Cementing

The first step for most wells in Canada is the installation of production casing. The casing—tubular steel pipe connected by threads and couplings—lines the total length of the wellbore to ensure safe control of production, to prevent water entering the wellbore and to keep rock formations from "sloughing" into the wellbore. Production casing is cemented in place by pumping a cement mixture into the casing and forcing the cement back up the annulus, between the casing and wellbore. The task must be done quickly but carefully because a poor cement job can adversely affect the finished wellbore.

Once the cement has set, the drilling rig is usually moved, and a smaller, truck-mounted service rig is brought in to complete the well. There are about 600 service rigs in Canada. They also return to wells periodically to perform maintenance, replace equipment or enhance production.

The second step is the installation of the production tubing. Production tubing is steel pipe smaller in diameter than the production casing. It is lowered into the casing and held in place by packers which also isolate the producing layers of rock. The tubing hangs from a surface installation called the wellhead. The wellhead includes valves, chokes and pressure gauges, and makes it possible to regulate production from the well.

Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.