misrun

A misrun is the abandonment of a planned pressure test or flow test on drilling equipment, tubing, or completed wellbores before useful data can be collected. It occurs when technical problems, equipment failure, or operational errors prevent the test from reaching its intended duration or flow rate. Unlike a successful test that generates pressure curves or production rates, a misrun produces little or no meaningful information about the well's or equipment's actual performance.

Misruns happen most often during drill stem tests (DSTs), which are used to evaluate formation pressure, permeability, and fluid type before completion. A common cause is pipe blockage from formation sand, clay particles, or debris that restricts flow and forces early test termination. Equipment leaks, valve malfunctions, faulty connections between drill pipe sections, or separator failures also trigger misruns. Surface instrumentation problems, such as pressure gauge malfunction or data logger failure, can render a test useless even if downhole equipment functioned correctly.

Cost and operational impact

A misrun is costly because rig time continues to accumulate while no productive data is generated. Operators must either attempt the test again, requiring additional rig time and materials, or proceed to the next well phase without the formation assessment that the test was meant to provide. Multiple misruns on the same well or program reduce the overall information quality available for development decisions and increase non-productive time (NPT) in the well cost baseline.

Field discipline and equipment maintenance directly affect misrun frequency. Wells with poor wellbore cleaning before testing, or with inadequate pipe inspection and pressure rating checks, show higher misrun rates. The term reflects the binary outcome in drilling: a test either runs successfully and delivers data, or it does not. Documentation of misrun causes, such as 'sand influx,' 'tubing rupture,' or 'surface equipment failure,' feeds operational reviews and helps operators refine procedures and equipment specifications for future wells in the same region or formation.