The gas flow stabilised in about one hour and remained stable for a further 90 minutes before the well was shut-in for a pressure build-up, the company said.

Wellhead pressure built up from 750psi to 2750psi after three hours of shut-in, the company added.

Managing director Lan Nguyen said the initial results from the clean-up are encouraging.

"This flow rate is consistent with the stabilised flow rate predicted for a horizontal Waggamba well by a reservoir modelling study undertaken by an independent reservoir engineering consulting company," he said.

Waggamba-4H has extended the lowest known gas structural depth by about 6m, Nguyen added.

The well in PL 202 is expected to be connected to the gathering network in the next two weeks for extended production testing, the company said.

Waggamba-4H is targeting mean recoverable reserves of 2.5 billion cubic feet of raw gas and is the second of up to 15 wells the company is drilling with the Century Rig 7 in the Surat Bowen Basin this year.

CS Energy pre-paid $3.5 million for drilling the well and, in return, will receive 50% of gas production and 35% of the associated free oil and condensate production.