Page 22 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

14 Hybrid Enhanced Oil Recovery using Smart Waterflooding

injections of twice-diluted, 10-times-diluted, and secondary mode, smart waterflood injecting 10-times-
20-times-diluted seawaters recover the additional oil diluted water improves the oil recovery by 10%
of 6.99%, 9.12%, and 1.63%, respectively. The last compared with the secondary injection of seawater.
injection of 100-times-diluted seawater provides negli- These results confirm the potential of smart waterflood
gible improvement of oil production. The second core- for secondary recovery as well as tertiary recovery. This
flooding experiment also reports the increasing oil study also investigated the temperature effect on the
recovery for tertiary recoveries using twice-diluted, wettability modification of smart waterflood and
10-times-diluted, and 20-times-diluted seawaters. The described the roles of the temperature. The new experi-
tertiary injection of 100-times-diluted seawater is also ment using a core, which has low temperature with

ineffective for improving oil recovery. These observa- 135 F, is carried out. The experiments are compared
tions from two sets of coreflooding experiments with the high-temperature experiments of Yousef et al.
confirm and validate the potential of various diluted (2011). The experimental temperature of the Yousef

seawater injections for EOR. The NMR experiments et al. (2011) is 212 F. Firstly, z-potential measurement
measure the distribution of T 2 values, which indicates using diluted seawaters describes that higher tempera-
the pore size distribution in carbonate rocks. The ture condition shifts the surface charge of carbonate
NMR tests investigate the cores, which are saturated rock toward negative, potentially releasing the adsorbed
with connate water or used in the previous coreflooding carboxylic components of oil from a carbonate rock sur-
experiments. In the results of NMR tests, core saturated face. Secondly, it is explained that temperature-
with connate water is determined to have macropore dependent anhydrite dissolution influences the ionic
and micropore distributions. In the NMR tests using composition of initial formation brine. The sensitivity
the core from the first coreflooding experiment, it is of anhydrite dissolution to temperature changes the
observed that seawater injection changes the pore distri- concentrations of SO 4 2 as well as Ca 2þ in initial for-
butions in the core. The results are explained that the mation brine. Generally, anhydrite shows the more
connectivity between macropore and micropore is dissolution with a decreasing temperature and the
enhanced because of the injection of various diluted anhydrate dissolution produces Ca 2þ and SO 4 2 . The
seawaters. Another NMR experiments measure the dis- higher concentration of SO 4 2 in low temperature
tribution of T 2 values of two cores, before and after condition is confirmed. In terms of the other
cleaning process. The negligible change on distribution potential-determining ions, the formation brine in
of T 2 values is observed. This observation clearly indi- high temperature has the lower concentration of Ca 2þ
cates that the cleaning process has a negligible effect and higher concentration of Mg 2þ compared with the
on T 2 values of NMR. Theses NMR tests prove that the brine in low temperature condition. It is explained
significant change of T 2 values is attributed to the ionic that the concentrations of Ca 2þ and Mg 2þ are deter-
composition of water and salinity and ionic composi- mined by the relative affinities of cations on the rock
tion of the water affects the carbonate rock surface. surface. The activity of Mg 2þ with rock surface increases
This study concluded that injections of various diluted in high temperature and the Mg 2þ substitutes the Ca 2þ
versions of seawater have the potential to impact the onto the carbonate rock surface. The study concluded
rock-fluid interactions and to alter surface charges of that the anhydrite dissolution and the substitution
carbonate rocks. Therefore, the alteration of the surface result in the different ionic compositions of the forma-
charge modifies the wettability of a carbonate rock and tion brine according to the temperature.
enhances oil production from carbonate rocks. Alotaibi and Yousef (2017) exploited an advanced
Yousef, Al-Saleh, and Al-Jawfi (2012) validated the technology to measure the surface charges of carbonate
previous study of Yousef et al. (2011) and evaluated and crude oil at different ionic composition and tem-
the potential of the smart waterflood as secondary perature conditions. The advanced technique of
recovery. In addition, they configured the impact of phase-analysis light scattering (z-PALS) could measure
temperature on the wettability modification during the electrophoretic mobility of charged, colloidal sus-
smart waterflood. The carbonate core is determined to pensions, and oil droplets. In this study, more attention
be composed of 85% calcite, 12% dolomite, and 3% is given to the analysis of how cations and anions, in the
anhydrite from an XRD analysis. In the previous equivalent salinity condition, impact on crude oil and
coreflood test of tertiary mode, the injections of twice- carbonate rock, respectively. The study examined the
diluted, 10-times-diluted, and 100-times-diluted sea- various brines of NaCl, CaCl 2 , MgCl 2 ,Na 2 SO 4 , smart
waters recover the additional oil recovery up to 9% water, key ions, and deionized water. Except for brine
over the secondary injection of seawater. In the test of of deionized water, all brines have the equivalent TDS