Research On Horizontal Directional Drilling Crossing Construction Risk Assessment Based On Bayesian Network

The long distance oil & gas pipelines are through the complex environment and terrain, for instance, rivers roads and other obstructions. Crossing construction can solve this problem. Horizontal directional drilling is a non-excavation construction method. This method has many advantages, such as adaptability, pipe laying of high precision, little environment impact, accurate of buried depth, well economic and social benefits and also can cross through rivers, roads, railways, buildings and obstacles. So, horizontal directional drilling construction is widely used in the construction of oil & gas pipelines crossing. However, throughout the construction process of horizontal directional drilling pipeline crossing, it strongly depends on drill and other equipment, limited by environment and terrain, mud difficult to control. Besides, the invisibility of the drilling and pullback process is also increasing the construction risk. Therefore, it is necessary to study risk assessment of horizontal directional drilling construction.In order to realistically evaluate the risk of oil &gas pipelines horizontal directional drilling construction, a risk assessment method was worked out based on Bayesian network and mechanical analysis. The construction process is divided into 8 stages according to the characteristics of horizontal directional drilling construction. Fishbone is used to identify the risk factors which can clarify the causal relationship among factors. In the construction process of horizontal directional drilling, there are many factors. For this feature, Bayesian network is proposed to analyzed failure possibility. Then, the failure possibility level is determined. Mechanical model of the construction process is established by ABAQUS finite element software. Characteristic factors are quantitative analyzed. The characteristic factors includ engineering design parameters, construction process parameters and formation geological parameters. The failure consequence level of horizontal directional drilling construction is evaluated by matt-element extension method according to casualties, project cost increases and environment pollution. Finally, the risk matrix is established to obtain the risk rank of horizontal directional drilling construction.Meanwhile, in this article, risk control method for horizontal directional drilling construction of oil & gas pipelines is preliminary discussed to reduce its risk rank. Risk mitigation measures are proposed to horizontal directional drilling construction, which ensure horizontal directional drilling construction meet the risk criteria and safe construction.