LONDON - British energy major BG Group and its partner Ophir Energy have made their fifth consecutive gas discovery at the Mzia-1 exploration well located in Block 1, offshore southern Tanzania, the companies announced Wednesday.

"Preliminary evaluation of the results indicates 55 metres of natural gas pay in good quality sands. An extensive logging programme has been completed, including the acquisition of pressure data and gas samples," said BG Group, which is the operator with 60 per cent stakes in Blocks 1, 3 and 4 offshore Tanzania.

Ophir Energy plc, a UK incorporated holding company of a group with oil and gas exploration assets in a number of African locations, holds the remaining 40 per cent stake in the three offshore blocks.

The Mzia-1 well in Block 1 intersected a 178m gas bearing column and 55m of net pay in the Upper Cretaceous, Ophir said.

"The mean average resource was estimated at 3.5 TCF with "significant" potential upside," Ophir added.

Prior to drilling Mzia-1, BG Group had estimated the mean total gross recoverable resources to be around 7 trillion cubic feet of gas from the four previous discoveries drilled in Tanzania.

Mzia-1 is approximately 45 kilometres offshore southern Tanzania in a water depth of 1 639 metres. It is some 23 kilometres from the Jodari-1 discovery and is part of the 2012 three-to-four well exploration programme.

Mzia-1, the first BG Group and Ophir discovery within the deeper Cretaceous section, will add substantially to the 7TCF recoverable resources in the earlier four discoveries.

It has opened an extensive new play fairway within the Group's offshore acreage to complement the now proven Rovuma Delta Upper Cretaceous intraslope play.

Significantly, the well has de-risked 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 programme. .

The new resources proven by Mzia and the potential of adjacent prospects are currently under evaluation. 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, BG Group stated.

Results from the Papa-1 well are expected in July 2012.