Page 123 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding
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CHAPTER 5   Hybrid CO 2 EOR Using Low-Salinity and Smart Waterflood  115


                          (A)
                                        Effect of Miscibility (1-ft Berea + 5% NaCl Brine)
                            100%


                             80%
                           Recovery (% ROIP)  60%             EXPT 2: IMM. WAG - 5%NaC
                                                              EXPT 1: IMM. CGI - 5%NaCl

                                                              EXPT 3: MIS. CGI - 5%NaC
                                                              EXPT 4: MIS. WAG - 5%NaCl
                             40%


                             20%


                             0%
                               0.0       0.5      1.0       1.5      2.0       2.5
                                                Total PV (G + W) Injected

                          (B)
                                        Effect of Miscibility (1-ft Berea + 50% NaCl Brine)
                             1.6
                                                               EXPT 1: IMM. CGI - 5%NaCl
                             1.4                               EXPT 2: IMM. WAG - 5%NaC
                                                               EXPT 3: MIS. CGI - 5%NaC
                           TRF (% ROIP / PVI CO 2 )  1.0
                             1.2
                                                               EXPT 4: MIS. WAG - 5%NaCl

                             0.8

                             0.6
                             0.4
                                           ∼ 0.6 PVI
                             0.2

                             0.0
                              0.0        0.5       1.0       1.5       2.0       2.5
                                                Total PV (G + W) Injected
                FIG. 5.1 The (A) oil recovery and (B) tertiary recovery factor of continuous CO 2 gas injection and CO 2 water-
                alternating gas process using 5% NaCl brine in miscible and immiscible conditions. (Credit: From Kulkarni, M.
                M., & Rao, D. N. (2005). Experimental investigation of miscible and immiscible water-alternating-gas (WAG)
                process performance. Journal of Petroleum Science and Engineering, 48(1), 120. https://doi.org/10.1016/j.
                petrol.2005.05.001.)

          out the potential of LSWF mechanism during the  water salinity. As the injected water has lower salinity,
          coinjection and alternating injection of CO 2 and  higher oil recovery is measured. As the brines have
          low-salinity water. Therefore, any contribution by using  salinities of 6 and 20 wt%, they are estimated to have
          low-salinity water on oil recovery is attributed to the  lower solubilities of CO 2 in water by at least 25% and
          CO 2 solubility in water. The coreflooding of CGI  60% compared with the distilled water. The relation-
          produces the additional oil by 21% over waterflood  ship between salinity and CO 2 solubility is also
          because of miscibility between CO 2 and oil.  confirmed through the CO 2 production at the outlet.
            The CO 2 WAG process produces the oil recovery  Another coreflooding of the simultaneous water and
          in the range of 74.3%e92.7% depending on the  CO 2 injection is investigated by controlling the salinity
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