Page 25 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 1 History of Low-Salinity and Smart Waterflood 17

well initiates and gas chromatography measures the MPL-11) in the targeted hydraulic unit are candidate
unreacted ester, ethanol, and propanol content. During wells and monitored in the test. The unit has natural
the production, the remaining ester in reservoir is depletion production for 4 years. A following water-
delayed because of the partition between the immobile flood, injecting brackish brine with 16,640 ppm TDS,
residual oil and the mobile water. However, the second- increases the oil production of the producer (MPL-07)
ary tracer directly flows back to the well without a delay. from 400 to 1100 bbls/day. After 3 years of the water-
The delay of production of the ester is related to the re- flood, oil production decreases and water-cut increases
sidual oil saturation. Various interpretation methods up to 95%. An additional injection of miscible additive
with the separation between the ester and secondary increases oil production from 200 to 500 bbls/day for a
tracer productions estimate the residual oil saturation. while, but the production rate falls off to 150 bbls/day
McGuire et al. (2005) described the two sets of SWCTTs after a year and a half. To increase the oil production
in the Ivishak sandstone, and each set in the Kuparuk rate and decrease water-cut, the LSWF with 2600 ppm
and Kekiktuk sandstones, respectively. In Prudhoe Bay TDS is performed in the hydraulic unit. The oil produc-
Unit, Kuparuck reservoir in L-122 has the reservoir tem- tion reaches to the maximum rate of 320 bbls/day and

perature of 150 C and the average porosity of 16%. A decreases to 200 bbls/day (Fig. 1.19). Water-cut also
set of two SWCTTs measures the residual oil saturations drops from 92% to 87%. In addition, the injection of
after high-salinity waterflood with 23,000 ppm and low-salinity water shows the constant injectivity indi-
LSWF with 3000 ppm, respectively. According to the re- cating no formation damage due to clay swelling or
sults of SWCTTs (Fig. 1.18), the high-salinity waterflood fines generation. In the analysis of produced water
and LSWF result in the residual oil saturations of from the MPL 07 producer, the Mg 2þ is completely
approximately 0.21 and 0.13, respectively. In the North- removed in the effluent water and the removal is
west Eileen of the Prudhoe Bay Field, the Ivishak Zone 4 regarded as the proof of interaction between the reser-
sand formation has a temperature of 217 F. The two voir rock and injecting brine. Based on the field obser-

SWCTTs in the reservoir show that high-salinity water- vations, a new well is drilled to conduct the SWCTT.
flood with 23,000 ppm approximately remains the The tests are performed injecting the four different
residual oil saturation of 0.19 and LSWF with brines: high-salinity water, produced water from
3000 ppm reduces the residual oil saturation by 0.04. MPL-07, Prine Creek aquifer water, and optimized
The another Kekiktuk reservoir in the Endicott Field low-salinity water in a sequence of decreasing salinity.

has 210 F and the average porosity of 0.24. Two The waterfloods using both high salinity and MPL-07
SWCTTs estimate the residual oil saturations of about produced water, approximately, remain the residual
0.43 after high-salinity waterflood and about 0.34 after oil saturation of 0.3. The injection of aquifer water
LSWF. The last set deploys the three SWCTTs in Ivishak makes the residual oil saturation of 0.2. The injection
Zone 4B formation in the Prudhoe Bay Field. The test of optimized low-salinity water lowers the residual oil
observes the residual oil saturations after injections of saturation by 0.08. The both field tests obviously
high-salinity, intermediate-salinity, and low-salinity confirm the EOR of LSWF and are in line with the
brines. High-salinity waterflood with 22,000 ppm previous experimental observations.
approximately results in the residual oil saturation of The BP has performed more field tests of LSWF. Sec-
0.21. Intermediate-salinity waterflood with 7000 ppm combe, Lager, Webb, Jerauld, and Fueg (2008)
hardly shows any discernible reduction in the residual described the five sets of SWCTTs at Endicott Field.
oil saturation. However, the LSWF recovers additional Because the LSWF is affected by reservoir mineralogy,
oil and reduces the residual oil saturation of 0.04. the study examined the Endicott petrology by SEM
This study clearly concluded that LSWF has the poten- and wireline log. The SEM photomicrograph describes
tial modifying wettability and reducing residual oil that the Kekituk formation at Endicott Field is
saturation, and there is an effective salinity level of composed of seven pore-filling constituents. Primary
5000 ppm TDS or less to observe the potential in sand- constituent is quartz and secondary is kaolinite clay.
stone reservoirs. The remainder less than 1% is attributed to calcite,
The Lager, Webb, Collins, et al. (2008) from BP dolomite, siderite, pyrite, and argillaceous matrix. The
deployed the LSWF at interwell test as well as SWCTT wireline log test assumes that the formation has only
in an Alaskan oil field and confirmed the direct field ev- pure quartz and kaolinite clay, neglecting the remaining
idences for EOR potential. A single hydraulic unit in the constituents. The test estimates the content of kaolinite
field is subject to the interwell test of LSWF. An injector clay in the test zone. This study correlated the concen-
(MPL-16A) and two nearby producers (MPL-07 and tration of kaolinite clay with the enhanced oil recovery