A marginal field defines as an oil and/or gas field that has a short production period, low proven reservoir, and could not be exploited using existing technology. As the demand for oil and gas keeps increasing, one of the solutions to tackle the issues is to build the modified platform which came to be more minimalist to conduct the oil and gas production in the marginal field. Naturally, the minimum offshore structures are cost less but low in redundancy, therefore, pose more risks. Although the study on the minimum structures is still uncommon, there are opportunities to find innovative systems that need to have a further analysis toward such invention. Therefore, this study took the modified jacket platform as a minimum structure, and local stresses analysis by using finite element method is applied for the most critical tubular joint with multiplanarity of the joint is taking into account. The analysis was carried out using the finite element program of Salome Meca with three-dimensional solid elements are used to model the multiplanar joint. Various loading types of axial force, in-plane bending moment, and out-of-plane bending moment are applied respectively to investigate the stress distribution along the brace-chord intersection line of the tubular joint. The results show that the hotspot stress occurred at a different point along each brace-chord intersection line for each loading type. Finally, as compared to the in-plane bending moment or out-of-plane bending moment loading types, the axial force loading state is thought to generate greater hotspot stress.
⎯ Offshore structure decommissioning is mandatory when an offshore oil and gas platform reaches the end of its service life. There are no less than 450 fixed offshore steel structures in Southeast Asia, and by 2030, more than 200 offshore fields will be terminated and need to be decommissioned. From an operational aspect, the decommissioning process is simply an inverse of installation. However, due to the structures' age and the uncertainties of the structural performance, the simple operation can be an obfuscating process. This paper discusses one of the most crucial processes during decommissioning: lifting. The dynamic performance of a lifted jacket in several rigging variations is investigated. We use a standard stern crane HLV (Heavy Lift Vessel) to simulate the process, with several wave attack angles. Sea condition is according to DNVGL benign wave during marine operation, with random waves generated using the JONSWAP spectrum. Coupled dynamics of HLV and jacket motion are analyzed.
This study has been carried out to evaluate the dynamic behavior of the Cylindrical FPSO Sevan Stabilized Platform (SSP) and the LNG Carrier (LNGC) during the process of tandem offloading. The study includes hydrodynamics modellings, computations, and simulations of both cases SSP and LNGC operated individually and in combination for offloading operations. The SSP is moored with two variations of mooring, namely taut and catenary. Environmental loads are waves with the incorporated winds and currents propagating 90 o , 210 o , and 330 o relative to the SSP headings. Excitation of random waves up to Hs = 4.50 m instigates the relatively low SSP motions in standalone condition. In offloading condition, when LNGC is connected, the SSP motion could magnify as much as 2.0 up to 5.0 times higher than that in standalone condition, but still considered in an acceptable level. The motion quality of LNGC in offloading operation is comparable with the SSP. For various random wave headings with Hs = 4.50 m during offloading operation may generate maximum tensions between 1,600 kN up to 2,600 kN in the casse of catenary mooring, and between 4,700 kN up to 7,000 kN in the case of taut mooring. Even then, this largest tension preserves a safety factor of 2.05 which is well above the limit of 1.67 as required by the governing standards. Finally, the study conclude an operability of as much as 90% could be achieved on SSP and LNGC offloading operation in the Masela Block of the Abadi Gas Field.
Waste steel from used ship propeller shafts is reused for the keel structures of InaTEWS buoys. Because of the application of waste material, fatigue life assessment is critical. The purpose of this study is to assess the mechanical and fatigue properties of the waste material and to estimate the fatigue life of the keel structure as a result of sea wave loading. Material tests, fatigue tests and model tests were performed to obtain the parameters required for the estimation of the fatigue life, together with application of the spectral analysis method, including the effects of spectral band width. Chemical and tensile tests identified the material as low-carbon steel, with mechanical properties comparable to AISI 1035 steel. The fatigue tests resulted in an S-N curve (NS m = K) with m = 7.7 and K = 3.2×10 24 , showing a lower fatigue strength than AISI 1035 steel. The observed reduction in fatigue strength is ascribed to the previous use of the shaft. The calculated fatigue life based on the experimental S-N curve and the observed in-situ wave data is approximately 9.5 years, with a safety factor of 5.
Motif Batik merupakan hasil dari cipta, rasa dan karsa manusia yang diekspresikannya melalui kegiatan membatik. Setiap motif yang dibuat pada kain Batik memiliki nilai-nilai filosofis yang terkandung di dalamnya. Guna menumbuh-kembangkan motif Batik di Kampung Jetis Sidoarjo sebagai pusat kegiatan Batik tulis di Jawa Timur, perlu dijaga kelestariannya dengan cara menumbuhkan minat dan gairah pada generasi muda. Salah satu upaya adalah melalui pengenalan variasi Batik motif kelautan, mulai proses desain dan produksi Batik tersebut. Harapannya agar pengrajin dan masyarakat tetap menjadikan Batik sebagai produk unggulan dan warisan budaya Nusantara.
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