• 한국산업융합학회 논문집
• /
• 제24권3호
• /
• pp.253-260
• /
• 2021

The implementation of subsea separation and liquid boosting is becoming a common development scheme for the exploration of deep water fields. Subsea separation is an attractive and economic solution to develop deep offshore fields producing fluid without hydrate or wax. A subsea separator can avoid or simplifying costly surface platforms of floating vessels, as well as being an efficient tool to enhance hydrocarbon production. Subsea separation system should be reliable to ensure successful operation in a wide range of 3-phase flow regime. In this study, multiphase flow characteristics inside in-line type subsea separation system are investigated for the design of subsea separation system.

• 한국산업융합학회 논문집
• /
• 제26권5호
• /
• pp.803-812
• /
• 2023

The subsea separator of an offshore plant for offshore oil and gas development performs the process of separating oil and gas from crude oil produced in the subsea. The oil-gas subsea separator can be divided into a gravity type that separates fluids by gravity and an in-line type that separates fluids using centrifugal force of density. In the case of the deep sea, the development of a small in-line type separator is required due to manufacturing cost and safety problems caused by water pressure. Therefore, in this study, the gas-liquid phase separation efficiency of the subsea separator was identified through the study of the multiphase flow characteristics of the in-line type separator. For the optimal design of the in-line type separator, the shape of the internal swirl element(ISE) was selected first, and the separation efficiency results for each section of the in-line type separator were analyzed. This study was conducted in parallel with experiments and numerical analysis, and it is expected that the reliability and efficiency of the in-line type separator will be improved through the results.

• 한국산학기술학회논문지
• /
• 제14권10호
• /
• pp.5105-5114
• /
• 2013

본 논문은 심해저 환경을 고려한 케이블 및 필터 설계에 관한 연구를 수행하였다. 심해저 플랜트에서 사용하고 있는 전기 아키텍처는 해상에서 고전압의 전원 공급 장치, 고용량 구동시스템, 장거리 케이블과 전동기로 구성되어있다. 전도 노이즈는 전동기 구동용 인버터의 고속 스위칭 시 발생하는 급속한 전압변화로 인해 발생하며, 케이블의 길이가 길어질수록 전동기에 심각한 과도 전압을 발생시킨다. 따라서 심해저 플랜트에 사용되는 장거리 케이블의 R, L, 선간 C, 선-접지 C를 고려한 선로를 설계하여 구동 전동기에 발생하는 과전압을 확인하였다. 또한, PWM 인버터 구동시스템의 전도 노이즈 저감을 위한 필터를 설계하여 심해저 플랜트 모델의 가이드라인을 제안하고자 한다.

• Corrosion Science and Technology
• /
• 제7권1호
• /
• pp.6-12
• /
• 2008

Non-metallic composite overwrap repair methods utilize resin based fiber-reinforced composite materials, which have higher specific strength to weight ratio and stiffness, superior corrosion and fatigue resistance, and substantially reduced weight when compared to carbon steel. Non-metallic repair methods/systems can allow desired functional properties to be achieved at a respectable economic advantage. For example, non-metallic composite repair systems have at least a 50 year design stress of 20 ksi and approximately 25% of the short term tensile strength of fiberglass. For these systems, the contribution of the repaired steel to the load carrying capability need not be considered, as the strength of the repair itself is sufficient to carry the internal pressure. Worldwide experience in the Oil & Gas industry confirms the integrity, durability, inherent permanency, and cost-effectiveness of non-metallic composite repair or rehabilitation systems. A case study of a recent application of a composite repair system in Saudi Aramco resulted in savings of 37% for offshore subsea line and 75% for onshore above grade pipeline job. Maintaining a pipeline can be costly but it is very small in comparison to the cost of a failure. Pipeline proponents must balance maintenance costs with pipeline integrity. The purpose is not just to save money but also to attain a level of safety that is acceptable. This technology involves the use of an epoxy polymer resin based, fiber-reinforced composite sleeve system for rehabilitation and /or repair pipelines.

• Journal of Electrical Engineering and Technology
• /
• 제7권6호
• /
• pp.1023-1033
• /
• 2012

An underwater planar covering problem is studied where the coverage region consists of polygonal cells, and line sweep motion is used for coverage. In many subsea applications, sidescan sonar has become a common tool, and the sidescan sonar data is meaningful only when the sonar is moving in a straight line. This work studies the optimal line sweep coverage where the sweep paths of the cells consist of straight lines and no turn is allowed inside the cell. An optimal line sweep coverage solution is presented when the line sweep path is parallel to an edge of the cell boundary. The total time to complete the coverage task is minimized. A unique contribution of this work is that the optimal sequence of cell visits is computed in addition to the optimal line sweep paths and the optimal cell decomposition.

• Ocean Systems Engineering
• /
• 제6권3호
• /
• pp.289-303
• /
• 2016

With more than 100 years exploration and development of offshore oil, more and more offshore oil fields will gradually lose the economic profit to operate. In this article, to take the target oil field for example, the procedure of decommissioning for FPSO, TCMS, subsea system and well abandonment have been analyzed. Meanwhile, the environment impact and mitigation measure have been proposed. The successful project experience will provide a guide line for the offshore facilities decommissioning and abandonment.

• 한국전자통신학회논문지
• /
• 제17권5호
• /
• pp.815-824
• /
• 2022

해상풍력발전과 같은 간헐성 재생에너지원의 급격한 성장은 바다를 횡단하는 장거리의 전기에너지의 변환 필요성을 증가시키고 있다. 넓고 깊은 바다에 걸쳐서 장거리 대용량 전력송전을 위한 해법중의 하나는 HVDC 해저 전력케이블을 사용하는 것이다. 그러나 교류자계가 없는 직류전력 케이블의 다양한 해양조건을 갖는 연속허용전류와 관련한 표준이나 연구가 없다. 본 연구에서는 대표적인 두 종류의 해저케이블 모델과 남해안과 서해안 두 지역의 해양 요건을 가정하여 직류케이블의 연속허용전류를 모의하였다. 모의 결과를 보면 직류케이블의 연속허용전류는 해저 지반 깊이에 기반한 감소 구배 특성을 갖고 있는 것을 확인하였다.

• Structural Monitoring and Maintenance
• /
• 제6권4호
• /
• pp.365-387
• /
• 2019

This study aims to provide useful information on the fatigue assessment of a top-tensioned riser (TTR) subjected to vortex-induced vibration (VIV) by performing parametric study. The effects of principal design parameters, i.e., riser diameter, wall thickness, water depth (related to riser length), top tension, current velocity, and shear rate (or shear profile of current) are investigated. To prepare the base model of TTR for parametric studies, three (3) riser modelling techniques in the OrcaFlex were investigated and validated against a reference model by Knardahl (2012). The selected riser model was used to perform parametric studies to investigate the effects of design parameters on the VIV fatigue damage of TTR. From the obtained comparison results of VIV analysis, it was demonstrated that a model with a single line model ending at the lower flex joint (LFJ) and pinned connection with finite rotation stiffness to simulate the LFJ properties at the bottom end of the line model produced acceptable prediction. Moreover, it was suitable for VIV analysis purposes. Findings from parametric studies showed that VIV fatigue damage increased with increasing current velocity, riser outer diameter and water depth, and decreased with increasing shear rate and top tension of riser. With regard to the effects of wall thickness, it was not significant to VIV fatigue damage of TTR. The detailed outcomes were documented with parametric study results.

• 해양환경안전학회지
• /
• 제28권2호
• /
• pp.414-421
• /
• 2022

해저 석유와 가스 탐사가 점점 더 깊은 수심으로 진행되고 있으며, 해저 파이프라인은 고압 및 고온 조건에서 작동하는 것이 일반적이다. 온도 및 압력 차이로 인하여 파이프 축 방향 힘이 축적되는 현상이 있다. 이러한 현상은 파이프라인을 구속하는 해저면 효과 때문에 파이프라인은 횡 좌굴이 발생하게 된다. 온도가 증가하는 경우 축 방향의 압축 하중이 가해지며 이 하중이 임계 수준에 도달하면 파이프가 수직방향으로 움직이게 된다. 또는 파이프라인의 구조적 완전성을 위태롭게 할 수 있는 횡 방향 좌굴이 발생하는 상황에서, 작동 중 파이프라인의 구조적 안전함을 보장하기 위해 파이프라인의 상세 구조 강도평가가 수행되어야 한다. 본 연구에서는 해저면의 마찰 효과 및 재료의 열 수축/팽창을 고려한 비선형 구조해석을 상용 유한요소해석 프로그램인 ANSYS를 활용하여 검토하였으며, 외부충격에 의한 횡 방향 좌굴 안전성을 분석하였다. 본 연구의 결과를 통하여 수치 해석적 단순화된 분석 모델을 통하여 해저면의 효과를 고려한 조건에서의 실제 파이프라인의 붕괴 조건을 예측할 수 있다.

• 대한조선학회논문집
• /
• 제60권5호
• /
• pp.375-387
• /
• 2023

The subsea power cables are increasingly important for harvesting renewable energies as we develop offshore wind farms located at a long distance from shore. Particularly, the continuous flexural motion of inter-array dynamic power cable of floating offshore wind turbine causes tremendous fatigue damages on the cable. As the subsea power cable consists of the helical structures with various components unlike a mooring line and a steel pipe riser, the fatigue analysis of the cables should be performed using special procedures that consider stick/slip phenomenon. This phenomenon occurs between inner helically wound components when they are tensioned or compressed by environmental loads and the floater motions. In particular, Vortex-induced vibration (VIV) can be generated by currents and have significant impacts on the fatigue life of the cable. In this study, the procedure for VIV fatigue analysis of the dynamic power cable has been established. Additionally, the respective roles of programs employed and required inputs and outputs are explained in detail. Demonstrations of case studies are provided under severely sheared currents to investigate the influences on amplitude variations of dynamic power cables caused by the excitation of high mode numbers. Finally, sensitivity studies have been performed to compare dynamic cable design parameters, specifically, structural damping ratio, higher order harmonics, and lift coefficients tables. In the future, one of the fundamental assumptions to assess the VIV response will be examined in detail, namely a narrow-banded Gaussian process derived from the VIV amplitudes. Although this approach is consistent with current industry standards, the level of consistency and the potential errors between the Gaussian process and the fatigue damage generated from deterministic time-domain results are to be confirmed to verify VIV fatigue analysis procedure for slender marine structures.