Page 27 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 1 History of Low-Salinity and Smart Waterflood 19

FIG. 1.19 History of oil production rate from a hydraulic unit in the Alaskan oil field. (Credit: From Lager, A.,
Webb, K. J., Collins, I. R., & Richmond, D. M. (2008b). LoSal enhanced oil recovery: Evidence of enhanced oil
recovery at the reservoir scale. Paper presented at the SPE Symposium on improved oil recovery, Tulsa,
Oklahoma, USA, 20e23 April. https://doi.org/10.2118/113976-MS.)

content of clay and 30e45 ft thickness. Firstly, the high- Skrettingland, Holt, Tweheyo, and Skjevrak (2011) re-
salinity water using produced water is injected into the ported the unsuccessful application of LSWF at the
reservoir and water-cut reaches to 95% after about Snorre oil field through experiments and SWCTT. The
6 months. The LSWF commences and total 1.5 PV of Snorre oil field has the two Lunde and Statfjord forma-
low-salinity water is injected for the next 4 months. tions of the late Triassic and early Jurassic. The sandstone
Then, high-salinity waterflood resumes as postflush. reservoir has the temperature of 90 C and total clay con-

The oil rate, water-cut, and ionic composition are moni- tent in the range of 5%e35%. The XRD experiments
tored at the producer. The LSWF increases the oil rate indicate that the primary composition of minerals is
and decreases water-cut with a detection reducing quartz and the remainders are mostly K-feldspar, plagio-
salinity (Fig. 1.20). The water-cut roughly drops from clase, and kaolinite. The formations are classified as
95% to 92%. The incremental oil production is the neutral-wet to weakly water-wet. The oil producer well
0.1 PV of swept zone. These field observations corre- P-07 in Statfjord formation is subject to the SWCTT.
spond to the experimental observations and the SWCTT The synthetic seawater of 34,300 ppm TDS and low-
results of Seccombe et al. (2008). The analysis of water salinity water of 440 ppm TDS are injected through the
chemistry shows that the increasing production of Fe is well. The low-salinity water is made by adding 1%
obtained without any injection of Fe. In addition, the seawater in freshwater. The SWCTTs after seawater injec-
production of Fe increases when the LSWF effect ap- tion and LSWF approximately result in the residual oil
pears. The study related the geochemical role of Fe to saturations of 0.23. There was no reduction of residual
wettability. It explained that the Fe bridges crude oil oil saturation by LSWF compared with the seawater injec-
and kaolinite clay mineral and the LSWF disturbs the tion. These results agree to the laboratory results of
bridge liberating the crude oil from the clay. An addi- LSWF. This study concluded that wetting condition in
tional analysis interpreting tracer data and water chem- the Snorre oil field is sufficiently efficient for seawater in-
istry determines the reduction of residual oil saturation jection and the initial wetting condition is a crucial factor
by 0.13 for tertiary LSWF. for the successful LSWF project.