Water Injection Wells
Water injection wells are used to inject water into a pre-existing oil or natural gas pool to produce oil or natural gas. This oilfield practice maintains pool pressure and helps sweep oil towards producing wells. The injection of water in a controlled manner maximizes both efficiency and recovery of the petroleum product. These operations are approved by the Commission as a condition of a Pressure Maintenance Approval granted under Section 75 of the Oil and Gas Activities Act.
The Commission requires industry to report monthly injection or disposal volumes. A Well Authorization (WA) number is assigned through the application and permitting process and an operator may convert an existing oil or gas production well to serve as an injection well. The injection or disposal well is carefully designed to confine dispersed water to a Commission authorized geological zone and to prevent the movement of fluids to potable groundwater sources. Injection wells are drilled into geologic rock formations and are lined with steel casing. The casing is cemented in place to prevent the migration of fluids into potable groundwater zones. Cement is placed behind the long string casing (in the casing by borehole annulus) for tens to hundreds of metres above the injection zone to prevent fluids from migrating upward. The long string casing and cement sheath are perforated in the injection zone to allow produced water to flow into the zone to be captured and permanently disposed.
The fluid pressure, fracturing pressure, water compatibility chemistry and geological characteristics of the injection zone are taken into consideration when evaluating areas suitable for injection. Confining or cap zones are impermeable (leak proof) rock formations that restrict the upward movement of the produced water. Confining zones overlie the injection zone.