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Wellbore construction is critical to protecting groundwater. We take great care to design and install effective well casing systems.
Proper wellbore construction is critical to protecting groundwater. We take great care to ensure the integrity of the wellbore and eliminate any pathway from the contents of the wellbore to drinking water aquifers.
During drilling, completions and production operations, all groundwater-bearing rock formations are protected from the contents of the well by layers of steel pipe (casing) and cement sheaths. The process of wellbore construction is highly regulated, including the depth to which casing must be set and the quality of cement used. The number of casing layers we use depends on the unique characteristics of the subsurface and can vary from well to well. Depending on a well’s design, well construction can have between two and four main components. These components include conductor, surface, intermediate and production casings.
Conductor casing is typically the first (and largest diameter) pipe installed during construction and usually extends between 25 and 45 metres (approximately 80 to 150 feet) below surface. Conductor casing is inserted into the surface hole and cemented in place along its full length to ground surface. Its two primary purposes are to hold back any unconsolidated surface sediments and to isolate shallow groundwater from the contents of the hole. We consider the depth of local water wells when setting the depth of our conductor casing. Depending on the shallow geology of our resource plays, we may not set conductor casing.
After the conductor casing is installed and cemented, the hole is drilled deeper and surface casing is installed and cemented in place. The main purpose of surface casing is for well control. Surface casing can be set anywhere up to 600 metres (approximately 2,000 feet) or more. It is also cemented all the way from the bottom of the hole to ground surface, completely isolating the well from groundwater aquifers. Surface casing is installed with the deepest local groundwater aquifers in mind and regulated accordingly.
After the surface casing has been set and properly cemented, drilling of the intermediate hole and installation of intermediate casing begins. The purpose of intermediate casing is to isolate any abnormally-pressured subsurface rock formations from causing instability. In some cases, depending on the unique characteristics of the subsurface, intermediate casing may not be needed.
Production casing is the final length of steel pipe used in wellbore construction. Production casing typically runs the entire depth of the well and may be cemented in place all the way to ground surface. The primary purpose of production casing is to isolate the zone containing natural gas from other subsurface formations. It’s also used to pump hydraulic fracturing fluids into the producing formation without contacting other formations along the wellbore.