Advances in seismic technology have helped Thailand’s national upstream company PTTEP to unlock multi-trillion cubic feet of gas resources at the Lang Lebah field off Malaysia, which became one of the largest global discoveries of 2019 and is the operator’s biggest ever find.

The Miocene structure was first identified by vintage 2D seismic acquired in the mid-1970s.

Two exploration wells were drilled back-to-back in 1994 targeting the expected gas accumulation in the Central Luconia basin off Sarawak, East Malaysia but high overpressure and operational issues meant that neither was successful, with both failing to reach total depth.

It was subsequently determined that Lang Lebah had limited potential because of poor reservoir quality and a small gas column.

Fast forward to 2016-2017 and a new 3D broadband seismic acquisition and the reprocessing of earlier data helped to derisk the prospect and encouraged PTTEP, which was awarded Block SK 410B in 2016, to again spin the drill bit.

Even then it was not plain sailing for the Thai operator. Downhole problems meant that the well needed to be sidetracked for a drill stem test to be performed.

The Lang Lebah discovery well flowed at up to 41 million cubic feet per day of gas, although this came with 9500 parts per million of hydrogen sulphide and a carbon dioxide content of 12%.

PTTEP is appraising Lang Lebah to determine the gas/water contact that has not been encountered in any of the three wells drilled to date and to help firm up reserves estimates.

Initial estimates from the Lang Lebah-1RDR2 shallow-water discovery put reserves at about 2 trillion cubic feet of gas but this could be revised upwards following successful appraisal work.

The discovery well drilled hit 252 metres of net gas pay in a Middle Miocene carbonate reservoir.

Exploration

Seismic advances helped PTTEP unlock Malaysia gas giant