Page 141 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 6 Hybrid Thermal Recovery Using Low-Salinity and Smart Waterflood 133

simulated to confirm the effectiveness of LS-hot water in- produces more oil recovery by about 0.1. In the compar-
jection after hot water injection. The observation of cor- ison between two coreflooding tests, it is clearly
eflooding corresponds to that of displacement observed that the LS-hot water injection introduces the
experiments using sand packs. The reduction in water- thermal expansion and heavy oil viscosity reduction,
cut and an increase in heavy oil production are also and secures the wettability modification effect of LSWF
observed during tertiary LS-hot water injection. mechanism. To assess the role of Ca 2þ on the perfor-
Based on these experimental observations, this study mance of LS-hot water injection, the third and fourth
summarized the benefits of LS-hot water injection to coreflooding tests are performed by changing connate
enhance the heavy oil production from sandstone reser- water from formation water to modified formation

voirs. The hot water injection can be comparable to the water. The third coreflooding at 70 C and fourth core-
steam injection by reducing the salinity of injecting flooding at 90 C show the higher effluent pH compared

brine in terms of intermediate heavy oil EOR potential to the first and second tests during the injection of low
in the BAW Field. The hybrid technology can introduce salinity water. In LSWF condition, the high content of
the thermal expansion, oil viscosity reduction, and Ca 2þ increases the pH regardless of temperature condi-
wettability modification of LSWF effect. Although the tion. However, LSWF leads to less improvement in oil
replacement of steam injection by LS-hot water injec- recovery for both temperature conditions when connate
tion could save the cost of steam generation and trans- water has higher Ca 2þ concentration. It is determined
portation, it requires the additional cost of the water that the increase in pH is not a necessary sign to improve
supply and desalination treatment. the effect of LSWF in hot and low temperature condi-
Al-Saedi, Flori, and Brady (2018) investigated the tions. In the study, a couple of conclusions are drawn
effect of hot water on the performance of LSWF process for LS-hot water injection. Both the reducing salinity
and, experimentally, quantified the heavy oil production and increasing temperature contribute to the heavy oil
of LS-hot water injection. Target reservoir is the Kansas production in sandstone reservoir. Controlling the
heavy oil reservoir in Midwestern reservoirs. The heavy chemistry of water could solve and supplement the lim-
oil in the field is hardly produced by natural depletion. itations in the hot water injection process.
It has the low temperature condition with high viscosity Studies (Lee, Jeong, & Lee, 2016; Mohammadi, 2017)
of oil. The oil sample has the viscosity of 600 cp at 20 C. have reported the numerical simulations of LS-hot water

The Berea sandstone core, which has permeability of injection for heavy oil recovery. The numerical simula-
about 100 md and porosity of 0.2, is used. The four tion employs the comprehensive geochemical reactions
sets of coreflooding test are carried out with different and temperature-dependent reduction of oil viscosity
temperature conditions (70 and 90 C) and different in the modeling of LS-hot water injection. The LS-hot

connate waters. Formation water has the salinity of water injection is compared to the LSWF in terms of
97,500 ppm TDS, and modified formation water is pre- geochemical reactions and oil viscosity. The wettability
pared by increasing the concentration of Ca 2þ by a factor mechanism of LSWF process is assumed to be attributed
of two. The formation water and modified formation to the cation exchange of Ca 2þ and the assumption is
water are used for the connate water. The low salinity applied to the simulation of LS-hot water injection.
water is manufactured by diluting the formation water The wettability modification is modeled by the modifi-
by a factor of 100. The injection design is set to apply cation of relative permeability. The high temperature
the secondary waterflood injecting formation water condition accelerates the dissolution of carbonate min-
and tertiary LSWF. The slug of secondary or tertiary injec- erals. More dissolution of carbonate minerals generates
2þ
tions is injected as much as 2 PV. the in-situ concentration of Ca , potentially modifying

The first coreflooding is operated at 70 C. The wettability. Therefore, the temperature-dependent
connate water is the formation water. The conventional geochemical reactions of mineral dissolution and cation
waterflood produces the oil recovery of about 0.42 and exchange enhance the wettability modification effect
tertiary LSWF produces the additional oil recovery of during LS-hot water injection compared to the LSWF.
about 0.08. The experimental condition of second The significant oil viscosity reduction also attributes to
coreflooding is the same with the first coreflooding the heavy oil production. Up to date, the numerical sim-
except for the temperature condition. The second core- ulations of hot-LSWI are limited.
flooding is simulated at 90 C to investigate the process The process of hot water injection is competitive in

of hot water injection. The secondary hot water injection relatively less viscous oil on the order of a few hundred
injecting formation brine results in the oil recovery of centipoises in specific conditions. However, the high
about 0.45. The succeeding LS-hot water injection risk of low thermal efficiency is the barrier of hot water