PR-469-173823-R01 In Line Inspection and Evaluation of Pinholes in Oil and Gas Pipelines

Abstract

Pinhole leaks have been reported as a significant cause of oil and gas pipeline failures in recent years. From 2010 to 2015, at least 131 significant incidents involving oil and gas pipelines in the United States (101 and 30, respectively) were attributed to pinhole leaks. The 9th European Gas Pipeline Incident Data Group Report states that as of 2013, the five-year moving average failure frequency for pinholes was equal to an approximate annual rate of 0.105 failures per 1,000 kilometers of pipeline(1). Pinholes may result from normal pipeline corrosion during routine operations, such as microbiologically induced corrosion, or can be created by third-party activities, such as illegal tapping. These small leaks have become a major risk for many pipeline companies. Pinhole leaks are more likely to lead to serious consequences than larger leaks because they are difficult to discover through normal monitoring and patrolling. An undetected pinhole leak can lead to significant soil and groundwater pollution over time. The research objective of this project was to investigate the applicability of magnetic flux leakage (MFL) to the inspection of oil and gas pipelines for pinhole defects. The MFL signal may be affected by pinhole diameter, depth, position, and so on. MFL inline inspection (ILI) technologies from five vendors were tested in blind scenarios involving pipeline with manufactured defects. Multiple pull through tests, field dig verification, and sampling were conducted to assess the effectiveness of MFL-ILI in pinhole detection. An optimal practice was developed by comparing the gap between MFL tracks, sampling frequency, intensity of magnetic field, etc. This report also outlines tests conducted to investigate the feasibility of using hydrostatic testing to detect pinholes.