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

Abstract : Chemical 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.
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Submitted on : Monday, December 2, 2019 - 2:33:29 PM
Last modification on : Friday, September 18, 2020 - 6:10:05 PM




Imane Guetni, Claire Marlière, David Rousseau, Isabelle Bihannic, Manuel Pelletier, et al.. Transport of HPAM Solutions in low Permeability Porous Media: Impacts of Salinity and Clay Content. SPE Europec featured at 81st EAGE Conference and Exhibition, Jun 2019, London, United Kingdom. 16 pp - SPE-195434-MS, ⟨10.2118/195434-MS⟩. ⟨hal-02389296⟩



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