A canyon at the bottom of the sea

Worker on board ship looks at the horizon

The exploration licence

This is the story of the exploration that yielded one of the most extraordinary gas resources in the deep waters of East Africa. In 2006, Mozambique launched a tender for a series of exploration blocks in the conventional deep and ultra-deep waters of the Rovuma Basin, on the border between Tanzania and Mozambique. There was very little geophysical data available for the first licencing round. However, on that data, was built a geological model. It followed the decision to submit an offer for two blocks, obtaining an operating licence for Block Four, named Area 4, which is what this story is about.


A geological model that made history

Eni’s geologists’ curiosity went further. They drilled, found gas, and were fascinated by the underground world they had not seen anywhere else. A seismic survey revealed unusual phenomena: the ripples created by the waves of the sea on the sand appeared on the surface of these bodies. Geologists tried to understand what these geometrical shapes could represent, and how to fit them into their depositional model. During the drilling operations, the drilling chisel delved into the history of these rocks and seas, grasping useful hints for understanding the mystery surrounding the deep waters of the Rovuma Basin. The rocks where the gas was trapped were so thick as to suggest the existence of mighty river systems, capable of carrying exceptional amounts of water and sediment. An example of this in Africa is the Congo River. In East Africa, instead, rivers are poor today, but their geological history reveals a different truth: 30-40 million years ago, there were powerful river systems also on the East African coast. The team of geologists, led by Luca Bertelli (Head of Exploration from 2011 to 2022), built a model which would become famous because it explains the deposition of these sands: how and where, under the pressure of strong deep-sea bottom currents, fine particles settle in all the systems in Rovuma in Mozambique.

Success as a result of Eni’s expertise

The discovery of the Mamba, Coral and Agulha fields in the Rovuma Basin offshore Mozambique confirms the effectiveness of our exploration strategy.

Bln m³

total gas discovered (Mamba, Coral, Agulha)


surface of Exploration block 4 (Area 4)


wells drilled by Eni


depth of drilling from sea level

Ideas, courage and technology: the keys to success

In this story, success was a combination of three factors: a good deal of risk-taking; the building of sound predictive geological models; technology, through the acquisition of three-dimensional seismic data, its rapid processing and interpretation. These elements allowed Eni to pioneer exploration activities in the Rovuma Basin. Courage lies at the root of great discoveries in exploration, and this has always been the company's hallmark. Then there are geology-based ideas. In Mozambique they were right, and yet we were not aware of the extent of the discovery. Technology allowed us to come to supergiant discoveries and to refine the model. Data must be constantly updated and revised. Frontier exploration is like this: it is a mixture of intuition, concepts and technology.

Why Coral

A large part of the discoveries in Area 4 also extended into Area 1 besides Coral. There were also other smaller discoveries. Unitisation treaties, which are used to estimate the percentage of resources in fields straddling two areas for which Eni has obtained exploration licenses, are the basis on which we decide how we will subdivide the amount of gas we have discovered, once it has entered production. These are complex processes in which everyone tries to make the most of their share, especially when a field is big. In Coral’s case, however, the field was entirely within Area 4. We therefore decided to start production with the Coral South project and to do it with a floating plant, as this was the best solution from a technical point of view, the way leading to the first offshore gas in Mozambique. Coral South is a landmark project for the industry and firmly places Mozambique onto the global LNG stage: first LNG cargo departed from Coral Sul FLNG on 13th November 2022.

Extracts from a conversation with Luca Bertelli (Head of Exploration at Eni from 2011 to 2022) published in the photobook "L'Energia di Coral".


Back to top
Back to top