International Journal of Offshore and Coastal Engineering (IJOCE)

Dynamic Lateral Stability Analysis On Pipeline Under Operating Conditions

Soni Fachryan Akbar — 2025-11-29

The stability analysis of underwater pipelines refers to DNVGL RP F109 [3] (On-bottom Stability Design of Submarine Pipelines) and DNVGL RP F114 [2] (Pipe Soil Interaction) from 2017. The selection of analysis methods depends on the required level of detail in the design analysis. Dynamic analysis introduces more complexity in terms of numerical calculations and field conditions. It involves simulating the pipe's response to hydrodynamic loads, including random waves, steady currents, and soil resistance in the time domain to replicate extreme conditions realistically. The study's outcomes demonstrate that hydrodynamic forces analyzed through numerical methods in CFD software can be compared to analytical approaches outlined in DNV GL F109 and F114 with an error margin of less than 10%. The Maximum Lateral Displacement is measured at 86.49 mm, falling within the allowable displacement range of 0.5 – 10 times the pipe's outer diameter, as specified in DNV GL F109 & DNVGL F114 guidelines. The Von Mises Stress along the pipeline reaches 266.18 MPa, satisfying the 90% SMYS criteria stipulated in ASME B31.8 [2].

Risk Estimation of Oil and Gas Industry Equipment

Dinda Febriani Analiyah — 2025-11-29

ABSTRACT The oil and gas industry is an essential part of the global energy supply. Offshore exploration and production are important. In drilling, both onshore and offshore, the Bottom Hole Assembly (BHA) plays a crucial role. Logging While Drilling (LWD) tools depend on electronic boards that are very sensitive to downhole conditions like high pressure, vibration, and temperature changes. When these boards fail, it can disrupt operations, increase costs, and affect safety. Traditional maintenance methods struggle because they can't respond to changing risk conditions. This study creates a probabilistic framework using the Hidden Markov Model (HMM) to estimate the failure risk of LWD electronic boards. The research uses operational data, including temperature, pressure, vibration severity, usage, and fault records as observation sequences. The model is trained with the Baum-Welch algorithm, which helps identify hidden degradation states and generate time varying failure probabilities. Results are divided into four risk levels: low, moderate, high, and extreme. This classification provides a clear risk profile for proactive monitoring. The findings indicate that HMM effectively captures degradation transitions. It also offers early warnings and improves the reliability assessment of LWD tools, potentially benefiting offshore asset integrity management.

Study Of Water Distribution Patterns and Temperature Changes in Waters Around Power Plant (Case Study of PLTU Tanjung Jati B Unit 5 & 6)

Fajar Lemanza Djazuli — 2025-11-29

Sea cooling discharge refers to heated wastewater produced during the operational of a Steam Power Plant (PLTU). This effluent is typically discharged into the sea via an ocean outfall, a process that can significantly impact the surrounding marine environment and ecosystems. One of the primary consequences of this discharge is the elevation of seawater temperature in the vicinity of the outfall. This study aims to analyze the distribution patterns and temperature increases of seawater around the ocean outfall of Tanjung Jati B Power Plant Units 5 & 6. Numerical modeling was conducted using the Delft3D software, employing both the FLOW and WAVE modules to simulate the dispersion of thermal effluent and to assess temperature variations under different environmental conditions. The simulation results show that, during the west monsoon, the dispersion of thermal effluent predominantly extends toward the northeast, while during the east monsoon, the dispersion is mainly directed toward the west, northwest, and north. These findings underscore the significant influence of ocean currents and waves on the distribution of thermal effluent. Additionally, the maximum observed temperature increases of the thermal effluent reached 9°C, with the average area experiencing a temperature rise greater than 2°C measured at 932.16 m² during the west monsoon and 1,487.62 m² during the east monsoon, when comparing the 2024 dispersion pattern to the baseline seawater temperature in 2015. To mitigate the spread of thermal effluent, three alternative solutions are proposed: (1) extending the outfall structure, (2) evaluating and optimizing the design of the existing outfall. There are several potential approaches to minimize the dispersal of thermal wastewater, but further study is required to evaluate the effectiveness of these solutions.

Operability Analysis During Topside Platform Removal with Dynamic Method Due to Wave Load

Muhammad Zakaria Al Amin — 2025-11-29

Topside removal is one of the main activities in the offshore platform decommissioning process, with one of the methods in this process being reverse installation-single lift. Corrosion, one of the common problem factors in steel structures, is used as a parameter to reduce the strength of topside structures. In the structural strength analysis with a thickness reduction of 1.5mm, the maximum unity check values for members and joints are 0.854 and 0.602, respectively. Meanwhile, the dynamic analysis results show that the hoisting line and sling tension increase with increasing wave height and period. The response to increasing tension due to wave loads increases exponentially. The beam seas loading direction produces the highest tension response due to the roll motion response to the crane barge. The shortest hoisting line influences tension due to the higher stiffness value, which results in velocity and acceleration in the topside movement as a pendulum, thereby increasing the snap force. This pattern also applies to the dynamic amplification factor (DAF) and factor of safety (FOS) sling values. The distribution fitting results on the DAF value, 3-Parameter Lognormal, is the correct distribution model with a correlation value 0.999. So, the operational operability in the range of conditions for this research model is 89.4%.

Analysis of potential skidway loadout failures based on the structural strength and Foundation settlement on the fabrication site in the Pre-Fabrication Phase.

Agus Juwarno — 2025-11-29

A fabrication company plans to undertake the construction of a topside structure with a weight exceeding 19,000 tons. Based on the Soil Investigation Report, it was found that the foundation in the fabrication area was previously used for the construction of a structure weighing 17,500 tons. Based on the consideration of the weight of the structure, it is necessary to review whether the fabrication area is capable of carrying out the construction of the topside structure until loadout. During the analysis process, it was found that the soil bearing capacity of the fabrication yard was 6108.99 MT at row support A1, while the minimum soil bearing capacity during the fabrication to loadout process at row support A1 was 6776.08 MT. Thus, it is necessary to modify the loadout area. In the process of assessing the strength of the soil foundation against structural loads, a support planning model is also made that will be used to support the topside structure during the fabrication process and also in carrying out loadout. The suitability of the structure and support will affect the process of assessing the strength of the soil foundation in parsing the potential for failure. In the process of analyzing the topside structure and support, under settlement conditions in the fabrication stage, it was found that there was a member that experienced a high enough stress with a UC value of 0.984 in member 2807-2808 on the deck leg above the row support. This occurred because during the settlement condition, there was a shift in the weight point of the structure with a joint reaction value of 4246.72 MT at the row support. During the analysis process on the bearing capacity of the foundation, topside structure, and support structure, the percentage of structural failure before modification of the loadout area is 2.12%, which is included in the failure category because it has a value above 1%.

Analysis The Effect of The Distance Between Concrete Floating Breakwater With Double Configuration On The Mooring Line Force In Catenary System Using Dualsphysics

Noris Yolanda — 2025-11-29

Ports are crucial infrastructure supporting a nation’s economy. However, port utilization in Indonesia remains suboptimal due to high sea waves that can damage infrastructure and disrupt operations. A solution is the construction of Floating Breakwaters (PGA). This study analyzes the effect of spacing between dual configured concrete PGAs on mooring rope forces using a catenary system. The Smoothed Particle Hydrodynamics (SPH) method with DualSPHysics software was used to determine maximum stress on the mooring ropes. Results show that PGA spacing influences mooring tension. In variant A, spacing from 20 30 cm reduces the force by 20%, while 30–40 cm increases it by 1%. In variant B, spacing from 50–75 cm increases tension by 8%, while 75 cm–1 m decreases it by 16%. Wave height and period also affect tension. The maximum force for variant A with a single configuration occurs at a wave height of 0.18 m and a period of 2.21 s, reaching around 185 kN at the anchor and 188 kN at the fairlead. For variant B, the maximum is at a height of 0.28 m and a period of 2.84 s, reaching about 360 kN. In dual configuration, maximum force occurs at 0.2 m spacing for variant A and 0.5 m for variant B.

Analysis of Lamong Bay Shoreline Changes Use Digital Shoreline Analysis System

Rikhul Jannah — 2025-11-29

Lamong Bay is a strategic area, and in 2010 a port was built to improve competitiveness. This study analyzed shoreline changes in the western part of Lamong Bay in 2004, 2009, 2014, 2019, and 2024 using Landsat 7 ETM+ and Landsat 8/9 OLI/TIRS imagery. Data extraction used the Normalized Difference Water Index (NDWI) method in ArcGIS, while shoreline change analysis used the Digital Shoreline Analysis System (DSAS) with End Point Rate (EPR), Net Shoreline Movement (NSM), and Shoreline Change Envelope (SCE). The results show the highest accretion occurred in Romokalisari Village from 2004 to 2009 at 13.80 meters/year, and the highest abrasion occurred in the same village from 2019 to 2024 at -34.21 meters/year. Based on NSM, the highest accretion occurred in Romokalisari from 2004 to 2009 at 67.42 meters, and the highest abrasion occurred from 2019 to 2024 at -163.38 meters. Based on SCE, the highest change occurred in Romokalisari at 331.93 meters from 2019 to 2024, and the lowest change occurred in Osowilangun Village at 0.01 meters in the same period. Overall, accretion dominates the study area, but extreme abrasion in Romokalisari from 2019 to 2024 is influenced by reclamation. This study is expected to support sustainable coastal management and shoreline change mitigation.

Model Planning of Maintenance Dredging (Study Case: East Java Pultipurpose Terminal at Lamongan Shorebase)

Tasya Putri Rhamadani — 2025-11-29

As one of the important entities in the sea transportation process chain, the port has a vital role as a connection point between regions. East Java Multipurpose Terminal (EJMT) is one of the port terminals which will be used as a connection point for the distribution of goods, especially around East Java Province. The purpose of this paper is to obtain effective and efficient model scenario for maintenance dredging plan at EJMT. The method used in this research is optimization method with a non-linear algorithm approach to determine the minimum cost. The results of this study indicate that the dredging scenario using sediment traps is the most optimum with the total volume of material dredged is 107,671.61 m3. The total duration of the dredging work is around 7 days with total cost around 7.1 billion rupiah or equivalent to 65-70 thousand rupiah per cubic meter.