Vol. 6, Issue 2 (2018)
Potential evaluation of low salinity water flooding for improved oil recovery in carbonate reservoirs
Author(s): Amin Ahmadi and Mirhasan Moosavi
Abstract: Flooding by low salinity water is a promising technology for improving oil recovery (IOR). However, this method is an efficient method for many sandstone reservoirs, the potential for low salt water injection in carbonate reservoirs is still not well established. Therefore, the purpose of this study is to investigate the improvement of oil recovery by low water salting in carbonate reservoirs by water injection in existing cores. Totally four flooding tests were conducted on three limestone cores(A,B,C ) and one chalk core( D), to evaluate the low salinity effect due to presence of anhydrite and different temperature. The concentration of SO42- is one of the key factors determining the wetting properties. It is stated that different parameters such as salinity and composition of initial formation brine are able to affect dissolution of CaSO4.Observing traces of SO42- during core cleaning in effluent of all limestone cores, indicate that the increased oil recovery with low salinity brine could be result of dissolution of anhydrite. Thus, in both cores A and B, the enhanced recovery about 4%, by switching the brine from FW to Diluted FW is due to low salinity and temperature effect on dissolution of anhydrate. The dissolution of anhydrite normally increases as the temperature decreases. We observed also an increased recovery for core C, when switching from SW to diluted SW, even the core was saturated and aged with a crude oil with AN=0.08. The core with low acid number tends to be more water-wet and it has a lower potential of increased recovery. Lowering the salinity of injection brine increases the reactivity of the surface’s active ions SO42- and Ca2+. The dissolution of anhydrite takes place in the injection front. SO42-, which is the catalyst for wettability alteration process are always present in the injection front in a viscous flooding process. A tertiary low salinity flooding was not to change the wetting condition of the cleaned chalk that did not contain any anhydrite. Thus, the recovery did not change. We should note that the low salinity effect is only be observed in the carbonate rock containing a mineral that can release sulfate ions.
Pages: 545-549 | 838 Views 62 Downloads
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How to cite this article:
Amin Ahmadi, Mirhasan Moosavi. Potential evaluation of low salinity water flooding for improved oil recovery in carbonate reservoirs. Int J Chem Stud 2018;6(2):545-549.
