Bullheading

Bullheading is a technique that may be used in certain circumstances during drilling operations to pump an influx back into the formation. In other words, it is a term to denote pumping into a closed-in well without returns. A major concern with this technique is that it may result in fracturing any exposed formation.
Bullheading is, however, a relatively common method of killing a well during workover operations when there is adequate reservoir permeability.