Studi kasus Pengaruh Vortex Induce Vibration (VIV) pada Freestanding Drilling Conductor SAKA Energi Sesulu
Feasability study Vortex Effect induce Vibration (VIV) on Freestanding Energy Drilling Conductor SAKA Sesulu
Keywords:
VIV, Conductor, Offshore, Periode getar alami, Vortex sheddingAbstract
[ID] Salah satu fase terpenting dalam proses eksplorasi minyak dan gas bumi adalah pengeboran sumur uji coba untuk mengetahui kandungan hidrokarbon pada sebuah reservoir minyak bumi dan gas. Arus laut dapat menyebabkan terjadinya VIV pada drilling conductor yang berujung pada terhambatnya operasi pengeboran atau kegagalan struktur akibat fatigue pada pipa conductor. Pada kondisi drilling test well, pipa conductor untuk test well harus diperlakukan sebagai struktur freestanding yang hanya mendapatkan kekangan arah lateral dari Texas Deck pada Drilling Rig pada bagian atas conductor. Paper ini akan menjelaskan metode yang dapat dipakai untuk melakukan analisa terhadap kemungkinan terjadinya VIV pada freestanding conductor. Studi kasus dilakukan pada struktur drilling conductor milik SAKA Energi Sesulu berdiameter 762 mm dengan tinggi 67.4 m. Analisa dilakukan dengan mempertimbangkan beban lingkungan pada kondisi servis dengan periode ulang beban gelombang 1 tahun dan kondisi storm dengan periode ulang beban gelombang 100 tahun. Berdasarkan analisa dinamik, dapat disimpulkan periode getar alami struktur untuk Mode 1 adalah 2.00 sec dan Mode 2 adalah 0.594. Dengan menggunakan hasil analisa dinamik tersebut pada analisa VIV berdasarkan kriteria yang disyaratkan pada peraturan DNV RP-C205 dapat disimpulkan bahwa in-line vortex vibration terjadi untuk mode 1 dan mode 2. Oleh karena itu, perlu diambil tindakan preventif untuk mencegah terjadinya kegagalan fatigue pada struktur conductor tersebut.
[EN] One of the most important phases in the of oil and gas exploration process is drilling the test wells to determine the hydrocarbon content in an oil and gas reservoir. Ocean currents can cause VIV on drilling conductors which resulted in delays or structural failure in drilling operations due to fatigue in the conductor. During drilling a test well, test well conductor should be treated as a freestanding structure which is only laterally restraint from the Texas Deck on Drilling Rig at the top of the conductor. This paper will describe a method that can be used to analyze the possibility of VIV on freestanding conductor. The case studies carried out on the structure of conductor-owned drilling SAKA Energy Sesulu 762 mm in diameter with a height of 67.4 m. The analysis was performed by considering the environmental load on the service conditions with a return period of 1 year and wave loads storm conditions with a return period of 100 years wave loads. Based on dynamic analysis, we can conclude the natural period for the structure is 2.00 sec and 0.594 for Mode 1 and Mode 2 respectively. Using the results of the dynamic analysis on VIV based on the criteria from DNV RP-C205, it can be concluded that the in-line vortex vibration occurs for mode 1 and mode 2. Therefore, it is necessary to take preventive measures to prevent the occurrence of fatigue failure in the conductor.
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References
DNV. (2010). Recommended Practice C205. Norway: DNV.
Guo, B. (2005). Offshore Pipeline. Burlington: Gulf Professional Publisher.
Naess, A. A. (1985). Fatigue Handbook Offshore Steel Structure. Trondheim.
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