1887

Abstract

Summary

A laboratory study was performed to evaluate the possibility of performing a low salinity waterflood in an offshore carbonate reservoir using its rock and fluid samples. A series of spontaneous imbibition and core flood tests were conducted and both tests confirmed the incremental oil recoveries when the composition of the injection brine was diluted and modified.

During the core preparation stage, three uncertainties were identified; the core cleaning procedure, the aging time and the reservoir heterogeneity. First, a core is conventionally cleaned with polar solvents. However, a new core cleaning procedure called the “mild cleaning” has been proposed by Austad, which recommends the use of non-polar solvents. In our laboratory studies, the similar core samples were cleaned by the two different techniques and subsequently the spontaneous imbibition test results were compared. It was found that the low salinity effect was confirmed regardless of the core cleaning procedure. Second, the wettability distribution is not clear in this field. To account for this, the core aging time was varied from eight weeks (more oil-wet) to no-aging (more water-wet). The similar cores were aged for different time and subsequently the spontaneous imbibition test results were compared. It was found that the low salinity effect was confirmed regardless of the aging time, although the core samples with longer aging time showed lower oil recoveries. And third, since the reservoir is heterogeneous, the above sensitivity investigations covered a wide range of rock types within the production intervals. It was found that all rock types showed the low salinity effect.

In addition to the above investigations, a number of water recipes were tested. It was found that the sea water performed better than the formation water, while the diluted sea water performed better than the sea water. The effect of sulfate ions was also investigated. Some core plugs showed the low salinity effect when the concentration of the sulfate ion was spiked, while other core plugs did not respond. The effect of sulfate ions therefore, needs to be further investigated in this field.

Based on the results from the zeta-potential and the contact angle measurements, the low salinity effect in this reservoir was considered to be due to a change in the surface-charge and the wettability, which is consistent with the mechanism proposed by Austad. The conclusion of this laboratory study highlighted the possibility of applying the low salinity waterflood in this field.

Loading

Article metrics loading...

/content/papers/10.3997/2214-4609.201700266
2017-04-24
2021-01-27
Loading full text...

Full text loading...

References

  1. Austad, T., Strand, S., and Puntervold, T.
    [2009] Is wettability alteration of carbonates by sea water caused by rock dissolution?, International Symposium of the Society of Core Analysis, Noordijk, The Netherlands, SCA 2009-43.
    [Google Scholar]
  2. Austad, T.
    [2013] Water-based EOR in carbonates and sandstones: New chemical understanding of the EOR potential using “Smart Water”, Chapter 13, Enhanced Oil Recovery Field Case Studies, Massachusetts, USA, Elsevier.
    [Google Scholar]
  3. Fathi, S., Strand, S., and Austad, T.
    [2011] Water-Based Enhanced Oil Recovery (EOR) by “Smart Water”: Optimal Ionic Composition for EOR in Carbonates, Energy Fuels, 2011, 25 (11), pp 5173–5179, DOI: 10.1021/ef201019k.
    https://doi.org/10.1021/ef201019k [Google Scholar]
  4. Fathi, S, Austad, T, and Strand, S.
    [2010] “Smart Water” as a Wettability Modifier in Chalk: The Effect of Salinity and Ionic Composition, Energy Fuels, 2010, 24 (4), pp 2514–2519, DOI: 10.1021/ef901304m.
    https://doi.org/10.1021/ef901304m [Google Scholar]
  5. Masalmeh, S. K., Sorop, T., Suijkerbuijk, B. M. J. M., Vermolen, E. C. M., Douma, S., van del Linde, H. A., & Pieterse, S. G. J.
    [2014] Low Salinity Flooding: Experimental Evaluation and Numerical Interpretation. International Petroleum Technology Conference. doi:10.2523/IPTC‑17558‑MS.
    https://doi.org/10.2523/IPTC-17558-MS [Google Scholar]
  6. Shariatpanahi, S., Strand, S., and Austad, T.
    [2010] Evaluation of Water-Based Enhanced Oil Recovery (EOR) by Wettability Alteration in a Low-Permeable Fractured Limestone Oil Reservoir, Energy Fuels, 2010, 24 (11), pp 5997–6008, DOI: 10.1021/ef100837v.
    https://doi.org/10.1021/ef100837v [Google Scholar]
  7. Strand, S., Hognesen, E., and Austad, T.
    [2005] Wettability alteration of carbonates—Effects of potential determining ions (Ca2+ and  SO42−) and temperature, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 275, Issues 1–3, 1 March 2006, Pages 1–10, http://dx.doi.org/10.1016/j.colsurfa.2005.10.061.
    [Google Scholar]
  8. Zhang, P. and Austad, T.
    [2006] Wettability and oil recovery from carbonates: Effects of temperature and potential determining ions, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 279, Issues 1–3, 15 May 2006, Pages 179–187, http://dx.doi.org/10.1016/j.colsurfa.2006.01.009.
    [Google Scholar]
http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609.201700266
Loading
/content/papers/10.3997/2214-4609.201700266
Loading

Data & Media loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error