Risk assessment of trans anatolian natural gas pipeline project

TANAP project is designed to carry the Azeri natural gas from Shah Deniz 2 Gas Field along with other areas in the South Caspian Sea to Turkey and Europe. TANAP begins from the Georgia/Turkey border, goes through the borders of 20 provinces, and ends at Turkey/Greece border. Trans Anatolian Natural Gas Pipeline (TANAP) Project has the potential to cause accidents defined under the titles of corrosion, sabotage, material and equipment, incorrect operations, natural damage, and third-party damages. Also, TANAP pass through the areas that underground and groundwater resources, ecologically and socio-economically sensitive areas are located. Therefore, it is very important to evaluate the failure possibility and to determine risk value of TANAP project. For this purpose, risk assessment method of gas transmission pipelines based on historical failure-related data that developed by (Shan, Shuai, Xu, & Zheng, 2018) has been used. Trans-Anatolian Natural Gas pipeline is separated into 16 segments according to the seismicity property of the pipeline crossings. Calculation of risk value of each segment has been done based on six main factors that lead natural gas transmission pipelines to the failure according to historical related data. The calculation of the risk value for these six main modification factors is done based on 34 secondary modification factors that carve out that six main factors. For increasing the objectivity of the risk calculation process, the modification factors was tried to be made as quantitative as possible. Given the different levels of difficulty in quantifying the sub level modification factors, they were divided into 3 different groups to calculate the second-order modification factors more precisely: a quantitative index, a semi-quantitative index, and a qualitative index. Quantitative indices are calculated by fitting functions that developed based on statistical data. However, qualitative and semi-quantitative indices are conceptualized by the expert-opinion based scale and fuzzy logic method which is developed by (Guo et al., 2016). After calculation of second level modifications factors, corresponding weight of each second level modification factor in first level modification factor is calculated according to their mean failure frequencies. Sum of multiplication of second level modification factors to their corresponding weight gave us first level modification factor. Failure frequency is the term used to show how often the failure is per kilometer of the pipeline. The basic failure frequency term defines the average failure frequency of the selected part of given pipeline. The basic failure frequency estimate for the TANAP project was derived from historical pipeline accidents collected by PIDs such as PHMSA, NEB, and ECIG. Data about failures in the pipelines in years 2002 and 2015 were used to calculate baseline failure frequency. The product of multiplication of baseline failure frequency to first level modification factors determines primary cause failure probability of each modification factor. Sum of every six determined primary cause failure probability demonstrates the failure probability of selected segment. The average failure probability of pipeline based on their length demonstrates failure probability of TANAP project. Failure probability of TANAP is equal to 2,25 x 10-4 per km per year. According to the assessment scale of failure probability, risk probability of selected segment was evaluated as medium level. For decreasing failure probability applicable recommendations are given such as enhancing subfactors of third party damage, corrosion, also material and equipment factors that are leading factors of TANAP project. In order to ensure the reliability of the results of the risk values calculated for the TANAP project, calculated results are compared with the risk assessment score of TANAP project based on K.W. Muhlbauer risk assessment methodology. Correlation between the results of two evaluation method has demonstrated an agreement.