Étude expérimentale et modélisation de la cristallisation d'hydrates de méthane en écoulement à partir d'une émulsion à pourcentages variables d'eau et d’anti-agglomérant

Crystallization of hydrates during oil production is a major source of hazards, mainly related to flow lines plugging after hydrate agglomeration. During the petroleum extraction, oil and water circulate in the flow line, forming an unstable emulsion. The water phase in combination with light hydrocarbon components can form hydrates. The crystallization of hydrates has been extensively studied, mainly at low water content systems. However, as the oil field matures, the water fraction increases and can become the dominant phase, a system less known in what concerns hydrate formation. Actually, several techniques can be combined to avoid or remediate hydrate formation. Recently, a new class of additives called Low Dosage Hydrate Inhibitor (LDHI) started to be studied, they are classified as Kinetic Hydrate Inhibitors (KHI-LDHI) and Anti-Agglomerants (AA-LDHI).This work is a parametric study about hydrate formation from emulsion systems ranging from low to high water content, where different flow rates and the anti-agglomerant presence were investigated. The experiments were performed at the Archimède flow loop, which is able to reproduce deep sea conditions. The goal of this study is enhancing the knowledge in hydrate formation and comprehending how the dispersant additive acts to avoid agglomeration. For this matter, it was developed a crystallization topological model for the systems without and with additive. A technique to determine the system continuous phase and a mechanism of the anti-agglomerant action from the chord length measurements were also proposed.La cristallisation des hydrates pendant la production de pétrole est une source de risques, surtout liés au bouchage des lignes de production dû à l’agglomération des hydrates. Pendant l'extraction de pétrole, l'huile et l'eau circulent dans le pipeline et forment une émulsion instable. La phase eau se combine avec les composants d'hydrocarbures légers et peut former des hydrates. La cristallisation des hydrates a été intensivement étudiée, principalement à faible fraction d’eau. Cependant, lorsque le champ de pétrole devient mature, la fraction d’eau augmente et peut devenir la phase dominante, un système peu étudié concernant à la formation d'hydrates. Plusieurs techniques peuvent être combinées pour éviter ou remédier la formation d'hydrates. Récemment, une nouvelle classe d'additifs a commencé à être étudiée : Inhibiteurs d'Hydrates à Bas Dosage (LDHI), divisés en Inhibiteurs Cinétiques (KHI-LDHI) et anti-agglomérants (AA-LDHI).Ce travail est une étude paramétrique de la formation d'hydrates à partir de l'émulsion, en variant la fraction d’eau, le débit, en absence et en présence d’AA-LDHI. Les expériences ont été réalisées sur la boucle d'écoulement Archimède, qui est en mesure de reproduire les conditions de la mer profonde. L'objectif de cette étude est d'améliorer la compréhension de la formation d'hydrate et de comprendre comment l'additif dispersant évite l'agglomération. Pour ce faire, un modèle comportemental de la cristallisation pour les systèmes sans et avec additif a été développé. Il a également été proposé une technique pour déterminer la phase continue du système et un mécanisme d'action pour l'anti-agglomérant a été suggéré

Kinetic modelling of methane hydrate formation and agglomeration with and without anti-agglomerants from emulsion in pipelines

GasHyDyn : Logiciel de simulation de la composition et de la stabilité des hydrates de gazNational audienceOffshore systems mainly containing crude oil, natural gas and water operate at low temperature and high pressure which favour conditions for gas hydrate formation and agglomeration. Gas hydrate is a serious issue in flow assurance; it may cause many troubles, especially, plugging in oil and gas pipeline. This work is to intend to develop a kinetic model to predict gas hydrate formation, agglomeration and plugging in flowlines based on the experimental data obtained from Archimede Flowloop from the work of Mendes-Melchuna (2015). In this model, the mean droplet size of emulsion will be calculated from flow parameters to evaluate the surface area of droplets which are very critical parameters for kinetic model of gas hydrate formation in emulsion. It is important to note that anti-agglomerants (AAs) may modify the water-oil interfacial tension leading to smaller mean droplet size. A preliminary study of the emulsion formation and behaviour will contribute to a better understanding of the hydrates formation and agglomeration

Formation d’hydrates sans et avec additif antiagglomérant en variant le débit et la fraction d’eau

National audienceLa cristallisation des hydrates de méthane pendant l’extraction de pétrole est une source majeure de risques, notamment concernant le bouchage des pipelines. La circulation d’huile et d’eau dans une pipe induit la formation d’une émulsion. A haute pression et basse température, l'eau peut être combinée avec des composants gazeux légers, résultant dans la formation d’hydrates, qui sont des structures solides dont l’agglomération est capable de boucher le pipeline.La cristallisation des hydrates de méthane a été étudiée de manière intensive au cours des 30 dernières années, surtout à basse teneur en eau. Cependant, les puits en fin de vie de production ont un pourcentage d’eau plus important que parfois l’eau devient la phase dominante, l’huile devenant la phase dispersée. Dans ce cas de figure le processus de cristallisation des hydrates de gaz doit être étudié et comparé aux systèmes où l'eau est la phase dispersée.Ce travail est une étude paramétrique réalisé dans une boucle de circulation capable de reproduire les conditions de la formation d’hydrate dans les pipelines sous marins, en faisant varier la teneur en eau (30% jusqu’à 100%) et le débit (200 L.h-1) et 400L.h-1), afin d'observer et comprendre la cristallisation d’hydrate à partir d’un mélange de Kerdane® (C11-C14) et d'eau, en présence de méthane. Ensuite, la même étude paramétrique a été réalisée en présence d'un additif dispersant, afin de comprendre le comportement de l’additif. Les expériences sont suivies par mesures de perte de charge, masse volumique, taille et forme des gouttelettes et hydrates. A partir de l’étude réalisée, le mécanisme de formation de l’émulsion et des hydrates sans et avec additif dispersant a été développé

Relative Pressure Drop Model for Hydrate Formation and Transportability in Flowlines in High Water Cut Systems

International audienceToday, oil and gas fields gradually become mature with a high amount of water being produced (water cut (WC)), favoring conditions for gas hydrate formation up to the blockage of pipelines. The pressure drop is an important parameter which is closely related to the multiphase flow characteristics, risk of plugging and security of flowlines. This study developed a model based on flowloop experiments to predict the relative pressure drop in pipelines once hydrate is formed in high water cutsystems in the absence and presence of AA-LDHI and/or salt. In this model, the relative pressure drop during flow is a function of hydrate volume and hydrate agglomerate structure, represented by the volume fraction factor (K&#957). This parameter is adjusted for each experiment between 1.00 and 2.74. The structure of the hydrate agglomerates can be predicted from the measured relative pressure drop as well as their impact on the flow, especially in case of a homogeneous suspension of hydrates in the flow

Bridging the gap between benchtop testing and field conditions in flow assurance studies

E-Book - ISBN: 978-1-61399-571-6International audienceObjectives/Scope: The goal for any flow assurance study is to capture the thermo-hydraulic conditions in flowlines without having large scale flow facilities that closely represent the field. As such, benchtop testing must as best as possible reproduce the shear and dispersion of the phases encountered in flowlines. With the increasing need of laboratory testing for solid precipitation and production chemicals, coupled with reduced CAPEX and OPEX, it is critically important to have a robust benchtop testing system that give reliable and transferable data that can be used for field applications.Methods, Procedures, Process: While many benchtop tools are widespread (e.g., autoclave cells, rocking cells, cold fingers) and are used extensively by industry, there is still a significant gap in bridging the results from these lab scale devices to field conditions. One of the major concerns with the current testing rigs is the inability to reproduce the shear AND phases dispersion that are present in pipe flow and are a consequence of the multiphase flow conditions. To bridge the gap To bridge the gap between benchtop testing and filed conditions, we demonstrate how an innovative testing rig, called rock-flow cell, can be used to capture flow assurance issues (e.g., hydrate, wax, asphaltene, scale, corrosion, sand transport) under pseudo-flow conditions.Results, Observations, Conclusions: This system is superior to existing testing systems due to its ability to reproduce flow conditions that are typically found in actual production flowlines, such as, stratified flow, stratified wavy flow, and slug flow. In addition, the system is compact and inexpensive to build and operate, unlike flow loop systems, which are currently the only reliable testing rig with proper flow conditions.Novel/Additive Information: The rock-flow cell can be easily used for testing of chemicals (e.g., anti-agglomerants and kinetic inhibitors) for hydrate management, for assessing wax deposition of crude oils, for testing of scale precipitation, and for testing of sand transport; each of these flow assurance issues can be tested separated or combined as desired. Moreover, the rock-flow cell is also a suitable setup for testing of steady-state and transient (shut-in/restart) conditions typically encountered in flow assurance with proper account of liquid loading, water cut, and GOR

Rock-Flow Cell: An Innovative Benchtop Testing Tool for Flow Assurance Studies

International audienceFlow assurance is a critical component in the design and operation of robust oil/gas production systems. Undesired precipitation of solids (gas hydrates, wax, asphaltenes, scale) reduces the production rate and often leads to costly and hazardous disruptions. Many experimental and modeling efforts have been made to build knowledge of managing such risks. However, a major difficulty is to transfer the laboratory data to the field conditions. We introduce a new experimental system, the rock-flow cell, which is compact and requires fewer resources to build and operate. This system can readily achieve different flow regimes by controlling the liquid loading, water cut, and rocking angle/speed. A sight glass visualizes when, where, how, and how much solid forms and precipitates out. Gas hydrate formation tests with anti-agglomerants are presented to demonstrate the capabilities. The rock-flow cell is an innovative testing tool for flow assurance studies by properly capturing thermohydraulic conditions in actual flowlines

A Multiscale Approach for Gas Hydrates Considering Structure, Agglomeration, and Transportability under Multiphase Flow Conditions: I. Phenomenological Model

International audienceA new topological model on how gas hydrates form, grow, and agglomerate for oil and water continuous flow, with and without surfactant additives, is presented. A multiscale approach is used to explain how the porous structure of gas hydrates and the affinity between the phases affect the particle morphology and their agglomeration. We propose that gas consumption due to hydrate growth happens mostly in the water trapped inside the capillaries of the hydrate structure near the outer surface of the particles. This approach is herein referred to as the “sponge approach” and is treated as a surface problem, instead of the volume problem often treated in literature (the “shell approach”). Affinity between phases (which in a macro point of view is interpreted as a wetted angle that gives rise to capillarity forces and that can be changed by the use of surfactant additives) describes the preferential entrapment of oil or water inside the hydrate sponge structure. Yet by splitting agglomeration into smaller processes and depending on the morphology of the particles and on the evolution of the porous structure of the hydrates, (i) capillarity bridges may form, causing particles to be sticky, and (ii) water may be available at the outer surface of the particles and may promote consolidation of particle–particle (agglomeration) or particle-wall (deposition). The settling of slurries is treated as a separated solid–liquid flow instability problem once mixture deceleration (due to phase consumption during crystallization) and particle size (due to growth and agglomeration) are known. We also propose a new explanation on how surfactants act as anti-agglomerants in oil continuous flow, differently from the common DLVO theory used in literature, which can only explain anti-agglomeration of particles much smaller than the ones formed over droplets of a very fine dispersion flow