Hydrate mitigation in sour and acid gases

While global demand for energy is increasing, it is mostly covered by fossil energies, like oil and natural gas. Principally composed of hydrocarbons (methane, ethane, propane...), reservoir fluids contain also impurities such as carbon dioxide, hydrogen sulphide and nitrogen. To meet the request of energy demand, oil and gas companies are interested in new gas fields, like reservoirs containing high concentrations of acid gases. Natural gas transport is done under high pressure and these fluids are also saturated with water. These conditions are favourable to hydrates formation, leading to pipelines blockage. To avoid these operational problems, thermodynamic inhibitors, like methanol or ethanol, are injected in lines. It is necessary to predict with more accuracy hydrates boundaries in different systems to avoid their formation in pipelines for example, as well as vapour liquid equilibria (VLE) in both sub-critical regions. Phase equilibria predictions are usually based on cubic equations of state and applied to mixtures, mixing rules involving the binary interaction parameter are required. A predictive model based on the group contribution method, called PPR78, combined with the Cubic – Plus – Association (CPA) equation of state has been developed in order to predict phase equilibria of mixtures containing associating compounds, such as water and alcohols. To complete database for multicomponent systems with acid gases, VLE and hydrate dissociation point measurements have been conducted. The developed model, called GC-PR-CPA, has been validated for binary systems and applied for different multicomponent mixtures. Its ability to predict hydrate stability zone and mixing enthalpies has also been tested. It has been found that the model is generally in good agreement with experimental data

Prediction of methanol content in natural gas with the GC-PR-CPA model

International audienceProduced reservoir fluids are principally composed of hydrocarbons but contain also impurities such as carbon dioxide, hydrogen sulphide and nitrogen. These fluids are saturated with the formation water at reservoir conditions. During production, transportation and processing ice and/or gas hydrates formation may occur. Gas hydrate and ice formation are a serious flow assurance and inherently security issues in natural gas production, processing and transport. Therefore, inhibitors are usually injected as a hydrate inhibitor and antifreeze. For example, methanol is often used for hydrate inhibition or in some cases during start up, shut down or pipeline plug removal. Therefore impurities, water and methanol usually end up in natural gas conditioning and fractionation units. These units produce end user pipeline gas subject to local specifications and natural gas liquids like ethane, LPG or heaviers. This is why the accurate knowledge of methanol content at different operating conditions is important. In this study, a group contribution model, the GC-PR-CPA EoS (Hajiw et al., 2015) (Group Contribution – Peng-Robinson – Cubic-Plus-Association), is successfully applied for hydrocarbons systems containing methanol. Predictions of phase envelopes of binary systems as well as partition coefficients of methanol in hydrocarbons mixtures are in good agreement with experimental data

Thermophysical Properties, Hydrate and Phase Behaviour Modelling in Acid Gas-Rich Systems

International audienceIn this communication we present experimental techniques, equipment and thermodynamic modelling for investigating systems with high acid gas concentrations and discuss experimental results on the phase behaviour and thermo-physical properties of acid gas-rich systems. The effect of high CO 2 concentration on density and viscosity were experimentally and theoretically investigated over a wide range of temperature and pressures. A corresponding-state model was developed to predict the viscosity of the stream and a volume corrected equation of state approach was used to calculate densities. The phase envelope and the hydrate stability (in water saturated and under-saturated conditions to assess dehydration requirements) of some acid gas-rich fluids were also experimentally determined to test a generalized model, which was developed to predict the phase behaviour, hydrate dissociation pressures and the dehydration requirements of acid gas rich gases

Étude des conditions de dissociation des hydrates de gaz en présence de gaz acides

The twentieth century has seen an important increase of the fossil energy demand, representing today 80% of world energy consumption. To meet the request, oil and gas companies are interested in new gas fields. 40% of these reserves are acid and sour gases, i.e. the percentage of carbon dioxide and hydrogen sulphide is significant, sometimes over 20% of CO2 or H2S. Natural gas production with high content of acid gases can be a challenge, due to their corrosiveness potential in pipelines in the presence of water and H2S toxicity. On another hand, as a result of world's dependence on fossil energies, the release of carbon into atmosphere is increasing and leads to climate changes. Carbon Capture and Storage (CCS) is one of the most promising ways to reduce CO2 emissions in the atmosphere. Whether in natural gas or carbon dioxide transport, water may be present. During production, transportation and processing, changes in temperature and pressure can lead to water condensation (cause of corrosion, and consequently a possible pipeline rupture), ice and/or gas hydrates formation. Hydrates are a serious flow assurance problem and may block pipelines. To avoid hydrates formation, chemical inhibitors are used. Therefore accurate knowledge of mixtures phase equilibria are important for safe operation of pipelines and production/processing facilities.La demande en énergies fossiles a connu une forte croissance au cours du vingtième siècle et représente aujourd'hui 80% de la consommation énergétique mondiale. Pour répondre à la demande, les industries pétrolières et gazières s'orientent vers de nouvelles sources. 40% des réserves de gaz contiennent un pourcentage important (jusqu'à 20%) de gaz acides (dioxyde de carbone et sulfure d'hydrogène). La production de ces gaz à forte teneur en gaz acides représente un défi pour les industries, étant donné la toxicité du sulfure d'hydrogène et la forte probabilité de corrosion des pipelines en présence d'eau (naturellement produite avec le gaz naturel). D'autre part, l'utilisation des énergies fossiles conduit au changement climatique avec des émissions importantes de dioxyde de carbone dans l'atmosphère. Le captage et le stockage du CO2 semble être un procédé prometteur. De l'eau est souvent présente lors du transport du gaz naturel et du CO2 capturé. Lors des étapes de production et de transport, les conditions de température et de pression sont sujettes au changement. La condensation de l'eau (à l'origine de la corrosion et donc d'une rupture possible des pipelines) et à la formation de glace et/ou d'hydrates en sont les conséquences principales. Or la formation d'hydrates est un sérieux problème avec un risque de blocage des pipelines. Pour éviter la formation des hydrates, des inhibiteurs chimiques sont utilisés. Il est donc indispensable de bien connaitre les équilibres entre phases pour les différents mélanges considérés pour un fonctionnement et une production en toute sécurité

Hydrocarbons - water phase equilibria using the cpa equation of state with a group contribution method

International audienceIt is proposed in this paper to extend the original group contribution method PPR78 to systems containing water, by combining it to the Cubic–Plus–Association (CPA) equation of state (EoS). Applying simple geometric combination rules, the binary interaction parameter kij(T) can be calculated frominteraction parameters between hydrocarbon groups and water. This model, called the GC–PR–CPA is applied to predict hydrocarbons – watermutual solubilities over a wide temperature and pressure range, depending on available literature data. Group interaction parameters, here CH4,C2H6, CH3, CH2, CH, C, CHaro, CH2,cyclic, CHcyclic/Ccyclic, C2H4, CH2,alkene/CHalkene with H2O have been defined with solubility data. Predictions ofthe developed model have been validated against independent solubility data as well as water content in hydrocarbon rich phase. Predictions of thenew model are in good agreement for light and medium hydrocarbons; however, some deviations are observed for heavier hydrocarbons

IMPACT OF IMPURITIES ON CO 2 STORAGE IN SALINE AQUIFERS: MODELLING OF GASES SOLUBILITY IN WATER

International audienceFlue gas captured contains different impurities (N 2 , O 2 , SO 2, NO etc) and their concentrations depend on the capture process and the industrial sector. Moreover, the presence of impurities may change the thermophysical properties of the stream and therefore impact the conditions of CO 2 storage. The aim of the paper is to investigate the solubility in water of carbon dioxide and some chosen impurities. In this work VLE calculations using a geochemical model (Corvisier, 2013) and two group contribution (GC-PR-CPA (Group Contribution-Peng Robinson-Cubic Plus Association) (Hajiw, 2014 and Hajiw et al., 2015) and E-PPR78 (Qian et al., 2013) equations of state) models are compared

Apparent Henry’s law constants of furan in different n-alkanes and alcohols at temperatures from 293 to 323 K

International audienceGreen chemical compounds with high added value can be obtained after pyrolysis of lignocellulosic biomass. This biomass is playing a major role in the chemical sectors as a substitution material. This study is focused on one of these compounds, furan. High selectivity of a solvent is the most important criteria for an optimised extraction. In other words, for the selected solvent, activity coefficients of the compounds to be separated must be different. Therefore, experimental activity coefficients of compounds of interest in different solvents are necessary. In this paper, apparent Henry’s law constants of furan in different n-alkane and alcohol solvents have been measured at temperatures from 293 to 323 K using the inert gas stripping method to analyse their potential for furan extraction. Besides, if the value of limiting activity coefficient is close to one, it is an indicator of its suitability for the compound extraction