Independent oil and gas exploration firm Heritage Oil is buying a 45% stake of an onshore oil producing block within the Niger Delta for US$850mn.

Heritage has joined forces with a Nigerian partner Shoreline Power to complete the deal. The acquisition includes eight producing fields, infrastructure and a section of the Trans Forcados pipeline.

The joint venture has bought the stake from Royal Dutch Shell, Total and Eni. Nigerian National Petroleum Corporation owns the remaining stake.

The acquisition of the onshore block called OML 30 is predicted to have a “transformational” effect on Heritage, according to an official statement from Tony Buckingham, chief executive officer of Heritage and former mercenary.

“OML 30 is expected to provide significant production and cash flow,” he said.

It is estimated the acquisition will help ramp up Heritage’s current net production from 605 barrels of oil a day to 11,350 barrels.

The acquisition will be initially financed by a US$550mn bridge loan from Standard Bank and a US$215mn bridge loan from JP Morgan.

Once the acquisition is completed, Standard Bank will provide long-term financing to refinance the bridge loan. JP Morgan Securities is also set to raise a further US$370mn via a rights issue.

Heritage Oil is known in the market for entering risky markets, having been one of the first oil firms to venture into post-war Iraq. It is also making forays into Libya, acquiring a 51% interest in Sahara Oil.

The Niger Delta region has been beset with difficulties ranging from kidnappings, bomb attacks and the illegal oil bunkering run by groups of local militants.

However, Nigeria has the largest proven oil reserves in Sub-Saharan Africa and the 10th largest reserves in the world.