Page 61 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 3 Modeling of Low-Salinity and Smart Waterflood 53

TABLE 3.1
Surface Complexation Model in Sandstone Reservoir (Brady et al. 2015)
Reactions
þ
Oil surface -NH % -N þ H þ
-COOH % -COO þ H þ

þ
-COOH þ Ca 2þ % -COOCa þ H þ

Mineral surface Quartz >SiOH % >SiO þ H þ
>SiOH þ Ca 2þ % >SiOCa þ H þ
þ
þ
>SiOH þ CaOH % >SiOCaOH þ H þ
Kaolinite >AlOH 2 % > AlOH þ H þ
þ

>AlOH % >AlO þ H þ

>SiOH % >SiO þ H þ

>AlOH % >AlO þ H þ
þ
>SiOH þ Ca 2þ % >SiOCa þ H þ
>AlOH þ Ca 2þ % >AlOCa þ H þ
þ
þ
>SiOH þ CaOH % >SiOCaOH þ H þ
þ
>AlOH þ CaOH % >AlOCaOH þ H þ
Kaolinite basal plane >H þ Na % >Na þ H þ
þ
2 > Na þ Ca 2þ % >Ca þ 2Na þ

Oil-kaolinite >Al:Si-O þ HN- % >Al:Si-OHN-
þ
>Al:Si-O þ CaOOC- % >Al:Si-O-CaOOC
þ

Ca 2þ and Mg 2þ is accomplished by surface complexa- introduced the concept of bond product sum (BPS)
tion model. Because of impure natural kaolinite, cation to indicate the mutual electrostatic adhesion, consid-
exchange occurs. Lastly, the surface complexation ering both the surface charge calculations of oil and
model of oil-reservoir surface speciation is used for kaolinite edges. The BPS is defined as the total of the
the modeling of LSWF effect. The complexation model products of the surface concentrations of oppositely
describes the adherences of the protonated nitrogen charged species on the oil and minerals. When only
bases and positively charged calcium carboxylate negatively charged species exist on both the oil and
groups to the negatively charged kaolinite edge. The mineral surfaces, the BPS is equal to zero because no
surface complexation model describes the interaction oppositely charged, i.e., positively charged, species ex-
of the oil-water-kaolinite system. It includes the sub- ists. There is no electrostatic adhesion meaning water-
models of (1) oil-water interface charge, (2) kaolinite wetness. When only oil has positively charged surface
edge surface charge, and (3) Ca 2þ and Mg 2þ sorption species and mineral has the negatively charged surface
to oil and kaolinite edges. The diffuse layer model, species, the BPS is high enough to introduce the poten-
which is the simplest model to describe the electric tial of adhesion, i.e., oil-wetness. The BPS is the indica-
double layer, is used to develop the submodels of sur- tor to imply the decreasing or increasing oil adhesion.
face complexation. Using the surface complexation The degree of BPS is controlled by the AN/BN of oil and
model, the concentration of species and electrostatic pH. The isotherm disjoining pressure of oil and
attraction concentration product can be determined kaolinite edges based on the DLVO theory is calculated
at the equilibrium state (Fig. 3.8). The developed to complement the BPS estimate (Fig. 3.9). Brady and
model is sensitive to ionic strength, temperature, and Thyne (2016) modeled the LSWF in the dolomite
pH conditions. Brady et al. (2012) additionally pro- and limestone reservoirs by adapting the approach of
posed the surface complexation model of calcite min- surface complexation modeling (Fig. 3.10). Referring
erals in sandstone reservoirs. Brady et al. (2015) the concept of fractional wettability, potential linkage