Page 21 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 1 History of Low-Salinity and Smart Waterflood 13

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and SO 4 to adjust the charge density of chalk surface measurement, contact angle measurement, coreflood-
by the adherence of potential-determining ions on the ing, and NMR tests. The IFT measurements are carried
surface modifies wettability of chalk. In addition, out using live oil and the various brines at the reservoir

Mg 2þ with SO 4 2 has a high affinity on the chalk sur- temperature with 212 F. The dilution of seawater
face, and the affinity increases in high temperature con- slightly decreases the IFT, but the reduction of IFT is
dition. Based on these conclusions, this study proposed less than 2 dyne/cm. There is a relatively higher reduc-
the different mechanisms for the wettability alteration tion of IFT when the brine is changed from connate
induced by seawater in low and high temperatures, water to seawater. Though the IFT changes from 40 to
respectively. 33 dyne/cm, the reduction changing fluid/fluid interac-
The upstream research team from Saudi Aramco has tion is not enough to modify wettability. In the contact
initiated a research program called “SmartWater Flood” angle measurements, contact angles are monitored over
to explore the IOR/EOR from carbonates by modifying a period of 2 days. The contact angle for twice-diluted
the brine composition. The research team reported seawater changes from 90 degrees to 80 degrees. When
the comprehensive results of laboratory studies to the twice-diluted seawater is switched to 10-times-
investigate the impact of salinity and ionic composition diluted seawater, the contact angle between the brine
in COBR system. In the study (Yousef, Al-Saleh, and crude oil changes from 80 degrees to 69 degrees.
Al-Kaabi, & Al-Jawfi, 2011), the carbonate cores, which For 20-times- and 100-times-diluted seawaters, there
is composed of 80% calcite, 13% dolomite, 6% anhy- is no more reduction of contact angle. These results
drite, and less than 1% quartz, are subject to the exper- demonstrate the potential of wettability modification
iments. The field connate water with 213,734 ppm TDS toward water-wetness when seawater is diluted by fac-
and seawater with 57,670 ppm TDS are used in these tors of 0.5 and 0.1. These observations lead to the two
experiments. To quantify the impact of ionic composi- sets of coreflood tests injecting various diluted seawa-
tion, the various diluted seawaters by factors of 0.5, ters into connate water-saturated cores. The secondary
0.1, 0.05, and 0.01 are exploited in the comprehensive recovery of seawater and tertiary recovery of the various
experiments. The seawater has more than 10 times diluted seawaters are deployed into cores. Fig. 1.15
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higher concentration of SO 4 over the connate water. illustrates the oil recovery of the first coreflooding

Crude oil has 30 API and total acid number (TAN) with experiment. The seawater injection for secondary recov-
0.25 mg KOH/g oil. This study conducted the IFT ery produces 67% of OOIP. In tertiary mode, the

FIG. 1.15 History of oil recovery and injection rate for the first coreflood experiment. (Credit: From Yousef, A.
A., Al-Saleh, S. H., Al-Kaabi, A., & Al-Jawfi, M. S. (2011). Laboratory investigation of the impact of injection-
water salinity and ionic content on oil recovery from carbonate reservoirs. SPE Reservoir Evaluation and
Engineering, 14(5), 578e593. https://doi.org/10.2118/137634-PA.)