scholarly journals Sequential injection mode of high-salinity/low-salinity water in sandstone reservoirs: oil recovery and surface reactivity tests

2018 ◽  
Vol 9 (1) ◽  
pp. 261-270 ◽  
Author(s):  
Hasan N. Al-Saedi ◽  
Ali K. Alhuraishawy ◽  
Ralph Flori ◽  
Patrick V. Brady
Keyword(s):  
Oil Recovery ◽  
High Salinity ◽  
Surface Reactivity ◽  
Sequential Injection ◽  
Injection Mode ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water ◽  
Sandstone Reservoirs

Enhancing Heavy-Oil-Recovery Efficiency by Combining Low-Salinity-Water and Polymer Flooding

SPE Journal ◽  
2020 ◽  
pp. 1-17
Author(s):  
Yang Zhao ◽  
Shize Yin ◽  
Randall S. Seright ◽  
Samson Ning ◽  
Yin Zhang ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
High Salinity ◽  
Polymer Flooding ◽  
Heavy Oil Recovery ◽  
Sweep Efficiency ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water ◽  
Increased Oil Recovery

Summary Combining low-salinity-water (LSW) and polymer flooding was proposed to unlock the tremendous heavy-oil resources on the Alaska North Slope (ANS). The synergy of LSW and polymer flooding was demonstrated through coreflooding experiments at various conditions. The results indicate that the high-salinity polymer (HSP) (salinity = 27,500 ppm) requires nearly two-thirds more polymer than the low-salinity polymer (LSP) (salinity = 2,500 ppm) to achieve the target viscosity at the condition of this study. Additional oil was recovered from LSW flooding after extensive high-salinity-water (HSW) flooding [3 to 9% of original oil in place (OOIP)]. LSW flooding performed in secondary mode achieved higher recovery than that in tertiary mode. Also, the occurrence of water breakthrough can be delayed in the LSW flooding compared with the HSW flooding. Strikingly, after extensive LSW flooding and HSP flooding, incremental oil recovery (approximately 8% of OOIP) was still achieved by LSP flooding with the same viscosity as the HSP. The pH increase of the effluent during LSW/LSP flooding was significantly greater than that during HSW/HSP flooding, indicating the presence of the low-salinity effect (LSE). The residual-oil-saturation (Sor) reduction induced by the LSE in the area unswept during the LSW flooding (mainly smaller pores) would contribute to the increased oil recovery. LSP flooding performed directly after waterflooding recovered more incremental oil (approximately 10% of OOIP) compared with HSP flooding performed in the same scheme. Apart from the improved sweep efficiency by polymer, the low-salinity-induced Sor reduction also would contribute to the increased oil recovery by the LSP. A nearly 2-year pilot test in the Milne Point Field on the ANS has shown impressive success of the proposed hybrid enhanced-oil-recovery (EOR) process: water-cut reduction (70 to less than 15%), increasing oil rate, and no polymer breakthrough so far. This work has demonstrated the remarkable economical and technical benefits of combining LSW and polymer flooding in enhancing heavy-oil recovery.

The Decisive Role of Microdispersion Formation in Improved Oil Recovery by Low-Salinity-Water Injection in Sandstone Formations

SPE Journal ◽  
2019 ◽  
Vol 24 (06) ◽  
pp. 2859-2873 ◽  
Author(s):  
Pedram Mahzari ◽  
Mehran Sohrabi ◽  
Juliana M. Façanha
Keyword(s):  
Crude Oil ◽  
Oil Recovery ◽  
High Salinity ◽  
Quartz Substrate ◽  
Water Injection ◽  
Improved Oil Recovery ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water ◽  
Low Salinity Water Injection

Summary Efficiency of low–salinity–water injection primarily depends on oil/brine/rock interactions. Microdispersion formation (as the dominant interfacial interaction between oil and low–salinity water) is one of the mechanisms proposed for the reported additional oil recovery by low–salinity–water injection. Using similar rock and brines, here in this work, different crude–oil samples were selected to examine the relationship between crude–oil potency to form microdispersions and improved oil recovery (IOR) by low–salinity–water injection in sandstone cores. First, the potential of the crude–oil samples to form microdispersions was measured; next, coreflood tests were performed to evaluate the performance of low–salinity–water injection in tertiary mode. Sandstone core plugs taken from a whole reservoir core were used for the experiments. The tests started with spontaneous imbibition followed by forced imbibition of high–salinity brine. Low–salinity brine was then injected in tertiary mode. The oil–recovery profiles and compositions of the produced brine were measured to investigate the IOR benefits as well as the geochemical interactions. The results demonstrate that the ratio of the microdispersion quantity to bond water is the main factor controlling the effectiveness of low–salinity–water injection. In general, a monotonic trend was observed between incremental oil recovery and the microdispersion ratio of the different crude–oil samples. In addition, it can be inferred from the results that geochemical interactions (pH and ionic interactions) would be mainly controlled by the rock's initial wettability, and also that these processes could not affect the additional oil recovery by low-salinity-water injection. To further verify the observations of geochemical interactions, a novel experiment was designed and performed on a quartz substrate to investigate the ionic interactions on the film of water between an oil droplet and a flat quartz substrate, when the high–salinity brine was replaced with the low–salinity brine. The results of the flat–substrate test indicated that the water film beneath the oil could not interact with the surrounding brine, which is in line with the results of the core tests.

scholarly journals Effect of Electrokinetics and Thermodynamic Equilibrium on Low-Salinity Water Flooding for Enhanced Oil Recovery in Sandstone Reservoirs

ACS Omega ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 3727-3735
Author(s):  
Yogarajah Elakneswaran ◽  
Amir Ubaidah ◽  
Miku Takeya ◽  
Mai Shimokawara ◽  
Hirofumi Okano
Keyword(s):  
Enhanced Oil Recovery ◽  
Thermodynamic Equilibrium ◽  
Oil Recovery ◽  
Water Flooding ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water ◽  
Sandstone Reservoirs

Double-Layer Expansion: Is It a Primary Mechanism of Improved Oil Recovery by Low-Salinity Waterflooding?

2014 ◽  
Vol 17 (01) ◽  
pp. 49-59 ◽  
Author(s):  
Ramez A. Nasralla ◽  
Hisham A. Nasr-El-Din
Keyword(s):  
Double Layer ◽  
Oil Recovery ◽  
High Salinity ◽  
Improved Oil Recovery ◽  
Low Salinity ◽  
Ph Values ◽  
Low Salinity Water ◽  
Primary Mechanism ◽  
Low Salinity Waterflooding ◽  
Salinity Water

Summary Literature review shows that improved oil recovery (IOR) by low-salinity waterflooding could be attributed to several mechanisms, such as sweep-efficiency improvement, interfacial-tension (IFT) reduction, multicomponent ionic exchange, and electrical-double-layer (EDL) expansion. Although these mechanisms might contribute to IOR by low-salinity water, they may not be the primary mechanism. Therefore, the main objective of this study is to investigate if the mechanism of EDL expansion could be the principal reason for IOR during low-salinity waterflooding. Low-salinity water results in a thicker EDL when compared to high-salinity water, so we tried to eliminate the effect of low-salinity brines on double-layer expansion to show to what extent IOR is related to EDL expansion caused by low-salinity water. The double-layer expansion is dependent on the electric surface charge, which is a function of the pH of brine; therefore, the pH levels of low-salinity brines were decreased in this study to provide low-salinity brines that can produce a thinner EDL, similar to high-salinity brines. ζ-potential measurements were performed on both rock/brine and oil/brine interfaces to demonstrate the effect of brine pH and salinity on EDL. Contact angle and coreflood experiments were conducted to test different brine salinities at different pH values, which could assess the effect of water salinity and pH on rock wettability and oil recovery, and hence involvement of EDL expansion in the IOR process. ζ-potential results in this study showed that decreasing the pH of low-salinity brines makes the electrical charges at both oil/brine and brine/rock interfaces slightly negative, which reduces the double-layer expansion caused by low-salinity brine. As a result, the rock becomes more oil-wet, which was confirmed by contact-angle measurements. Moreover, coreflood experiments indicated that injecting low-salinity brine at lower pH values recovered smaller amounts of oil when compared to the original pH because of the elimination of the low-salinity-water effect on the thickness of the double layer. In conclusion, this study demonstrates that expansion of the double layer is a dominant mechanism of oil-recovery improvement by low-salinity waterflooding.

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