Splitting a seam

Fraccing involves pumping fluid at high pressure into a coal seam to fracture the seam and allow gas to flow into wells.

FRACTURE stimulation, hydraulic fracturing or “fraccing” is a process used to stimulate or fracture underground coal seams in order to increase the flow of gas and water.

A fluid called “frac fluid”, which primarily consists of water and sand, is pumped down the well bore into an isolated section at high pressure to fracture the coal seam. The sand holds the fracture open to provide a pathway for the gas and water to flow to the gas well for extraction.

Fraccing involves pumping fluid at high pressure into a coal seam to fracture the seam and allow gas to flow readily into wells.

Fraccing fluids used in Queensland are commonly 99 per cent sand and water. According to the government about one per cent is made up of additives such as widely-used chemicals including sodium hypochlorite, hydrochloric acid, cellulose, acetic acid and small amounts of disinfectants.

The coal seam gas companies submit that fraccing enables a more effective release of gas and water from underground gas reservoirs, and also increases the drainage area of the well.

There are several types of fraccing which can be used to release coal seam gas, with the main process using a combination of two types, namely water fraccing and gel fraccing. Water fraccing uses only treated water, sand and a small amount of additives. This technique needs large volumes of water to hold the sand in suspension while pumping.

In more recent operations, companies have been using gel fraccing. This process uses some additives in very low concentrations to make a thick fluid which carries more sand and therefore a fracture can be created and propped open by using less water.

According to the companies, the risk of groundwater contamination is minimal as shallow aquifers are protected by using a steel casing or liner which is then cemented into place, isolating the surrounding rock from the producing coal seams.