Drill Pipe Failures: Heat Checking, SSC, and Oxygen Corrosion Case Studies

Drill Pipe tubulars are the basis for oil and gas well exploration. Significant technology has been dedicated into their alloy development, connection geometry, and manufacturing processes. Despite these technological developments, the harsh operational and environmental conditions subject these components to extreme limits.

We will showcase three main case studies that include high localized operational drill pipe temperatures due to frictional heating, Environmental Assisted Cracking (EAC) by means of Hydrogen Sulfide exposure, and Oxygen induced corrosion.

During the drilling operations the drill pipe is subjected to tensile, torsional, and bending forces. The loss of circulating drilling mud and the continuous rotation can generate extremely high temperatures due to friction against the casing where the base metal microstructure is transformed from its manufactured condition. These events transform the microstructure which reflects in mechanical and toughness changes which compromise the operational integrity of the drill pipe.

Exposure to hydrogen sulfide can occur depending on the reservoir location. The use of chemicals to inhibit the damage and prevent oxygen corrosion and sulfide stress cracking (SSC) are typically used to mitigate accelerated corrosion attack and SSC. The continuous exposure to H₂S and careless storage and handling practices will affect the base material rendering it more prone to failure. The high tensile and torsional loads have higher detrimental effects to the damaged tubulars causing catastrophic failures.

In the same manner as hydrogen sulfide, oxygen corrosion, CO₂ corrosion or exposure to formation fluids also affects the drill pipe performance. Countermeasures such as oil-based mud and Internal Plastic Coatings are employed to minimize the effect of corrosive species at the metal surface. The corrosion develops pitting that grows into cavities that reduce the effective cross section (wall thickness), introduce stress risers and weaken the integrity of the string.