1,720,994 research outputs found
Experimental and modelling study of subsea oil releases: focusing on small leaks from an aging oilfield off the Norwegian Continental Shelf
No full textWith advances in exploration and extraction technology, oilfields that would otherwise have been ready for decommission are expected to produce oil for many more years. While beneficial to extract as much resource as possible from existing fields, this prolonged usage also increases the potential for oil leaks from aging pipelines. These pipeline leaks can produce high velocity conditions that emit plumes of small droplets of oil, gas and produced water. This is in contrast to large diameter blowouts where much larger droplets are expected. The exit parameters and resulting size distribution of oil droplets have a significant impact on the fate of oil in the environment.
Using the SINTEF MiniTower in conjunction with a silhouette camera, the droplet size distributions for discharge conditions representative of small diameter, high velocity leaks of oil and produced water were obtained. These distributions were then used to empirically optimize the coefficients, A 8.5 and B 7.68, for use in droplet size prediction with the Modified Weber algorithm. These optimized coefficients predicted larger droplet sizes than the previously reported values, for small diameter, high velocity releases. A series of pipeline leaks and blowouts operating under different seasonal and release conditions were generated with the SINTEF oil spill modelling simulation tool, OSCAR. The Njord field was selected as a proxy for mature oilfields along the Norwegian Continental Shelf. The releases modelled produced thin and spread out surface slicks, which limited the effectiveness of response methods. The low surface oil thickness limited shoreline oiling, and the formation of tarballs would not be expected. This makes the Njord field an unlikely candidate source for oil pollution samples collected in the Frøya municipality region during an excursion in 2017. This fieldwork was carried out as part of the course Marine Organic Environmental Chemistry KJ3050 as a requisite of the Environmental Toxicology and Chemistry Master program at NTNU. Experimental and modelling studies are necessary to ensure appropriate monitoring and contingency planning for maturing oilfields
Experimental and modelling study of subsea oil releases: focusing on small leaks from an aging oilfield off the Norwegian Continental Shelf
No full textWith advances in exploration and extraction technology, oilfields that would otherwise have been ready for decommission are expected to produce oil for many more years. While beneficial to extract as much resource as possible from existing fields, this prolonged usage also increases the potential for oil leaks from aging pipelines. These pipeline leaks can produce high velocity conditions that emit plumes of small droplets of oil, gas and produced water. This is in contrast to large diameter blowouts where much larger droplets are expected. The exit parameters and resulting size distribution of oil droplets have a significant impact on the fate of oil in the environment.
Using the SINTEF MiniTower in conjunction with a silhouette camera, the droplet size distributions for discharge conditions representative of small diameter, high velocity leaks of oil and produced water were obtained. These distributions were then used to empirically optimize the coefficients, A 8.5 and B 7.68, for use in droplet size prediction with the Modified Weber algorithm. These optimized coefficients predicted larger droplet sizes than the previously reported values, for small diameter, high velocity releases. A series of pipeline leaks and blowouts operating under different seasonal and release conditions were generated with the SINTEF oil spill modelling simulation tool, OSCAR. The Njord field was selected as a proxy for mature oilfields along the Norwegian Continental Shelf. The releases modelled produced thin and spread out surface slicks, which limited the effectiveness of response methods. The low surface oil thickness limited shoreline oiling, and the formation of tarballs would not be expected. This makes the Njord field an unlikely candidate source for oil pollution samples collected in the Frøya municipality region during an excursion in 2017. This fieldwork was carried out as part of the course Marine Organic Environmental Chemistry KJ3050 as a requisite of the Environmental Toxicology and Chemistry Master program at NTNU. Experimental and modelling studies are necessary to ensure appropriate monitoring and contingency planning for maturing oilfields
Oil spill forensics - Identification of possible sources for oil spills found along the coastline of mid-Norway - An experimental study combining GC-MS analysis and multivariate statistics.
No full textThis thesis aims to characterize 112 weathered oil samples collected on shore, at 18 islands, along the coastline of Mid-Norway during a time period of 2011-2015. Emphasis have been made on characterizing samples by three different multivariate methods; Principal component analysis (PCA), Partial least square-discriminant analysis (PLS-DA) and Hierarchal cluster analysis (HCA), however univariate methods have been applied as a starting point.
In multivariate data analysis, diagnostic ratios were calculated between biomarkers and PAH components and applied to look for interesting structures in the plot. The classification from univariate methods, were combined to identify the position of different oil types in the plots.
PCA, PLS-DA and HCA demonstrated their ability to categorize weathered samples, and identified samples that could not be identified by the traditional univariate method. The multivariate techniques were able to classify samples without some of the typical identifying biomarkers that are used in univariate oil spill forensics and indicates that multivariate techniques could be a promising method for identifying heavily weathered samples that often have inconclusive or missing measurements for typically used biomarkers and diagnostic ratios.
Selected samples were imported into an international oil spill database to identify matches to external samples from other projects and laboratories. Six samples in this study were a probable match to oil samples collected at the Shetland islands
Analysis of petroleum oil droplet behavior during a subsea release
No full textUnder et undervannsutslipp flyter millioner av oljedråper gjennom vannkolonnen og opp mot havoverflaten. Hvordan dråpene oppfører seg når de når overflaten vil avgjøre både oljefilmtykkelsen, emulgeringen og livsløpet til dråpen. Oppførselen til dråpene vil være avgjørende for oljevernberedskap, spesielt når det gjelder opprydding og miljøpåvirkninger av utslippet. Oljen vil mest sannsynlig trenge forskjellige opprydningsmetoder avhengig av om dråpen er størknet eller flytende når den når overflaten. I dag er det mangel på kunnskap rundt dette feltet. Hvordan overflatedråper vil oppføre seg, og da spesielt dråper fra oljer med høyt stivnepunkt, er det ikke mange som har forsket på tidligere. Denne studien tar sikte på å lukke noe av dette kunnskapsgapet ved å se på hvordan dråper med forskjellige stivnepunkt oppfører seg når de når overflaten, med et spesielt fokus på hvordan de størkner.
I denne studien er det blitt brukt både eksperimenter og simuleringer, OSCAR ble brukt til å simulere undervannsutslipp for å finne nøyaktige stigetider for dråpene, mens beregninger med Stokes lov ble brukt for å finne passende dråpestørrelser. Den eksperimentelle delen ble utført ved bruk av Inverted Cone, hvor dråpene ble holdt under vann i en forhåndsbestemt tid, før de ble sluppet opp til overflaten. I det dråpene nådde overflaten ble de filmet for å kunne observere dråpens oppførsel.
Konklusjonen ble at en dråpe med mer enn 10º celsius høyere stivnepunkt enn sjøvannstemperaturen ville være i fastfase når den nådde havoverflaten. Det ble videre konkludert med at en dråpe med mer enn 10º Celsius lavere stivnepunkt enn sjøvannstemperaturen ville bli flytende umiddelbart når den nådde overflaten. Det ble også konkludert med at det er en midtfase hvor dråpene gjennomgår en mer komplisert prosess. Det ble observert dekonstruksjon av dråpene i denne midtfasen, men oppgaven var ikke i stand til å komme til en konklusjon av hva som skjer i dette intervallet
Analysis of petroleum oil droplet behavior during a subsea release
No full textUnder et undervannsutslipp flyter millioner av oljedråper gjennom vannkolonnen og opp mot havoverflaten. Hvordan dråpene oppfører seg når de når overflaten vil avgjøre både oljefilmtykkelsen, emulgeringen og livsløpet til dråpen. Oppførselen til dråpene vil være avgjørende for oljevernberedskap, spesielt når det gjelder opprydding og miljøpåvirkninger av utslippet. Oljen vil mest sannsynlig trenge forskjellige opprydningsmetoder avhengig av om dråpen er størknet eller flytende når den når overflaten. I dag er det mangel på kunnskap rundt dette feltet. Hvordan overflatedråper vil oppføre seg, og da spesielt dråper fra oljer med høyt stivnepunkt, er det ikke mange som har forsket på tidligere. Denne studien tar sikte på å lukke noe av dette kunnskapsgapet ved å se på hvordan dråper med forskjellige stivnepunkt oppfører seg når de når overflaten, med et spesielt fokus på hvordan de størkner.
I denne studien er det blitt brukt både eksperimenter og simuleringer, OSCAR ble brukt til å simulere undervannsutslipp for å finne nøyaktige stigetider for dråpene, mens beregninger med Stokes lov ble brukt for å finne passende dråpestørrelser. Den eksperimentelle delen ble utført ved bruk av Inverted Cone, hvor dråpene ble holdt under vann i en forhåndsbestemt tid, før de ble sluppet opp til overflaten. I det dråpene nådde overflaten ble de filmet for å kunne observere dråpens oppførsel.
Konklusjonen ble at en dråpe med mer enn 10º celsius høyere stivnepunkt enn sjøvannstemperaturen ville være i fastfase når den nådde havoverflaten. Det ble videre konkludert med at en dråpe med mer enn 10º Celsius lavere stivnepunkt enn sjøvannstemperaturen ville bli flytende umiddelbart når den nådde overflaten. Det ble også konkludert med at det er en midtfase hvor dråpene gjennomgår en mer komplisert prosess. Det ble observert dekonstruksjon av dråpene i denne midtfasen, men oppgaven var ikke i stand til å komme til en konklusjon av hva som skjer i dette intervallet.During a subsea blowout, millions of oil droplets will travel through the water column towards the sea surface. Their behavior upon reaching the surface will affect the optimal procedure to minimize the environmental impact. The droplets' behavior will determine the oil film thickness, emulsification, and persistence. Droplet behavior is necessary for oil spill contingency, especially regarding the clean-up and environmental impacts of the release. Different clean-up responses will be needed depending on whether the droplets breach the sea surface solidified or liquefy. There is a lack of knowledge on how surfacing droplets will behave, especially high pour point oil droplets. This study aims to close some of this knowledge gap by looking into how droplets with different pour points behave upon reaching the surface, especially regarding the solidification process.
Experiments and simulations were used in this study to determine the droplet behavior when reaching the surface. OSCAR was used to simulate subsea blowouts to find accurate rising times of the droplets, while Stokes law calculations were used to find appropriate droplet sizes. The experimental part was done using the Inverted Cone, where the droplets were kept under water for a pre-decided time and filmed upon reaching the water surface.
By using the inverted cone, it was determined that a droplet with more than 10ºC higher pour point than seawater temperature would be solid upon reaching the sea surface. It was further concluded that a droplet with more than 10º centigrade lower pour point than seawater temperature would liquefy immediately upon reaching the surface. It was also concluded that a middle phase exists where the droplets undergo a more complicated process. This thesis was not able to conclude what happens in this interval. However, deconstruction of the droplets was observed in the middle phase
Leaching of surfactants as a function of oil droplet size and surfactant properties. An approach using mass spectrometry and multivariate data analysis
Full text linkOil dispersants are used extensively in order to minimize the environmental damage that often follows an oil spill. A widely used dispersant, Corexit 9500A, consists of four surfactants with different properties and a solvent making sure that the interfacial tension between the oil and water is as low as possible. Low interfacial tension enhances natural dispersion of the oil. Due to the surfactant's different affinities to water and oil, individual leaching rates occur for the surfactants. This changes the relative composition, and thus decrease the efficiency of the dispersant. Experiments to determine these leaching rates have been conducted on oil slicks at the sea surface by Resby et al. (2007). Such rates are equally interesting subsurface, but have not been investigated.
By using SINTEF's Inverted Cone system, single oil droplets, treated with the dispersant Corexit 9500A, were captured and analyzed. The instrument used for analyses was a liquid chromatography-mass spectrometer. Direct injection of the samples into the electrospray ionization source was used to reduce unwanted effects due to the different chemical and physical properties of the surfactants. To extract information from the analyzed droplets, prediction models were built using partial least squares regression.
It was discovered that the relative composition of surfactants in a rising oil droplet changes over time. The total amount of surfactants was found to decrease to 63% of the initial mass after 15 minutes, and to 60% after 120 minutes. The relative concentration of the surfactants was found to mainly be determined during the first 15 minutes of contact time with seawater. The relative amount of the anionic surfactant, DOSS, was decreasing compared to the nonionic surfactants, Span 80, Tween 80 and Tween 85, before stabilizing.
It has been proven that the relative composition of the dispersant are changing while the oil droplet is rising towards the surface. This changed composition are affecting the dispersant effectiveness
Leaching of surfactants as a function of oil droplet size and surfactant properties. An approach using mass spectrometry and multivariate data analysis
No full textOil dispersants are used extensively in order to minimize the environmental damage that often follows an oil spill. A widely used dispersant, Corexit 9500A, consists of four surfactants with different properties and a solvent making sure that the interfacial tension between the oil and water is as low as possible. Low interfacial tension enhances natural dispersion of the oil. Due to the surfactant's different affinities to water and oil, individual leaching rates occur for the surfactants. This changes the relative composition, and thus decrease the efficiency of the dispersant. Experiments to determine these leaching rates have been conducted on oil slicks at the sea surface by Resby et al. (2007). Such rates are equally interesting subsurface, but have not been investigated.
By using SINTEF's Inverted Cone system, single oil droplets, treated with the dispersant Corexit 9500A, were captured and analyzed. The instrument used for analyses was a liquid chromatography-mass spectrometer. Direct injection of the samples into the electrospray ionization source was used to reduce unwanted effects due to the different chemical and physical properties of the surfactants. To extract information from the analyzed droplets, prediction models were built using partial least squares regression.
It was discovered that the relative composition of surfactants in a rising oil droplet changes over time. The total amount of surfactants was found to decrease to 63% of the initial mass after 15 minutes, and to 60% after 120 minutes. The relative concentration of the surfactants was found to mainly be determined during the first 15 minutes of contact time with seawater. The relative amount of the anionic surfactant, DOSS, was decreasing compared to the nonionic surfactants, Span 80, Tween 80 and Tween 85, before stabilizing.
It has been proven that the relative composition of the dispersant are changing while the oil droplet is rising towards the surface. This changed composition are affecting the dispersant effectiveness
Experimental and modeling study of subsea releases of oil and gas. - Oil behavior and effects in a cold or Arctic marine environment as a function of release conditions, oil chemistry and dispersant injection.
No full textAbstract
With oil exploration going into deeper waters and more extreme environments, more detailed knowledge is needed about the fate of oil in case of a release.
This thesis focuses on initial droplet formation, secondary breakup and fate of oil in a subsurface release and the effect of subsurface injection of dispersants.
The objectives were to study initial droplet formation, the effectiveness of different surfactant blends when injected in warm oil, secondary droplet breakup and to model hypothetical oil releases in the Barents Sea.
The effectiveness of tested surfactant combinations increased when the temperature of Troll B oil increased. However, a decrease was observed when the commercially available dispersant Corexit 9500A was injected in Kobbe oil at increasing temperatures. This observed change in behavior and effectivity could be related to surfactant and/or oil chemistry.
The secondary breakup mechanism tip-streaming, where small droplets shed of the parent droplet due to deformation after surfactant treatment, has been studied and observed to be finished within 10 minutes after the release at different dispersant-to-oil ratios. After one hour in very turbulent conditions, the droplets were stable and spherical in shape.
Simulations with the OSCAR model have shown how a reduction in droplet size due to dispersant injection can change the environmental fate of the released oil.
Further research could be of interest to see whether the change in dispersant effectiveness is a result of oil or surfactant chemistry and to study tip-streaming at higher oil temperatures
Oil spill forensics - Identification of possible sources for oil spills found along the coastline of mid-Norway - An experimental study combining GC-MS analysis and multivariate statistics.
Full text linkThis thesis aims to characterize 112 weathered oil samples collected on shore, at 18 islands, along the coastline of Mid-Norway during a time period of 2011-2015. Emphasis have been made on characterizing samples by three different multivariate methods; Principal component analysis (PCA), Partial least square-discriminant analysis (PLS-DA) and Hierarchal cluster analysis (HCA), however univariate methods have been applied as a starting point.
In multivariate data analysis, diagnostic ratios were calculated between biomarkers and PAH components and applied to look for interesting structures in the plot. The classification from univariate methods, were combined to identify the position of different oil types in the plots.
PCA, PLS-DA and HCA demonstrated their ability to categorize weathered samples, and identified samples that could not be identified by the traditional univariate method. The multivariate techniques were able to classify samples without some of the typical identifying biomarkers that are used in univariate oil spill forensics and indicates that multivariate techniques could be a promising method for identifying heavily weathered samples that often have inconclusive or missing measurements for typically used biomarkers and diagnostic ratios.
Selected samples were imported into an international oil spill database to identify matches to external samples from other projects and laboratories. Six samples in this study were a probable match to oil samples collected at the Shetland islands
Releases of oily produced water from offshore installations - A combined laboratory and modelling study comparing resulting surface oil slicks and oil slicks detected by satellite
Full text linkProdusertvann er et biprodukt fra petroleumsindustrien som blir sett på som avfall, og blir ført opp til overflaten sammen med olje og gass. Etter at produsertvannet har gått gjennom nødvendige renseprosesser på oljeplattformen for å imøtekomme dagens miljøkrav, er den vanligste håndteringen å slippe produsertvannet ut i havet. Flere oljeplattformer på norsk sokkel har kontinuerlige produsertvann-utslipp som under visse forhold kan føre til oljeflak på havoverflaten som kan detekteres av satellittradar. Det er knyttet bekymring til den mulige skaden oljeflakene har på fugleliv og annet marint dyreliv som oppholder seg på eller nært havoverflaten. Målet med denne studien har vært å bidra til en økt forståelse knyttet til hvordan produsertvann oppfører seg når det slippes ut i havet, i tillegg til økt kunnskap om deteksjon med satellittradar, dråpestørrelse og utslippsforhold.
Eksperimenter og simuleringer ble gjennomført for å imøtekomme målet med studien. Eksperimentene ble gjort innendørs i en bølgerenne under en rekke varierte forhold og fokuserte på utslippsvinkel, hastighet, temperatur og salinitet. Det ble også gjennomført produsertvann-utslipp hvor gasstrøm eller oljedråper ble tilført. I tillegg ble det gjort simuleringer i programmet OSCAR for å bedre forstå hvordan vind, strøm, tidevann og bølger påvirker oppførselen til produsertvann-plumen. Fem simuleringer ble gjennomført med en varierende størrelse på oljedråpene i produsertvannet.
Den observerte trenden fra eksperimentene gjort i bølgerennen var jo større tetthet produsertvannet hadde, jo dypere sank det. Det ble vist at utslippsvinkelen påvirket hvor dypt produsertvannet sank, ettersom utslipp med en nedovervendt utslippsvinkel sank dypere sammenlignet med utslipp som hadde en horisontal utslippsvinkel. Temperaturen spilte også en viktig faktor for tettheten til produsertvannet, som igjen påvirket oppførselen til produsertvannet i havet. Tilførselen av gass i produsertvann-utslippet førte til at plumen steg nærmere vannoverflaten. Størrelsen på oljedråpene påvirket ikke oppførselen til plumen, men om produsertvannet steg til havoverflaten ble det observert at større oljedråper var en favoriserende faktor for dannelse av oljeflak. I tillegg kan denne oppgaven bidra med kunnskap om produsertvann-utslipp og dens oppførsel i havet.Produced water is a liquid waste byproduct from the petroleum industry and is brought up to the surface along with the extraction of oil and gas. After the produced water has gone through cleaning treatments to meet environmental regulations, discharge to sea is the most common practice used on offshore installations to handle the oily water. Several petroleum fields have a continuous release of produced water and can under certain conditions lead to the formation of oil sheens on the sea surface that are detected by satellite radar. There is raised a concern regarding the potential harm for seabirds and other marine life that resides on or near the sea surface. The aim of this study was to contribute to a better understanding of the behavior of produced water once it is discharged at sea, satellite radar detection, droplet size and discharge conditions.
Experiments and simulations were carried out to meet the aim of the study. The experiments were conducted indoor in a wave basin under varying conditions and focused on release angle, velocity, temperature and salinity. It was also conducted produced water releases that included a gas flow or oil droplets. Additionally, simulations were carried out in the OSCAR model to comprehend how winds, currents, tide and waves might affect the plume behavior. Five simulations were conducted with a varying oil droplet size in the produced water.
The observed trend from the conducted experiments in the wave basin were that the denser produced water plumes sank deeper. It was shown that the outlet angle influences how deep the plume sinks, as releases with a downward outlet angle sank deeper compared to releases with a horizontal outlet angle. Also, the temperature played an important factor to the produce waters density, which was seen to influence its behavior. The inclusion of gas in the produced water release affected the plume to rise towards the surface. The oil droplet size did not affect the plume behavior, but bigger droplets were observed to favor the formation of oil sheens if the plume surfaced. This thesis also helps fill some of the knowledge gaps regarding PW releases and its behavior once let out in the ocean
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