The most basic type of completion, used formations unlikely to cave in. Consists of running the casing directly down the formation, leaving the end of the piping open without any other protective filter. Very often, this type of completion is used on formations that have been “acidized” or “fractured”.

Consists of production casing being run through the formation. The sides of this casing are perforated, allowing for the flow of hydrocarbon into the well hole while still providing a suitable amount of support and protection. The perforation process involves the use of specialized equipment designed to make tiny holes in casing, cement, and other barriers. In the past, “bullet perforators” were used, which were essentially small guns lowered into the well that, when fired, sent small bullets to penetrate the casing and cement. Today, “jet perforating” is preferred, where small, electrically-ignited charges are lowered into the well. When ignited, these charges poke tiny holes through to the formation.

Designed for production in areas that contain large amounts of loose sand. These completions allow for the flow of natural gas and oil into the well, while at the same time preventing sand from entering. Sand inside the well hole can cause complications, such as the erosion of casing and other equipment. The most common methods of keeping sand from the well hole are screening and filtering systems. These systems can either be a type of screen hung inside the casing or a layer of specially-sized gravel just outside, filtering out the sand. Both types of sand barriers can be used in open holes and perforated completions.

Those in which components are assembled and installed only once. Installing the casing, cementing, perforating, and other completion work is done with small diameter tools to ensure the permanent nature of the completion. Completing a well in this manner can lead to a significant cost savings compared to other types.

The practice of completing a well so that hydrocarbons from two or more formations may be produced simultaneously, yet separately. For example, a well may be drilled that passes through a number of formations as it descends. Alternatively, it may be more effective in a horizontal well to add multiple completions to drain the formation efficiently. Although it is common to separate multiple completions so that fluids do not intermingle, the complexity of achieving complete separation can present a barrier. In some instances, the different formations being drilled are close enough to allow fluids to intermingle in the well hole. When it is necessary to prevent this intermingling, hard rubber “packing” instruments are used to maintain separation among different completions.

A form of horizontal or slant drilling. This type of completion consists of drilling out horizontally into the formation from a vertical well, providing a “drain” for hydrocarbons. In certain formations, drilling a drainhole completion may allow for more efficient and balanced extraction of the targeted hydrocarbons. Drainhole completions are more commonly associated with oil wells than with natural gas wells.