Bien Dong 20-Inch Pipeline Span Field Observation and Span Correction

Abstract

Abstract The 44 km-long Bien Dong 20-inch pipeline (PL-BD2) was installed at the Hai Thach gas fields in 2013. Since the gas export pipeline started to operate, Bien Dong Petroleum Operating Company (BDPOC) has been annually conducting in-water video surveys. From the field surveys, BDPOC found significant changes in pipeline span length and location every year. Some of the free spans were observed to have exceeded the allowable span length, prompting BDPOC to perform span corrections in 2015 and 2016 by placing grout bags at over-span locations. Despite the two span correction campaigns, pipeline free spans were still observed to exceed the allowable span length at new locations in 2017. The objective of this paper is to discuss and interpret field observations of non-stationary free span based on the five in-water surveys from 2013 to 2017. Over 3000 lines of free span data have been gathered, processed or matched such that the development of over 800 free spans in five years can be traced. The free span data is then analyzed with a focus on the free span development characteristics (form/disappear, increase/reduction in length) and the effectiveness of invention work using grout bags in reducing the span length. Probability distributions of span number in one kilometer and span length are also provided. The field observations and statistical data presented in this paper may complement any future free span research on integrating the characteristics of non-stationary span, and they could be informative references for regional operators to plan their strategy for non-stationary span rectification.