Riaz, Muhammad

Energisektoren for undervandsoperationer repræsenterer i dag et af de hurtigst voksende områder inden for olie- og gas industrien. For at imødekomme udfordringerne med korrosion, afskalning, samt hydrat- og skumdannelse anvender olie- og gas industrien store mængde kemikalier, og forbruget af disse kemikalier er stærkt stigende. For at forhindre dannelsen af gas hydrater anvender olie- og gas industrien store mængder monoethylene glycol (MEG) og methanol i deres undersøiske rørledninger. Det er vigtigt at kende distributionen af disse kemikalier i olie- og vand systemer, både for den økonomiske drift af produktionsanlæg, samt for at evaluere virkningen på marint liv. Derudover er viden om kemikaliedistributionen vigtigt for oprensningsprocesser af olie og gas. Formålet med dette projekt er at foretage eksperimentelle målinger samt at udføre termodynamisk modellering af distributionen af disse komplekse kemikalier i olie og vand systemer.  Traditionelt anvendes fordelingskoefficienter for oktanol-vand til at udregne distributionen af kemikalier i olie/vand systemer. Men eksperimentelle resultater opnået af Statoil R&amp;D, har vist at disse octanol-vand fordelingskoefficienter (Kow) ikke altid passer sammen med olie-vand fordelingskoefficienter (Koil-water). I dette projekts første fase, blev eksperimentelle data for Kow, Koil-water og Khw (hexane-vand fordelingskoefficient) indsamlet. Det blev undersøgt hvorvidt man kunne udvikle en korrelation til beregning af Koil-water ved brug af Kow og Khw. Dette kunne dog kun opnås for nogle få familier af kemikalier, såsom alkoholer, glykoler og alkanolaminer, og med en varierende grad af pålidelighed. Dette skyldes en stor mangel på eksperimentelle data og begrænset information omkring molekylær struktur af produktionskemikalier.  Eksperimentelle data er essentielle for udviklingen af en termodynamisk model, der er i stand til at forudsige distributionen af kemikalier i olie- og vand systemer. Data for kondensat- og oliesystemer er dog meget sjældne i litteraturen. I dette projekt er der blevet udført eksperimentelt arbejde hos Statoil R&amp;D, hvor en eksperimentel metode er blevet etableret og testet for målinger af denne type blandinger. Den gensidige opløselighed af to Nordsø gas kondensater med MEG og vand er blevet målt i et temperatur område på 275-326 K og ved atmosfærisk tryk. Den detaljerede sammensætning er målt med GC analyse, hvor 85 komponenter er identificeret op til n-nonane og med hundredvis af udefinerede komponenter i decane plus fraktionen.  Ved brugen af methanol og MEG som gashydrat inhibitor, er den største svaghed, specielt for methanol, tabet til den kulbrinterige fase. Hvis man kunne estimere dette tab af inhibitor, ville manvære i stand til at optimere injektionen af inhibitorer som funktion af systemparametre, såsom temperatur og vandsnit.  I dette projekt anvendes tilstandsligningen CPA (Cubic Plus Association) til at modellere distributionen af vand og inhibitorer (methanol, MEG) i forskellige faser. Den kulbrinte rige fase består af mixture-1 (methane, ethane, n-butane) eller mixture-2 (methane, ethane, propane, n-butane, n-heptane, toluene and n-decane). CPA giver tilfredsstillende resultater med at forudsige vandindholdet i gasfasen af et multikomponent system indeholdende mixture-1. Ligeledes kan CPA forudsige methanolindholdet i gasfasen af en blanding af mixture-1 + vand + methanol med en nøjagtighed inden for eksperimentel usikkerhed. For yderligere væske-væske-gas systemer indeholdende mixture-2 + vand, mixture-2 + vand + MEG og mixture-2 + methanol + vand, opnås tilfredsstillende forudsigelser for sammensætningen af kulbrinte fasen, hvorimod modelleringsresultaterne er relativt mindre tilfredsstillende for sammensætningen i gas fasen, delvist på grund af usikkerheder i de eksperimentelle data.  Ud over de ovenfor beskrevne multikomponent systemer, blev gas-væske ligevægten af det binære system methanol + methane undersøgt. Her opnås tilfredsstillende resultater af methane i væskefasen, ved brug af en enkelt temperatur uafhængig kij over en række temperaturer og tryk. Her giver CPA gode resultater for methanol indholdet i gasfasen ved høje temperaturer og lave tryk ved anvendelsen af den samme kij, mens der ved lave temperaturer og høje tryk ses afvigelse fra eksperimentelle data. For at kunne anvende CPA til modellering af reservoirmedier (olie/gas etc.), har det interesse at undersøge LLE af binære systemer med kulbrinter og vand. Dette er blevet gjort i dette projekt for alkane + vand og alkylbenzene +vand med CPA, hvor der er blevet fundet de binære interaktions parametre (kij) og cross-association volumen.  CPA er blevet udvidet til at kunne anvendes på reservoir medier med MEG og MEG + vand. Reservoir medierne består af tre kondensater og 2 olier fra oliefelter i Nordsøen. Den gensidige opløselighed af kondensater og MEG bliver modelleret tilfredsstillende ved anvendelse af en enkelt gennemsnitlig og temperatur uafhængig kij for alle MEG-HC par. Beregningen af den gensidige opløselighed af kondensat/olie, MEG og vand er ligeledes tilfredsstillende ved anvendelse af den samme gennemsnitlige kij for MEG-HC par, samt en kij for vand-HC fra en generaliseret korrelation som er en funktion af kulstofantal. De eksperimentelle tendenser i den gensidige opløselighed som funktion af temperatur og MEG indhold i den polære fase er tillige fanget tilfredsstillende og lever op til industriens krav om beregnede resultater i den samme størrelsesorden som de eksperimentelle.The deepwater energy sector represents one of the major growth areas of the oil and gas industry today. In order to meet the challenges of hydrate formation, corrosion, scaling and foaming the oil and gas industry uses many chemicals and their use has increased significantly over the years. In order to inhibit gas hydrate formation in subsea pipelines monoethylene glycol (MEG) and methanol are injected in large amounts. It is important to know the distribution of these chemicals in oil and water systems for economical operation of a production facility and to evaluate their impact on marine life. Furthermore distribution of chemicals is important information for downstream processing of oil and gas. The purpose of this project is the experimental measurement and the thermodynamic modeling of distribution of these complex chemicals in oil-water systems.  Traditionally distribution of chemicals in oil-water system is calculated using octanol-water partition coefficients. But experiments carried out by Statoil R &amp; D have shown that octanol-water partition coefficients (Kow) do not always mimic oil-water partition coefficients (Koil-water) and therefore calculations may not be always correct. In the first phase of this project experimental data on Kow, Koil-water and Khw (hexane-water partition coefficients) are collected and investigations were carried out to develop correlations so that Koil-water can be predicted using Kow and Khw. However, due to scarcity of experimental data and limited information about the molecular structure of production chemicals the correlation could only be obtained for few families like alcohols, glycols and alkanolamines with varying degree of reliability. In order to develop a thermodynamic model for the distribution of chemicals in oil-water systems experimental data are required but such data with natural gas-condensate/oil systems are very rare in the literature. In this project experimental work has been carried at Statoil R &amp; D and an experimental method has been established and tested for such measurements. The mutual solubility of two North Sea condensates, MEG and water has been measured in the temperature range of 275-326 K at atmospheric pressure. The detailed composition of condensates is measured by GC analysis and 85 components are identified up to n-nonane and hundreds of ill-defined components in decane plus fraction.  In order to develop a thermodynamic model for the distribution of chemicals in oil-water systems experimental data are required but such data with natural gas-condensate/oil systems are very rare in the literature. In this project experimental work has been carried at Statoil R &amp; D and an experimental method has been established and tested for such measurements. The mutual solubility of two North Sea condensates, MEG and water has been measured in the temperature range of 275-326 K at atmospheric pressure. The detailed composition of condensates is measured by GC analysis and 85 components are identified up to n-nonane and hundreds of ill-defined components in decane plus fraction.  When methanol and MEG are used as gas hydrate inhibitors, the most significant disadvantage, especially for methanol, is their loss in hydrocarbon phase(s). The successful estimation of inhibitor loss would enable the inhibitors injection optimization as a function of the system parameters such as temperature and water cut. In this project the distribution of water and inhibitors (methanol, MEG) in various phases is modeled using the CPA EoS. The hydrocarbon phase consists of mixture-1 (methane, ethane, n-butane) or mixture-2 (methane, ethane, propane, n-butane, n-heptane, toluene and n-decane). CPA can satisfactorily predict water content in the gas phase of the multicomponent systems containing mixture-1 over a range of temperature and pressure. Similarly the methanol content in gas phase of mixture-1 + water + methanol systems is predicted satisfactorily with accuracy in the range of experimental uncertainty. For VLLE of mixture-2 + water, mixture-2 + MEG + water and mixture-2 + methanol + water systems, the organic phase compositions are satisfactorily predicted whereas modeling results are relatively less satisfactory for vapor phase compositions partially due to uncertainties in the experimental data.  In addition to the multicomponent systems described above, the VLE of the binary system of methane-methanol is also investigated using CPA with satisfactory calculations of methane content of liquid phase using a single temperature independent kij over a range of temperature and pressure. The methanol content in the gas phase is satisfactorily correlated at higher temperatures and lower pressures using the same kij but deviations from experimental data are observed at lower temperatures and higher pressures. In order to extend CPA to reservoir fluids it is of interest to investigate the LLE of binary systems of hydrocarbons and water. In this work CPA is also applied to alkane + water and alkylbenzene + water systems to obtain binary interaction parameters and cross-association volumes respectively.  Finally, CPA has been extended to reservoir-fluid + MEG and reservoir-fluid + MEG + water systems. The reservoir fluid consists of three condensates and two oils from the gas fields in the North Sea. The mutual solubility of condensates and MEG is satisfactorily correlated using a single, average and temperature independent kij for all MEG-HC pairs. Similarly the mutual solubility of condensate/oil, MEG and water is predicted satisfactorily using the same average kij for MEG-HC pairs and water-HC kij from a generalized correlation as a function of carbon number. The experimental trends in mutual solubility as a function of temperature and MEG content in polar phase are predicted satisfactorily which are correct in order of magnitude according to the industrial requirements.</p

Online Research Database In Technology

Distribution of Complex Chemicals in Oil-Water Systems

http://orbit.dtu.dk/ws/files/7941536/PhD%20Thesis%20M%20%20Riaz%20September%202011.pdf

Distribution of Complex Chemicals in Oil-Water Systems

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Online Research Database In Technology