1. n. [Well Testing]
A fluid column (usually water or nitrogen) put in the drillstem to provide the desired backpressure at the start of a drillstem test. The cushion usually serves to limit the differential pressure across the test string and packer to avoid flow below the bubblepoint pressure (in which case water is the usual cushion) or to enable a depleted reservoir to flow (nitrogen is the likely cushion).
