Results from a study undertaken by IPSA Consulting determined that the Epenarra structure could contain up to 800 million barrels of in-place condensate, based on a wetness ratio of 150bbl of condensate per million cubic feet of gas.

Estimated to contain 5.62 trillion cubic feet of P50 reserves, the Epenarra structure is a broad, low relief anticline at the Darwin Formation level with a mapped closure of about 1200 square kilometres.

But Methanol Australia managing director Chris Hart said the absolute wetness of reservoired hydrocarbons would ultimately depend on a combination of the source rock type, depth and timing of hydrocarbon generation.

“In a best-case scenario, where the gas in Epenarra was generated solely from the Echuca Shoals Formation immediately underlying the reservoir, it is possible that gas could contain up to 300 barrels of liquid hydrocarbon per million standard cubic feet of gas, which may be regarded as a P10 value,” he said.

“The worst-case scenario, where the gas was sourced further away from a combination of the Echuca Shoals and Flamingo formations, indicated a wetness of approximately 120 barrels per million standard cubic feet of gas (P90 value).”

The IPSA Consulting study reviewed regional hydrocarbon source rock and gas compositions, as well as undertaking new basin modelling simulations, to determine the likely wetness of the hydrocarbon gases detected by Heron-1 and potentially reservoired in Epenarra.

As a result, the study was able to establish the probable condensate-to-gas ratios for a range of hydrocarbon charge and migration scenarios.

Heron-1, drilled by ARCO in 1972, recorded several interpreted gas-bearing zones, including a 50m fractured carbonate interval in the lower section of the Darwin Formation.

Methanol Australia is currently trying to secure a rig to drill Heron-2 next year to fully test the Epenarra structure.

Last month, the company contracted PGS Australia to undertake a 3D seismic survey over Epenarra this month using the M/V Orient Explorer.