In its search for brown coal across Moorabool, the company hopes to complete preliminary drilling by February.

Exploration manager Callum Lamont said if results were positive, the mineral resources would be granted 'inferred' status.

Drilling would then continue at a second stage with the number of bore holes increasing and the space between the holes declining.

The next level of confidence, an 'indicated' resource status, would mean the company could seek financial backers for mining plans.

Mr Lamont said the timeframe was on "a scale of years."

"It's hard to estimate a timeframe because there are so many considerations. The administration process slows things down. We have systems set up deliberately to do this so that we are adequately addressing all concerns."

Greens senator Greg Barber said the exploration "wasted time and energy for all involved".

He said Energy and Resources Minister Michael O'Brien should cancel the Department of Primary Industries-approved licence to search for coal on 38,000 hectares around Bacchus Marsh and Ballan.

Mr O'Brien said the government took into account all the environmental impacts of mining.

"I am satisfied that the current regulatory regime under the Mineral Resource Act is robust enough to ensure a balance between the sustainable development of mining in Victoria alongside the interests of residents."

If Mantle is granted a mining licence in Moorabool, it intends to employ coal-drying technology to upgrade brown coal into a black coal-equivalent for export to India and China.

Mr Lamont said the process would reduce carbon emissions by up to 40 per cent.

But Greens senator Richard Di Natale said there was no such thing as "clean coal".

"Essentially, what they're aiming for is to set the benchmark to where black coal is. This makes a mockery of technology solutions."