Page 113 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 4 Hybrid Chemical EOR Using Low-Salinity and Smart Waterflood 105

100 900
LS LSP
90 800
0.5PV
80 LSS slug
700
Oil recovery [% OOIP] 60 WBT 500 dP [mbar]
70
600
50
400
40
30
200
20 Oil recovery 300
dP 100
10
0 0
0 1 2 3 4 5 6 7
Injected volume [PV]
FIG. 4.35 The oil recovery and differential pressure of coreflooding of low salinityeaugmented surfactant/
polymer floods. (Credit: From Johannessen, A. M., & Spildo, K. (2014). Can lowering the injection brine
salinity further increase oil recovery by surfactant injection under otherwise similar conditions? Energy and
Fuels, 28(11), 6723e6734. https://doi.org/10.1021/ef500995y.)

brine. The LSSP is designed with the coinjection of poly- on the synergetic effects and mechanisms of the hybrid
mer and surfactant additives. The polymer concentra- ASP process. The studies (Dang, Nghiem, Nguyen, et al.
tion to be injected in LSSP halves but has the 70% of 2018; Farajzadeh, Matsuura, Batenburg, & Harm, 2012;
target viscosity compared with the chemical solution Ghadami, Deo Tewari, Zarubinska, & Motaei, 2018;
of conventional surfactant-polymer flood. In terms of Hosseini-Nasab, Padalkar, Battistutta, & Zitha, 2016;
surfactant, the equal concentration of surfactant is Nghiem, Skoreyko, Gorucu, Dang, & Shrivastava,
used for both low- and high-salinity water conditions, 2017) have developed the mechanistic simulation of
and comparable IFT reduction is observed. The hybrid ASP process to be coupled with fully geochemical reac-
LSSP shows the higher oil cut and differential pressure tions. Based on the comprehensive studies of ASP pro-
despite less polymer injection. This study also demon- cess, the application of low-salinity water/smart water
strated that the hybrid LSSP improves both sweep and as the makeup brine is implemented into the hybrid
displacement efficiencies and secures the practicality ASP process. Reducing the salinity, ionic strength might
and economics of chemical EOR process. be optimistic for polymer flood but might not be for
The hybrid alkaline/surfactant/polymer flood (ASP) surfactant and alkaline floods owing to optimum
has been widely investigated because of a number of salinity condition. Reduction in hardness could bring
reasons. This hybrid process improves both sweep and the overall positive benefits to chemical EOR.
displacement efficiencies and highly enhances the oil Therefore, many studies have investigated hybrid ASP
production. The alkali addition produces the in situ sur- process optimizing the salinity, hardness, ionic compo-
factant generation, which means the less injection of sition, etc.
expensive surfactant. It also reduces the adsorption of Battistutta, van Kuijk, Groen, and Zitha (2015) con-
surfactant on the rock surface at high pH condition ducted the comprehensive experiments of ASP process.
and secures the stability of surfactant by reacting with The study estimated the optimal salinity to make the
the divalent cations. The application of low-salinity Winsor type Ⅲ of microemulsion as the 1.5 wt%
water as makeup brine into the hybrid ASP process is ex- NaCl. At the optimal salinity, the ultralow IFT is ob-
pected to employ the additional synergy of low-salinity tained from the IFT measurement and phase behavior
water and chemical additives, as discussed in previous test. A variety of ASP formulations are designed. The
sections, and enhance wettability modification into makeup brines of the ASP formulations have the salin-
ASP process. ities of 0.5, 1, 1.5, and 2.0 wt% NaCl. Because the
Because the mechanisms of ASP processes are sensi- optimal salinity is determined as 2.0 wt%, the ASP for-
tive to the salinity, pH, etc., a number of studies have a mulations having the salinity less than 2.0 wt% are at
primary object to quantify the effects of geochemistry underoptimum salinity condition representing Winsor