Types Of Crude Oil Research Articles

Combustion study of a surrogate jet fuel

The oxidation of a three-component surrogate jet fuel (consisting of n-dodecane 66.2%, n-propylbenzene 15.8% and 1,3,5-trimethylcyclohexane 18.0%, in mol) was studied experimentally and numerically within a wide range of temperature, fuel equivalence ratio, and pressure. Three different experimental set-ups were exploited, here a jet stirred reactor (JSR), a shock tube, and a laminar burner referring to measured data of species profiles (φ = 2.0, T = 575–1100 K, p = 1 bar), ignition delay times (φ = 1.0, p = 16 atm, T = 700–1500 K), and burning velocities (T = 473 K, p = 1atm, φ = 0.6–2.0). Based on the experimental measurements, an updated detailed chemical-kinetic mechanism involving 401 species and 2838 reactions was developed, for a more detailed understanding of the oxidation and combustion of the surrogate fuel. In addition, quantum chemical methods have been applied for the determination of important initiation reactions by using the Gaussian and ChemRate software. In general, the predictions obtained with the mechanism developed in this work show a reasonable, often good agreement with respect to the measured mol fraction profiles (JSR), ignition delay time data (shock tube), and burning velocities data (flame). A negative temperature coefficient (NTC) behavior was observed in the JSR and shock tube experiments, due to the long-chain alkanes, here n-dodecane. The NTC effect was successfully predicted by the reaction model, with the predictions matching the measurements well. From the JSR experiments, 1-octene, 2-propenylbenzene, and propene were detected by GC and GC–MS as major intermediates within the oxidation of the surrogate. According to rate-of-production analysis performed at 675 K and 900 K, 1,3,5-trimethylcyclohexane (T135MCH) was found to be mainly consumed through H-abstraction reactions and forming C9H17 radicals, which mostly isomerize to iso-alkane radicals and further on, decompose to light hydrocarbons. According to the comparison of predicted data on ignition (shock tube) and burning velocity (flame) with experimental ones, the selected surrogate fuel is considered to be able to reproduce the combustion behavior of a typical crude-oil stemming jet fuel. The surrogate fuel mechanism as well as the experimental data will be of significant impact on the use in the further work of the combustion of a jet fuel and of other synthetic aviation fuels as well.

Experimental investigation of the rheological behavior of algerian crude oils from the quagmires

In this work, the rheological behavior for three types of crude oil coming from different quagmires namely Amassak, Tamendjelt and Tin Fouye of the TFT sector (Tin Fouye Tabankort/South Algeria) has been experimentally investigated. A controlled stress rheometer (AR 2000, TA Instrument) was used throughout this investigation. The experimental measurements in terms of flow and dynamic tests were carried out at different temperatures during the shear rate over the range of 0–700 s−1 and frequency range of 0.1–10 rad/s. The obtained results show that the viscosity and shear stress of the crude oils decreases about 53.30%, 58.80%, and 59% respectively, when the temperature increased from 10 to 20 °C. The yield stress required to flow of crude oils also decreased to 37.06%, 89.78%, and 77.53% respectively. The dynamic analysis of the crude oils by identifying of the storage modulus (G′) and the loss modulus (G″) has indicated that the rheological properties of crude oils were significantly temperature-dependent.

Classification of waxy crude oil odor-profile using gas sensor array

Nowadays, waxy crude oil becomes one of the major concerns in the oil and gas industry. The waxy crude oil affects the production and transportation of the crude oil from offshore to onshore. Differentiation by image visualization in determining the type of waxy crude oil, with or without wax sometimes appear rather similar between each other. Hence, a new method needs to be used to differentiate and classify the waxy crude oil type. An electronic nose (E-Nose) is one of the devices that could detect and measure the odor data of the waxy crude oil type using gas sensor array. This paper aims to classify four types of Malaysian waxy crude oil from different fields at room temperature. There are 16,000 odor data that has been collected by using the E-Nose. Then, the measured data were normalized and analyzed using boxplot analysis. The unique odor-profile for each type of waxy crude oil sample has been extracted and classified using intelligent classification technique. The four types of waxy crude oil have been classified 100% using k-NN intelligent classification technique with zero percentage of error in this paper.

Electronic nose for smart identification of roofing and paving grade asphalt

Abstract Asphalt is a complex mixture of hydrocarbons, whose properties strongly depend on the source and type of crude oil and refining processes. From a technical standpoint, intensive investigations carried out by the construction sector, above all by road researchers, have attempted to understand relationships between asphalt binder chemical structure, morphology and physical characteristics. Nevertheless, one challenge that the advance research on asphalt products actually face is to transfer this extremely high level of knowledge to applied industrial technologies for finding easy-to-use, quick and cost-effective test methods for quality control and identification of asphalt binders at refinery, terminal and plant. Thus, this paper focused on the development of a protocol for fingerprinting, including identification and discrimination, of asphalt cements using two different electronic noses (e-noses), also known as artificial olfactory systems (AOS). E-nose is a biomimetic non-destructive intelligent sensing instrument, which is designed to mimic the human sense of smell to detect, compare and classify odor sample, producing a qualitative output (fingerprint). Results suggested that a complementary combination of electronic nose technique and well-established analytical methodologies could be successfully used for the identification and discrimination of roofing and paving grade asphalt cements. Specifically, both sensing instruments were able to perform a good discrimination between products characterized by a different chemical nature and to verify the refinery process stability during production and a batch-to-batch crude oil consistency.

Prices

Assessed or estimated prices and values for the major types of crude oils traded on spot markets. Updated on a monthly basis.Official sales prices (except as otherwise noted) and are generally market‐related, subject in some cases to retroactive adjustment. Updated on a monthly basis.

Fluorescence Hyperspectral Imaging of Oil Samples and Its Quantitative Applications in Component Analysis and Thickness Estimation.

The fast response and analysis of oil spill accidents is important but remains challenging. Here, a compact fluorescence hyperspectral system based on a grating-prism structure able to perform component analysis of oil as well as make a quantitative estimation of oil film thickness is developed. The spectrometer spectral range is 366–814 nm with a spectral resolution of 1 nm. The feasibility of the spectrometer system is demonstrated by determining the composition of three types of crude oil and various mixtures of them. The relationship between the oil film thickness and the fluorescent hyperspectral intensity is furthermore investigated and found to be linear, which demonstrates the feasibility of using the fluorescence data to quantitatively measure oil film thickness. Capable of oil identification, distribution analysis, and oil film thickness detection, the fluorescence hyperspectral imaging system presented is promising for use during oil spill accidents by mounting it on, e.g., an unmanned aerial vehicle.

A new hybrid technique using low salinity water injection and foam flooding for enhanced oil recovery in sandstone rock

Foam flooding has been applied to improve oil recovery. However, interactions between crude oil and foam destabilize the foam and reduce its efficiency. Many researchers have examined the effects of interactions between crude oil and foam with a focus on the negative effects of these interactions. The goal of this study is to investigate the potential of a new hybrid Enhanced Oil Recovery (EOR) method termed Low Salinity Water Assisted Foam flooding (LSWAF) in sandstone rocks. This method involves the injection of Low Salinity Water (LSW) followed by the alternate injection of a Surfactant Aqueous Solution (SAS) and CO2 gas. LSW solutions were prepared using different salinities of NaCl, KCl, CaCl2, and MgCl2. Experiments were carried out using two types of crude oil with a different Total Base Number (TBN) and Total Acid Number (TAN), namely crude oil A and B. In terms of changes in wettability, for both crude oils, the experimental results revealed that the test with LSW of 500 ppm KCl outperformed other salinities. For crude oil with a higher TBN, the proposed hybrid technique led to improved performance. The insights presented in this study provide a good reference for further research in this area.

Swelling behavior of heavy crude oil during injection of carbonated brine containing chloride anion

Carbonated brine (CB) injection, known as one of the effective enhanced oil recovery processes, is highly dependent on the reservoir conditions (i.e. temperature and pressure) as well as the type of dissolved salt in aqueous solution. This study is aimed to investigate the influential parameters on the swelling of crude oil as the most important mechanism during CB injection. The swelling of crude oil in the presence of different CB solutions consisted of different salts such as KCl, NaCl, CaCl2 and MgCl2 with constant concentration of 15,000 ppm is studied using a high-pressure, high-temperature visual cell which measures the volume of drop using image processing software based on Young-Laplace method. Also, the Δ Bond number of crude oil is examined to more reliably find out the mechanisms. According to the results, it can be concluded that the solubility of CO2 in aqueous phase is not the only parameter affecting the swelling behavior, and that the crude oil and ion type as well as temperature have remarkable effect on the mobility of CO2 molecules and their partitioning from aqueous phase toward oil phase.

Damage evaluation of acid-oil emulsion and asphaltic sludge formation caused by acidizing of asphaltenic oil reservoir

Acidizing is one of the most effective techniques to remove the formation damage and restore (or even increase) the permeability of the near wellbore region. Although this technique is widely used to resolve the skin problem, it could initiate new damages itself that hinder the fluid flow and decrease the well production, consequently. Acid-oil emulsion and sludge formation are known as two major induced formation damage and the main reasons for the oil well acid treatment failures. Despite its critical effects, no comprehensive study has been addressed this specific type of formation damages in details.In this study, the acid-oil emulsion and asphaltic sludge formation were evaluated quantitatively. Multiple compatibility tests were conducted using HCl and six Iranian acid sensitive crude oil samples. The acid concentration, ferric ion presence, and acid-mixture ratio were selected as the main factors affecting the emulsion stability and the amount of sludge. To mimic the real condition the interference of the effects of these factors was noticed besides the crude oil type which has not been addressed before.The results revealed that controlling the iron ion presence, choosing the best acid concentration, and regulating the acid-mixture ratio would drastically reduce the risk of emulsion and sludge formation without any preventative additives presence. The quantitative values derived from this experimental work showed that the weight of dried asphaltic sludge formed was diminished to 7%, 5.6%, 2.4%, 22%, 7.5% and 10% of the most critical sludging condition for the crude oil samples A, B, C, D, E, and F respectively. Besides, for the first time, the volumetric measurement of the massive asphaltic sludge was performed to approach more realistic damage evaluation. The results confirmed it is possible that the solid sludge occupies 60 vol % of the primitive acid-oil mixture volume at high concentration of HCl and ferric besides high acid-oil ratio condition.

Re-equilibrium of Asphaltenes by Repressurizing after Precipitation in Natural Depletion and CO2 Enhanced Oil Recovery Schemes

In a series of isothermal depressurizing tests to measure asphaltene onset pressure (AOP), several depressurizing operations are usually conducted to multiple AOPs using the same lot of fluid subsamples. After one depressurizing operation is finished, the pressure/temperature condition is reset to the initial condition. Then, the next depressurizing run is performed. Before the next run, the fluid sample must equilibrate again by dissolving precipitated asphaltenes from the previous step. According to our many experiences with isothermal depressurizing tests for measuring AOPs, we know that redissolving asphaltenes depends highly upon the characteristics of a fluid sample. Some fluids redissolve asphaltenes quickly, while other samples need a lot of time. This study focused on fluid-dependent asphaltene re-equilibrium during a series of isothermal depressurizing tests. To investigate asphaltene re-equilibrium, the authors re-examined past experimental data for two types of crude oils. In the experiment, c...

Removal of crude oil residue from solid surfaces using microemulsions

This paper presents a study on the removal of crude oil residue from sand using microemulsions. A newly developed experimental technique referred to as the Shaken Bottle test was developed to quantify the amount of crude oil residue removed. This technique consists of coating sand with crude oil, baking it in an oven for 24 h and then treating it with a surfactant solution or a microemulsion. The percentage of crude oil residue removal was quantified using UV–Vis spectroscopy. In this study, microemulsion removed a much larger amount of crude oil residue from sand surfaces compared to using the same surfactant alone. The amount of removal was strongly dependent on the crude oil composition, microemulsion concentration, solvent amount and type contained within the microemulsion.

Comparative study of the physical and chemical properties of the crude oil mixture of the El-Wafa field in practically and through the use of an advanced program [Aspen HYSYS

The accuracy in measuring the physical properties of any crude oil has become a very difficult task because the price of crude oil in the global market depends on it in addition to the process of producing lubricating oil , chemical products and refinery. Accordingly, this research effort focuses on comparative study of Libyan crude oil (El-Wafa field) by measuring the physical and some chemical properties experimentally and by Aspen HYSYS V8.4 programs. Also, test the possibility to know the volume percentage of the production of lubricants from this crude oil by the two methods mentioned above.Test carried out on these measurements practically and theoretically the physical properties are include: normal boiling point, pour point, Specific gravity (Sp. gr.), standard density (API), dynamic viscosity , kinematics viscosity , molecular weight, Acentric factor and Watson factor (K or Kw ). Some chemical properties have also been experimentally measured, for example the sulphur content ( wt.%), Asphaltenes content( wt.%) , water and sediment content (vol.%), Conradson carbon residue ( wt.%) , salt content (as NaCl, mg\L), ash content(wt. %) and metals content ( wt.%).The results from the tests showed that, there is a very small convergence between the results of calculations of physical properties by use this modern software with experimental measurements in the lab to the crude oil of El-Wafal field up to 99% and this blend is not suitable for production the lubricated oil at atmospheric distillation column. Also, the results observed that’s the useful mole percentage of lubricated oil cutoff has volume percentage range not significant from 1 to 1.8% for this type of Libyan crude oil. Through practical and theoretical results possible to classify this type of crude oil as Brent mix according to the global market for the sale of crude oil, which is characterized by its lack of sulfur element and metals in addition to its standard relative density API is very high more than 55.

Comparative degradation between heavy and light crude oil mediated by nitrogen‐induced cell‐surface hydrophobicity

AbstractA bacterial strain UKMP‐10M2 isolated from a Malaysian petroleum refinery was able to degrade 84% of heavy Khafji sour crude and 68% of light Tapis sweet crude within seven days. Analysis of gas chromatography‐flame ionization detector chromatograms show the strain UKMP‐10M2 degraded up to 90% pristane and 50% phytane in heavy crude, but significantly lower pristane (50%) and phytane (30%) were degraded from the light crude. A mixture of aliphatic hexadecane and three‐ring phenanthrene better supported the growth of isolate UKMP‐10M2 compared to using phenanthrene alone, suggesting cometabolism influenced how crude oil with different individual hydrocarbon contents affected the degradation. Peptone as the source of nitrogen increases the emulsifying index in UKMP‐10M2 exposed to heavy Khafji sour crude 20% higher than in light Tapis sweet crude. However, BATH assay showed the same nitrogen source increases bacterial cell surface hydrophobicity of UKMP‐10M2 up to 14% higher in light Tapis crude oil compared to heavy Khafji. This study suggest the nitrogen source plays a decisive role in elevating UKMP‐10M2 bacterial cells hydrophobicity, and in correlation with types of crude oil. Phylogenetic tree analysis based on 16S rDNA sequence results identified the strain to be Rhodococcus ruber.

Fouling modelling and mitigation for crude oil heat exchanger networks using reconciled operating data

In crude oil refineries, fouling in heat exchangers and heat exchanger networks represents one the most complex and challenging issues. Its occurrence produces major impacts in thermal, hydraulic and economic performance on every heat transfer process. Increasing in fuel consumption, pressure drop and CO2 emissions across heat exchangers are examples of a wide series of consequences that are attributed to fouling in different petro-chemical process industries. Predictive models for fouling deposition have become a useful tool for analysing thermal performance on heat exchanger networks. A wide range of semi-empirical models have been reported in the literature considering different types of crude oil. Most of these models present a series of parameters that need to be fitted using experimental data. However, there is an uncertain relation between field and laboratory conditions, compromising the quality of predictions and greatly affecting further simulation and optimisation of heat exchanger networks. The proposed approach presents an alternative method for determining fouling models using reconciled operating data. Data reconciliation is included in order to account for the effect of measurement errors and presence of faulty instruments within a given set of measurements. Depending on the available redundancy, further analysis can take place regarding feasibility of the data reconciliation problem, along with process variable classification. Once the data have been reconciled, the specific set of fouling model parameters can be fitted and implemented into the framework for operational optimisation for fouling mitigation, or optimisation of cleaning schedules. Different sets of cleaning actions can be analysed and further optimised by minimising the total operating cost, once the specific fouling models are successfully determined, resulting and economic and environmental savings.

Sustainability assessment for crude palm oil production in Malaysia using the palm oil sustainability assessment framework

AbstractThe sustainability of production is one of the greatest challenges experienced by the Malaysian palm oil industry. Palm oil products consistently receive negative press and criticism, for causing deforestation, land use changes, peat land conversion, species loss, greenhouse gas emissions, biomass waste generation, violation of indigenous people's rights and limited local employment. This paper evaluates the sustainability of the most common crude palm oil supply chain in Malaysia, located in Sarawak, using the Palm Oil Sustainability Assessment (POSA) framework. The results show that the overall sustainability score for a typical crude palm oil supply chain in Malaysia is 3.47/5, which is below the sustainability target of 5/5. Hotspots identified include smallholder inequity, lack of biomass waste recycling and recovery, improper plantation practices, lower average wages and local employment. The site‐specific application of the POSA framework in the current study demonstrates its potential to be used universally across Malaysia.

Steady-state and time-resolved fluorescence spectroscopic study of petroleum crudes in aqueous-surfactant solutions: Its implications for enhanced oil recovery (EOR) during surfactant flooding

Surfactant flooding, a widely used chemical enhanced oil recovery (EOR) method, involves reduction of interfacial tension of the crude oil-aqueous surfactant system. During the surfactant flooding micelle structures have been formed in aqueous media where crude oil components are entrapped inside it. The nature of the surfactants in the aqueous injection fluids and the crude oil compositions are the key controlling factors for understanding the efficacy of the surfactant flooding during EOR. Therefore, understanding of the molecular level interaction between crude oils and aqueous surfactant solutions is very crucial for designing injection fluids during surfactant flooding for subsurface reservoirs having different types of crude oils. Two crude oils (Cambay basin, India) and three surfactants: cationic (cetyltrimethylammonium bromide i.e. CTAB), anionic (sodium dodecyl sulfate i.e. SDS) and neutral (Triton X-100 i.e. TX100) were used in this study for understanding their interaction behavior. The chemical characterization by various analytical methods supports the presence of different sizes of the fused aromatic ring (FAR) associated with the polycyclic aromatic hydrocarbons (PAH) of the used crude oils. In this study, we have investigated the type of oil components present in the micelles formed by the surfactant solutions of various charges using steady-state and time-resolved fluorescence spectroscopic measurements. The extracted oil components in the micelles of different charges show different emission peaks with varying excitation wavelength and different fluorescence lifetime, indicating incorporation of PAH with variable sizes of FAR. Ionic surfactants (CTAB and SDS) are more compatible to exploit small (2–3 FAR) as well as medium (4–7 FAR) PAH structures whereas non-ionic surfactant (TX100) dominantly entraps medium PAH structures within their micelles. This study established that the intrinsic fluorescence of the crude oil can monitor its interaction with surfactant micelle of different charges and helps to design effective injection fluids for optimized crude oil recovery during surfactant flooding.

ANCF analysis of the crude oil sloshing in railroad vehicle systems

With the increase in crude oil rail transportation, accurate modelling of non-Newtonian crude oil rheological properties and the corresponding nonlinear sloshing effects becomes necessary in order to establish safety and operation guidelines. In this investigation, nonlinear continuum-based crude oil constitutive models are used in a total Lagrangian formulation to study the effect of the sloshing on railroad vehicle dynamics and stability. In particular, the Oldroyd constitutive model is employed to capture the non-Newtonian characteristics of three different crude oil types; classified as light, medium, and heavy. The crude oil complex deformation shapes are captured using the finite element (FE) absolute nodal coordinate formulation (ANCF). The FE continuum-based liquid sloshing formulation is systematically integrated with a fully nonlinear multibody system (MBS) railroad vehicle algorithm that allows for wheel/rail separation. A general penalty contact approach is developed to allow for studying the effect of sloshing suppression devices such as bulkheads. Different braking scenarios, including electronically controlled pneumatic (ECP) braking are considered to study the effect of crude oil sloshing on the train longitudinal stability. The ECP braking computer simulations show that increasing the crude oil viscosity can lead to approximately 30% reduction in the maximum coupler force compared to the light oil case. It is observed that the coupler force response to the sloshing excitations as the result of ECP braking reaches steady state faster as the viscosity increases. Furthermore, installing the bulkheads in tank cars can lead to a 70% reduction in the maximum coupler force and more uniform distribution of the normal contact forces to the front and rear wheels. The effect of crude oil rheological properties on the centrifugal forces during curve negotiation is also evaluated. The curve negotiation results show that the increase in crude oil density is responsible for exacerbating train lateral instability effects, thus the risk of vehicle roll over, especially when the train travels at a speed higher than the balance speed.

Investigation of ionic liquids based on pyridinium and imidazolium as interfacial tension reducer of crude Oil−Water and their synergism with MgCl2

Ionic liquids (ILs) can be tailored as chemical surfactants and surface active agents to reduce the interfacial tension (IFT) of crude oil/aqueous solutions for enhanced oil recovery processes. The current investigation was aimed to explore the nature of ingenious active agents in crude oil, including asphaltene and resin, and their possible interactions with two families of ILs, namely pyridinium and imidazolium, on the IFT of crude oil/aqueous solutions, both in the presence and absence of MgCl2. To the best of our knowledge, the effect of crude oil type on the IFT of crude oil/aqueous solution containing salts and IL has not been ever investigated. Accordingly, IFTs of light, medium and heavy crude oils (labeled as LCO, MCO and HCO, respectively) and two ILs, i.e. [C8mim] [Cl] and [C8Py] [Cl] were measured. In addition, the effects of the total acid number of crude oils, the amount of ingenious active agents in the crude oils as well as their major structural, molecular parameters such as hydrogen/carbon ratio and type and amount of heteroatoms (i.e. nitrogen, sulfur and oxygen) were investigated. The obtained results indicated that the performance of ILs was influenced by the crude oil and IL types. In details, the aromatic section of cationic part and their interactions with heteroatoms of crude oil showed the most influential role on the IFT variation.

Radiological Risk Assessment in A Type of Complex Petroleum Refinery in Egypt

Abstract The radiological and radioecological impacts associated with the uncontrolled release of TENORM in products and wastes released in the petroleum industry are of great concern. In this study, radiological risk assessment of TENORM in refined products, sludge, non-oil wastes and produced water are presented. Thirty-four statistically representative samples are divide into four groups; fourteen samples were refined petroleum products, nine samples were sludge waste, six samples were taken from used and fresh non-oil wastes and five samples were produced water. The activity concentrations of 232Th, 226Ra and 40K in all samples were measured by using gamma-ray spectrometry with high purity Germanium (HPGe) detector. The radium equivalent activity, external and internal hazard indices, gamma radiation absorbed doses rates and the annual effective dose were estimated. It was noticed that the maximum value of radium equivalent activity was found to be 308.773 Bq/kg and observed in ceramic balls used for catalyst bed support and it was lower than its recommended upper limit, which is 370 Bq/kg. The external and internal hazard indices were indicated. It is recommended that for workers who are working in maintaining and repairing equipment must use safety tools to protect them from the dangers of inhaling radon gas. Generally, the overall results revealed that the radiation levels would not pose any radiological risk occupationally or for the ambient environment. The results obtained in this study are very important in terms of establishing indicators and standards for radiation protection in this type of crude oil refining technology.

Biomonitoring of Benzene and Effect of Wearing Respirators during an Oil Spill Field Trial at Sea

The main aim of this study was to assess the biological uptake of benzene and polycyclic aromatic hydrocarbons (PAHs) for subjects exposed to fresh crude oil released at sea. The study included 22 subjects participating in an 'oil-on-water' field trial in the North Sea. Over 2 consecutive days, there were six releases with two different types of fresh crude oils. Exposed subjects (n = 17) were either located in small, open-air boats downwind and close to the released oil (<50 m) or on the main deck of two large vessels further from the released oil (100-200 m). Subjects assumed to be unexposed (n = 5) were located indoors on the command bridge of either vessel. Full-shift personal benzene exposure was monitored with passive thermal desorption tubes (ATD-tubes) packed with Tenax TA and subsequent gas chromatographic analysis. Urine samples were collected before and after work-shift on both days and analyzed for urinary markers of benzene [(S-phenylmercapturic acid (SPMA)] and PAHs [1-hydroxypyrene (1-OH)]. Information about the use of personal protective equipment, smoking habits, location, work tasks, and length of work-shift were recorded by a questionnaire. Subjects located in the small boats downwind and close to the released oil were exposed to relatively high concentrations of benzene (arithmetic mean = 0.2 ppm, range 0.002-1.5 ppm) compared to the occupational exposure limits (OELs) for 8 h (1 ppm) and 12 h (0.6 ppm). Although respirators were available to all exposed subjects, SPMA was detected in post-shift urine (0.5-3.3 µmol mol-1) of five exposed subjects reporting not wearing respirators, all located in the small boats downwind and close to the released oil. For exposed subjects wearing respirators (n = 12), the post-shift urinary SPMA was below the detection limit (0.8 µmol mol-1) even when the benzene exposure exceeded the OELs. Urinary levels of PAH were within the reference range of what is considered as background levels (<0.4 µmol mol-1). During the initial stages of a bulk oil spill at sea, when the evaporation of benzene is at its highest, it is important to use appropriate respirators to prevent biological uptake of benzene.