Evaluation Method for Applicability of Tubing with Corrosion Pits in Certain Oil Field

A research is performed on major types of defects and applying working conditions of tubings with corrosion pits in a certain oil field.Using the structure service safety and reliability theory as an analyzing method,the chemical composition and properties of the defected tubings with corrosion pits are evaluated through material performance test,real product tesile test,internal-pressure burst test and external-pressure collapse test.Applying the 3σ criterion and comparing with the investigations of the working conditions,the terms for defected tubings to be applicable under different well conditions of a certain oil field are determined.The results show that the material properties of a repaired tubing meet the requirements of API Spec 5CT-2011,the tensile load and anti-internal pressure strength meet the requirements of SY/T 6417-2016,while the anti-external-collapse properties of 50% of the samples do not meet the requirements of SY/T 6417-2016.Defected tubings can meet the load requirements under working conditions such as rod puming well,submersible pump well and low-pressure flowing well.Real application results approve that the above-mentioned evaluation method is reliable.