Mozambique Rovuma Basin: An Emerging World Gas Province

Orsi, Marco ¹; Ciurlo, Barbara ¹; Fonnesu, Franco ¹; Haliru, Salihu ¹; Meciani, Lorenzo ¹; Moltifiori, Gaia G.¹; de Finis, Francesca ¹
(1) Exploration, Eni E&P, San Donato Milanese, Italy.

The Rovuma Basin represents one of the major basins located along the East African passive margin system and straddles the Mozambique-Tanzanian border. The basin includes the Rovuma delta, one of the largest tertiary delta systems on Africa's East coast.

Despite the several oil seeps present in the onshore area of the basin, the exploration carried out from the 60s to the 80s brought only to the Tertiary gas discovery of the Mnazy Bay by Agip (now eni) at that time deemed not commercial. The lack of onshore oil discoveries put the Rovuma basin in a long sleeping phase which lasted through the 90s and the first years of 21st century, while the exploration of West Africa deep water basins went through a period of extraordinary successes.

In the recent years, new ideas supporting the possible presence of oil plays and the opportunity given by LNG technology to export gas determined a new surge of interest for the Tanzania and Mozambique deep water basins. In 2006 eni was awarded Area 4 license thus becoming one of the first E&P players to enter the Rovuma offshore of Mozambique.

The exploration is mainly in the pre-drilling phase but the few wells drilled so far would confirm the presence of a considerable gas potential in the tertiary whilst the existence of a deeper oil play is still to be proven.

In Area 4, the importance of the tertiary gas play was recognized in the early stage of exploration allowing a timely acquisition of a dedicated 3D seismic survey. The results of the interpretation confirmed the presence of DHI supported prospects with significant hydrocarbon potential. The seismic based sedimentological model suggests the presence of high quality tertiary reservoirs constituted by turbidite deep sea fans. These fans show geometrical characteristics and lateral seismic facies changes that are unusual in “normal” gravity-flow dominated systems and are interpreted as intensively reworked by bottom currents. Prospect identification and derisking was pursued through the exhaustive employment of all feasible and integrated geological and geophysical technologies, reaching a good confidence on a number of drilling locations for the 2011- 2012 drilling campaign.

The results of the wells drilled by other operators in 2010 are very encouraging and possibly the large potential of the basin will be proven by new wells to be drilled in the next years.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.