Study On Survey Technique For The Corrosion Protection Status Of Submarine Pipelines

As the development of the offshore petroleum and gas exploitative engineering, more and more submarine pipelines have been used broadly, so it is very important to inspect the status of submarine pipeline protection. Xia Weijun's thesis brought out a theory based on the measurement of environment's potential difference to evaluate the corrosion protection status of submarine pipelines. BP Neural Network Algorithm was used to establish the non-linear relationship between potential difference and those determined influence factors of the status of submarine pipeline cathodic system: the average coat defection of sacrificial anode, the current of sacrificial anode, remaining weight of sacrificial anode and etc. However, such research is still far from the actual engineering application. Therefore, the goal of this thesis is to bring out a system about how to improve this technique and take it into actual application.Firstly, "infection factors database of electric field under cathodic protection system" is extended to cover the actual engineering submarine pipelines. The pipeline radius and distance of sacrificed anode are parametric, and the key calculated data of the database are extended to 25,920 groups, hence it can evaluate corrosion protection status of every submarine pipeline in the actual engineering. Meanwhile, the real-time & automatic and man-handed corrosion protection status evaluation software for the submarine pipelines is programmed, it can real-time deal with the data wave of the potential difference, which is probed by underwater potential probe and transmitted by data collection hardware, and can automatically judge the position of the anode, automatically evaluate the parameter of the corrosion protection status.Secondly, as to the working mode of that vehicle hauls towed body in the actual submarine pipeline survey, the integrated solution of both technique and equipments is studied. The Survey System for the Corrosion Protection Status of Submarine Pipelines is divided into four main child systems: real-time positioning of the underwater towed body, magnetic anomaly detection for the exact position of submarine pipeline, underwater data acquisition and survey, equipment integration of underwater towed body. Each child system is theoretically studied, and application solutions are designed and verified. The underwater GPS positioning system, which combines both differential GPS system of the vehicle and underwater ultra short baseline acoustical positioning system, is used to real-time track the position of towed body. Magnetic anomaly detection for the submarine pipeline is used to track the exact position of the pipeline in small range. Standard electrode probe and underwater cable transmitting system are utilized to measure the potential data of cathodic system. Remote Operated Vehicle, which integrates acoustic transponder, potential and magnetic probe, data transmitting system, is utilized to act as the main body of the underwater survey.Meanwhile, consummate software for corrosion protection status survey of submarine pipelines is developed, based on Geographical Information System technique, programmed by Visual Basic combining Microsoft SQL Server database system. Such software has graphic visual digital sea map interface, can real-time track and display the position of both working vehicle and underwater towed body, can automatically judge the position of submarine pipeline and sacrificed anode and meanwhile export the result of corrosion protection status evaluation, and also can search and replay the survey date, predict the future corrosion protection status. This software, which is functionally powerful, is also easy to operate; moreover, it can be used as a survey guide system to actual submarine pipelines survey; therefore, great potential application value may be contained in it.