Estimates of contingent resources at Namibia's Mopane offshore field, operated by Galp, have risen 57 per cent to 1.38 billion barrels of oil equivalent (boe) after recent appraisal drilling, Canadian shareholder Sintana Energy said.
Contingent resources are considered potentially recoverable, but remain subject to technical, economic and other contingencies.
Sintana said in a statement on its website on Monday that the increase underscored "the significant resource potential of Mopane and the broader Petroleum Exploration Licence 83 (PEL 83)" complex offshore Namibia.
Galp, which operates PEL 83 and owns 80 per cent, declined to comment.
The Mopane discovery is estimated to hold at least 10 billion boe in total resources, but contingent resources are a fraction of that.
International oil companies have flocked to Namibia, which currently has no hydrocarbon production, after a string of high-profile discoveries since 2022 raised expectations the country could emerge as a significant oil producer.
Sintana, which has a 4.9 per cent indirect stake in PEL 83, said contingent resources had previously stood at 875 million boe, rated "3C" under the petroleum resources management system, implying optimistic recoverable volumes if contingencies are resolved.
TotalEnergies is in the process of acquiring a 40 per cent stake in PEL 83 and is set to assume operatorship ahead of a planned three-well drilling campaign due to start in the second half of 2026.
Sintana said, "TotalEnergies has indicated the potential for significant further resource growth," from a possible inboard extension of Mopane, as well as two newly identified large prospects, Quiver and Sobreiro.
A final investment decision is targeted for 2028, with first oil expected in 2032, Sintana said. TotalEnergies and Chevron both hold oilfield stakes near Mopane.
(Reporting by Sergio Goncalves. Editing by Mark Potter)