Page 10 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

2 Hybrid Enhanced Oil Recovery using Smart Waterflooding

60 6 1

50 5 0.8
Residual oil saturation, % 40 4 3 2 Pressure gradient across core, psi/ in I w-o Wettability index 0.6 High calcium brine

30
Low calcium brine
20

10 1 0.4
Brine Swi
0.2 Symbol
0 0 NaCI CaCI 2 T =26°C T =50°C T =80°C
A
A
A
0 5 10 15 4 0.2 26.4 24.6 27.1
28.4 25.0 25.8
% NaCI 24.7
4 1.0 24 28
26.3
FIG. 1.1 Effects of salinity on the residual oil saturation and 0
0 20 40 60 80 100
pressure gradient. (Credit: From Bernard, G. G. (1967). Effect
of floodwater salinity on recovery of oil from cores containing T A Aging temperature °C
clays. Paper presented at the SPE California Regional FIG. 1.2 Effects of salinity and aging temperature on
Meeting, Los Angeles, California, USA, 26e27 October. wettability index. (Credit: From Jadhunandan, P. P., &
https://doi.org/10.2118/1725-MS.) Morrow, N. R. (1995). Effect of wettability on waterflood
recovery for crude-oil/brine/rock systems. SPE Reservoir
increases the oil recovery and pressure drop across core. Engineering, 10(1), 40e46. https://doi.org/10.2118/22597-PA.)
Another fresh water injection at the same pressure
differential produces no additional oil. The study
concluded that oil recovery increase should be accompa- spontaneous imbibition experiment. The spontaneous
nied with the additional pressure drop, and the imbibition experiments using the crude oils are carried
proposed mechanisms could explain these observations. out by controlling initial water saturation, aging
Extensive research studies have investigated the temperature, and salinity. Results of these experiments
relationship between oil recovery and low salinity in indicate that wettability index increases when initial
terms of wettability. The reservoir wettability is a water saturation increases and aging temperature
complex property to determine multiphase flow in decreases. Another experimental results using the Mou-
porous media and oil recovery of waterflood. Morrow tray crude oil, not ST-86, report that brine composition
(1990) investigated the wettability of crude oil/brine/ and aging temperature change the wettability index
rock (COBR) system and its effect on oil recovery of (Fig. 1.2). In addition, more than 50 coreflooding tests
waterflood. Because the accurate understanding and describe that the close-to-neutral wettability maximizes
duplicating wettability of reservoir rocks are of impor- oil production of waterflood. From these observations,
tance for numerical simulation and experiment of wettability is shown to be sensitive to crude oil type,
waterflood, a series of research studies by Morrow and brine composition, aging temperature, and initial
coworkers have tried to quantify the parameters to saturation. However, this experimental study hardly
control the wettability and oil production of water- reported the effect of brine composition on the wetta-
flood. Jadhunandan and Morrow (1995) reported bility and waterflood recovery. Yildiz and Morrow
dominant parameters relating to the wettability of (1996) investigated the potential of brine composition
COBR system through experiments. The experiments to affect crude oil recovery in coreflooding and sponta-
include wettability index measurements and coreflood- neous imbibition tests. It tested the same crude oil from
ing tests of waterflood. Various brines are formulated Moutray and two different brines. The Brine 1 is made
with NaCl and CaCl 2 and tested in the experiments. up of 4% NaCl and 0.5% CaCl 2 and Brine 2 had
The brines have NaCl from 4% to 6% and CaCl 2 from only 2% CaCl 2 . The experiments investigate various
0.2% to 2%. Crude oils from West Texas (Moutray) combinations for initial formation and injecting brines
and ST-86, and Berea sandstones are used in the exper- using the two types of brine (Brine 1 and Brine 2)
iments. The wettability index of the Berea core samples and examine the secondary or tertiary recoveries of
is determined by a modified Amott method and brine injections. The results of secondary recovery