Page 108 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

100 Hybrid Enhanced Oil Recovery using Smart Waterflooding

simulation of LSWF process, the modification of rela-
tive permeability is a function of the cation exchange.
For the simulation of hybrid LSSF, another approach
of modification of relative permeability is proposed as
a function of both cation exchange and IFT reduction
(Fig. 4.32). This study successfully validated the numer-
ical models of both LSWF and LSSF using the history-
matching process based on the experimental study
(Alagic & Skauge, 2010).

ALKALINE FLOOD
Backgrounds of Alkaline Flood
The knowledge of mechanisms and properties of alka-
line flood would assist the understanding of low
salinityeaugmented alkaline flood or low salinitye
augmented other chemical EOR. Before the description
of low salinityeaugmented alkaline flood, the key fea-
tures of alkaline flood are briefly summarized. Detailed
discussion can be found in the references (Lake, 1989;
Sheng, 2011). The alkaline flood, i.e., caustic flood,
used the in situ surfactant generation and emulsifica-
tion to enhance oil recovery and also supports the other
chemical EOR processes such as polymer flood and/or
surfactant flood. The chemicals such as sodium carbon-
ate (Na 2 CO 3 ) and sodium hydroxide (NaOH) are the
FIG. 4.30 Distribution of remaining oil in oil-wet pore (A) common alkali agents. Other types of alkali chemicals
before coreflooding and after (B) waterflood and (C) low- and organic alkali are also used to avoid precipitation
salinity surfactant flood. (Credit: From Mirchi, V. (2018). Pore- problem. In alkali flood, the chemical reaction between
scale investigation of the effect of surfactant on fluid alkali chemicals and organic acids of crude oil generates
occupancies during low-salinity waterflooding in carbonates. in situ surfactants, i.e., soap, reducing IFT. The common
Paper presented at the SPE Annual technical Conference and alkali agents of NaOH and Na 2 CO 3 dissociate, respec-
exhibition, Dallas, Texas, USA, 24e26 September. https:// tively. Although both alkali agents yield OH control-

doi.org/10.2118/194045-STU.) ling pH, Na 2 CO 3 requires the hydrolysis reactions
Eqs. (4.19e4.21).
simulation matches the experimental data of core-
þ
flooding including oil recovery, pressure gradient, NaOH % Na þ OH (4.19)
and effluent ion concentration. Simulations of LSWF
Na 2 CO 3 % 2Na þ CO 2 (4.20)
þ
and LSSF successfully reproduce the historical data of 3

experiments of LSWF and LSSF. CO 2 þ H 2 O % HCO þ OH (4.21)
3 3
Dang, Nghiem, Fedutenko, et al. (2018) developed
three-dimensional interpolation approach to model The alkaline reacts with the crude oil formulating the
the modification of relative permeability considering in situ soap and emulsification. In addition, the ionic
both mechanisms of LSWF and surfactant flood. The strength and pH of solution influence the reactions to
study also incorporated the modeling of comprehensive form the in situ soap and emulsification.
geochemistry, which is a crucial factor for the LSWF Firstly, the in situ soap generation is described.
mechanism, and IFT reduction using the solubilization When the injected alkali chemicals contact crude oil,
ratio and Huh’s equation (Huh, 1979). In comparison saponifiable components, i.e., naphthenic acids, of
with Tavassoli et al. (2016), Dang, Nghiem, Fedutenko, crude oil react with the alkali component. The majority
et al. (2018) used the cation exchange, not total ionic of naphthenic acids represent the mixture of cyclopentyl
strength, on the clay to simulate the wettability modifi- and cyclohexyl carboxylic acids, which approximately
cation of LSWF in sandstone reservoirs and IFT reduc- have molecular weight of 120 to well over 700. The
tion to simulate the mechanisms of surfactant. For the simplified form of alkali-crude oil chemistry is