Cuba-focused Melbana Energy said it more the doubled its reserve estimates for onshore oil, though recovery rates there are low so far.

Melbana is one of the few Western oil companies, and the only one listed on the Australian exchange, with a footprint in Cuba. In a statement on its reserve estimates, CEO Peter Stickland said the 612 million barrels of prospective oil in its Block 9 onshore area was "extraordinary."

"Significantly, these leads have the potential for billions of barrels of oil-in-place however the prospective resources so far assume only the historical 5 percent recovery factor from offset fields in Cuba," he said. "The application of modern enhanced oil recovery techniques may increase the recovery factor and therefore has the potential to substantially increase the potential recoverable oil."

Primary recovery from oil deposits relates to natural pressure in the reservoir. Secondary recovery involves water or gas injection into the well to increase production. Enhanced oil recovery techniques include further stimulation from steam, gas or chemical injections into the well.

The latest estimate for Block 9 is more than double its previous forecast. Melbana said plans for an acceleration of its drilling programs onshore Cuba are underway with the aim of finalized well proposals by the end of the quarter.

The national oil company of Cuba, CUPET, extended its contract last year for early exploration efforts in Block 9 by eight months to November 2017. Melbana estimates Cuban programs have a competitive operating cost of around $7 per barrel of oil.

"Melbana is currently undertaking a detailed investigation of the in-country operating environment to support the drilling program," the company said.