DART Energy has a gas exploration licence that covers 2400 square kilometres of Sydney, including parts of Blacktown and Eastern Creek.

The gas company AGL holds an exploration licence that covers the south-west to the north-west of Sydney, including Schofields, Riverstone and the Alex Avenue precinct.

A member of the Blacktown Residents Against Coal Seam Gas group, Ben Hammond, 18, said he was opposed to the drilling on environmental grounds.

The technique used to extract gas from coal seams, hydraulic fracturing, or fracking, requires water and chemicals to be injected into the seam via a borehole.

"Once the chemicals (used in fracking) get into the aquifers, they are there forever," Mr Hammond said.

"Then there's the land clearing, noise pollution and waste water created."

The environmental activist from Doonside said people might have heard about gas drilling but many would not know that the suburb they live in could one day have a gas well.

A spokesman for DART energy said the company had "no current plans" for the western Sydney area and that geo-technical drilling would not start until at least 2013.

The Blacktown Residents Against Coal Seam Gas rally will be held in the Blacktown Village Green on Saturday, 9am-10am.

The group hopes to have guest speakers from The Greens and Lock the Gate Alliance.