Seawater Depleted in NaCl as a ‘Smarter’ Enhanced Oil Recovery Fluid in Carbonates
Improved oil recovery by using SW depleted in NaCl has also been observed in limestone reservoir cores. Thus, the potential is quite well documented in the lab; it just a question of modifying seawater in an economical way. An increase in oil recovery up to 10 % of OOIP compared with using SW at specific conditions, which already is a very good wettability modifier, is dramatic and should be tested in the field.
Conclusions
Modified seawater, regarding salinity and composition, as wettability modifier has been compared with ordinary seawater during a spontaneous imbibitions process at temperatures between 100°C and 120°C, and the following observations were noted.
Spontaneous Imbibition •
The imbibition rate and ultimate oil recovery increased relative to ordinary seawater when the imbibing seawater was depleted in NaCl. The effect was more significant at high temperatures: about 10 % of OOIP at 120°C.
1.
Strand S, Puntervold T, Austad T, Effect of temperature on enhanced oil recovery from mixed-wet chalk cores by spontaneous imbibition and forced displacement using seawater, Energy & Fuels, 2008;22:3222–5.
2.
Zhang P, Tweheyo MT, Austad T, Wettability alteration and improved oil recovery by spontaneous imbibition of seawater into chalk: Impact of the potential determining ions: Ca2+, Mg2+ and SO42-, Colloids and Surfaces A: Physicochem Eng Aspects, 2007;301:199–208.
3. RezaeiDoust A, Puntervold T, Strand S, Austad T, Smart water • •
The ultimate oil recovery decreased compared with seawater when the concentration of NaCl in the imbibing fluid was increased to four times the concentration in seawater.
When diluting seawater, oil recovery decreased drastically. Oil recovery by seawater diluted to 1,600 ppm at 120°C was in the range of 15 %, while the recovery by ordinary seawater was about 60 % of OOIP. Thus, the wettability alteration is not a low salinity effect.
•
The order of improved water wetness by the different fluids was confirmed by separate chromatographic wettability tests, and the increase in the water-wet fraction after spontaneous imbibition at 120°C was: Dil-SSW10000 <SSW <SSW0NaCl. The initial water-wet fraction was 0.53, which was close to neutral condition, and after imbibitions by SW depleted in NaCl at 110°C, the water-wet fraction increased to 0.82. n
Acknowledgment
The authors thank the University of Stavanger and TOTAL for financial support.
as wettability modifier in carbonate and sandstone: a discussion of similarities/differences in the chemical mechanisms, Energy & Fuels, 2009;23(9):4479–85.
4.
Frykman P, Spatial variability in petrophysical properties in Upper Maastrichtian chalk outcrops at Stevns Klint, Denmark, Marine and Petroleum Geology, 2001;18(10):1041–62.
5.
Røgen B, Fabricius IL, Influence of clay and silica on permeability and capillary entry pressure of chalk reservoirs in the North Sea, Petroleum Geoscience, 2002;8(3):287–93.
6.
Puntervold T, Strand S, Austad T, New method to prepare outcrop chalk cores for wettability and oil recovery studies at low initial water saturation, Energy & Fuels, 2007;21(6):3425–30.
7. 8.
Strand S, Standnes DC, Austad T, New wettability test for chalk based on chromatographic separation of SCN- and SO42-, J Petrol Sci Eng, 2006;52:187–97.
Pierre A, Lamarche JM, Mercier R, Foissy A, Calcium as a potential determining ion in aqueous calcite suspensions, J Dispersion Sci Technol, 1990;11(6):611–35.
Stavanger Norway
EXPLORATION & PRODUCTION – VOLUME 9 ISSUE 2
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