Chemical flooding of sandstone reservoirs having different types and contents of clays and non-clay minerals requires special attention to understand the interaction between the injected fluids and the reservoir rock minerals.

Four coreflood experiments were conducted in this study using two different sandstone samples (Gray Berea and Gray Bandera) with different clay contents (8 - 12wt%). The core samples were characterized through XRD, SEM and NMR firstly before coreflood experiments to identify the presence and distribution of the different minerals inside the pore system and after the flooding experiments to evaluate the rock integrity after interaction of these minerals with the injected EDTA solutions. The effluent was analyzed by inductively coupled plasma (ICP) and ionic chromatography (IC) analyses to study the exchange ability of the different cations between sandstone cores and EDTA solutions. The core samples permeability was also measured before and after the flooding experiments to study the compatibility of the different clays with different concentrations of EDTA solutions.

The EDTA solutions with concentrations up to 10wt% were found to be compatible with Gray Berea sandstone as indicated by the permeability enhancement, NMR results and the pressure drop during the flooding tests; which indicates that there was no clay minerals swelling or fine migration occurred or nonclay minerals dissolution duo to the interaction of Gray Berea/EDTA solutions. On the other hand, EDTA solutions of concentrations higher than 5wt% were found to be incompatible with Gray Bandera samples as indicated by the high permeability enhancement duo to the interaction of EDTA with Ankerite mineral. The pressure drop along both Gray Berea and Gray Bandera core samples during the flooding experiments confirmed the stability of the different clays with EDTA solutions.

This study focused on evaluating the interaction of the sandstone rock surfaces with the high pH EDTA chelating agent solutions and the ability of this chemical to chelate the multivalent cations from clay minerals and its effect on the integrity of different sandstone rocks.

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