This study characterizes the impact of hybrid nano-acid fluids (HNAF) to improve oil recovery from tight carbonate reservoirs. While acidizing creates continuous channels (wormholes), wettability alteration takes place by nanoparticles in penetrating through the tight pore throats and adsorbing on the surface of pore wall. In addition, it is validated that the application of HNAFs with pulsed electrokinetics (EK) effectively stimulates the tight formation, which is being investigated by dual energy computed tomography (DECT) scan, showing efficient wormholes. Methodology is divided into two parts. The fisrt part is to identify optimum concentration of hybrid nano-acid fluids by conducting IFT measurements. The second part is to verify the combined effect of hybrid nano-acid fluids with electrokinetics and relative contribution of acid, nanoparticles, and electrokinetics by conducting spontaneous imbibition tests, core flood experiments, and zeta potential data.
Selected HNAF formulations, such as SiO2-Acid (HNAF1), Al2 O3-Acid (HNAF2) and ZnO-Acid (HNAF3), produced a significant IFT reduction under HPHT conditions from 18 dyne/cm (formation water and oil) to 3.14 dyne/cm, 2.89 dyne/cm, and 4.14 dyne/cm respectively. When conducted with sequential application of EK, HNAF1 showed higher performance compared to HNAF2, followed by HNAF3, in terms of displacement efficiency (DE). During pulsed simultaneous application of EK, HNAF1 showed higher performance followed by HNAF3 and HNAF2. The DE and PE averaged at 9% and 180% during sequential application. The displacement efficiency recorded a significant increase in the case of simultaneous versus sequential application while requiring 27% less pore volumes injected. The zeta potential verified the coreflood (CF) ranking order through matched shifts in zeta potential before and after CF, which confirms a drastic alteration in wettability post flooding.
The summary of research presents promising potential to overcome the limitations reported from the previous studies, and improved the understanding of the application of HNAFs in tight carbonate reservoirs. This integrated study has assisted in successful formulation of HNAF assisted with the EK in lab scale.