An independent valuation of Sea Lion

Rockhopper Exploration, the AIM-listed company whose main asset is a 35% working interest in the Sea Lion Oil Field in the North Falkland Basin, commissioned an updated independent evaluation of the field from Netherland, Sewell & Associates. (LSE:RKH) The results, announced on 26 August 2026 and effective at 31 July, are the clearest third-party statement of what the project could be worth, and they are worth reading closely alongside their assumptions.

What the report found

For the first two phases of the northern development area, the report assigns gross proved plus probable (2P) reserves of about 314 million barrels, of which Rockhopper's 35% share is about 110 million barrels. (LSE:RKH) The net present value of Rockhopper's share of future net revenue, discounted at 10%, is about US$1,176 million for 2P reserves, after royalties, Capital and operating costs, abandonment and estimated Falklands corporate tax. Proved Reserves alone account for about US$928 million of that.

Beyond reserves, the report lists unrisked best-estimate (2C) contingent resources net to Rockhopper of about 219 million barrels. (LSE:RKH) For the development-pending portion, linked to the Central Development Area phases and a later northern phase, the 2C NPV10 of contingent cash flows is about US$1,781 million. The company said the combined 2P plus 2C value of its interest had risen by about US$788 million compared with the evaluation effective December 2025.

Why the figures rose

The company attributed the increase to higher resource volumes, updated Commodity prices and the acceleration of the Central Development Area, which the operator plans to develop using the OSX-1 floating production vessel. (LSE:RKH) On 7 October Rockhopper agreed to subscribe US$44.0 million, its 35% share of the estimated US$125 million cost, for shares in the special purpose vehicle that owns the vessel, funded from existing cash, with net Holding Costs of about US$1.4 million a year.

Reading the numbers with care

The report itself warns that NPV10 should not be treated as fair market value, and that contingent resources are unrisked and should not simply be added to reserves. The base case assumes Brent-linked prices of US$82.99 per barrel for 2026, US$76.74 for 2027 and US$75.95 thereafter, so lower oil prices would reduce these values. The figures also exclude corporate costs and financing.

For context, Rockhopper had 1,071,985,689 shares in issue following its 16 October share issue. At the LSE delayed price of 62.8p for the 3 November 2026 session, that implies a Market Value of about £673 million, our calculation. Using the Exchange Rate implied by the company's August placing figures, that is roughly US$915 million. On our reading, the gap between that figure and the NPVs reflects, among other things, execution, funding, timing and political risks that the reserve report does not price.

Risks that sit outside the report

Sea Lion is not yet producing, and value depends on the operator delivering the development on schedule and on budget. Rockhopper raised about US$180 million in an August 2026 placing at 70p a share, alongside an open offer, and its share of future capital spending remains a call on funding. On 5 October the operator, Navitas Petroleum, said it was acting to replace two contractors amid Argentine sanctions activity, while estimating no material adverse effect.

What to watch

The disclosed milestones are progress on the OSX-1 Acquisition and the Central Development Area, and further operator updates. Any revised independent evaluation would show how the reserve base and price assumptions have moved. Oil price movements against the report's base case will also matter. No date for the next update was given in the announcements reviewed.