Large Crude Oil Research Articles

Advanced dynamic modeling study of fire and smoke of crude oil storage tanks

The combustion properties of large-scale crude oil pool fire have great significance for security design and firefighting of current crude oil reserves. Burning rate, flame shape and radiation intensity are the most important parameters for fire properties. The novelty of this study is that the Fire Dynamics Simulator (FDS) is adopted to simulate pool fires in a tank farm. It does not only investigate and analyze heat radiation flux, but also the temperature difference rise and flame/smoke temperature contours behavior. This simulation is performed in order to predict the potentials of a large crude oil storage tank fire outbreak and the smoke temperature distribution that counters in and around the tank. These data are used in designing tank farms and applying the firefighting strategy. A super CPU with large RAM is used to operate the simulation program, to simulate one of the largest crude oil farms in the world. The model will be investigated for identifying the worst-case scenarios that might occur in a large crude oil tank. One of these scenarios might be fire outbreak in rim seal in one of the four storage tanks, where the fire is transferred to full surface fire. The model predicts the potential of tank fire outbreak, smoke tracing and both smoke/flame temperature that spreads at wind speed of 3 m/s, 9 m/s, 18 m/s in south-west direction. FDS model provides qualitative data that increase the level of safety, such as the minimum safe separation distances and the location of firefighters during the firefighting process. It also determines the most critical area, which is needed for water-cooling system. This study also tackles the duration after which human beings feel pain after being exposed to heat radiation.

Stress analysis of large crude oil storage tank subjected to harmonic settlement

Differential settlement has a significant effect on the safe operation of tanks. In order to investigate the stress response of crude oil storage tank subjected to harmonic settlement. A numerical simulation model of the steel storage tank was developed in this study. Based on a validated finite element model, parametric analysis was conducted based on the main factors. The results show that the stress at the top of the tank wall is symmetrically distributed along the circumference of the tank. The stress result increases linearly with the increasing harmonic amplitude. The axial stress increases firstly, and then decreases for large wave number. Meanwhile, The stress value increases with the increment of the height-to-radius ratio, and decreases with the increment of the radius-to-thickness ratio. Especially, when the height-to-radius ratio ranging from 1.0 to 1.5 or the ratio r/t is more than 1500, the tendency of stress variation is slighter. This study could be referenced in strength or safety assessment of crude oil storage tank subjected to harmonic settlement.

The time-to-failure assessment of large crude oil storage tank exposed to pool fire

In large crude oil tank farm, fire is a major primary event in domino effects according to past accidents. The quantitative risk assessment of domino fire accident is a key issue for the accident prevention of large storage tank farm. The most widely used equation for the estimation of the tank's time to failure (TTF) exposed to pool fire is not suitable for 100,000 m3 external floating roof tank. The purpose of this study is to establish simplified models for the calculation of the tank TTF with respect to heat radiation intensity, filling level and the availability of safety protections under different fire conditions. The finite element transient heat transfer modeling of 100,000 m3 external floating roof tank in the case of fire scenarios was performed. The quantitative assessment of safety protection performance in delaying the tank failure under fire conditions was performed according to the simulation results. The application of the TTF equation to case-studies of crude oil tank farm showed the importance of safety protection for the prevention and mitigation of the domino effect. The TTF model provides a basis to the risk management and emergency response in large tank farm.

Picking up the Slack: Kenya and Tanzania's Energy Sectors

With large crude oil consumers and investors like China, France, the USA, the UK, and Italy being the biggest victims of the COVID-19, it is clear that the pandemic will have further ramifications on the foreign direct investment in nascent energy resource-rich countries. This chapter conducts a case study of Kenya and Tanzania, two countries harboring ports that are the gateway of the East African region to larger markets such as Asia and Europe. Tanzania was still negotiating an agreement with gas companies to construct its LNG infrastructure; while Kenya was finalising its environmental assessments for upstream and midstream and planning to reach a final investment decision in 2020. Both country's plans have been altered due to the pandemic, and stakeholders have to innovate on how best to engage in the sector and protect it from such uncertain shocks. This paper is an insight into the current situation and how the drivers of energy law can facilitate legal frameworks to absorb such uncertain events in the future.

Effects of sublethal application of Deepwater Horizon oil to bird eggs on embryonic heart and metabolic rate.

Following large crude oil spills, oil from feathers of brooding birds and oiled nesting material can transfer to eggs, resulting in reduced embryonic viability for heavily oiled eggs. Eggs may also be subjected to trace or light oiling, but functional teratogenic effects from sublethal crude oil exposure have not been examined. We assessed whether sublethal application of weathered Deepwater Horizon crude oil to the eggshell surface alters heart rate and metabolic rate in Zebra Finch (Taeniopygia guttata) embryos. We first determined sublethal applications with a dosing experiment. Embryo viability for eggs exposed to 5 μL or more of crude oil decreased significantly. We conducted a second experiment to measure heart rate and metabolic rate (CO2 production) 5 and 9 d after 1 sublethal application of crude oil to eggshells on day 3 of incubation. One application of 1.0 or 2.5 µL of crude oil reduced embryonic heart rate and metabolic rate on day 12 of incubation. Using unfertilized eggs, we measured the transfer of polycyclic aromatic hydrocarbons (PAHs) from the eggshell surface to egg contents 9 d after a single application of sublethal crude oil. Our results suggest avian eggs externally exposed to small amounts of crude oil may exhibit protracted embryonic development and impaired postnatal cardiac performance.

Determining the influence of ship hull deformations caused by draught change on shaft alignment application using FE analysis

This paper was to address the shortcomings of current design practice to evaluate the stability of the shaft alignment for a 300,000 DWT Very Large Crude Oil Carrier. An enhanced approach using FE was applied to identify the influence of hull deformation on the alignment of the shafting system. The effectiveness of this method was demonstrated in comparison with Jack up technique. Analysis results showed that the hull deformation could be a key factor affecting the offset distortion of each bearing supporting the shaft line. Moreover, it was confirmed that the deformation pattern of cargo hold was opposite to the deformation of engine room structure when hull deformation occurred due to draught change of the case ship. As new research findings, they are believed to contribute significantly to the prevention of shaft damage associated with hull deformations, thereby improving the reliability of shaft alignment for similar types of vessels.

Study on Corrosion Law of Large Crude Oil Storage Tank Floor and Risk-Based Inspection and Maintenance Technology

In this paper, the author''s team has carried out a comparative experimental study on the corrosion characteristics of Q235 steel commonly used in large-scale storage tanks under the specific bottom water environment found with Russian and Daqing crude oil. It was found that there is a certain degree of uniform or local corrosion on the tank floor depending on the kind of bottom water. The bottom water corrosion of Daqing crude oil is a uniform corrosion caused by carbon dioxide. While the Russian crude oil bottom water corrosion is clearly local corrosion caused by co-corrosion of carbon dioxide and hydrogen sulfide, here the corrosion rate is obviously higher than that caused by Daqing crude oil. There are two modes of storage tank inspection and maintenance that have been currently adopted by Chinese refining and chemical enterprises: a regular inspection mode and a API581-2016 risk-based detection mode. These modes have been effectively combined to form an intelligent tank inspection and maintenance mode, software tools to support this intelligent inspection and maintenance management have been developed.

EFD and CFD Study of Forces, Ship Motions, and Flow Field for KRISO Container Ship Model in Waves

Ship motion responses and added resistance in waves have been predicted by a wide variety of computational tools. However, validation of the computational flow field still remains a challenge. In the previous study, the flow field around the Korea Research Institute for Ships and Ocean Engineering (KRISO) Very Large Crude-oil Carrier 2 tanker model with and without propeller condition and without rudder condition was measured by the authors, as well as the resistance and self-propulsion tests in waves. In this study, the KRISO container ship model appended with a rudder was used for the higher Froude number .26 and smaller block coefficient .65. The experiments were conducted in the Osaka University towing tank using a 3.2-m-long ship model for resistance and self-propulsion tests in waves. Viscous flow simulation was performed by using CFDShip-Iowa. The wave conditions proposed in Computational Fluid Dynamics (CFD) Workshop 2015 were considered, i.e., the wave-ship length ratio λ/L = .65, .85, 1.15, 1.37, 1.95, and calm water. The objective of this study was to validate CFD results by Experimental Fluid Dynamics (EFD) data for ship vertical motions, added resistance, and wake flow field. The detailed flow field for nominal wake and self-propulsion condition will be analyzed for λ/L = .65, 1.15, 1.37, and calm water. Furthermore, bilge vortex movement and boundary layer development on propeller plane, propeller thrust, and wake factor oscillation in waves will be studied.

Risk assessment of large crude oil depot based on interpretative structural model and system dynamics

In this paper, the interpretative structural model is used to determine the causality among the risk factors and a system dynamics model is established. The method is applied to the risk analysis of a large crude oil depot. The results show that the safety atmosphere and supervision play critical roles on the risk of the oil depot. At the mature stage of risk development, improvements in the equipment risk and management risk has the greatest impact on the overall risk. The degree of education, equipment usage time, safety atmosphere and supervision are the key risk factors for the human, equipment, environmental and management risk subsystems, respectively. This result provides a scientific basis to understand the trend of risk dynamic, risk evolution mechanism and fundamental risk factors and fundamentally prevent the occurrence of large crude oil depots. [Received: March 16, 2018; Accepted: December 17, 2018]

Oil spill detection in the east of Sri Lanka with Sentinel-1 SAR

In September 2020, two major fires broke out in a large crude oil tanker in Sri Lanka’s maritime zones. An island with a vast sea area in the Indian Ocean, Sri Lanka, is prone to vessel sourced pollution. Crude oil can have a damaging impact on the environment, and therefore tracking the spill in the water is essential. Spaceborne sensors support monitoring oil pollution; however, optical sensors need clear skies for observation. The detection of pollution caused by vessels; in Sri Lanka’s maritime zones has previously been investigated by the author. This study examines the data collected by the Sentinel-1 satellite, whose sensing corresponds to the oil spill event, manually and using algorithms to detect the presence of oil spills. Two detected oil spill areas were measured to be 0.6 km and 1.4 km long. Further, in this study, the SAR sensor’s vertical signal transmission and reception mode produced acceptable results in detecting the spills and the vessel. Sentinel-1 SAR data is essential, in this case, to detect the presence of the oil spills and the vessels.

Risk assessment of large crude oil depot based on interpretative structural model and system dynamics

In this paper, the interpretative structural model is used to determine the causality among the risk factors and a system dynamics model is established. The method is applied to the risk analysis of a large crude oil depot. The results show that the safety atmosphere and supervision play critical roles on the risk of the oil depot. At the mature stage of risk development, improvements in the equipment risk and management risk has the greatest impact on the overall risk. The degree of education, equipment usage time, safety atmosphere and supervision are the key risk factors for the human, equipment, environmental and management risk subsystems, respectively. This result provides a scientific basis to understand the trend of risk dynamic, risk evolution mechanism and fundamental risk factors and fundamentally prevent the occurrence of large crude oil depots. [Received: March 16, 2018; Accepted: December 17, 2018]

Numerical Modeling of a Very Large Crude Oil Carrier Using ANSYS CFX: A Case Study of SALINA

Specification of the frictional resistance values of tankers is the first step in managing their fuel consumption. Drag force of a very large crude oil carrier has been calculated using the numerical simulation method. With application of the ANSYS CFX software, the scaled model of the mentioned tanker with the length of 2.74 meters, width of 0.5 meters, draft of 0.17 meters was used for numerical simulation of the drag force in the tanker. Furthermore, the numerical solution of the drag force of the model was performed for 5 different speeds ranging from 0.65 to 0.85m/s. Based on the validations carried out, with mean drafts of 8 and 16.5cm, the difference between the results of the experimental and numerical models at low speeds was about 7%. However, the difference was observed to be up to 15% at higher Froude numbers. The results of the present study with respect to the SALINA are based on the method presented in ISO 19030 standard addressing the performance monitoring during vessel servicing.

Towed underwater PIV measurement of propeller wake in self-propelled condition

A series of particle image velocimetry measurements was conducted in a towing tank to analyze the propeller wake dynamics of a fully appended very large crude oil carrier model. The Froude number and the Reynolds number of the test condition based on the model length and towing speed were 0.142 and 2.32 × 106, respectively. The propeller wake dynamics was investigated in terms of vortical structure and wake acceleration. It was found that the propeller loading on the starboard side was larger than that on the port side, as upward component of the propeller inflow resulted in a higher inflow speed on that side. The different propeller loading deformed the wake structure and bent it towards the port side. Between neighboring tip vortices, the local maxima of the turbulence kinetic energy and corresponding local turbulence structure were found. The rudder effects on the propeller wake were also investigated, proving that the rudder blocked the progress of the hub vortex and straightened the propeller wake.

Experimental and numerical study of uniaxially compressed stiffened plates with different plating thickness

Abstract This paper presents a numerical - experimental research to evaluate the effect of corrosion in panels subjected to uniaxial compression and subsequent repair. The effects of corrosion are approximated by a uniform reduction in the plating's thickness. Currently, repairing a corroded offshore structure involves the change of the hull plating, which is excessively expensive and, therefore, other alternatives should be investigated in order to extend its useful life. The experimental study considers a set of five panels with an average scale of 1:3.5, representing a typical intact panel of a VLCC (Very large Crude Oil Carrier) converted into a FPSO (Floating Production Storage and Offloading) platform and two different plating reduction thickness levels. These experiments are reproduced through a numerical model that considers geometric and material nonlinearities. The geometrical imperfections in the surfaces of plates and stiffeners are reconstructed from measurements using techniques of laser scanning and optical capture. Thickness distributions are measured with an ultrasonic sensor in several predetermined panel sections points. True stress vs true strain curves for all panel's elements are obtained by tensile tests and employed in the numerical model. Once the numerical model is validated, the effect of the axial load eccentricity, the supported element load redistribution due to changes in the thickness, and the effects of the inclusion of intermediate repair on the plate are studied. The results show that the inclusion of an intermediate light stiffener allows recovering the panel load capacity and prolonging the useful life of offshore platforms. Likewise, it is concluded that the selection of the repair should be based on the local strength recovery of the plate, which is most affected.

Numerical Simulation of Large Crude Oil Storage Tank Fire under Various Wind Speeds

In order to analyse the influence of the wind speed on the fire characteristics and hazards of large crude oil storage tanks, this paper used the fire dynamics simulation software FDS to simulate the fire of a large crude oil storage tank under various wind speeds. The fire characteristics such as flame, smoke and temperature distributions of the tank under different wind speeds were studied. The thermal effects on the adjacent tank and the way that the firefighters cool the hazardous area were discussed. The results show that with the increase of the wind speed, the flame, smoke and temperature distributions shift and spread downwind. When tank fire occurs, the firefighters should set up movable firefighting water gun near the dangerous area and lay fire water hose to the burning tank and its neighbours, which provides a good preparation for the subsequent firefighting operation near the burning tank.

VLCC (Very Large Crude Oil Carrier)

VLCC (Very Large Crude Oil Carrier)

Foreword for Special Issue “VLCC (Very Large Crude Oil Carrier)”

Foreword for Special Issue “VLCC (Very Large Crude Oil Carrier)”

The eye in the sky – Freight rate effects of tanker supply

We show how the evolution of crude oil tanker freight rates depends on the employment status and geographical position of the fleet of very large crude oil carriers (VLCCs). We provide a novel measure of short-term capacity in the voyage charter market which is a proxy for the percentage of vessels available for orders. We find that our capacity measure explains parts of the freight rate evolution at weekly horizons, where traditional supply measures are uninformative. The fact that freight rates directly influence shipowners’ profitability and charterers’ expenditures makes our measure particularly relevant for these groups of market participants.

Empirical Analysis of Crude Oil Price Effects on Exchange Rate Volatility

This study examined the effects of crude oil price on nominal exchange rate volatility for oil and non-oil exporting countries. Immediately after the global financial crisis, the swings in the movement of crude oil price revealed how vulnerable the currencies of oil exporting countries and other commodity exporting countries. Using the Structural VAR method and the sample data from 2011 to 2016, the study estimated the effects of crude oil price on exchange rate stability and its impulse responses. Empirical results show that exchange rates for oil exporting countries are highly vulnerable to crude oil price shocks. As crude oil price declines, exchange rate volatility increases, similarly large crude oil price increases are associated with low exchange rate volatility. Currencies such as Angolan Kwanza, Russian Ruble, and Mexican Peso are very sensitive to crude oil price shocks. SVAR results show that oil price shocks significantly reduce exchange rate volatility of oil exporting countries. Meanwhile, the exchange rate volatility for non-oil exporting countries was driven by other factors than the price of crude oil.

Full-Scale Measurements of Welding-Induced Initial Deflections and Residual Stresses in Steel-Stiffened Plate Structures

Plated structures such as ships and offshore structures are constructed using welding techniques that attach support members (or stiffeners) to the plating. During this process, initial imperfections develop in the form of initial deformations (deflections or distortions) and residual stresses. These initial imperfections significantly affect the buckling and ultimate strength of these structures. Therefore, to assess the strength of welded plate structures, it is very important to predict the magnitude and pattern of welding-induced initial imperfections and their effects on buckling and ultimate strength. To determine the reliability of the prediction methods, it is desirable to validate the theoretical or numerical predictions of welding-induced initial imperfections through comparison with full-scale actual measurements. However, full-scale measurement databases are lacking, as they are costly to obtain. This study contributes to the development of a full-scale measurement database of welding-induced initial imperfections in steel-stiffened plate structures. The target structures are parts of real (full-scale) deckhouses in very large crude oil carrier class floating, production, storage and offloading unit structures. For parametric study purposes, four test structures by varying plate thickness are measured while the stiffener types and weld bead length are fixed. Modern technologies for measuring initial deformations and residual stresses are applied. The details of the measurement methods are documented for the use of other researchers and practicing engineers who want to validate their computational models for predicting welding-induced initial imperfections.