With further large gas discoveries offshore Mozambique and Tanzania, it would appear that East Africa is on track to becoming a major hydrocarbons province in its own right.
The latest successes have been notched up by Anadarko, Eni and BG.
Mozambique
Anadarko’s Golfinho exploration well off Mozambique in Offshore Area 1 of the Rovuma Basin has encountered a new, major natural gas accumulation 32 km north-west of the Prosperidade complex.
The US independent reported last month that the Golfinho discovery well encountered more than 59m net (193ft net) of natural gas pay in two high quality Oligocene fan systems that are age-equivalent to, but geologically distinct from, the previous discoveries in the Prosperidade complex.
The Golfinho discovery, which is entirely contained within the Offshore Area 1 Block, adds some 7-20trillion cu.ft of incremental recoverable resources over a significant areal extent.
This newly-found resource is only 16km (10 miles) offshore, providing potential cost advantages for future development options.
Golfinho-1 was drilled to a total depth of about 4,537m (14,885ft) in waters just over 1,000m (3,300ft) in depth with the Belford Dolphin drillship. Once operations at Golfinho are complete, the vessel will drill the Atum-1 exploration well.
Meantime, at the Barquentine-1 well location in the Prosperidade complex, Andadarko and its licence partners successfully tested the Upper Oligocene zone, which flowed at a facility-constrained rate of about 100million cu.ft per day of natural gas. This is the third successful drillstem test flowing at this facility-constrained rate.
This flowtest result is seen as providing further support for future development well designs capable of 100-200million cu.ft per day and confirms the high deliverability of the reservoir.
Also off Mozambique, Eni has reported an apparently giant gas find in Area-4.
The Coral-1 well was drilled with the drillship Saipem 10000 to a total depth of 4,869m (15,975ft) in some 2,260m of water and penetrated 75m of gas pay in a single high-quality Eocene sand.
Eni said that the results for this well, in the southern part of Area 4, are of particular significance, as the Coral discovery is estimated to have in-place reserves in the range 7-10TCF.
With these new results at Coral-1, Eni estimates that the Area-4 resources alone range 15-20TCF of gas in place and that it further increases the total potential of the Mamba complex discovered so far in Area 4 Offshore Rovuma, which is now thought to hold 47-52 TCF in total.
Coral-1 is located 65km off the Capo Delgado coast about 26km south-east of the Mamba South-1 discovery wellsite. A production test is to be run, and Eni intends to drill at least another five wells to fully establish the upside potential of Area 4.
Tanzania
The BG Group has achieved its fifth consecutive Tanzania gas discovery with the Mzia-1 deepwater exploration well on offshore block 1.
BG has indicated that the Mzia-1 well is its first find in the deeper Cretaceous section and opens an extensive new play fairway within the offshore acreage on blocks 1, 3, and 4, to complement the now proven Tertiary fairway.
BG said that preliminary evaluation of the results indicated 55m of gas pay in good quality sands. An extensive logging program has been completed, including the acquisition of pressure data and gas samples.
The company said that the well has derisked a number of adjacent Cretaceous prospects, which could form part of a future Mzia hub.
These prospects are expected to be tested in a future appraisal program to be defined following incorporation of data from this new well and 3D seismic.
The new resources proven by Mzia and the potential of adjacent prospects are currently under evaluation. Prior to drilling Mzia-1, BG had estimated mean total gross recoverable resources approaching 7TCF from the four previous discoveries drilled in Tanzania.
Mzia-1 is some 23km (14.3 miles) from the Jodari-1 discovery and is part of the 2012 three-to-four well exploration campaign.
Following the imminent completion of operations at Mzia, the Deepsea Metro-1 will relocate to block 3 for the drilling of the next exploration prospect, Papa-1.