How does hydraulic fracturing work?
Hydraulic fracturing (sometimes also referred to as ‘fraccing’ or ‘fracking’) is a technique used after a well has been drilled to increase the flow of oil and gas into a well from gas trapped in underground reservoirs. Without hydraulic fracturing, natural gas would not flow at commercial rates and would remain trapped and unrecoverable.
- Why do we use hydraulic fracturing?
- Do all wells need hydraulic fracturing?
- How does hydraulic fracturing work?
- Water management above and below ground
Why do we use hydraulic fracturing?
Once a potential source of natural gas has been identified, AWE undertakes extensive studies to assess the viability of the gas reserves, which often involves drilling test wells in the area of interest to assess the quality of the gas resource.
- If a gas field is found to be technically and commercially viable, then production can commence. Production wells are either vertically or horizontally drilled, depending on where the gas reserves lie within the target formation.
- Shale and tight gas wells are drilled to depths between 2 and 5 kilometres below the surface of the earth and may require hydraulic fracturing to extract the resource.
- The hydraulic fracturing process is used to increase the flow of oil and gas to a well, therefore increasing production and reducing the total number of wells needed to develop a resource.
- It allows for the commercialisation of low permeability reservoirs, such as shale and tight gas, in which oil and gas may otherwise not flow.
Do all wells need hydraulic fracturing?
Not all wells require hydraulic fracturing, as some may be permeable enough to allow the oil or gas to flow without the additional stimulation provided by hydraulic fracturing, such as conventional reservoirs.
The process of hydraulic fracturing isn’t used automatically in the exploration and production process. In fact, the technique occurs after the actual drilling of a well and is considered a separate process in the development of a tight oil and gas field.
How does hydraulic fracturing work?
Hydraulic fracturing involves pumping a mixture of water, sand and chemicals down the well at high pressure to open tiny fissures in the target rock reservoir.
- This water contains ‘proppants’, such as sand or tiny ceramic beads, which are used to hold the fissures open and improve the flow of gas or oil.
- Most fluid contains a small percentage – less than one per cent – of chemical additives to help carry proppants into the tiny fissures within the rock formation and increase efficiency.
Once the fluid containing the proppants has been injected into the rock formation, the pressure on the well bore is gradually reduced, allowing the flowback of fluid into the well and up to the surface.
As the pressure on the rock formation reduces the fissures close under the pressure of rock above, but are held open by the proppants remaining within the fissures.
These tiny fissures now provide large surface areas on the rock formation for gas to flow through, as well as providing flow paths for the gas to reach the well bore.
While the proppants remain behind in the rock formation, much of the injected fluid either breaks down into harmless materials (such as starch or water) or flows back to the surface.
- The majority of injected fluids are recovered to the surface during flowback.
- All recovered fluids are isolated in sealed storage areas designed to prevent leakage, including specially designed and constructed ponds which are lined with heavy duty plastic.
- Where possible, these fluids are then reused in subsequent well stimulation activities.
- If the fluid cannot be used it is treated for other uses or disposed of through an approved facility in accordance with government regulations.
Water management above and below ground
A traditional vertical well will require between approximately 4,000-6,000 kL of water, which includes the water for the camp and drilling operations.
- To put that into perspective that is the equivalent of two-and-a-half Olympic-sized swimming pools.
- The water for all drilling operations is obtained from either a local existing water bore or a new bore will be constructed if necessary.
- Any aquifers in proximity to the well bore will be protected by both natural and mechanical barriers. AWE’s mechanical barrier is the multiple layers of steel casing plus cement and impermeable layers of rock also prevent water migration.
- Water abstraction and water bore construction is licensed by the Department of Water (DoW). AWE establishes monitoring or observation bores within proximity of operations following consultation with DoW.
History of hydraulic fracturing in Australia
In Australia, hydraulic fracturing can be traced back over 40 years where it was used in the production of energy resources including conventional natural gas.
Find out more about the history of hydraulic fracturing from the Department of Mines and Petroleum – an overview of Western Australia’s regulatory framework.