Sequential Monte Carlo applied to virtual flow meter calibration

Soft-sensors are gaining popularity due to their ability to provide estimates of key process variables with little intervention required on the asset and at a low cost. In oil and gas production, virtual flow metering (VFM) is a popular soft-sensor that attempts to estimate multiphase flow rates in real time. VFMs are based on models, and these models require calibration. The calibration is highly dependent on the application, both due to the great diversity of the models, and in the available measurements. The most accurate calibration is achieved by careful tuning of the VFM parameters to well tests, but this can be work intensive, and not all wells have frequent well test data available. This paper presents a calibration method based on the measurement provided by the production separator, and the assumption that the observed flow should be equal to the sum of flow rates from each individual well. This allows us to jointly calibrate the VFMs continuously. The method applies Sequential Monte Carlo (SMC) to infer a tuning factor and the flow composition for each well. The method is tested on a case with ten wells, using both synthetic and real data. The results are promising and the method is able to provide reasonable estimates of the parameters without relying on well tests. However, some challenges are identified and discussed, particularly related to the process noise and how to manage varying data quality.Comment: 20 pages, 12 figures, and 3 table

Maritim transport i EUs kvotehandelssystem - En vurdering av om det geografiske virkeområdet er egnet til å oppnå formålet bak kvotehandelssystemet

Temaet for denne oppgaven er endringsdirektivet som inkluderer maritim transport i EUs kvotehandelssystem (EU ETS). Oppgavens problemstilling er i hvilken grad det geografiske virkeområdet til endringsdirektivet, slik det er formulert av EU, gjør regelverket egnet til å oppnå formålet bak kvotehandelssystemet.MasteroppgaveJUS399MAJUR-2MAJU

En snarvei til å bli offiser? En kvalitativ studie vedrørende forbedringer til årsstudium ved Luftkrigsskolen

Utdanningsreformen av 2018 fjernet kravet om å ha fullført befalsskole for å kunne gå krigsskoleutdanning. Dette åpnet muligheten for å gjennomføre offisersutdanning ved Forsvarets høgskole (FHS) uten tidligere militær erfaring. Det ble her også åpnet for at sivile med bachelor- eller mastergrad uten militær erfaring kunne gjennomføre et årsstudium ved FHS og bli utdannet offiser. I 2021 ble betegnelsen «Grunnleggende offiserspåbygging» (GOP) endret til «Årsstudium i ledelse og militære operasjoner». Forsvarets nettsider beskriver denne utdanningsordningen på følgende måte: «Utdanningen er en grunnleggende militærfaglig tilleggsutdanning som gjør deg kvalifisert til å jobbe som offiser i Forsvaret» (Forsvaret, 2023). Videre beskrives kompetansen som tilegnes i løpet av årsstudiumet slik: «Du lære mer om fagområder som militært lederskap, militærmakt, operasjonsplanlegging, og du får en grunnleggende forståelse for den militære profesjonen» (Forsvaret, 2023). «Hvordan kan årsstudiumsordningen ved Luftkrigsskolen tilrettelegge for relevant kompetansedannelse, og hvordan kan utbyttet fra ordningen forbedres?»publishedVersio

Ansettelse ved første blikk? -en studie av «Hjem til jul», et rekrutteringsarrangement i regi av Sandefjord Næringsforening.

Nettverksbygging er en spennende måte å bygge en karriere og få nye muligheter på. I dagens kunnskapssamfunn, med alle sosiale medier vi har tilgjengelig, er dette mer aktuelt enn noensinne. «Hjem til jul» er et prosjekt som ønsker å trekke utflyttede Sandefjordinger hjem til byen ved å sette de i kontakt med aktuelle arbeidsgivere på et arrangement rett før jul hvert år. Rekrutteringsprosessen deles inn i syv steg: tidlige rekrutteringsaktiviteter, gjennomføre jobbanalyse, sikre kandidattilfang, administrasjon av søknader, seleksjon, ansettelse og introduksjon av den nyansatte for organisasjonen. Ved å se nærmere på de fem stegene som kan erstattes av et rekrutteringsarrangement har denne studien belyst problemstillingen «Hvilken plass har rekrutteringsarrangementer i rekrutteringsprosessen?». Det ble gjennomført en kvalitativ studie med totalt åtte semi-strukturerte intervjuer hvor ett ble ekskludert fra studien på bakgrunn av gitte avgrensninger. I tillegg svarte samt fire informanter på et selvutfyllingsskjema. Studien viste at «Hjem til jul» arrangementet har en verdi i rekrutteringsprosessen. Både bedrifter og kandidater kunne melde om ansettelser, og det viser seg å være et godt supplement til den tradisjonelle rekrutteringsprosessen. Studien viste derimot at arrangementet har liten verdi som tidlig rekrutteringsaktivitet både for bedriftene og kandidatene, og det kom frem at kompetansekrav til stillinger presentert og kompetansen til deltagende kandidater ikke er sammenfallende. Samtidig er det er gap mellom tidsperspektivet kandidater og bedrifter ser for seg at relasjonen som bygges skal kunne lede til en stilling, da de fleste bedrifter stiller med definerte stillinger, mens kandidatene etterlyser langsiktige kontakter. Det etterlyses segmenterte arrangementer, både i henhold til bransje og kompetanse, men også i henhold til tidsperspektiv

Bayesian Neural Networks for Virtual Flow Metering: An Empirical Study

Recent works have presented promising results from the application of machine learning (ML) to the modeling of flow rates in oil and gas wells. Encouraging results and advantageous properties of ML models, such as computationally cheap evaluation and ease of calibration to new data, have sparked optimism for the development of data-driven virtual flow meters (VFMs). Data-driven VFMs are developed in the small data regime, where it is important to question the uncertainty and robustness of models. The modeling of uncertainty may help to build trust in models, which is a prerequisite for industrial applications. The contribution of this paper is the introduction of a probabilistic VFM based on Bayesian neural networks. Uncertainty in the model and measurements is described, and the paper shows how to perform approximate Bayesian inference using variational inference. The method is studied by modeling on a large and heterogeneous dataset, consisting of 60 wells across five different oil and gas assets. The predictive performance is analyzed on historical and future test data, where an average error of 4-6% and 8-13% is achieved for the 50% best performing models, respectively. Variational inference appears to provide more robust predictions than the reference approach on future data. Prediction performance and uncertainty calibration is explored in detail and discussed in light of four data challenges. The findings motivate the development of alternative strategies to improve the robustness of data-driven VFMs.Comment: 34 pages, 11 figure

Bayesian seismic inversion for stratigraphic horizon, lithology, and fluid prediction

We have developed an efficient methodology for Bayesian prediction of lithology and pore fluid, and layer-bounding horizons, in which we include and use spatial geologic prior knowledge such as vertical ordering of stratigraphic layers, possible lithologies and fluids within each stratigraphic layer, and layer thicknesses. The solution includes probabilities for lithologies and fluids and horizons and their associated uncertainties. The computational cost related to the inversion of large-scale, spatially coupled models is a severe challenge. Our approach is to evaluate all possible lithology and fluid configurations within a local neighborhood around each sample point and combine these into a consistent result for the complete trace. We use a one-step nonstationary Markov prior model for lithology and fluid probabilities. This enables prediction of horizon times, which we couple laterally to decrease the uncertainty. We have tested the algorithm on a synthetic case, in which we compare the inverted lithology and fluid probabilities to results from other algorithms. We have also run the algorithm on a real case, in which we find that we can make high-resolution predictions of horizons, even for horizons within tuning distance from each other. The methodology gives accurate predictions and has a performance making it suitable for full-field inversions.We have developed an efficient methodology for Bayesian prediction of lithology and pore fluid, and layer-bounding horizons, in which we include and use spatial geologic prior knowledge such as vertical ordering of stratigraphic layers, possible lithologies and fluids within each stratigraphic layer, and layer thicknesses. The solution includes probabilities for lithologies and fluids and horizons and their associated uncertainties. The computational cost related to the inversion of large-scale, spatially coupled models is a severe challenge. Our approach is to evaluate all possible lithology and fluid configurations within a local neighborhood around each sample point and combine these into a consistent result for the complete trace. We use a one-step nonstationary Markov prior model for lithology and fluid probabilities. This enables prediction of horizon times, which we couple laterally to decrease the uncertainty. We have tested the algorithm on a synthetic case, in which we compare the inverted lithology and fluid probabilities to results from other algorithms. We have also run the algorithm on a real case, in which we find that we can make high-resolution predictions of horizons, even for horizons within tuning distance from each other. The methodology gives accurate predictions and has a performance making it suitable for full-field inversions.publishedVersio

Subchronic dietary exposure to ethoxyquin dimer induces microvesicular steatosis in male BALB/c mice

The use of the synthetic antioxidant ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; EQ) in animal feed results in the presence of EQ residues and metabolites, including the EQ dimer (1,8′-bi(6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline); EQDM) in animal food products. To investigate the toxicity and dose-response of dietary exposure to EQDM, male BALB/c mice were exposed to one of six dietary doses of EQDM, ranging from 0.015 to 518 mg/kg body weight/day for 90 days. Doses above 10 mg/kg body weight/day affected whole body lipid metabolism resulting in increased liver weights and decreased adipose tissue mass. Metabolomic screening of livers revealed alterations indicating incomplete fatty acid β-oxidation and hepatic oxidative stress. Histopathological evaluation and biochemical analyses of the liver confirmed the development of microvesicular steatosis and activation of the glutathione system. Hepatic protein profiling and pathway analyses suggested that EQDM-induced responses are mediated through activation of CAR/PXR nuclear receptors and induction of a NRF2-mediated oxidative stress response. Based on the development of microvesicular steatosis as the critical endpoint, a Reference Point for dietary EQDM exposure was established at 1.1 mg/kg body weight/day (BMDL10) from benchmark dose modelling. Applying an uncertainty factor of 200, an Acceptable Daily Intake of 0.006 mg EQDM/kg body weight was proposed.publishedVersio

Calcification of intervertebral discs in the dachshund: a radiographic and histopathologic study of 20 dogs

<p>Abstract</p> <p>Background</p> <p>The purpose of the study was to compare radiographic and histopathologic findings with regard to number and extent of calcified discs in the dachshund.</p> <p>Methods</p> <p>The intervertebral discs of 20 dachshunds were subjected to a radiographic and histopathologic examination. The dogs were selected randomly from clinical cases euthanased for reasons unrelated to research at the Norwegian School of Veterinary Science. Lateral radiographs were taken of the vertebral columns after removing them from the carcasses. The histopathologic examination included 5 μm thick sections in the transverse plane, stained with hematoxylin-eosin and von Kossa. Radiographs and histological sections were evaluated independently.</p> <p>Results</p> <p>A total of 148 (28.5%) calcified discs were identified at the radiographic and 230 (45.7%) at the histopathologic examination. Of 92 discs found to be calcified by histopathology, but not by radiography, the degree of calcification was evaluated as 'slight' in 84 (91.3%). All the intervertebral discs (n = 138) that were found to be calcified by radiography were also found to be calcified by histopathology.</p> <p>Conclusion</p> <p>A sensitivity of 0.6 and specificity of 1.0 for radiography was calculated when using histopathology as the gold standard.</p

Use of the rSpaA415 antigen indicates low rates of Erysipelothrix rhusiopathiae infection in farmed cattle from the United States of America and Great Britain

Background Clinical cases of Erysipelothrix rhusiopathiae, a zoonotic gram-positive bacterium, have been reported in many ruminant species, including in cattle, deer, moose and muskoxen. Fatal cases have been repeatedly reported in cattle over the years but to date there is only one Japanese study investigating the seroprevalence of this bacterium in cattle using the growth agglutination test (GAT). This technique is subjective, time-consuming, expensive and hazardous compared to modern serological tests such as enzyme-linked immunosorbent assays (ELISA) or the newly developed fluorescent microbead-based immunoassays (FMIA). Results The FMIA based on the surface protein SpaA (rSpaA415) antigen of E. rhusiopathiae developed in this study had an almost perfect agreement with the GAT (k = 0.83) and showed a sensitivity of 89.7% and a specificity of 92.9% when compared to the GAT. Overall, detection rates of E. rhusiopathiae antibody positive samples were 13.8% (51/370) in British herds and 6% (12/200) in US herds. Positive cattle were present in 34.3% (24/70) of the investigated British farms and in 34.7% (8/23) of the US farms with an on-farm prevalence of 7.1 to 100% for the British farms and 8.3–30% for the US farms. Conclusions FMIA is a fast, safe and economic alternative to the GAT for the diagnosis of E. rhusiopathiae in cattle. This work is the first seroprevalence study of E. rhusiopathiae in healthy farmed cattle in Great Britain and the US and revealed that infection occurs at a low level. Further investigations to evaluate risks of zoonotic transmission when handling cattle are needed