Evaluation of the synergistic effect of nanocomposite hydrogel based on imidazolium nitrate ionic liquids for enhanced oil recovery

[Display omitted] •The ionic liquid [C8mim][NO3] improved the thermal resistance of the hydrogel.•The study investigated the use of IL with hydrogels and nanoparticles for EOR.•NCH-IL modified the carbonate core wettability from oil to water-wet.•IL improved and strengthened the rheological and mechanical properties of NCH.•The electrochemical properties of NCH-IL, along with its successful effect on the IFT change, were investigated. A comprehensive research study was conducted to examine the synergistic properties of ionic liquids, and hydrogels. Two nanocomposite hydrogel samples were created: one with ionic liquid and the other without. The samples were made using hydrogel with acrylamide (AM) backbone, Al2O3 nanoparticles, and ionic liquid [C8mim][NO3]. The effectiveness of a nanocomposite hydrogel containing an ionic liquid was tested to improve the wettability alteration and sweeping efficiency of reservoirs. Various tests were performed including IFT, electroconductivity, micromodel, SEM, and equilibrium swelling tests. The tests showed that the presence of the ionic liquid increased the swelling up to 102 %. IL increased conductivity by 124.24 % and 44.86 % at ambient temperature and 90 °C respectively. In the strain sweep test, the maximum elastic modulus for NCH-IL was recorded as 40,350 Pa, while for the sample without ionic liquid, it was 27,100 Pa. The frequency sweep test confirmed the three-dimensional structure of the gel. IL increased the maximum elastic modulus from 13,200 Pa to 27,400 Pa. The critical frequency value also increased by 87.5 %. Moreover, the suspension, which contains 1 wt% of Nanocomposite Hydrogel based on Imidazolium Nitrate Ionic Liquids, has shear-thinning properties, making it easy to inject into reservoirs. The reduction of the contact angle from 109° to 14.2° demonstrated the ability of IL to alter the wettability of NCHs. This result stemmed from the release of part of the ionic liquid within the hydrogel structure, as confirmed by the UV test. During the emulsion stability test, it was observed that the NCH-IL sample created a stable emulsion and a more complete two-phase separation than the sample without the ionic liquid. The sample that contained IL recorded 85 % and 78.4 % oil recovery in homogeneous and heterogeneous micromodels, respectively. Whereas, the sample without IL recorded 71.27 % and 60.73 % in the same micromodels.