PRODUCTION D'HUILES LOURDES PAR DÉPRESSURISATION : ÉTUDE DES INTERFACES HUILE-AIR ET MODÉLISATION DU PROCÉDÉ

Rapporteur : H. Bertin Examinateur : P. Cordelier President : J.P. Hulin Examinateur (responsable IFP) : R. Lenormand Rapporteur : L. TadristThis thesis is an experimental and theoretical contribution to the modeling of the crude oil production in petroleum reservoirs under depressurization. Oil is produced under the bubble point in order to take advantage of gas expansion to displace the oil phase, a process called « solution gas drive ». So far, existing reservoir simulators are able to simulate such a mechanism only for light oils. For heavy oils, there is a problem due to the high viscosity and the physicochemical properties of the oils. Standard numerical simulators can account neither for out of equilibrium mechanisms, nor flow of a dispersed gas phase. A large number of studies have been published, especially at pore level, but a literature study shows the need for a model described by continuous equations (Darcy's approach). The experimental study of physicochemical properties (dynamic surface tension, surface elasticity) of the crude components show that asphaltenes can act as a surfactant which enhance foam production above a concentration threshold. A continuum model has been developed, based on the physical mechanisms and involving only measurable variables. Gas nucleation and mass transfer are modeled using a volumic transfer function, nucleation being described by preexisting bubbles. Gas can be present either as a continuous phase or as bubbles dispersed in the oil phase. The simulations of several experiments with various rocks and fluids had proven that the model can predict the amount of oil and gas produced during the experiments.La thèse est une contribution expérimentale et théorique à la modélisation d'écoulements de bruts pétroliers produits par dépressurisation du réservoir. Il s'agit de produire l'huile en dessous du point de bulle et de profiter de l'expansion de la phase gaz pour déplacer l'huile (procédé appelé "Solution Gas Drive"). Jusqu'à présent les simulateurs de réservoir permettaient la simulation d'un tel mécanisme pour les huiles légères. Un problème se pose avec les huiles lourdes dont la forte viscosité et la physico-chimie intensifient l'état hors d'équilibre dû au mécanisme de changement de phase. Les simulateurs numériques classiques ne prennent pas en compte ce type de mécanisme hors équilibre, ni l'écoulement du gaz sous forme dispersée. Bien qu'un grand nombre de travaux aient déjà été réalisés essentiellement à l'échelle des pores, l'étude bibliographique montre qu'il est nécessaire d'avoir un modèle décrit par des équations continues (approche de Darcy). L'étude expérimentale des propriétés physico-chimiques (tension dynamique, élasticité de surface) des principaux constituants des bruts montre que les asphaltènes ont un effet tensioactif favorisant la formation de mousse au dessus d'une concentration seuil. Enfin, l'étude théorique des différents processus physiques permet d'établir un modèle d'écoulement continu, ne faisant intervenir que des grandeurs macroscopiques mesurables. La nucléation et le transfert de masse sont modélisés par une fonction volumique de transfert, la nucléation étant basée sur le modèle de bulles préexistantes. Deux phases gaz peuvent coexister : l'une continue à l'échelle du milieu, l'autre dispersée dans l'huile sous forme de bulles. Les simulations de plusieurs expériences, réalisées avec des roches et des fluides différents, montrent que le modèle permet d'interpréter et de prédire les productions de gaz et d'huile

Production d'huiles lourdes par dépressurisation (étude des interfaces huile-air et modélisation du procédé)

La thèse est une contribution expérimentale et théorique à la modélisation d'écoulements de bruts pétroliers produits par dépressurisation du réservoir. Il s'agit de produire l'huile en dessous du point de bulle et de profiter de l'expansion de la phase gaz pour déplacer l'huile (procédé appelé "Solution Gas Drive"). Jusqu'à présent les simulateurs de réservoir permettaient la simulation d'un tel mécanisme pour les huiles légères. Un problème se pose avec les huiles lourdes dont la forte viscosité et la physico-chimie intensifient l'état hors d'équilibre dû au me canisme de changement de phase. Les simulateurs numériques classiques ne prennent pas en compte ce type de mécanisme hors équilibre, ni l'écoulement du gaz sous forme dispersée. Bien qu'un grand nombre de travaux aient déjà été réalisés essentiellement à l'échelle des pores, l'étude bibliographique montre qu'il est nécessaire d'avoir un modèle décrit par des équations continues (approche de Darcy). L'étude expérimentale des propriétés physico-chimiques (tension dynamique, élasticité de surface) des principaux constituants des bruts montre que les asphaltènes ont un effet tensioactif favorisant la formation de mousse au dessus d'une concentration seuil. Enfin, l'étude théorique des différents processus physiques permet d'établir un modèle d'écoulement continu, ne faisant intervenir que des grandeurs macroscopiques mesurables. La nucléation et le transfert de masse sont modélisés par une fonction volumique de transfert, la nucléation étant basée sur le modèle de bulles préexistantes. Deux phases gaz peuvent coexister : l'une continue à l'échelle du milieu, l'autre dispersée dans l'huile sous forme de bulles. Les simulations de plusieurs expériences, réalisées avec des roches et des fluides différents, montrent que le modèle permet d'interpréter et de prédire les productions de gaz et d'huile.This thesis is an experimental and theoretical contribution to the modeling of the crude oil production in petroleum reservoirs under depressurization. Oil is produced under the bubble point in order to take advantage of gas expansion to displace the oil phase, a process called " solution gas drive ". So far, existing reservoir simulators are able to simulate such a mechanism only for light oils. For heavy oils, there is a problem due to the high viscosity and the physicochemical properties of the oils. Standard numerical simulators can account neither for out of equilibrium mechanisms, nor flow of a dispersed gas phase. A large number of studies have been published, especially at pore level, but a literature study shows the need for a model described by continuous equations (Darcy's approach). The experimental study of physicochemical properties (dynamic surface tension, surface elasticity) of the crude components show that asphaltenes can act as a surfactant which enhance foam production above a concentration threshold. A continuum model has been developed, based on the physical mechanisms and involving only measurable variables. Gas nucleation and mass transfer are modeled using a volumic transfer function, nucleation being described by preexisting bubbles. Gas can be present either as a continuous phase or as bubbles dispersed in the oil phase. The simulations of several experiments with various rocks and fluids had proven that the model can predict the amount of oil and gas produced during the experiments.LIMOGES-ENSCI (870852305) / SudocORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

A root functional-structural model allows to assess effects of water deficit on water and solute transport parameters

International audienceAbstract Root water uptake is driven by a combination of hydrostatic and osmotic forces. Water transport was characterized in primary roots of maize seedlings grown hydroponically under standard and water deficit (WD) conditions, as induced by addition of 150 g.L -1 polyethylene glycol-8000 (water potential= -0.336MPa). Flow measurements were performed by the pressure chamber technique in intact roots or on progressively cut root system architectures (RSA). To account for the concomitant transport of water and solutes in roots under WD, we developed within realistic RSAs a Hydraulic Tree Model integrating both solute pumping and leak. This model explains the high spontaneous sap exudation of roots grown in standard conditions, the non-linearity of pressure-to flow relationships, and negative fluxes observed under WD conditions at low external hydrostatic pressure. The model also reveals the heterogeneity of driving forces and elementary radial flows throughout RSA, and how this heterogeneity depends on both plant treatment and water transport mode. The full set of flow measurement data obtained in individual roots grown under standard or WD conditions was used in an inverse modeling approach to determine their respective radial and axial hydraulic conductivities. This approach allows to resolve dramatic effects of WD on these two components

Phenotyping and modeling of root hydraulic architecture reveal critical determinants of axial water transport

International audienceWater uptake by roots is a key adaptation of plants to aerial life. Water uptake depends on root system architecture (RSA) and tissue hydraulic properties that, together, shape the root hydraulic architecture. This work investigates how the interplay between conductivities along radial (e.g. aquaporins) and axial (e.g. xylem vessels) pathways determines the water transport properties of highly branched RSAs as found in adult Arabidopsis (Arabidopsis thaliana) plants. A hydraulic model named HydroRoot was developed, based on multi-scale tree graph representations of RSAs. Root water flow was measured by the pressure chamber technique after successive cuts of a same root system from the tip toward the base. HydroRoot model inversion in corresponding RSAs allowed us to concomitantly determine radial and axial conductivities, providing evidence that the latter is often overestimated by classical evaluation based on the Hagen–Poiseuille law. Organizing principles of Arabidopsis primary and lateral root growth and branching were determined and used to apply the HydroRoot model to an extended set of simulated RSAs. Sensitivity analyses revealed that water transport can be co-limited by radial and axial conductances throughout the whole RSA. The number of roots that can be sectioned (intercepted) at a given distance from the base was defined as an accessible and informative indicator of RSA. The overall set of experimental and theoretical procedures was applied to plants mutated in ESKIMO1 and previously shown to have xylem collapse. This approach will be instrumental to dissect the root water transport phenotype of plants with intricate alterations in root growth or transport functions

Phenotyping and modeling of water transport in roots

International audienceWe developed a mathematical model to better understand how water enters into the roots segments and how those flows are integrated within a complete architecture. As a functional/structural Plant Model (FSPM), it combines the architecture and the hydraulic conductivities in plants. The originality of our approach is the tight relation between modeling and experimentation. In particular, we were able to unravel that, in Arabidopsis, the xylem vessels are a limiting factor. Genetic evidences also showed that all components of water transport interplay with each other

ROCK TYPING AND PETROPHYSICAL PROPERTY ESTIMATION VIA DIRECT ANALYSIS ON MICROTOMOGRAPHIC IMAGES

ABSTRACT Correlations for petrophysical parameters and saturation dependent transport properties are usually grouped by "rock type". This is a broad classification including quantitative measures such as porosity, permeability, pore and throat size distributions, pore connectivity and qualitative descriptions of rock fabric and texture. Rock typing is based on conventional core analysis data (porosimetry, permeametry, mercury injection capillary pressure (MICP)), special core analysis (SCAL), wireline logs (electrofacies), description of cuttings and depositional environment, and thin-section analysis. The broad nature of this classification has obvious limitations and fails to fully capture the complex dependence between pore space geometry and topology (rock micro-structure) and petrophysical properties. We propose an alternate classification for rocks based on high resolution X-ray computed microtomography which is complementary to the conventional approach and allows the establishment of a more direct relationship between rock micro-structure and petrophysical properties. Petrophysical properties are computed directly from 3D microtomographic images of clastic and carbonate cores drawn from a wide range of reservoirs. The computed petrophysical properties are used to test empirical correlations between permeability and other important petrophysical parameters (e.g., hydraulic radius, drainage capillary pressure, NMR response, grain size and sorting) for various rock types. We find that the most universally robust correlations are based on the critical pore radius determined from drainage capillary pressure data. The results clearly demonstrate the potential for digital imaging and computations on 3D images to develop improved correlations for petrophysical properties

Analysis of the impact of papermaking variables on the structure and transport properties of paper samples by X-ray microtomography

The effect of papermaking variables on the structure and transport properties of paper samples was analyzed Various newsprint samples were prepared on a pilot paper machine by varying the raw material furnish and process parameters, including headbox consistency, retention aids and calendering. Three-dimensional digital images of the sample structure were obtained by using the synchrotron X-ray computed tomography facility at ESRF, Grenoble, France. Structural parameters (porosity, specific surface area, pore-size distribution and tortuosity) and transport properties (permeability and diffusivity) were calculated directly on the digitized images. Results indicate that the calendering operation plays a dominant role in altering the structure and transport properties of the samples