SPWLA Glossary

Steel pipe cemented in place in an oil or gas well as the drilling progresses or when the well is completed. The casing serves several purposes:

(1) to prevent the formation walls from caving or squeezing into the hole during drilling;

(2) to protect one formation from damage when heavy mud weights are required in drilling another;

(3) to provide a means to isolate porous and permeable formations from one another at the wellbore;

(4) to prevent contamination of shallow aquifers by drilling muds. See also casing string.