Objective In-line inspection of oil and gas pipelines, as a critical component of pipeline integrity management, plays a pivotal role in providing a scientific basis for preventing and undertaking appropriate maintenance measures against pipeline accidents.

Methods To provide a comprehensive understanding of the current state and future trends in in-line inspection techniques for oil and gas pipelines, this study conducted an industrial review including two key aspects: the current development status in inspection techniques and data analysis methods. In the first aspect, an investigation was made on the testing principles of various types of typical techniques, including singleprinciple testing techniques, composite testing techniques, and novel testing techniques. Additionally, the technical levels and industrial applications of in-line testing devices were examined. A comparative analysis between China and foreign countries was conducted with a specific focus on the development progress and application levels of similar techniques. The second aspect centered on the widely used magnetic flux leakage testing, presenting a methodology review based on the data analysis approaches, including defect recognition, classification, and inversion.

Results In-line inspection techniques of oil and gas pipelines have witnessed widespread industrial applications. In foreign countries, several techniques, such as magnetic flux leakage testing (MFLT), ultrasonic testing (UT), and eddy current testing (ECT), have been extensively standardized and serialized. China entered this field at a later stage and still lags behind international advancements. However, China has made progress in successfully implementing MFLT and ECT techniques in diverse oil and gas pipelines by leveraging the expertise. To expand the scope of applications and overcome limitations associated with traditional in-line inspection techniques, there has been the development of composite inspection techniques that combine the strengths of various inspection techniques.Consequently, the industry is endeavoring to explore the feasibility of emerging techniques, particularly those targeting the inspection of pipeline axial stress and pipe performance.

Conclusion Notable advancements have been achieved in the development of in-line inspection techniques for oil and gas pipelines. However, several challenges persist, requiring enhancement and further research, primarily including the detection capabilities of tiny defects and the methods for detecting additional stress. In addition, there is an urgent demand to focus on intelligent analysis methods for processing the vast amounts of testing data collected during in-line inspections, to provide technical support for the further development of in-line inspection techniques.