The electrokinetic properties and colloidal stability behavior of styrene/N-isopropylacrylamide and styrene/ N-isopropylacrylamide-co-aminoethyl methacrylate core-shell latexes were investigated. The electrophoretic mobility was first measured as a function of pH, temperature, and ionic strength. On the basis of the results obtained for the electrokinetic measurement, a charge distribution model (volume charge distribution) was proposed to help the suggested interpretation. By use of Eversole and Bordman's equation, the shear plane positions were estimated as a function of ionic strength and good correlation was found between the calculated values and the values obtained from the quasi-elastic light scattering measurement. The colloidal stability of those core-shell latexes was examined above and below the low critical solution temperature (LCST) (∼32 °C). Below the LCST, stabilization was mainly attributed to the combination of both electrostatic and steric stability. Whereas, above the LCST, only the electrostatic stability was the driving parameter. In addition, an apparent Hamaker constant of the core-shell latex was experimentally determined above the LCST.
Résumé -L'approche colloïdale : une voie prometteuse pour la modélisation des dépôts d'asphaltènes -Il est généralement admis que les asphaltènes existent dans les bruts sous forme dissoute et particulaire et que les bruts asphalténiques se comportent en solution comme des systèmes colloïdaux. L'objectif de ce travail était de vérifier qu'en présence d'écoulement et au sein d'une matrice poreuse, les asphaltènes conservent ce comportement colloïdal. Pour cela, nous avons étudié expérimentalement la cinétique du dépôt en milieux poreux en fonction des paramètres pertinents tels que la vitesse, l'état d'agrégation des asphaltènes, le contenu en résines et l'origine de l'huile. L'étude a été menée à la fois sous des conditions bien contrôlées avec des systèmes modèles et sous des conditions plus représentatives de l'application avec des huiles réelles et des roches d'affleurement. Les résultats obtenus nous ont permis d'établir que le dépôt des asphaltènes obéit effectivement aux mêmes lois cinétiques que le dépôt des colloïdes en milieux poreux. Ils nous ont permis de proposer des lois cinétiques de type lois d'échelle de la forme η ∝ Aγ -s , η étant l'efficacité du dépôt et γ le cisaillement. Les exposants, s, sont des exposants universels caractéristiques des régimes de dépôt alors que les pré-facteurs A englobent l'ensemble des autres caractéristiques spécifiques au système considéré (asphaltènes et milieux poreux). Ces lois cinétiques montrent que l'épaisseur du dépôt, qui se fait par multicouche, croît fortement lorsque le cisaillement diminue. Par conséquent, si les conditions sont favorables, la formation rapide d'un dépôt épais est attendue lors de la récupération des bruts lourds dans des formations très perméables et à des faibles vitesses d'écoulement. Un tel dépôt peut donc avoir un impact significatif sur l'efficacité de la récupération des bruts lourds. L'estimation de cet impact devrait donc faire partie intégrante de l'évaluation et de l'optimisation de tout procédé de récupération. À cette fin, l'approche dite « Colloïdale » constitue une voie nouvelle et prometteuse pour la modélisation du dépôt et de l'endommagement associé. Abstract
In a previous paper [1], the synthesis of various polystyrenepoly[NIPAM] core-shell latexes bearing cationic amidino and/or amino charges has been described. Several colloidal properties of these cationic latexes have been characterized such as: particle size, surface charge density, electrophoretic mobility and finally colloidal stability. Due to the poly[NIPAM]-rich layer in the shell, it was found that temperature played a significant role on all these properties, a LCST around 33°C being exhibited. In addition, ionic strength was also found to affect the colloidal behavior of these latexes, the largest effect being observed with latexes having both amidino and amino surface charges. The critical coagulation concentrations (CCC) of the various latexes above and below the LCST were determined, highlighting the contribution of electrostatic and steric repulsive forces to the stability of these particles.
Les propriŽtŽs d'Žcoulement de plusieurs bruts asphaltŽniques ont ŽtŽ ŽtudiŽes ˆ la tempŽrature du rŽservoir d'origine dans des roches de morphologie et minŽralogie diffŽrentes.Les expŽriences rŽalisŽes mettent en Žvidence une rŽduction progressive de la permŽabilitŽ ˆ l'huile au cours de l'injection, plus ou moins rapide selon les cas. L'existence de dŽp™ts organiques a ŽtŽ vŽrifiŽe par des mesures de pyrolyse Ç Rock-Eval È effectuŽes sur des sections d'Žchan-tillons prŽlevŽes en fin d'Žcoulement ˆ diffŽrentes distances de la face d'entrŽe. Cette technique permet de quantifier le profil des dŽp™ts.L'interprŽtation des expŽriences de colmatage et leur simulation sont traitŽes en assimilant les asphalt•nes dans l'huile ˆ des particules collo•dales en suspension, susceptibles de se dŽposer ˆ la surface des pores et ainsi de rŽduire la permŽabilitŽ du milieu poreux. Les premi•res simulations ont ŽtŽ rŽalisŽes en utilisant le mod•le IFP d'endommagement particulaire Ç PARIS È, qui a ŽtŽ rŽcemment gŽnŽralisŽ au cas de dŽp™t en multicouches. On observe un accord qualitatif satisfaisant avec les rŽsultats expŽrimentaux. PERMEABILITY DAMAGE DUE TO ASPHALTENE DEPOSITION: EXPERIMENTAL AND MODELING ASPECTSThe flow properties of several asphaltenic crudes were studied at reservoir temperature in rocks of different morphology and mineralogy.The experiments performed showed a progressive reduction in permeability to oil during injection, varying in rate according to the system considered.The existence of organic deposits was verified by ÒRock-EvalÓ pyrolysis measurements made on sections of samples taken at the end of flow at different distances from the entry face. This technique enables the profile of the deposits to be quantified.The interpretation of the permeability damage experiments and their simulation are treated by comparing the asphaltenes in oil to colloidal particles in suspension, capable of being deposited at the surface of the pores and thus reducing the permeability of the porous medium. The first simulations were carried out using the ÒPARISÓ IFP particle damage model, which has recently been Se ha procedido al estudio de las propiedades de circulaci-n de varios crudos asfaltŽnicos a la temperatura del yacimiento de origen en rocas de morfolog'a y mineralog'a de distinta 'ndole.Las experimentaciones llevadas a cabo hacen resaltar una reducci-n progresiva de la permeabilidad al petr-leo durante el transcurso de la inyecci-n, m ‡s o menos r ‡pida segoen los casos.La existencia de sedimentos org ‡nicos se ha verificado mediante mediciones de pir-lisis "Rock-Eval" efectuadas mediante secciones de muestras extra'das al final de la circulaci-n fluida y a distintas distancias de la cara de entrada. Esta tŽcnica permite cuantificar el perfil de las sedimentaciones La interpretaci-n de las experimentaciones de entarquinamiento (obstrucciones) y su simulaci-n se tratan asimilando los asfaltenos en el petr-leo a part'culas coloidales en suspensi-n, susceptibles de depositarse en la superficie de los poros y, por ende, r...
This paper was prepared for prescl]totion It the SPE Irrterno!inn~l Symposium on Formation Darnogc Control held in kfc~yctte, I.,)uisiami, 18-19 February 1998. This paper was selected for prcsel]tnli{~r]by an SPE Program Committee following review of inform~tion con[aincd in on :Lbstmc[ submitted by the author(s) Contents oof the paper, as presented, ha~te M)( heed reviewed by the Snciety of Petroleum Engineers and are subject to cor;e$tion by the author(s) The mil[erial, as presented, does no[ necessarily reflect any poslt!ur] of the S,>cicty of Petroleum Engineers, IIS officers, or members. PaWrs presented at SPE mettings arc subje~t tc~publication review by Editorial Committee of he Society of Petroleum Engitleers Electronic reproduction, distribution. or sfo[age of any pwt of this paper for r~>mmercial purposes witbu~tt the written crmsen[ of the Society of Petroleum Engineers is prnbibited Permissimr [o reprnduce in print is restricted to mr abstract of t]ot more tbtn 300 words; illustrations i~my not be copied, The abstract must conttin conspicuous acknowledgement of where mrd by whom the paper was presented. Write Librarim], SPE. P,O. Box 833836. Richwdson, TX 75083-3836, USA, fax 01-972-952-9435. AbstractThe different mechanisms leading to permeability damages due to particle deposition are analyzed under various situations relevant for oil production. The analysis is based on the relative importance (of the forces involved in the various deposition processes.In this way, different deposition regimes, characterized by the values of a few non-dimensional numbers, are defined. Among the major parameters, some are conventional and usually considered, such as particle and pore sizes, flow rate, particle concentration and suspending fluid viscosity.However, other parameters, which are often ignored, such as particle and pore shape and roughness, particle-particle and particle-pore wall interaction energies as well as pore surface physiochemical heterogeneity play an even more important role. In all cases, the regime determines deposition kinetics and the location~'here particles are deposited inside porous structure. As a consequence, determining both the deposition regime and the mechanism of permeability damage involved are prerequisites before any attempt to model and to predict permeability reduction. Due to the complexity of practical cases, experiments must be carried out to define the regime and the values of the major References and illustrations at end of paper parameters used as input in a suitable formation damage model.Comparisons between model predictions and experimental results obtained under well-controlled conditions show the cases where presently the permeability damage modeling is reliable.
Summary Injectivity decline during produced-water reinjection (PWRI) originates not only from filter-cake buildup but also from in-depth deposition of oil droplets or solid particles. Physical modeling of particle-deposition mechanisms in porous media is thus of key interest for optimizing PWRI operations. The present work brings new insights on oil-droplet and solid-particle-deposition mechanisms in porous media. The experimental conditions were selected such that the ratio between pores and particle sizes is sufficiently large to ensure in-depth propagation. The parameters are the nature of the particles injected and a Peclet number calculated on the size of the collector grains (Pg) that encompasses in a nondimensional form the impact of both the flow rate and the particle size. The results are analyzed within the framework of the "colloidal approach." For oil droplets and solid particles, the collection efficiency (?) shows a transition from a behavior in which ? varies as a power law of Pg, with exponent values -? [(diffusion-limited deposition (DLD)] to -1 [reaction-limited deposition (RLD)] that are typical of the convection/diffusion regime, to a behavior characterized by an increase of ? vs. Pg, typical of the hydrodynamic deposition regime. In the case of oil droplets (slightly charged), the transition occurs at a critical Pg value, PgC ˜ PgCgeom/10, corresponding to a diffusion-layer thickness around the collector grain of the same order of magnitude as the droplet diameter. In the case of electrosterically stabilized solid particles, the transition takes place at PgC << PgCgeom for small particles and at PgC > PgCgeom for larger particles. Introduction As the environmental regulations for water discharge are becoming increasingly stringent, PWRI is now recognized as an important issue with respect to environmental protection and profitability. In many mature zones, PWRI is becoming an economically attractive option. It enables reduction in processing costs of the produced water before disposal and allows handling the ever-increasing volumes of produced water without increasing environmental risks associated with water discharges. PWRI also can be used for waterflooding or pressure maintenance in the initial stage of production. Therefore, most of the produced water has to be reinjected either in a suitable formation for disposal or in the producing formation for improved-oil-recovery purposes. However, great uncertainties still remain about the consequences of PWRI and the actual injectivity behavior. If injectivity decline is severe, sustainable injection rate for extended periods will become impossible, jeopardizing the entire reinjection operation. From field observations, it was acknowledged that:With produced water, plugging is important and injectivity is lower than expected. The solids and the oil do not behave separately.With matrix PWRI, a continuous loss of injectivity is obtained, even in high-permeability formation (soft rock) (Detienne and Po 2005).Successful PWRI is likely to require fracturing (Detienne and Po 2005; Raaen 2005; van den Hoek and Bjoerndal 2005; Sweeney 2005). Thus, the injectivity performance is viewed increasingly as being dictated by a dynamic coupling between fracture growth and plugging of fracture faces. This general scheme raises additional challenges related to the issues of fracture containment, sweep efficiency, and conformance, especially in soft-rock formations. Simulation of PWRI under fracturing conditions is therefore necessary to optimize the injectivity behavior and to establish a PWRI strategy (Detienne et al. 2005; Ochi et al. 1999; van den Hoek et al. 1996). However, until now, development of models with reliable prediction ability suffers from the lack of a clear insight into the actual physics of the damage process. Understanding the damaging mechanisms when injecting water containing solid particles and oil droplets and evaluating the impact of such damage on injector performance are, thus, important research needs. PWRI-induced damage results from in-depth particle penetration into the surrounding formation and from particle accumulation on formation/fracture face to form a heterogeneous and highly compressible filter cake. The filter-cake permeability is among the important parameters that have a great impact on injectivity. Hence, a representative estimation of this parameter is required to forecast the injection behavior (van den Hoek et al. 1996). More generally, the impact of particles, including mixtures of oil and solids, on injectivity has received increasing attention recently (van den Hoek et al. 1996; Al-Abduwani et al. 2003; Al-Riyamy and Sharma 2002; Bedrikovetsky et al. 2001; da Silva et al. 2004; Hofsaess and Kleinitz 2003; Sæby et al. 2005). Regarding oil-in-water-emulsion flow and deposition in porous media, despite significant experimental and theoretical work (Soo and Radke 1984, 1986; Soo et al. 1986), impact on injectivity is still not understood clearly, especially under severe injection conditions (high flow rate into low-permeability formation). The objective of this study was to bring new insights into the impact of flow rate on in-depth deposition mechanisms of the colloidal particles present in produced water. The present work was focused on two kinds of particles:uncharged oil droplets in dilute and stable oil-in-water emulsions andelectrosterically stabilized latex microspheres. For both kinds of particles, a broad range of velocities was investigated. In the next section, some useful results regarding the theoretical background of the colloidal approach are presented. In the section after that, materials and experimental procedures are described. Experimental results are presented and discussed in the last section.
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