INSTALLATION AND FREE SPAN ANALYSIS OF SUBSEA PIPELINE ON MARTUBO PROJECT IN LAUT ISLAND SEA

• Main Author: Padang, Febiyola
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86397
• Institution: Institut Teknologi Bandung

The consumption of oil and natural gas as the main energy sources in Indonesia has increased year by year. Throughout 2022, Indonesia produced 31.4 million tons of oil, with usage reaching 69.7 million tons. To avoid a deficit in oil supply, exploration and exploitation of potential oil reserves in Indonesia have been undertaken. SKK Migas has set a target for oil production of 1 million barrels of oil per day (bopd) and natural gas production of 12 billion standard cubic feet per day (bscfd) by 2030. One of the efforts to achieve this target is by building exploration and exploitation facilities for oil and gas, such as submarine pipeline systems. These submarine pipeline systems are designed to function optimally in transporting oil and natural gas. Therefore, appropriate design and analysis following applicable standards are needed to ensure the safety and efficiency of the submarine pipeline systems. In this study, the submarine pipeline system is divided into two zones classified based on waves and currents. The Kolmogorov-Smirnov distribution test is conducted to obtain environmental data, including significant wave height, current speed, and storm surge for return periods of 1, 10, and 100 years. This environmental data will be used in the subsequent design and analysis of the submarine pipelines. The design stages of the submarine pipeline begin with determining the wall thickness of the pipe based on the DNV-ST-F101 design standard, considering failure criteria such as internal overpressure, external overpressure, and propagation buckling. The wall thickness is adjusted according to the availability of pipes from the API 5L catalog. In this study, the pipe wall thickness that meets all design criteria is 12.7 mm. The next design stage involves analyzing on-bottom stability based on the DNV-RP-F109 design standard to determine the thickness of the concrete coating required to keep the pipeline stable. The concrete coating thickness that meets the on-bottom stability criteria is 72 mm and 55 mm for zones 1 and 2, respectively, if no trenching is applied. The application of 30 mm trenching reduces the required concrete coating thickness to 40 mm for both zones. The installation analysis is conducted by considering the movement response of the lay barge due to waves from several directions. In this analysis, the lay barge configuration is optimized so that the stress and strain on the pipeline meet the criteria based on DNV-ST-F101. The final design process in this study is to determine the allowable free span length for fatigue screening and ultimate limit state criteria based on the DNV-RP-F105 design standard to prevent structural failure of the pipeline. The allowable free span length is 11.2 m for zone 1 and 13.8 m for zone 2.