Feasibility study of dual-energy limited-number-detector computed tomography of oil and gas pipelines

Fluid transmission pipelines are prone to corrosion and sediment deposition due to the nature of the materials they carry. Deposits inside of the pipeline may worsen corrosion, leading to micro-cracks and pitting. Neglecting to assess these factors can lead pipelines to failures with catastrophic consequences. Therefore, monitoring and measuring corrosion, erosion, and sedimentation levels within pipelines are crucial. Various methods have been developed for this purpose, with techniques using penetrating X-rays and gamma rays being the most accurate and non-destructive. In this study, gamma-ray dual-energy computed-tomography was utilized as a precise and non-destructive method for detecting corrosion in pipeline walls. Projections were obtained using the Limited-Number-Detector Computed Tomography (LNDCT) technique for pipeline phantoms. Dual-energy techniques were employed, emitting gamma rays from suitable radioactive isotopes such using two radioisotopes, Am-241 and Cs-137. Projections at different angles were recorded using 15 NaI(Tl) 2-inch detectors, and the corresponding full-energy-peak were separated and organized in the sinogram matrix. Subsequently. Image reconstruction was performed using the Filtered-Back-Projection (FBP) algorithm, and the quality of the reconstructed image was assessed. The reconstructed images demonstrate the effectiveness of the dual-energy method in distinguishing between light and heavy materials, potentially leading to higher image quality compared to single-energy methods. Detailed analysis of the data obtained from dual-energy tomography enables precise identification of defects, failures, and sedimentation, without damages to pipeline structures. This research contributes to enhancing the evaluation and monitoring methods for pipelines, improving the efficiency of these systems, and ultimately advancing safety and productivity in the oil and gas industry.