BG Group has raised its resource estimates for its gas reserves off the east coast of Africa to more than 5 Tcf after drilling its latest appraisal well, further improving the prospects for a second planned Liquefied Natural Gas (LNG) hub development.

The UK company’s partner Ophir Energy said that the Mzia-3 appraisal well drilled approximately 6 km north of the original Mzia discovery well in Block 1 had targeted the main Lower sands that comprise the majority of the field’s resources, as well as upside in the Middle sand package also encountered in the Mzia-1 well.

The appraisal well encountered 56 m (184 ft) of net pay combined in the Lower and Middle sands and has confirmed reservoir quality in-line with that seen in the Mzia-1 and Mzia-2 wells, said Ophir.

In addition, the gas down to the level proven in Mzia-3 is 107 m (351 ft) deeper than that seen in the previous wells, it added, leading to an increase in discovered resource estimates. Provisional interpretation of the Mzia-3 result has increased the overall mean contingent recoverable resource for the Mzia discovery by circa 0.7 Tcf to a total of approximately 5.2 Tcf. Well completion operations are currently ongoing, it added, with the well having been drilled by the Deepsea Metro-1 drillship.

Ophir’s CEO, Nick Cooper, said: “The Mzia-3 result is another positive appraisal well on our discoveries in Blocks 1, 3 and 4 and confirms Mzia as an anchor asset in the planned LNG development. Total discovered resources are now comfortably in excess of that needed for two trains of LNG and demonstrate the potential for further long-term growth of the project.”

Ophir holds 40% of Blocks 1, 3 and 4, with BG operating all three with 60%.

A recent successful drillstem test off southern Tanzania by BG has already given it the confidence to proceed with plans for a northern production hub utilising three fields with 4 Tcf of gas reserves discovered so far (see DI, 14 October 2013, page 6). The test results on the deepwater Pweza gas field in Block 4 saw that well flow at a maximum 57 MMcf/d of gas, and was constrained by equipment. The other discoveries in Block 4 are Chewa and Ngisi, with these three to form the basis of the northern production hub.

The Deepsea Metro-1 has now moved on to drill the “high impact” Mlinzi Mbali prospect in Block 7. It is targeting mean recoverable prospective resources of circa 10 Tcf.