Page 59 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 3 Modeling of Low-Salinity and Smart Waterflood 51

Gibbs free energy decreases, as the salinity of injecting
brine decreases. Maintaining the constant water relative HA w 4HA o (3.69)
permeability curve, the residual oil saturation, oil ½HA w Š
K D ¼ (3.70)
endpoint, and oil Corey’s exponent are historically ½HA o Š
adjusted to reproduce the oil recovery and pressure

HA w 4A þ H þ (3.71)
drop of the coreflooding experiments. w

þ
½H Š A
N aq w
X K a ¼ (3.72)
G ¼ x i m i (3.66) HA w
i¼1
where HA w and HA o are the acidic component in the
S or ¼ F IF S LS þð1 F IF ÞS HS (3.67) aqueous and oleic phases, A w and A o are the partitioned
or
or
HS carboxylic organic components in aqueous and oleic
G G
F IF ¼ LS HS (3.68) phases, respectively, K D is the partition coefficient,
G G
and K a is the dissociation constant of HA w in aqueous
where G is the effective molar Gibbs free energy of phase.
solution, N aq is the number of aqueous species i, In addition to the modeling of comprehensive
HS LS
and G and G are the effective molar Gibbs free reactions, the numerical simulation study using the
energy of solution at high and low salinity threshold IPreeqc-UTCOMP modeled the LSWF process following
conditions. wettability modification mechanism. The wettability
The UTCOMP is another in-house simulator of the modification is assumed to be controlled by a total
University of Texas at Austin and it is the EOS and ionic strength. The hypothetic simulations investigate
compositional simulator to model the miscible and the effects of the two additional reactions involving
immiscible gas injection EOR processes. Kazemi Nia water-soluble hydrocarbon components and acidic/
Korrani, Jerauld, and Sepehrnoori (2016) also basic components of the hydrocarbon phase on the
advanced the UTCOMP coupled with the IPhreeqc performance of LSWF process. The numerical simula-
module. In the coupling of UTCOMP and IPhreeqc, tions with and without the reactions clearly show the
two additional reactions involving water-soluble hydro- difference in the oil recovery (Fig. 3.6). Because the
carbon components and acidic/basic components of dissolution of CO 2 in aqueous phase potentially
the hydrocarbon phase are implemented. Firstly, there changes the total ionic strength, the simulations with
are soluble hydrocarbon component and CO 2 in water. and without the reactions have different degree
Especially, the dissolution of CO 2 in water influences of wettability modification and produce unequal oil
recovery. Consequently, the study validated the numer-
the aqueous and mineral reactions. The dissolved CO 2
in water controls the pH owing to aqueous reactions, ical model of LSWF process through the simulations of
and the pH of brine affects the mineral reactions. the two coreflooding experiments (Kozaki, 2012).
The previous study of Nghiem et al. (2004) already Using the reported parameters from Kozaki (2012),
implemented these reactions in the GEM software the coreflooding simulation of LSWF carries out the
incorporating the equilibrium of fugacities between history matching process tuning unknown parameters.
aqueous and gaseous phases. Kazemi Nia Korrani The history-matched model accurately reproduces the
et al. (2016) also modeled the reactions of the water- oil recovery as well as the effluent ion concentrations.
soluble hydrocarbon component and CO 2 as well as The study also suggested the other approach to model
the relevant geochemical reactions. Secondly, the wettability modification of LSWF process. The exchange
acidic/basic components in hydrocarbon phase can be reaction of organometallic complex (carboxylic organic
distributed between the aqueous and oleic phases component-divalent cation) by pure cations on the
(Havre, Sjöblom, & Vindstad, 2003). Following the rock, potentially, changes the wettability of rock from
equilibrium relationship of Eq. (3.69), the distribution oil-wet to water-wet (Fig. 3.7). Simplifying the reaction,
of partitioned acids in each phase is determined by the detachment of organometallic complex from the
partition coefficient of Eq. (3.70). The partitioned acid rock surface can be used as the interpolation factor for
in the aqueous phase dissociates in the aqueous phase wettability modification modeling. The study briefly
as shown in Eqs. (3.71) and (3.72). The dissociation explained this approach and performed the hypotheti-
of the partitioned acid is also affected by the pH cal LSWF simulations with the approach of wettability
of brine. modification modeling.