The wells contain layers of steel and cement that isolate the coal seams we target from the geologic layers and aquifers above.
The steel casing which lines the wells is specially designed to withstand operational pressures during drilling operations, testing and production and resist corrosive subsurface conditions. The steel casing is also protected by specially formulated cement designed to be as strong as the rock into which the well is drilled.
Click here: Drilling with Care fact sheet
Our wells are drilled to the highest industry standards to ensure there are no integrity issues and layers of steel casing and cement seal off the well from the shallow aquifers as we drill down to the coal seams.
The Well integrity Code of Practice requires Santos to keep and maintain extensive records of each well’s construction and its on-going monitoring and maintenance. These records must be lodged with, and reviewed by, the petroleum regulator each year.
The coal seams we are targeting in the Narrabri area are between 500 to 1,200m below the surface. They are separated from the shallow aquifers used by farmers and the community by hundreds of metres. When we drill through the aquifers they are isolated behind single or double layers of steel and pressure tested cement, which prevents cross-contamination.
Click here: Protecting Local Aquifers fact sheet
The shallow aquifers, (including the Pilliga sandstone, which is an extension of the Great Artesian Basin), generally lie between 5 – 300 metres below the surface in the Project area. In the Narrabri area, the coal seams we are targeting typically lie between 500 – 1,200 metres underground.
There are layers of solid rock between the Pilliga sandstone and the coal seams. These rock layers are known as aquitards and act as barriers to the water travelling up and down.
This geology, along with existing information from previous research on the area in which we are working, gives us confidence we will not impact local water resources.
We have established a network of shallow and deep aquifer monitoring bores around our project area. Data from these wells will give the community added confidence our work is not impacting the aquifers. Water quality and water level data from these wells can be accessed by the community via Santos’ water portal.
Explore further: Santos Water Portal
The Narrabri Gas Project and the GAB
The Namoi Catchment Water Study, carried out by independent experts and commissioned by the Government, showed no harmful impacts on groundwater from natural gas developments on a much larger scale than we are proposing with the Narrabri Gas Project.
The study predicted there would be a drawdown of less than 0.5m over 90 years – which is within the range of existing seasonal variations.
Click here: Final Report Namoi Catchment Water Study
Hydraulic fracture stimulation (commonly referred to as “fraccing” or “fracking”) is a technique used to improve the flow of natural gas from a well. Water, sand and a small amount of chemicals are pumped into a well and down into the coal seam at high pressure to open up fractures in the coal. The sand remains in the fractures to hold them open, allowing more gas to flow, and the fluid is pumped back out of the well. The technique has been safely used throughout Australia for over 40 years.
Santos has no plans to use hydraulic fracture stimulation as part of the Narrabri Gas Project. We are not seeking approval for its use as part of the Narrabri Gas Project EIS.
Due to the geology of the coals in the Project area, we do not believe the technique will increase gas flows in the coal seams we are targeting.