How is a well completed after engineers find a commercially productive oil or gas formation?

Once a commercially productive formation is identified, engineers prepare the well for continuous production through a series of technical steps:

Casing and Tubing

First, casing is installed to the bottom of the borehole, and cement is forced into the space between the casing and the borehole wall to isolate formations. A string of production tubing is then inserted from the surface to the productive zone, with expandable packing devices used to seal the annulus between the casing and the tubing.1

Perforating and Stimulation

Because the casing is sealed with cement, engineers must create paths for fluids to enter the well. A perforator tool is lowered on a wire line to fire explosive charges through the casing and cement. If the formation has low permeability, engineers may use fracking—injecting high-pressure fluids and proppants—to create or enlarge fissures in the rock.23

Surface Completion

Finally, a network of valves known as a "Christmas tree" is installed at the wellhead to regulate flow and provide access for future maintenance. If natural pressure is insufficient, lifting devices are installed at the bottom of the production tubing.341