Sierra Leone has entered into a new offshore petroleum agreement with Nigerian company Marginal Energy Limited in a move aimed at boosting exploration activity in its underdeveloped oil sector.

The deal, signed through the Petroleum Directorate of Sierra Leone, grants the company rights to explore and produce hydrocarbons across five offshore blocks covering roughly 6,800 square kilometres. The licensed areas include blocks G-145, G-146, G-147, G-160 and G-161.

Under the arrangement, Marginal Energy is expected to invest more than $225 million in seismic surveys and drilling activities as part of an initial exploration programme designed to assess the region’s petroleum potential.

The government will retain a 10% carried stake in oil developments and a 5% interest in gas projects during the exploration and production phases. Authorities will also have the option to acquire an additional equity share of up to 9% once commercial production begins, provided payment terms are met.

Officials say the agreement is part of a broader strategy to attract foreign investment into Sierra Leone’s offshore basins, which remain largely unexplored despite growing interest in frontier energy markets. The signing took place during the Invest in African Energy conference in Paris, where the country presented its updated offshore licensing opportunities to global investors.

Sierra Leone’s President, Julius Maada Bio, described the partnership as a step toward strengthening national revenue prospects while ensuring long-term benefits from natural resource development.

The agreement also reflects growing energy cooperation between Sierra Leone and Nigeria, as West African countries look to expand participation in upstream oil and gas exploration.