Tanzania deepwater wildcat penetrates gas reservoir

Statoil and ExxonMobil have reported gas shows at a deepwater wildcat in the Mafia Deep subbasin offshore Tanzania which, if successful, will further cement the emerging vast gas prospectivity and liquefied natural gas prospects along the East African margin.

Without giving depths, the companies said the Zafarani-1 on Block 2 “encountered indications of natural gas in a good quality reservoir.” First well on 5,500 sq km Block 2, Zafarani is to go to 5,150 m in 2,582 m of water.

The companies, which spudded the well in early January 2012 and expected it to take as long as 3 months to complete, said they are still drilling and it is too early to give any indication of size and commerciality.

The drillsite is 80 km off mainland Tanzania and 160 km north-northwest of the Area 1 and Area 4 blocks off Mozambique operated by Anadarko Petroleum Corp. and Eni SPA, respectively, in the Ruvuma basin. Those two companies have declared discoveries totaling 60 tcf of gas in place, and the Anadarko group is designing an LNG project.

The Zafarani well is also 100 km north of the Ophir Energy PLC-BG Group’s Chaza gas discovery on Block 1 about 18 km off Mnazi Bay, Tanzania, in the Ruvuma basin. Zafarani is also 115-120 km south of Ophir-BG’s Chewa and Pweza gas discoveries on Tanzania offshore Block 4 in the Mafia Deep subbasin and 75 km east-northeast of Songo Songo gas field (OGJ Online, Apr. 4, 2011).

Ophir-BG have tagged Pweza and Chewa, drilled in 2010, with contingent resources of 1.7 tcf and 611 bcf, respectively, and Chaza, drilled in 2011, with 92 bcf.

Ophir-BG plan to drill as many as five exploratory wells on Blocks 1, 3, and 4 in 2012 and have said those blocks and the shoreward East Pande block contain numerous untested leads and prospects with stacking potential.

Ophir said Tertiary-age river deltas along the coast have acted as provenance for high-quality slope channel and slope/basin-floor-fan (reservoir) sands.

The company said the Ophir-BG discoveries to date have chased stratigraphic plays with a strong structural influence but that the Anadarko-type basin floor fan purely stratigraphic play, mapped as extending into Block 1, is untested in Tanzania with 3D seismic yet to be acquired.

North of Block 4, Petrobras and Shell hold Block 5 off Dar es Salaam, and numerous blocks are under license even farther north in the Lamu basin off Kenya, which has no hydrocarbon production.

Statoil operates Block 2 on behalf of Tanzania Petroleum Development Corp. and has a 65% working interest, and ExxonMobil Exploration & Production Tanzania Ltd. has 35%. Statoil was awarded the Block 2 license in 2007.