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22 Hybrid Enhanced Oil Recovery using Smart Waterflooding

SWCTT application. The first SWCTT follows the high- from the numerical simulations of SWCTTs and
salinity water injection and provides a baseline of the estimates the residual oil saturation reductions by
residual oil saturation to compare the residual oil satu- LSWF using an analytical method and a direct determi-
ration after LSWF. The second SWCTT aims to monitor nation method. In the Well A, LSWF with twice-diluted
the reduction of residual oil saturation by LSWF. The seawater is numerically determined to reduce residual
LSWF with 2 PV is applied into the Well A, before oil saturation by 0.06e0.07. In the Well B, numerical
the second SWCTT. Using the three-layer tracer flow models and both interpretation methods of SWCTT pre-
simulation method, the tracer data sets from the two dict the reduction up to 0.03 for twice-diluted seawater
SWCTTs indicate that LSWF reduces residual oil satura- injection. For the injection of 10-times-diluted
tion by 0.03. seawater, the analytical method predicts the additional
Previous field trials including log-inject-log and reduction of residual oil saturation by 0.04, but the
SWCTT demonstrate that LSWF sufficiently has poten- direct method calculates the reduction by 0.06. Consid-
tial to reduce residual oil saturation when the sandstone ering the uncertainty of the SWCTT, the numerical
reservoir satisfies some perquisites. simulations of LSWF in the Well B predict the total
reduction of 0.07e0.09. With the clear confirmation
Carbonate Rocks of numerical simulations, the real field trials of SWCTT
Compared with the previous studies of sandstone, to are executed in Well A and Well B. In the real field trials,
the best of our knowledge, only one study published the residual oil saturations are calculated by a history
the field trials of LSWF in carbonate reservoirs. Yousef match method and the analytical method. In the Well
et al. (2012) reported the first field test of LSWF, i.e., A, the tracer results of SWCTT show good quality.
SmartWater, in a carbonate reservoir based on the Both interpretation methods of the analytical and the
experimental observations (Yousef, Al-Saleh, and history match methods using the real tracer results,
Al-Jawfi 2012; Yousef et al. 2011). The previous experi- consistently, show that LSWF of twice-diluted seawater
mental observations concluded that injections of the reduces the residual oil saturation by 0.07, compared
twice-diluted seawater and 10-times-diluted seawater with seawater injection (Fig. 1.21). In addition, the
have EOR potential. Yousef et al. (2012) validated the real field test and the preliminary study of numerical
two types of diluted seawater as the candidate brines simulation show the consistent results in the Well A.
of LSWF through SWCTT. The study reported a prelim- In the Well B, a field implementation of LSWF with
inary study of numerical simulation and a real field twice-diluted seawater lowers the residual oil saturation
implementation. It designed to deploy the SWCTT by 0.03 in the test zone and that with 10-times-diluted
and LSWF in two potential wells, Well A and Well B. seawater additionally decreases the residual oil satura-
Different scenarios of SWCTT were designed for each tion by 0.03. In comparison with the preliminary nu-
well. The test in Well A has a plan with three trials of merical simulation, the real field test shows a different
SWCTT to observe residual oil saturation reduction by reduction of residual oil saturation for the injection of
LSWF with 10-times-diluted seawater. The first trial of 10-times-diluted seawater. This difference is within
SWCTT measures the residual oil saturation after the range of the uncertainty of the implementation of
seawater injection. The second trial confirms the results SWCTT test. This study concluded and demonstrated
of the first SWCTT. The last trial measures the saturation that the field trials of SWCTT agree with experimental
after 10-times-diluted seawater injection. The test in observations and reducing residual oil saturation in car-
Well B is also designed with three trials of SWCTT. bonate reservoirs can be achieved by diluted seawater
The first trial detects the residual oil saturation after injection.
seawater injection. The second one captures residual The extensive LSWF research studies have reported
oil saturation reduction by the twice-diluted seawater various experimental evidences for IOR/EOR and vali-
injection. The third trial has an objective to determine dated the potential to reduce residual oil saturation
the residual oil saturation after LSWF with 10-times- through the field tests. The research studies have formu-
diluted seawater. Firstly, a preliminary study numeri- lated the potential mechanisms of LSWF to explain the
cally simulates and predicts the two different scenarios IOR/EOR observations in sandstone and carbonate res-
of SWCTTs in Well A and Well B using experimental ervoirs. Hence, next chapter discusses the up-to-date
measurements, before real field implementations. The mechanisms proposed in sandstone and carbonate
preliminary study interprets the tracer data obtained reservoirs.