What is the purpose of a surface casing?

The surface casing serves a critical function in well construction primarily aimed at protecting freshwater aquifers. This layer of casing is installed at the beginning of the drilling process, extending from the surface down to a specified depth. Its primary role is to create a barrier that prevents contaminants from reaching and affecting the underlying freshwater sources during the drilling of the well.

By isolating the freshwater zones from the drilling operations and any potential contaminants that may be present in drilling fluids or produced fluids, surface casing plays an essential role in maintaining water quality and safeguarding the environment. This aspect is especially vital in areas where natural aquifers are located near drilling sites, as it helps to ensure that the drinking water supply remains uncontaminated.

While aiding in drilling, fluid circulation, and supporting the drill rig are important aspects of the drilling operation, they are not the primary purpose of surface casing. Instead, the principal focus of surface casing is environmental protection and the preservation of freshwater resources.