Processes and technology
Coal seam gas drilling and wells
To extract coal seam gas a well is created by drilling a hole in the earth about 22cm wide.
After the hole is drilled to the required depth (between 200 and 1,000 metres), steel casing is installed and cement is pumped to fill the space between the casing and the well bore. When the cement hardens it provides a barrier between the extraction process and outlying areas.
All casing and tubing used in Australia Pacific LNG’s operations are manufactured to American Petroleum Institute (API) 5CT requirements. This sets minimum standards for manufacture and testing. It also sets minimum performance properties, allowing each well to be designed and operated safely for its entire producing life.
Safely extracting coal seam gas
Depending on how permeable the seams are, a process known as fracture stimulation, commonly referred to as 'fraccing', may be used to stimulate, or fracture, the seams in order to increase the flow of gas and water.
A fluid called ‘fraccing fluid’ or ‘frac fluid’, which primarily consists of water and sand, is pumped down the well bore into an isolated section of the well 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.
Australia Pacific LNG will fracture about 30% of our wells over the life of the Project.
Why do we use hydraulic fracture stimulation or fraccing?
Hydraulic fracturing stimulation or fraccing increases gas production from the well, so it means fewer wells need to be drilled in order to recover the same amount of gas.
There are several types of fraccing processes available but we most commonly use water fraccing and gel fraccing.
Water fraccing uses treated water, sand and a small amount of additives. This technique uses water to hold the sand in suspension while pumping.
Gel fracturing uses some additives in small concentrations to make a thick fluid which carries more sand and therefore a fracture can be created and popped open by using less water.
Gel fraccing has been used in Australia and around the world for more than 50 years.
A small amount of additives are used in fraccing but are not considered harmful in the diluted and small amounts in which we use them. Most of the ingredients we use can be found around the home, such as breaker (enzymes in washing powder), potassium chloride (a substitute for table salt), ethanol (drinking alcohol), and surfactants (sweet orange oil, an essential oil). Importantly, we do not use BTEX (benzene, toluene, ethylene, xylene) in our fraccing fluids.
The chemicals are further diluted when injected into the coal seams by the water already present in the seams, so that when they are brought back up to the surface they are barely detectable.
What about groundwater?
The cemented steel casing in the well protects shallow aquifers from contamination.
Fracturing takes place hundreds of meters below any water supply aquifers.
We only use experienced service contractors to conduct fracturing operations and their equipment is tested and certified and tested prior to occurrence fraccing program, minimising impacts to the environment.
A fraccing site is a very controlled and monitored work environment.
Want to know more about hydraulic fracturing or fraccing processes?
Read our fraccing fact sheet
Applying new thinking
One of the biggest challenges faced by the CSG industry is what to do with the water extracted from the coal seam. Often it’s ‘brackish’ which means it contains salt.
Australia Pacific LNG embraces new thinking that combats this problem by treating the water at a reverse osmosis plant. Here the water can be treated and returned for use in industrial and construction processes; for irrigation other beneficial uses.
Australia Pacific LNG joint venture partner Origin pioneered the adaptation of reverse osmosis technology to treat CSG water and was the first to apply it in Australia’s CSG industry.
Continuing the thought process
Australia Pacific LNG continues to investigate the feasibility of injecting treated water back into aquifers underlying and overlying the coal seams. While the technical and economic feasibility of injection is still being investigated, early indications are that this could be one of the ways, when combined with other solutions, to sustainably manage water produced from CSG extraction.
Australia Pacific LNG is investing significant funds and effort into the research, development and monitoring of groundwater to advance the most appropriate solution, or set of solutions, to minimise any impact on precious water resources.
Want to know more about Origin's innovative groundwater techniques?
Read the Managing CSG water fact sheet