The Montney formation consists of a mixture of low permeability sandstone, siltstone and shale lying about 2,500 metres below the surface. Low permeability means it is difficult for the gas to flow through the rock and so we must employ special technology to produce this resource.
When a well is drilled we use water and drilling fluids to lubricate the drill bit and flow drill cuttings to surface. Once a well is drilled, it is completed using a technology called hydraulic fracturing that involves injecting water mixed with sand plus additives down through the well bore and into the formation deep below the Earth’s surface.
The pressure created by the water fractures the rocks providing a path for the gas to flow into the wellbore. Sand is used to keep the fractures open so the gas flows more freely.
For Groundbirch, fracturing occurs at depths approximately 8,000 feet or 2,500 metres below the surface – this means there are many layers of rock (about 2.5 km) between where the fracturing occurs and the shallow freshwater aquifers and the surface.
During initial production approximately 20 per cent of water injected comes back to the surface as flowback water. The rest of the water flows back during the long-term production (otherwise known as produced water). The flowback and produced water is collected, stored and reused for other completion operations.