A device or material which may be temporarily or permanently placed in the wellbore to block off or isolate lower zones so that upper zones may be completed, stimulated, tested, cemented, produced, or injected into.
Source: API BULLETIN E3, Environmental Guidance Document: Well Abandonment and Inactive Well Practices for U.S. Exploration and Production Operations, First Edition, January 1993 (Reaffirmed June 2000). Global Standards
“Plug” means the closing off, in a manner prescribed by the Commission, of all oil, gas, and waterbearing formations in any producing or nonproducing wellbore before such well is abandoned.
Source: Corporation Commission, Oil and Gas Conservation, Oklahoma Administrative Code 165:10, February 2013. Regulations