The Effect of Low-salinity Water on Wettability and Oil Recovery by Core Flooding Test: A Case Study in the Shadegan Oil Field

Document Type : Research Paper


Petrolume, Mining And Materials Group, Faculty of Civil and Earth Resources Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran



In most carbonate reservoirs, the amount of oil recycled depends on the spontaneous uptake of brine in the matrix and oil extraction in that matrix towards the cracks. The injection of modified water makes this process possible by changing the wettability of the matrix block towards more water-wet. The rate of wettability change is one of the factors that makes the injection of low-salt water economically. Therefore, this study aims to identify the effect of ion type on the rate of wettability change to modify the composition of the water used for flooding into the reservoir so that the maximum use of this process is to increase oil production from the reservoir. The effect of sodium, magnesium, calcium and sulfate ions on oil recovery from carbonate reservoirs was investigated by a dynamic contact angle test. The results show that increasing the concentration of surfactants such as magnesium, calcium, and sulfate could rise (1) the wettability towards water-wet and (2) the rate of wettability change. In contrast, neutral ions, such as sodium ions, were resulted in a rate reduction in which surface ions change to wettability. Elimination of sodium ions would result in approximately the same amount of change in wettability but in a lesser time from 24 to 2 hrs. The results of the secondary injection showed that although the presence of sodium did not have a significant negative effect on oil recovery, the removal of sodium ions significantly could be improved the sweep efficiency of oil. In modified water, the sodium ion from +0.1 mol to +0.001 magnesium sulfate solution was eliminated. Instead, +0.1 mol sodium sulfate was added to enhance the breakthrough time from 0.31 to 0.43 seconds for injected pore volume. So, the second enhcanced recovery was increased in compare to first EOR.


  1. Austad T (2013) Water-based EOR in carbonates and sandstones: new chemical understanding of the EOR potential using smart water, University of Stavanger, Norway, 301-335.##
  2. Høgnesen E J (2005) EOR in fractured oil-wet chalk, Doctoral thesis, UTNU, Norway. ##
  3. Young Th (1805) An essay on the cohesion of fluids, philosophical transactions of the royal society of London, 95: 65-87. ##
  4. Zhang P, Tweheyo M T, Austad T (2007) 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 Physicochemical and Engineering Aspects, 301: 199–208. ##
  5. Zhengxin T (2005) Oil recovery by spontaneous imbibition from mixed-wet rocks, doctoral thesis, University of Wyoming, USA. ##
  6. Fathi S J, Austad T, Strand S (2012) Water-based enhanced oil recovery (EOR) by “Smart Water” in carbonate reservoirs, Presented at the SPE EOR Conference at Oil and Gas West Asia, Muscat, Oman. ##
  7. Fathi S J, Austad T, Strand S, Puntervold T (2010) Wettability alteration in carbonates: the effect of water-soluble carboxylic acids in crude oil, Energy and Fuels, 24:2514-2979. ##
  8. Ayirala S, Yousef A (2014) Injection water chemistry requirement guidelines for IOR/EOR, presented at the SPE Improved Oil Recovery Symposium, Tulsa, Oklahoma, USA. ##
  9. Shojaei M J, Ghazanfari M H, Masihi M (2015) Relative permeability and capillary pressure curves for low salinity water flooding in sandstone rocks, Natural Gas Science and Engineering, 25:30-38. ##
  10. Safavi M S, Masihi M, Safekordi A A, Ayatollahi S, Sadeghnejad S (2020) Effect of SO4−2 ion exchanges and initial water saturation on low salinity water flooding (LSWF) in the dolomite reservoir rocks, Dispersion Science and Technology, 41: 841-855. ##
  11. Siadatifar SE, Fatemi M, and Masihi M (2021) Pore scale visualization of fluid-fluid and rock-fluid interactions during low-salinity waterflooding in carbonate and sandstone representing micromodels, Petroleum Science and Engineering, 198: 108156. ##
  12. Kumar S, Burukhin A A, Cheremisin A N, Grishin P A (2020) Wettability of carbonate reservoirs: effects of fluid and aging, presented at the SPE Russian Petroleum Technology Conference, Virtual, OnePetro. ##
  13. Standnes D C (2001) Enhanced oil recovery from oil-wet carbonate rock by spontaneous imbibition of aqueous surfactant solutions, University Publication, UTNU, Norway. ##
  14. Zhang P, Austad T (2006) Wettability and oil recovery from carbonates: Effects of temperature and potential determining ions, Colloids and Surfaces Physicochemical and Engineering Aspects, 279: 179–187. ##
  15. RezaeiDoust A, Puntervold T, Strand S, and Austad T (2009) Smart water as wettability modifier in
  16. carbonate and sandstone, Energy Fuels, 23: 4479–4485. ##
  17. Young, T (1805) An essay on the cohesion of fluids, Philosophical Transactions of the Royal Society of London, 95: 65-87. ##
  18. Høgnesen E J (2005) EOR in fractured oil-wet chalk”, Doctoral thesis, Of Petroleum Engineering, UTNU, Norway. ##
  19. Al-Shalabi E W, Sepehrnoori K Y, Delshad M (2013) Mechanisms behind low salinity water flooding in carbonate reservoirs, presented at the SPE Western Regional and AAPG Pacific Section Meeting 2013 Joint Technical Conference, California, USA. ##