## 4 Conclusions  
This study represents an evaluation of the hydride huff-n-puff-based enhanced oil recovery (EOR) technique. The single-channel microfluidic experiments showed improved CO\({}_{2}\) dissolution in oil at low pressure upon the addition of 2% (\(w/v\)) SDS, attributing to  
Figure 10: Cumulative oil recovery in flooding experiments. (**a**) DI water floodings with intermediate oil swelling at 5 psig. (**b**) SDS-DI water floodings with intermediate oil swelling at 5 psig. (**c**) DI water floodings with intermediate oil swelling at 10 psig. (**d**) SDS–DI water floodings with intermediate oil swelling at 10 psig. (**e**) DI water floodings with intermediate oil swelling at 15 psig. (**f**) SDS–DI water floodings with intermediate oil swelling at 15 psig. surfactant micelles formation at the CO\({}_{2}\)-oil interface. The viability of the SDS-CO\({}_{2}\)-assisted EOR via oil swelling was demonstrated by the huff-n-puff flooding using the'reservoir-on-a-chip' approach with the PMMA-based micro reservoir. Six different experiments, including both DI water and SDS-DI water flooding with 5, 10 and 15 psig CO\({}_{2}\) pressureed intermediate oil swelling, were tested. The DI water flooding showed a breakthrough at 808 s, whereas SDS-DI water flooding at 850 s. The 42 s delayed breakthrough can be attributed to the larger sweep area of SDS-DI water flooding compared to DI water flooding. The longer breakthrough time in SDS-DI water flooding is due to reduced interfacial tension and wettability alteration from the adsorption mechanism. The DI water-based flooding with 5 psig CO\({}_{2}\)-pressured oil swelling showed cumulative oil recovery of 16% of OOIP. In the same experiment, the cumulative oil recovery was 25% with SDS-DI water flooding. At 10-psig CO\({}_{2}\) pressure, the cumulative oil recovery in DI water and SDS-DI water flooding was 20% and 36%, respectively. At 15-psig CO\({}_{2}\) pressure, the oil recovery was 28% and 37% in DI water and SDS-DI water flooding, respectively. The trend of achieving high oil recovery with higher pressure was maintained in the DI water flooding. However, in the case of SDS-DI water flooding, the improvement in oil recovery from 10 psig to 15 psig was less pronounced, possibly due to the saturation limit of oil recovery. This study concludes that the nonionic surfactant flooding with a CO\({}_{2}\)-based intermediate oil swelling approach holds great promise as a future EOR method. To further validate the applicability of this method in reservoir recovery, future studies could focus on incorporating sandstone or carbonate rock-mimicking surfaces in the microchannel setup to better replicate geological reservoir conditions. Additionally, conducting core flooding experiments on actual reservoir cores or rock analogs would provide further insights into the performance of the method under more realistic reservoir conditions. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app142412078/s1](https://www.mdpi.com/article/10.3390/app142412078/s1)]([https://www.mdpi.com/article/10.3390/app142412078/s1](https://www.mdpi.com/article/10.3390/app142412078/s1)), Figure S1: Comprehensive figure of cumulative oil recovery; Video S1: Flooding comparison with and without SDS  
**Author Contributions:** Conceptualization, A.R. and M.K. ; Methodology, A.R., J.D., M.P. and M.K. ; Software, A.R. ; Validation, A.R. and M.K. ; Formal analysis, A.R., I.A. and M.K. ; Investigation, A.R., J.D., M.P., I.A. and M.K. ; Resources, M.K. ; Data curation, A.R., J.D., C.S. and M.K. ; Writing--original draft, A.R. and M.K. ; Writing--review & editing, A.R., J.D., C.S., M.P., P.M., R.L.A.-R., R.I. and M.K. ; Supervision, P.M., R.I.A.-R., R.I. and M.K. ; Project administration, M.K. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the National Science Foundation, USA (grant number: 2207642). **Informed Consent Statement:** Not applicable.