Frequently Asked Questions
Shale gas is natural gas found in very fine-grained sedimentary rock. The gas is tightly locked in very small spaces within the reservoir rock requiring advanced technologies to drill and stimulate (fracture) the gas bearing zones. The creation of fractures within the reservoir is critical in allowing the natural gas to flow to the well. Once stimulated, the shale gas reservoirs are produced in the same way as conventional gas wells. The application of these technologies has led to a rapid rise in shale gas production, especially in the United States.
Water is an important resource that natural gas companies pay close attention to, following government regulations, securing appropriate permits and applying industry best practices. The interface between water and natural gas development occurs in four main ways: surface water used during drilling; water pumped into tight and shale gas formations for reservoir stimulation; water produced from reservoirs where it is naturally occurring but not drinkable; and the penetration of ground water aquifers by wells drilled for natural gas production. In every case, drinking water is protected and water is recycled for use again and again wherever possible.
Regulations vary between jurisdictions but, generally, the oil and gas sector is designed to protect drinking water and water quality in lakes and streams and always isolates and protects drinking water (groundwater) from natural gas operations. In some oil and gas regimes, regulation requires that natural gas development provide an extensive barrier (both vertically and laterally) between any shallow stimulation interval and existing water wells, in addition to isolating the aquifer and the fractured zone. Many countries have increased the focus on water well education and standards in oil and gas producing areas.
Hydraulic fracturing (also called “fracking”) is the process of pumping a fluid or a gas down a well, many hundreds or thousands of metres below ground, to a depth considered appropriate for natural gas production. The pressure this creates causes the surrounding rock to crack, or fracture. A fluid (usually water and largely food additives) holding a suspended proppant (usually sand) then flows into the cracks. When the pumping pressure is relieved, the water disperses leaving a thin layer of the sand to prop open the cracks. This layer acts as a conduit to allow the natural gas to escape from tight (low permeability) formations and flow to the well so that it can be recovered. The technology is carefully used and managed to minimize any environmental impact, particularly on groundwater.
Wellbores are carefully constructed to efficiently recover gas while protecting the surrounding environment, particularly underground drinking water. A well bore is drilled to allow a narrow pipe to be sunk deep into the ground. This pipe is surrounded in the bore hole with cement to ensure that both the pipe and the underground area it travels through are completely separated. At the production site, deep underground and several thousand meters below the water table, the production pipe is perforated to allow the natural gas to flow into the pipe and rise up to the surface.