| Summary: | Ultra-low permeable reservoirs are considered unconventional reservoirs with a permeability of less than two mD. Thereby, oil production by conventional techniques has some problems and challenges rather than other types of reservoirs. This paper aimed to experimentally investigate different injectivity scenarios such as water alternating gas injection, surfactant flooding (anionic and cationic surfactants), and carbon dioxide injection both as continuous and cyclic, and carbonated water injection. To do this, surfactant and carbon dioxide concentration should be optimized first to provide efficient results. According to the results of this study, LABSA (linear alkylbenzene sulfonic acid) and CTAB (cetyl trimethyl ammonium bromide) have their optimum concentration at 300 and 350 ppm, which is indicated that after this concentration, there is no significant alteration in IFT (Interfacial tension) The maximum oil recovery factor for LASBA and CTAB is 46 and 42%, respectively. 750 mg/L of CO2 has provided the highest oil recovery (54.5%), and by the increase of CO2 concentration, there is no significant change in oil production. The maximum oil recovery increase by a surfactant (LABSA), continuous CO2 injection, cyclic CO2 injection, water alternating gas injection, and carbonated water (CW) injection is about 15%, 24.5%, 30%, 27%, and 34%, respectively. The highest oil recovery factor for secondary CW injection and CW after brine injection is about 68% and 63%, which indicated the proper efficiency of secondary CW injection in ultra-low permeable reservoirs.
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