Page 131 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 5 Hybrid CO 2 EOR Using Low-Salinity and Smart Waterflood 123

Ca 2þ might modify the wettability additionally toward Because the role of clay is important to simulate
more water-wetness. Another study of Dang, Nghiem, the wettability modification effect following LSWF
Chen, Nguyen, and Nguyen (2014) reported more mechanism in sandstone, the dispersed clay is addition-
wettability modification effect with more cation ally modeled. The reservoir model has the high uncer-
2þ
exchange of Ca . The comparison between LS-CO 2 tainty in clay distribution of reservoir. Considering
WAG process with and without calcite reaction the different facies and clay mapping, a number of
obviously confirms that higher recovery is obtained geological realizations of clay distribution in reservoir
when the calcite mineral dissolves. Higher adherence are investigated. Considering the uncertainty, the
of Ca 2þ on rock by more cation exchange is observed LS-CO 2 WAG process provides the additional oil
because of calcite mineral dissolution. It is implied recovery from 4.5%e9% over conventional CO 2 WAG
that CO 2 solubility in brine might reduce the amount process.
of CO 2 to be miscible with oil. However, it can promote The numerical studies (Al-Shalabi, Sepehrnoori, &
the wettability modification of LSWF mechanism. In Pope, 2014; Al-Shalabi, Sepehrnoori, & Pope, 2016)
addition, the LS-CO 2 WAG overcomes the delay in have reported the modeling of LS-CO 2 WAG process
oil production, which is observed in CO 2 injection in carbonate rocks based on the numerical models of
(Kulkarni & Rao, 2005). Comparing with CGI and LSWF and CO 2 WAG process. The LS-CO 2 WAG process
conventional CO 2 WAG process, LS-CO 2 WAG shows is assumed to be involved with the mechanism of LSWF
the higher oil production rate as soon as CO 2 is and immiscible/miscible mechanisms of CO 2 WAG. It
injected (Fig. 5.6), which indicates the less delay in oil adapts the modeling of LSWF mechanism as empirical
production. Dang et al. (2014) extended the numerical approach of wettability modification (Al-Shalabi,
simulation of LS-CO 2 WAG process to the field-scaled Sepehrnoori, Delshad, & Pope, 2015). Because LSWF
assessment. Brugge benchmark field (Peters et al. model considers only two-phase flow of oil and water,
2010) is used for the deployment of LS-CO 2 WAG. the empirical approach of wettability modification

60

50
High Salinity WAG
Low Salinity WAG
Pure CO2 Flooding
40
Oil Rate SC (bbl/day) 30

20

10

0
200 400 600 800 1,000
Time (day)
FIG. 5.6 Comparison of oil production rate of continuous CO 2 gas injection, conventional CO 2 water-
alternating gas injection, and low salinityeassisted CO 2 water-alternating gas injection. (Credit: From Dang,
C. T. Q., Nghiem, L. X., Chen, Z., Nguyen, N. T. B., & Nguyen, Q. P. (2014). CO 2 low salinity water alternating
gas: A new promising approach for enhanced oil recovery. Paper presented at the SPE improved oil recovery
symposium, Tulsa, Oklahoma, USA, 12e16 April. https://doi.org/10.2118/169071-MS.)