Sea was shifting beneath the surface, a more seismic transformation was occurring on the global stage. In 2007, a landmark Financial Times investigation identified a new group it called the “New Seven Sisters” — entirely state-owned national oil companies from outside the OECD nations.
They were:
| Company | Country | Nature |
|---|---|---|
| Saudi Aramco | Saudi Arabia | State-owned NOC |
| Gazprom | Russia | State-controlled |
| CNPC | China | State-owned NOC |
| NIOC | Iran | State-owned NOC |
| PDVSA | Venezuela | State-owned NOC |
| Petrobras | Brazil | State-controlled |
| Petronas | Malaysia | State-owned NOC |
Together, the New Seven Sisters controlled almost one-third of the world’s oil and gas production and more than one-third of its total reserves. By stark contrast, the descendants of the original Sisters – ExxonMobil, Chevron, BP, and Shell – produced just 10% of the world’s oil and gas and held a mere 3% of global reserves.
The numbers underscore the magnitude of the power shift. Saudi Aramco alone holds a current market capitalisation of approximately $1.79 trillion, dwarfing ExxonMobil at approximately $448 billion. At its 2023 peak, Aramco was capitalised at more than $2.1 trillion, at a time when it controlled 25% of the world’s proven oil reserves. No private Western energy company can come close to that concentration of resources.
The Current North Sea: A New Generation of Players
Back in UK waters, the retreat of the Anglo-American majors has created an industry almost unrecognisable from its founding era. Today, the dominant producers in the North Sea are a varied group of independents, state-backed ventures, and private-equity-supported operators.
| Company | Status | Key Assets |
|---|---|---|
| Harbour Energy | UK’s largest independent producer | Acquired Premier Oil and ConocoPhillips UK assets; production ~473,000 boepd in 2025 |
| Equinor/Shell JV | Jointly formed December 2024 | Mariner, Rosebank, Buzzard, Shearwater, Clair, Schiehallion; ~140,000 boepd |
| Ithaca Energy | Aberdeen-based major producer | Acquired Siccar Point Energy; operates Cambo area |
| EnQuest | UK independent | Specialises in mature field redevelopment |
| Serica Energy | Mid-tier independent | Key gas assets, among top North Sea gas producers |
| INEOS | Private conglomerate | Owns the Forties Pipeline System — sold by BP |
The Equinor-Shell deal, announced in December 2024, is particularly emblematic of the new order. The two companies agreed to merge their entire UK offshore asset portfolios into a new 50/50 joint venture, creating the single biggest independent producer in the North Sea. The new company will be headquartered in Aberdeen. It is a telling arrangement: Shell, one of the last surviving original Sisters, effectively pooling what remains of its North Sea legacy into a structure dominated by a Norwegian state-owned company.
Who Now Owns the North Sea?
The ownership picture reveals the full extent of the transformation. Research by the Common Wealth think tank, analysing data from the North Sea Transition Authority, found that 41.3% of North Sea licences are now held by firms based overseas. Of those, 10.8% are backed by foreign governments, including Abu Dhabi’s TAQA (3.9%), Norway’s Equinor (3.4%), and South Korea’s Dana (2.1%). State-owned entities from China, Russia, the UAE, and elsewhere have all established footprints in what was once an exclusively Western enterprise.
Meanwhile, private equity-backed firms hold almost 30% of equity licences. In 2010, that figure stood at just 8%. The practical consequence is that the North Sea is now significantly funded by capital structures optimised for short-term extraction returns rather than long-term stewardship – a dynamic that carries its own financial risks as the energy transition accelerates.
Official forecasts, meanwhile, project that North Sea tax receipts could fall by as much as 93% by 2030, to just £0.3 billion. A BP exit would accelerate that decline, shrinking the tax base still further. After 50 years of drilling, the UK has consumed over 85% of its economically viable reserves. The geography of abundance that made the North Sea the defining energy story of the late twentieth century is, by any measure, behind us.
The Significance of BP’s Potential Departure
If BP does ultimately exit the North Sea, whether in full or in part, it would mark the end of more than six decades of continuous presence in UK waters. It would also be a symbolic bookend on the entire era of Seven Sisters dominance: the company that began as the Anglo-Persian Oil Company, shaped the twentieth century energy order alongside Rockefeller’s heirs, discovered Britain’s greatest oilfield, and built the pipeline infrastructure that underpins UK energy supply would be leaving the stage.
What replaces it is a more fragmented, less nationally rooted, and arguably more precarious set of stewards. Harbour Energy is the largest producer, but it is a relatively young company assembled through acquisition. The Equinor-Shell JV is half owned by a Norwegian state enterprise. Private equity funds manage nearly a third of the basin’s output. The era of British and American supermajor dominance is, without question, over.
In Case You Missed it:
Whether the New Seven Sisters – and the state capitalism they represent – are a more durable foundation for global energy security than the old order they replaced is a question that will define the energy politics of the coming decades. What is not in question is that the world Enrico Mattei once mocked, and that John D. Rockefeller’s ghost once haunted, has fundamentally and irrevocably changed.
This article draws on reporting from Reuters, Bloomberg, The Telegraph, the BBC, City A.M., the Financial Times, and research by the Common Wealth think tank.
