Heat Checking | Materials And Corrosion Control
| Damage Mechanism | Heat Checking |
Damage Description |
· Heat checking results from frictional heating causing the skin temperature of a drilling component to exceed the critical temperature for steel in the absence of mud circulation (i.e., about 700°C, the temperature above which the transformation from martensite to austenite starts), followed by rapid quenching by the drilling mud. Heat checking could promote quench cracking or changes in dimensions, surface appearance, microstructure, or mechanical properties. |
Affected Materials |
· Carbon steel and low alloy steels |
Critical factors |
· Loss of mud circulation is critical to cause heat checking to drill pipe and rotary elements
· Increasing rotating speed during beck reaming or other drilling operations would accelerate the susceptibility to heat checking in the absence of mud circulation. · Increasing side load against the formation or casing accelerate heat checking in the absence of mud circulation. · Increasing the wall thickness of rotating components increases the susceptibility to heat checking. · The coefficient of friction between rotating components and casing or formation. · The availability of cooling medium |
Affected Units or Equipment |
· Drilling equipment: drill pipe, heavy weight drill pipe, drill collars, drill jars, cross-over subs, tool joints, drill bits, bit subs, Kellys
· Fishing equipment (over-shots, tubing/casing spears, milling tools, reverse circulating junk catchers, fishing magnets, fishing jars, wash over pipe) |
Appearance or Morphology of Damage |
· Micro and/or macro cracks: The rapid heating and quenching results in numerous shallow quench cracks in the surface of the component, giving a “crazed” cracking pattern with cracks running in both the longitudinal and transverse directions. These cracks, if undetected or not removed, may then propagate due to other mechanisms, e.g., fatigue as result of vibration or cyclic loading of the string, resulting in component failure. It is worth noting that optimizing other material features, such as assuring good toughness and mechanical properties can help mitigate against catastrophic failure (twist-offs) resulting from heat checking. · Hardness change: Heat checked portion would lose its tensile strength leading to outer diameter reduction during rapid heating · Color change: The metal skin changes its color to bluish dark to form a magnetite film due to the high temperature exposure · Dimensional change: If the rotating components are subject to the weight of the connected components, heated areas could be elongated. · Due to rapid heating and quenching, heat checked areas might have martensite. |
Prevention/Mitigation |
· Ensure mud circulation throughout drilling or fishing operations · Minimize the side load on the drill pipe or fishing tools |
Inspection &Monitoring |
· Prior to next drilling or fishing operation, visual inspection and ultrasonic testing need to be performed on heat checked drill pipe, rotating elements or fishing tools. Not all heat-checked components should be rejected. Visual or metallographic inspection would note changes in dimensions, cracks, color, microstructure and hardness. Reject any changes in dimensions
· Reject any cracks by heat checking |
Inspection Frequency |
· After each job |
Key Performance Indicators (KPIs) |
· # Total Heat Checking failures · # Heat Checking failures due to dimensional changes · # Heat Checking failures due to cracking |
Plant Integrity Windows (PIWs) |
· Not applicable |
Competencies and Training |
Corrosion Courses
· e-COE 101 Corrosion Basics · e-COE 701 Corrosion & Corrosion Prevention · PEW 407 Corrosion Technology · COE 104 Chemical Treatment for Producing Operations |
Reference Resources (Standards/GIs/BPs) |
· H. J. Choi, “Understanding Heat Checking, an Overlooked Failure Mechanism of Drilling Components,” JPT Drilling Technology, pp-34, February 1998
· L. F. Eaton, “Tool Joint Heat Checking While Pre-drilling for Auger TLP Project” SPE/IADC 25776, 1993 SPE/IADC Drilling Conference in Amsterdam, Netherland, 1993 |
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