Page 11 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding
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CHAPTER 1 History of Low-Salinity and Smart Waterflood  3

          show that injection with Brine 2 into core, which is  crude oil samples (Dagang, A-95 of Prudhoe Bay,
          saturated with Brine 1, increases oil production.  and CS) are subject to the experiments. In the imbibi-
          However, none of tertiary recovery tests clearly shows  tion and waterflooding tests, the synthetic brines and
          the potential of improved oil recovery/enhanced oil  various diluted versions of the synthetic brines, which
          recovery (IOR/EOR) by switching brine composition.  have salinities by factors of 0.01, 0.1, and 2, are used.
            Tang and Morrow (1997) proceeded the compre-  Additional experiments use the modified crude oils in
          hensive investigations of spontaneous imbibition and  which light ends are removed or alkanes (pentane,
          waterflooding experiments using Berea sandstone  hexane, and decane) are added. The summarized results
          and configured the effects of brine composition,  of the tests indicate that both imbibition rate and oil
          temperature, and crude oil composition on the wetta-  recovery increase with a decreasing salinity. In detail,
          bility and oil recovery. Compared with previous studies,  higher oil recovery is obtained when either connate or
          this study made a significant effort on the assessments  invading brines have low salinity (Figs. 1.3 and 1.4).
          of crude oil and brine compositions in the temperature  In the assessments of crude oil composition, the exis-


          range from 22 Cto80 C. The synthetic brines and three  tences of light ends and alkanes decrease oil recovery.
                        (A)  100
                            90
                            80
                            70
                           R im  (%OOIP)  50
                            60

                            40
                            30
                            20
                            10
                             0
                                                           1000      10000    100000
                                                            __ ______  t __
                                                             φ  μ μ  L 2 c
                                                                w  o
                        (B)




                            R wf  (% OOIP)  50



                             40
                             30
                             20
                             10
                              0
                               0        2       4       6        8       10      12
                                               Injected brine volume (PV)
                FIG. 1.3 Effects of invading brine concentration on recovery of Dagang crude oil (RB ¼ Dagang brine): (A)
                spontaneous imbibition and (B) waterflood. (Credit: From Tang, G. Q., & Morrow, N. R. (1997). Salinity,
                temperature, oil composition, and oil recovery by waterflooding. SPE Reservoir Engineering, 12(04), 269e276.
                https://doi.org/10.2118/36680-PA.)
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