scholarly journals Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

2018 ◽  
Vol 15 (3) ◽  
pp. 564-576 ◽  
Author(s):  
Mohammad Reza Zaeri ◽  
Rohallah Hashemi ◽  
Hamidreza Shahverdi ◽  
Mehdi Sadeghi
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Carbonate Reservoirs ◽  
Spontaneous Imbibition ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water

Successful in the Lab, Not as Effective in the Field? Uncertainties in the Field Observations of Low Salinity Water Flooding in Sandstone and Carbonate Reservoirs-A Critical Analysis

2021 ◽  
Author(s):  
Navpreet Singh ◽  
Hemanta Kumar Sarma
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Experimental Studies ◽  
Carbonate Reservoirs ◽  
Water Flooding ◽  
Water Salinity ◽  
Field Scale ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water

Abstract Low salinity waterflooding has been an area of great interest for researchers for almost over three decades for its perceived "simplicity," cost-effectiveness, and the potential benefits it offers over the other enhanced oil recovery (EOR) techniques. There have been numerous laboratory studies to study the effect of injection water salinity on oil recovery, but there are only a few cases reported worldwide where low salinity water flooding (LSW) has been implemented on a field scale. In this paper, we have summarized the results of our analyses for some of those successful field cases for both sandstone and carbonate reservoirs. Most field cases of LSW worldwide are in sandstone reservoirs. Although there have been a lot of experimental studies on the effect of water salinity on recovery in carbonate reservoirs, only a few cases of field-scale implementation have been reported for the LSW in carbonate reservoirs. The incremental improvement expected from the LSW depends on various factors like the brine composition (injection and formation water), oil composition, pressure, temperature, and rock mineralogy. Therefore, all these factors should be considered, together with some specially designed fit-for-purpose experimental studies need to be performed before implementing the LSW on a field scale. The evidence of the positive effect of LSW at the field scale has mostly been observed from near well-bore well tests and inter-well tests. However, there are a few cases such Powder River Basin in the USA and Bastrykskoye field in Russia, where the operators had unintentionally injected less saline water in the past and were pleasantly surprised when the analyses of the historical data seemed to attribute the enhanced oil recovery due to the lower salinity of the injected water. We have critically analyzed all the major field cases of LSW. Our paper highlights some of the key factors that worked well in the field, which showed a positive impact of LSW and a comparative assessment of the incremental recovery realized from the reservoir visa-a-vis the expectations generated from the laboratory-based experimental studies. It is envisaged that such a comparison could be more meaningful and reliable. Also, it identifies the likely uncertainties (and their sources) associated during the field implementation of LSW.

scholarly journals Efficiency of enhanced oil recovery by injection of low-salinity water in barium-containing carbonate reservoirs

2018 ◽  
Vol 15 (4) ◽  
pp. 772-782 ◽  
Author(s):  
Hyemin Park ◽  
Yongjun Park ◽  
Yeonkyeong Lee ◽  
Wonmo Sung
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Carbonate Reservoirs ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water

Osmosis as Mechanism for Low-Salinity Enhanced Oil Recovery

SPE Journal ◽  
2016 ◽  
Vol 21 (04) ◽  
pp. 1227-1235 ◽  
Author(s):  
K.. Sandengen ◽  
A.. Kristoffersen ◽  
K.. Melhuus ◽  
L. O. Jøsang
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Salinity Gradient ◽  
Spontaneous Imbibition ◽  
Model Systems ◽  
Wettability Alteration ◽  
Connate Water ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water

Summary We believe that osmosis has been overlooked as a possible mechanism for observed low-salinity enhanced-oil-recovery (EOR) effects. Osmosis can occur in an oil/water/rock system when injecting low-salinity water, because the system is full of an excellent semipermeable membrane—the oil itself. In the present work, water transport through oil films was visualized both in 2D micromodels and in sandstone cores imaged in a microcomputed tomography (CT). After treating these model systems with hexamethyldisilazane (HMDS) to render them more oil-wet, water became discontinuous, and it was possible to establish osmotic gradients. Either expansion or contraction of the connate water was observed, depending on the direction of the imposed salinity gradient. Because osmosis could be the underlying mechanism for low-salinity EOR, two changes in research strategy are proposed: Most importantly, the use of spontaneous-imbibition tests as evidence for wettability alteration in low-salinity water should be critically reinvestigated. This is because observed production could have stemmed from “osmotic expansion” of the connate water rather than wettability change. Second, much research focus should be shifted from sandstone reservoirs to fractured oil-wet carbonates. Osmosis potentially yields larger responses for the latter reservoir type, whereas from a mechanistic perspective the reason behind low-salinity EOR functioning in both sandstones and carbonates deserves further attention.

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