Some Investigations on the role of microparticles on the low salinity process

Several papers dealing with laboratory experiments or field operations confirm that, in some circumstances, low salinity waterflooding improves oil recovery. However, the basic mechanisms explaining the oil recovery improvement are not clearly established. The literature points out several hypotheses, among them is the role of clay particles detachment and migration. Experiments using an intermediate-wet clayey sandstone were first performed showing an oil recovery increment when the injected brine salinity was reduced. SEM observations on native and flushed cores show the differences of pore surfaces before and after the low salinity waterflooding and the peculiar role of clay particles. Following this trail, in a second set of experiments we investigated the role of microparticles on the formation and stability of brine/oil emulsions when the salinity is changed. For that, we used calibrated latex particles negatively charged and several oils (mineral, crude and a blend of the two). Emulsion samples were observed using an optical microscope to determine their droplet size distributions and interface structures. The macroscopic stability of the emulsions was also investigated. The results show that the particle wettability, which is related to its surface charge and brine salinity, plays a central role. For high salinity the particles are hydrophobic and migrate toward the brine/oil interface forming a stable emulsion known as “Pickering emulsion”. For low salinity the particles are hydrophilic and the emulsion is not stable. In a third step the same latex particles were deposited in an artificial consolidated porous medium prior to two phase flow experiments. Our results show that even if no recovery improvement is observed, colloidal particles are recovered at the outlet when low salinity waterflooding is performed. The additional oil recovery during a low salinity brine injection is not a direct consequence of the particles mobilization but involves several mechanisms such as rock and brine composition, particle and oil nature, wettability, …. A thorough analysis of all these mechanisms calls upon further studies.Collaboration avec TOTA

Some Investigations on the role of microparticles on the low salinity process

Several papers dealing with laboratory experiments or field operations confirm that, in some circumstances, low salinity waterflooding improves oil recovery. However, the basic mechanisms explaining the oil recovery improvement are not clearly established. The literature points out several hypotheses, among them is the role of clay particles detachment and migration. Experiments using an intermediate-wet clayey sandstone were first performed showing an oil recovery increment when the injected brine salinity was reduced. SEM observations on native and flushed cores show the differences of pore surfaces before and after the low salinity waterflooding and the peculiar role of clay particles. Following this trail, in a second set of experiments we investigated the role of microparticles on the formation and stability of brine/oil emulsions when the salinity is changed. For that, we used calibrated latex particles negatively charged and several oils (mineral, crude and a blend of the two). Emulsion samples were observed using an optical microscope to determine their droplet size distributions and interface structures. The macroscopic stability of the emulsions was also investigated. The results show that the particle wettability, which is related to its surface charge and brine salinity, plays a central role. For high salinity the particles are hydrophobic and migrate toward the brine/oil interface forming a stable emulsion known as “Pickering emulsion”. For low salinity the particles are hydrophilic and the emulsion is not stable. In a third step the same latex particles were deposited in an artificial consolidated porous medium prior to two phase flow experiments. Our results show that even if no recovery improvement is observed, colloidal particles are recovered at the outlet when low salinity waterflooding is performed. The additional oil recovery during a low salinity brine injection is not a direct consequence of the particles mobilization but involves several mechanisms such as rock and brine composition, particle and oil nature, wettability, …. A thorough analysis of all these mechanisms calls upon further studies.Collaboration avec TOTA

Etude expérimentale des interactions Huile brute/Saumure/Roche sur la récupération d'hydrocarbures par injection d'eau de faible salinité

Several laboratory and oilfield experiments demonstrated that brine salinity can have an influence on oil recovery. The first extensive study on the ability of low salinity waterflooding to become an EOR method started in the 90th [Jadhunandan & Morrow, 1991] and has been followed by several experimental campaigns to understand the mechanisms leading to additional recovery of oil. The objective of our study was, on one hand, to quantify the additional oil recovery by low salinity waterflooding using a well characterized system (Core Oil and Brine). On the other hand, from the different physicochemical measured parameters, to propose some explanations of the microscopic displacement improvement. Our experiments were held on a COBR system composed of a consolidated outcrop sandstone (DU3) with an average permeability (400-800mdy) containing 10% of clays without kaolinite, a filtered crude oil (Oil A) containing 2.3%w of asphaltenes, a connate high salinity brine of 50g/l (90%w NaCl, 10%w CaCl2) and different low salinity brines containing, or not, divalent ions. The results of secondary and tertiary experiments put in evidence additional oil recoveries ranging between 9 and 11% (OOIP) when changing the brine salinity from 50g/l to 1g/l and between 4 and 6% (OOIP) when changing from 1g/l to 0,1g/l. This oil recovery improvement, that is still accompanied by pH increase and permeability reduction, appears only below a salinity value threshold ranging between 2.5 and 1g/l for our COBR system. Additional oil recovery was also observed whereas no divalent ion was present in the injection brine. The production increment is observed after injection of 2 to 3 PV of brine. This is due to a dispersive effect which is in coherence with the salinity value threshold. SEM observations of the cores show that pore walls are partially preserved by the residual oil, therefore clay particles release and production are prevented. pH increase appears to be a consequence rather a cause of low salinity mechanism. Permeability reduction was also observed without additional oil recovery. This is due to interparticular expansion as explained in DLVO theory. Clay particles release during one phase dispersion experiments and partial divalent ions retention when reducing salinity show the importance of ionic exchanges in the microscopic displacement of hydrocarbons.De nombreux travaux effectués en laboratoire ou sur des champs pétroliers ont mis en évidence l'influence que peut avoir la salinité de l'eau de balayage sur le déplacement des hydrocarbures. Les premières études documentées sur la capacité de l'injection d'eau de faible salinité à devenir une méthode EOR (augmentation de la récupération) ont débuté dans les années 90 [Jadhunandan & Morrow, 1991] suivies par d'autres auteurs [Lager et al., 2006]. Cependant il n'existe pas, à ce jour, d'explication générale du phénomène. L'objectif de notre étude est d'une part de quantifier, sur un système Huile/Saumure/Roche bien caractérisé, les récupérations additionnelles d'hydrocarbure par injection d'eau diluée, d'autre part, à partir de l'évolution des paramètres physico-chimiques, de proposer des explications aux réactions du milieu poreux conduisant à l'amélioration du déplacement microscopique de l'huile brute. Nous avons effectué nos expériences en considérant un système composé d'un grès d'affleurement (DU3) consolidé de perméabilité moyenne (400-800mdy) contenant 10% d'argile mais pas de kaolinite, d'une huile de gisement (Huile A) contenant 2,3% d'asphaltènes, d'une saumure résidente de concentration égale à 50g/l (90%w NaCl, 10%w CaCl2) et de saumures de faible salinité (1g/l) contenant ou pas des ions divalents. Les résultats des expériences de balayages tertiaires et secondaires ont mis en évidence des récupérations additionnelles d'hydrocarbure comprises entre 9 et 11% (OOIP) lorsqu'on passe de l'injection d'une saumure à 50g/l à une saumure à 1g/l et entre 4 et 6% (OOIP) lorsqu'on passe de 1g/l à 0,1g/l. Ces récupérations additionnelles, qui sont toujours accompagnées de l'augmentation du pH et de la réduction de la perméabilité de l'échantillon, ont lieu à partir d'une valeur seuil de salinité comprise entre 2,5 et 1g/l. Elles sont également observées en l'absence d'ions divalents dans l'eau d'injection. La reprise de production observée après injection de 2 à 3 VP a pour origine un effet de dispersivité diphasique qui est cohérente avec le seuil de salinité nécessaire à la reprise de production. Des observations à l'aide d'un MEB montrent que l'huile résiduelle préserve partiellement les surfaces et empêche le décollement et la libération des particules argileuses. L'augmentation du pH n'est pas le moteur de ce phénomène, elle est due aux réactions simultanées d'échanges ioniques à la surface de la roche et de dissolution des carbonates. La réduction de la perméabilité, comme l'augmentation du pH, est également observée dans les cas où aucune récupération additionnelle d'huile n'a été mise en évidence. Cette réduction de perméabilité est due à l'expansion interparticulaire prévue par la théorie DLVO lors de la diminution de la force ionique. La libération de particules argileuses lors des expériences de traçages monophasiques et le comportement de l'ion divalent Ca++ qui disparaît plus vite des effluents montre l'importance des échanges ioniques dans le déplacement microscopique des hydrocarbures

Some Investigations on the role of microparticles on the low salinity process

Several papers dealing with laboratory experiments or field operations confirm that, in some circumstances, low salinity waterflooding improves oil recovery. However, the basic mechanisms explaining the oil recovery improvement are not clearly established. The literature points out several hypotheses, among them is the role of clay particles detachment and migration.Experiments using an intermediate-wet clayey sandstone were first performed showing an oil recovery increment when the injected brine salinity was reduced. SEM observations on native and flushed cores show the differences of pore surfaces before and after the low salinity waterflooding and the peculiar role of clay particles. Following this trail, in a second set of experiments we investigated the role of microparticles on the formation and stability of brine/oil emulsions when the salinity is changed. For that, we used calibrated latex particles negatively charged and several oils (mineral, crude and a blend of the two). Emulsion samples were observed using an optical microscope to determine their droplet size distributions and interface structures. The macroscopic stability of the emulsions was also investigated. The results show that the particle wettability, which is related to its surface charge and brine salinity, plays a central role. For high salinity the particles are hydrophobic and migrate toward the brine/oil interface forming a stable emulsion known as “Pickering emulsion”. For low salinity the particles are hydrophilic and the emulsion is not stable. In a third step the same latex particles were deposited in an artificial consolidated porous medium prior to two phase flow experiments. Our results show that even if no recovery improvement is observed, colloidal particles are recovered at the outlet when low salinity waterflooding is performed.The additional oil recovery during a low salinity brine injection is not a direct consequence of the particles mobilization but involves several mechanisms such as rock and brine composition, particle and oil nature, wettability, …. A thorough analysis of all these mechanisms calls upon further studies.Several papers dealing with laboratory experiments or field operations confirm that, in some circumstances, low salinity waterflooding improves oil recovery. However, the basic mechanisms explaining the oil recovery improvement are not clearly established. The literature points out several hypotheses, among them is the role of clay particles detachment and migration.Experiments using an intermediate-wet clayey sandstone were first performed showing an oil recovery increment when the injected brine salinity was reduced. SEM observations on native and flushed cores show the differences of pore surfaces before and after the low salinity waterflooding and the peculiar role of clay particles. Following this trail, in a second set of experiments we investigated the role of microparticles on the formation and stability of brine/oil emulsions when the salinity is changed. For that, we used calibrated latex particles negatively charged and several oils (mineral, crude and a blend of the two). Emulsion samples were observed using an optical microscope to determine their droplet size distributions and interface structures. The macroscopic stability of the emulsions was also investigated. The results show that the particle wettability, which is related to its surface charge and brine salinity, plays a central role. For high salinity the particles are hydrophobic and migrate toward the brine/oil interface forming a stable emulsion known as “Pickering emulsion”. For low salinity the particles are hydrophilic and the emulsion is not stable. In a third step the same latex particles were deposited in an artificial consolidated porous medium prior to two phase flow experiments. Our results show that even if no recovery improvement is observed, colloidal particles are recovered at the outlet when low salinity waterflooding is performed.The additional oil recovery during a low salinity brine injection is not a direct consequence of the particles mobilization but involves several mechanisms such as rock and brine composition, particle and oil nature, wettability, …. A thorough analysis of all these mechanisms calls upon further studies

Ligueyante

The songs are mostly about the ancient kingdoms of the Senegambia region and its landscapes, community belonging and values, and he favoured reuniting the Gambia with Senega

Baladjigui Moussa

The songs are mostly about the ancient kingdoms of the Senegambia region and its landscapes, community belonging and values, and he favoured reuniting the Gambia with Senega

Yalla Bahna

The songs are mostly about the ancient kingdoms of the Senegambia region and its landscapes, community belonging and values, and he favoured reuniting the Gambia with Senega

Manore

The songs are mostly about the ancient kingdoms of the Senegambia region and its landscapes, community belonging and values, and he favoured reuniting the Gambia with Senega

Madame Siby

The songs are mostly about the ancient kingdoms of the Senegambia region and its landscapes, community belonging and values, and he favoured reuniting the Gambia with Senega