London-listed Ophir Energy’s latest ultra-deepwater wildcat offshore Equatorial Guinea has hit gas with recoverable reserves estimated at 800 Bcf, raising the prospect for a further LNG train on Bioko Island.

The company said the Tonel-1 (R-4) well in Block R is estimated to hold recoverable mean resources of 800 Bcf (133 MMboe) of gas and is the third find made in the block by the explorer, which holds an 80% stake as operator. It is the fifth discovery in the block overall.

The discovery exceeded pre-drill expectations, it continued, with an estimated mean in-place resource of 1.1 Tcf (177 MMboe).

Ophir said Tonel took the total de-risked, recoverable gas resources in Block R to circa 2.2 Tcf (367 MMboe), approaching the minimum commercial threshold for a second LNG train on Bioko Island, which is estimated to be around 2.5 Tcf.

The Tonel well encountered a 182 m (597 ft) gas column in the mid-Miocene sandstone target with a total 117 m (384 ft) of net pay. Cumulative de-risked, recoverable gas resources in Block R are now estimated at circa 2.2 Tcf (367 MMboe), according to Ophir.

Tonel is the first in a 3-well Ophir-operated drilling campaign in the block this year using the Eirik Raude semisubmersible rig. The well was spudded on 7 July in a water depth of 1,599 m (5,246 ft) and drilled to a total depth of 3,072 m (10,079 ft) subsea.

The gas-bearing column was encountered in mid-Miocene aged sands, trapped within a thrust belt anticline. The gas quality appears to be consistent with that observed in previous dry gas discoveries in Block R, Ophir said.

The Erik Raude rig will now move to undertake appraisal and satellite exploration drilling around Ophir’s previous Fortuna-1 (R-2) gas discovery. The Fortuna East and Fortuna West wells have been designed with dual objectives. The primary objective is to appraise elements of the Miocene age Fortuna Fan as discovered by the Fortuna-1 well and thereby convert discovered resource into contingent (2C) resource. The secondary objective is to separately target medium risk amplitude supported, stacked secondary targets of Miocene to Pliocene age.

The Fortuna East-1 (R-5) well will start next week and results are anticipated during August. It will appraise 304 Bcf (51 MMboe) of the earlier Fortuna Fan discovery and will separately test the 359 Bcf (60 MMboe) Viscata exploration prospect.

Fortuna West-1 (R-6) will follow with results anticipated in early September 2012. It will appraise another 299 Bcf (50 MMboe) of the Fortuna Fan discovery and will separately test the 474 Bcf (79 MMboe) Felix target.

“We are very pleased to announce our third major discovery of 2012. Tonel represents the fifth and largest gas discovery on Block R to date and importantly represents a significant step towards the commercial threshold volumes required for a second train of LNG from Equatorial Guinea,” said Nick Cooper, CEO of Ophir.

“The drilling program will now return to the vicinity of our earlier Fortuna-1 discovery. The Fortuna East-1 and Fortuna West-1 wells are designed to appraise 603 Bcf (101 MMboe) of the Fortuna Fan discovery and also to target additional cumulative exploration volumes of 833 Bcf (139 MMboe). The 3-well campaign is due to complete by September.”