Page 133 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 5 Hybrid CO 2 EOR Using Low-Salinity and Smart Waterflood 125

the production of residual oil is the miscibility effect In the 1960s, it was firstly deployed in K&S project
by CO 2 injection. The low-salinity water boosts the oil by ORCO (Oil Recovery Cooperation) in the
production rate by controlling oil relative permeability. Dewey-Bartlesville Field, Washington County, North-
Further simulations of SWAG using low-salinity water east Oklahoma, for commercial production (Hickok,
validate the synergetic effects of LS-CO 2 EOR. In Christensen, & Ramsay, 1960). Hickok and Ramsay
addition, the fractional flow analysis of SWAG is (1962) reported that CWI produced 43% of additional
performed. The analysis suggests that the SWAG using oil in K&S project and Project 33. A number of studies
low-salinity water is a stable process and reduces the have tried to visualize the CWI phenomenon in glass
solvent addition to achieve an optimal condition. micromodels or investigate the geochemical reactions
Hamouda and Pranoto (2016) numerically investi- associated with CWI process (Kechut, Sohrabi, & Jamio-
gated the LS-CO 2 WAG process in terms of oil production lahmady, 2011; Nunez, Vaz, Koroishi, Vidal Vargas, &
and geochemical analysis. The numerical model of Trevisan, 2017; Sohrabi et al., 2015). These studies
LS-CO 2 WAG process refers the previous study of LSWF confirmed oil swelling, oil viscosity reduction, the
in chalk (Hamouda & Maevskiy, 2014) and applies the generation of CO 2 -enriched gas, and mineral dissolu-
CO 2 injection into the LSWF process. Similar to the tion changing porosity and permeability during CWI.
previous studies (Dang et al., 2013, 2014), the numerical Moreover, the studies (Kechut et al., 2011; Sohrabi
model adapts a few geochemical reactions considering et al., 2015) have conducted coreflooding experiments
CO 2 solubility in water, aqueous reactions associated and numerical simulations to observe whether oil
with the CO 2 dissolution in brine, calcite mineral production is enhanced or not.
reaction, and cation exchange. Because the wettability Recently, the experimental attempts of combination
modification of LSWF mechanism is assumed to follow between CWI and LSWF have been investigated
MIE theory, cation exchange determining the equivalent (Kilybay et al., 2016, 2017). The low salinitye
fraction of Ca 2þ contributes the modification of relative augmented CWI (LS-CWI) is proposed to recovery oil
permeability. A number of low-salinity waters are from oil-wet carbonate reservoir. Kilybay et al. (2016)
prepared by diluting seawater. The LS-CO 2 WAG process carried out the coreflooding of LS-CWI process to
is designed to follow the LSWF. During the LS-CO 2 WAG estimate the EOR potential. The comprehensive
process, an increased oil recovery is observed. The experiments of IFT measurement, phase behavior test
geochemical analysis in terms of the equivalent fraction of microemulsion, NMR test, z-potential measurement,
of Ca 2þ and Na þ is performed. The process of LSWF and ICP analysis investigate the understanding of rock-
increases the equivalent fraction of Ca 2þ and decreases oil-brine interaction during LS-CWI in carbonate rocks.
þ
the equivalent fraction of Na . The more adherence Before the implementation of LS-CWI into coreflood-
of Ca 2þ on the rock surface indicates the wettability ing, the optimized low-salinity water or smart water
modification improving relative permeability. The is evaluated. Five different brines are used such as
succeeding LS-CO 2 WAG additionally increases the deionized water, seawater, low-salinity water as
equivalent fraction of Ca 2þ and decreases the equivalent 10-times-diluted seawater, modified seawater by adding
þ
fraction of Na . Although the increment in the equiva- 4-times sulfate concentration, and low-salinity water by
lent fraction of Ca 2þ is small, it implies the potential to adding 4-times sulfate concentration. The degassed and
achieve additional wettability modification effect by dewatered, and filtered oil samples are obtained from
CO 2 injection. As explained in the previous studies the oil reservoir of Abu Dhabi.
(Dang et al., 2013, 2014), calcite mineral dissolution The microemulsion test using crude oil and brines is
by CO 2 injection could lead to the more cation exchange carried out at different pH conditions. The interface of
and additional wettability modification effect. oil and brine is stable, and no microemulsion is formed

between oil and different brines at 95 C. The IFTs
between the oil and brines of deionized water and
CARBONATED WATER INJECTION seawater are measured by controlling the pH from
The carbonated water injection (CWI) is water-based 1 to 7. At pH around 1, the IFT is reduced down to
CO 2 flood. When carbonated water (CW) comes into 12 dyne/cm for all brines. However, the IFT is
contacting with oil, the CO 2 dissolved in CW transports not enough to provide remarkable change to the
to the oil, resulting in oil viscosity reduction and oil production. The PALS technique measures the
swelling (Sohrabi, Emadi, Farzaneh, & Ireland, 2015). z-potentials of two different systems of brine-rock and
These effects depend on the CO 2 solubility of brine. brine-rock-oil. For the deionized brine, z-potentials
The potential of CWI has been investigated for decades. of both systems show negative values. Basically, the