Transport de solutions de polymère dans des milieux poreux contrôlés de différentes minéralogies

Chemical Enhanced Oil Recovery (EOR) is considered as an attractive option for low permeability reservoirs, in particular where lack of gas supply does not allow gas injection processes. However, its application can be challenging for permeabilities below 100mD, as poor injectivity and high chemical retention are frequently observed in these cases. This work aimed at investigating the impact of both chemical and mineralogical parameters on the transport of polymer solutions in well-controlled low permeability porous media. For that, polymer injection tests were carried out using HPAM solutions of different ionic strengths and hardnesses and four granular sand-clay packs using quartz and three types of clays: kaolinite, illite and smectite. Results confirm the major role played by the injection water composition (salinity and hardness) on polymer conformation and on polymer-minerals interactions. Strong interactions between polymer and clay are evidenced with significant differences according to the clay type: good propagation and high polymer retention in an uncharged and non-swelling clay (kaolinite) and poor propagation with lower retention than expected in charged or swelling clays (illite, smectite). These outcomes stand as new elements for understanding the transport of polymer solutions in low permeability sandstone reservoirs.La récupération assistée du pétrole est considérée comme une option intéressante pour les réservoirs à faible perméabilité. Cependant, son application peut s'avérer difficile pour des perméabilités inférieures à 100mD, en raison des problèmes d'injectivité et de rétention élevée des additifs chimiques fréquemment observés dans ces cas. Ce travail de thèse vise à étudier l'impact des paramètres physico-chimiques et minéralogiques sur le transport des solutions de polymère dans des milieux poreux modèles de faibles perméabilités. Pour cela, des expériences d'injection de polymère ont été menées en utilisant des solutions d'HPAM de différentes forces ioniques et duretés et quatre milieux granulaires à base de quartz et trois types d'argiles: kaolinite, illite et smectite. Les résultats confirment le rôle majeur joué par la composition de l'eau d'injection (salinité et dureté) sur la conformation des polymères et sur les interactions polymères-minéraux. De fortes interactions entre le polymère et l'argile sont mises en évidence avec des différences significatives selon le type d'argile : bonne propagation et rétention élevée du polymère dans une argile non chargée et non gonflante (kaolinite) et faible propagation avec une rétention plus faible que prévu dans les argiles chargées ou gonflantes (illite, smectite). Ces résultats constituent de nouveaux éléments pour la compréhension du transport des solutions de polymères dans les réservoirs de grès à faible perméabilité

Transport of EOR polymer solutions in low permeability porous media: impact of clay type and injection water composition

International audienceThe application of polymer flooding for enhanced oil recovery (EOR) to low-permeability porous media (below 100mD) can be very challenging as high polymer retention and poor injectivity are frequently observed. The challenges are mostly related to polymer solutions properties (ionic strength and hardness) and porous media mineralogy (clay content). This paper reports on an experimental study that aims at drawing a better picture of the mechanisms governing the transport of polymer solutions in low permeability clayey porous media. Results confirm the major role played by the injection water composition (salinity and hardness) on polymer conformation and on polymer-minerals interactions. Strong interactions between polymer and clay are also evidenced with significant differences according to the clay type: good propagation and high polymer retention in an uncharged and non-swelling clay (kaolinite) and poor propagation with lower than expected retention in charged or swelling clays (illite, smectite). For kaolinite, the results are interpreted in terms of fast formation of a polymer adsorbed layer on the solids surface whereas, for illite and smectite, they can be explained by the slow diffusion of polymer into clay aggregates, whose presence was evidenced by microscopic analysis. These outcomes stand as new elements for understanding and modeling the transport of polymer solutions in low permeability sandstone reservoirs. They also allow classifying the clays in view of their practical impact on the feasibility of polymer flooding operations

Transport of HPAM Solutions in low Permeability Porous Media: Impacts of Salinity and Clay Content

International audienceChemical EOR is now considered as an attractive option for low permeability reservoirs, in particular wherelack of gas supply does not allow gas injection processes. However, its application can be challenging forpermeabilities below 100 mD, as poor injectivity and high chemical retention are frequently observed inthese cases. This work aimed at investigating the impact of both chemical and mineralogical parameters onthe transport of polymer solutions in well-controlled low permeability porous media.The intrinsic viscosity and hydrodynamic size of partially hydrolyzed polyacrylamide (HPAM)solubilized in brines of variable ionic strengths and hardnesses were firstly investigated. Polymer injectioncorefloods were then conducted using granular packs (sand and clays mixtures) with similar petrophysicalcharacteristics (permeability 60-80 mD) but having several controlled mineralogical compositions. Thegranular packs were especially characterized in terms of structure (SEM) and specific surface area (BET)before and after polymer injections. The main observables from the coreflood tests were the resistanceand residual resistance factors generated by the polymer, the polymer inaccessible pore volume and itsirreversible retention.Homogenous and reproducible granular packs were successfully prepared thanks to a dedicatedmethodology and using different ratios of quartz and clays (kaolinite and illite separately).Results from the viscometric analysis showed that the intrinsic viscosity of the HPAM solutions decreasedwith increasing total salinity, as expected from charge screening, and that it decreased sharply in presenceof divalent cations, even at low ionic strength, which was less expected.Coreflood experiments showed that polymer retentions, resistance factors and irreversible resistancefactors increased significantly:– with increasing ionic strength and hardness for porous media of a given mineralogicalcomposition. This appeared consistent with the outcomes of the viscometric study andconfirmed the major impact of hardness;– in presence of kaolinite and illite, even at low ionic strength and hardness.The polymer inaccessible pore volume was significantly impacted by the presence of clays, but not bythe ionic strength and hardness. Analysis of the results indicated that these effects could not be attributedonly to polymer adsorption linked to the increase of specific surface area, but that more complex polymeradsorption/retention mechanisms occur depending on the clay type (layer charge and expandability).This systematic study allows dissociating the impacts of salinity, hardness and clay contents/types on thetransport of polymer solutions in low permeability porous media. The results obtained should be of interestto the chemical EOR industry as they provide guides to help tuning the injection brine composition andpolymer concentration to the reservoir properties

Stabilisation de suspensions colloïdales argileuses par un polyacrylamide anionique

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