Scour Monitoring And Evaluation Of Submarine Pipelines Based On Active-thermometry

The effective exploitation of submarine oil and gas is of key importance for the modern society facing the energy crisis. As the lifeline of submarine oil and gas transmission, submarine pipeline systems are major assets. Scour monitoring is an very important concern to ensure the integrity of pipeline systems. This dissertation introduced a scour monitoring technology based on active thermometry. On top of that, a series of research work had been done, which include the following.1. The theoretical derivation of active thermometry. According to the specific problem faced in scour monitoring, simplified heat transfer models had been proposed for in-water and in-sand scenarios, respectively. Based on "Transient heat method" and "Lumped parameter method", the analytical temperature solutions were obtained for both models, which provided the theoretical foundation for further analysis.2. The introduction of the active-thermometry-based scour monitoring system and exper-iments. The system was comprised of three main components, namely thermal cable, data ac-quisition unit and data processing unit. The thermal cable ran parallel to the pipelines and can generate heat and sampling temperature concurrently. Based on the system, a small-scaled sub-marine pipeline environment was constructed in the laboratory. Three tests were conducted and the temperature data were obtained during heating and cooling periods. Through analysis of the acquired temperature data, whether feature extraction or pattern recognition, the surround-ing media could be identified as being sand or water, and thus we could obtain the location and length of free spans.3. A DS18B20-based scour monitoring system for the nearshore section of submarine pipe-lines and a three-index estimator. DS18B20s, which were cheap and easily deployable, were employed as the temperature sensors in the thermal cable. The three-index estimator was used to analyze the data and deduce the lengths of free spans. The three indices were temperature intensity, temperature curve accordance and temperature fluctuation.4. A BOTDA-based scour monitoring system for long distance submarine pipelines. Con-sidering the many advantages of optical fiber technology and its peculiar convenience used for submarine pipeline monitoring, distributed optical fiber sensors was employed as the tempera-ture sensors in the thermal cable to build a scour monitoring system. Three features were drew from the experimental temperature curves. They were magnitude, temporal stability and spatial continuity.5. The exploration of Artificial Neural Network’s application in scour monitoring systems. Based on the experimental data of the DS18B20-based scour monitoring system, a two-layer BP neural network was trained and checked of performance. It realized media identification with very high accuracy. It demonstrated good universal applicability and anti-noise capability and expected to take on the challenges of practical application.