Investigation of the effect of diethylene triamine pentaacetic acid chelating agent as an enhanced oil recovery fluid on wettability alteration of sandstone rocks

This study used the diethylene triamine pentaacetic acid (DTPA)-sea water (SW) system to change the sandstone rock wettability and increase oil recovery, and carried out wettability measurement, Zeta potential measurement and spontaneous imbibition experiments. The 5% DTPA-SW solution changed the rock-oil contact angle from 143° to 23°, and decreased the Zeta potential from −2.29 mV to −13.06 mV and made the rock surface charge more negative, finally altered the rock wettability towards a strongly water-wet state from oil-wet state. The presence or absence of potential determining ions (Ca2+, Mg2+, SO42−) in the solution did not affect the performance of DTPA regarding the change in the wettability. However, by tripling the concentration of these ions in the solution, the performance of 5% DTPA-SW solution in changing wettability was impaired. Spontaneous imbibition tests also showed that the 5% DTPA-SW solution increased oil recovery up to 39.6%. The optimum mass fraction of DTPA for changing sandstone wettability is 5%. © 2023 Science Press. All rights reserved.