Low Salinity Flooding in a Selected Carbonate Reservoir: Experimental Approach (original) (raw)
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Low-salinity waterflooding has been used to improve oil recovery for many decades. Several theories regarding the mechanism of low-salinity flooding have been discussed in the literature including interfacial tension reduction, wettability alteration, change in pH value, emulsion formation, and clay migration. This work presents the results of flooding tests on selected carbonate core samples taken from Bu Hasa field in Abu Dhabi using sea water and two field injection waters, Um-Eradhuma (UER) at 197,357 ppm and Simsima at 243,155 ppm. These results were used to evaluate the effects of brine salinity and ionic composition on the possible interactions of limestone rock/ brine/and oil system and to identify the oil recovery mechanism. The field injection waters were diluted to salinities of 5,000 and 1,000 ppm and the optimum salinity was determined and then modified by varying the sulfate and calcium ion concentrations. Wettability alteration was determined by contact angle measurements. Interfacial tension measurements of the studied systems were also performed in an attempt to evaluate the flow mechanism with low-salinity flooding. The experimental results revealed that a significant improvement in the oil recovery can be achieved through alteration of the injection water salinity. Reducing the salinity of UER water from 197,357 to 5,000 ppm resulted in an improvement of oil recovery from 63 to 84.5 % of OOIP and the latter salinity was used to evaluate the impact of changing the sulfate and calcium ion concentrations on oil recovery. Results also indicated that sulfate concentration has a significant effect on the flooding process and that increasing the sulfate concentration beyond some optimum concentration of 46.8 ppm resulted in a negative effect on the flooding process. Contact angle measurements indicated that lowering the solution salinity could shift the wettability of the system towards intermediate wettability levels and that the UER water exhibits higher shift toward intermediate wettability compared to other waters. Results also indicated that there is no clear correlation between the improvements in oil recovery and interfacial tension and the pH of the studied systems. The results of this work are useful for people working in this field.
An Experimental Investigation of Low Salinity Oil Recovery in Carbonate and Sandstone Formation
2015
Water flooding has for a long time been employed to improve oil recovery in many oil fields. Formation damage due to water injection was the main issue of water flooding design process for many years and oil companies conducted different compatibility tests between injection water and formation water to eliminate any possibility of formation damage. In recent years, the results of extensive research work demonstrated that alteration of water salinity concentration and composition improves significantly the ultimate oil recovery of water flooding. Up to date there is no universal agreement among the researchers on the mechanism of low salinity flooding. Different mechanisms are proposed in the literature such as wettabiliy modification, fine migration, interfacial reduction, emulsion, and ionic exchange. In this paper an experimental investigation on the possible mechanism of low salinity flooding was conducted. Contact angle changes as function of time, and low salinity water flood ...
2015
Brine ion improvement and optimization in water flooding is one of the topics which have attracted many researchers in the recent years. Numerous studies have identified Crude Oil/Brine/Rock (COBR) interactions as the main factor contributing to oil recovery factor in both sandstone and carbonate rocks. The current study is a review on previous researches on brine ions and mechanism of Low Salinity Water Injection (LSWI) in Enhanced Oil Recovery (EOR). Results of this literature show that Low Salinity Surfactant Flooding (LSSF) can be introduced as the inter medium method between LSW and surfactant flooding, which includes both of their late benefits (wettability alteration and interfacial tension reduction) simultaneously. Moreover application of software as powerful tools for both simulation and optimization as new cost effective and precise utilization methods have been looked at. In regard with the latest argument two software are introduced; Design of Experiment (DOE) programs which dedicate to LSWI studies as a core medium to simulate LSWI experiments and on the other hand simulation programs to identify the corresponding COBR interactions while LSWI using new software such as UTCHEM software. According to combined results from UTCHEM and experimental tests the main mechanism behind LSWI is wettability alteration to identifying contributors of which special attention is required to determine the main factors involved in, which requires more detailed researches as the actual attributors are not yet known.
Brine Ions and Mechanism of Low Salinity Water Injection in Enhanced Oil Recovery: A Review
Research Journal of Applied Sciences, Engineering and Technology, 2015
Brine ion improvement and optimization in water flooding is one of the topics which have attracted many researchers in the recent years. Numerous studies have identified Crude Oil/Brine/Rock (COBR) interactions as the main factor contributing to oil recovery factor in both sandstone and carbonate rocks. The current study is a review on previous researches on brine ions and mechanism of Low Salinity Water Injection (LSWI) in Enhanced Oil Recovery (EOR). Results of this literature show that Low Salinity Surfactant Flooding (LSSF) can be introduced as the inter medium method between LSW and surfactant flooding, which includes both of their late benefits (wettability alteration and interfacial tension reduction) simultaneously. Moreover application of software as powerful tools for both simulation and optimization as new cost effective and precise utilization methods have been looked at. In regard with the latest argument two software are introduced; Design of Experiment (DOE) programs which dedicate to LSWI studies as a core medium to simulate LSWI experiments and on the other hand simulation programs to identify the corresponding COBR interactions while LSWI using new software such as UTCHEM software. According to combined results from UTCHEM and experimental tests the main mechanism behind LSWI is wettability alteration to identifying contributors of which special attention is required to determine the main factors involved in, which requires more detailed researches as the actual attributors are not yet known.
pH effect on wettability of oil/brine/carbonate system: Implications for low salinity water flooding
Journal of Petroleum Science and Engineering, 2018
Wettability of oil/brine/carbonate system is a critical parameter to govern subsurface multi-phase flow behaviour, thus remaining oil saturation and ultimate oil recovery in carbonate reservoirs. Despite the fact that salinity level, ionic strength, oil composition and rock chemistry (e.g., limestone and dolomite) have been extensively investigated, few work has been done regarding the effect of pH on oil/brine/rock interaction, thus wettability. We thereby measured contact angles at two different pH (pH=3 and 8) in the presence of either 1mol Na 2 SO 4 or 1mol CaCl 2 using a crude oil with acid number of 1.7 and base number of 1.2 mg KOH/g. Moreover, we performed a geochemical modelling study in light of the diffuse double layer to understand how pH controls the number of surface species at interfaces of oil/brine and brine/carbonate. Our results show that pH scales with oil/brine/carbonate wettability, demonstrating that pH is one of the controlling factors to govern the system wettability. Further, our results suggest that pH (6.5-7.5) likely triggers an oil-wet system, which is favourable for low salinity water flooding, but pH<5 usually exhibits a water-wet system, which explains why low salinity effect is not always observed in carbonate reservoirs. This also confirms that CO 2 flooding, carbonated water flooding, and CO 2 huff-and-puff EOR very likely renders a strongly water-wet system due to H + adsorption on the interface of oil/brine and brine/carbonate as a result of CO 2 dissolution.
Journal of Molecular Liquids, 2019
Wettability alteration has been identified as an important mechanism during low salinity water flooding in carbonate reservoirs. Oil composition, in particular, acidic and basic functional groups, plays an important role in regulating wettability. In this paper, we explored the potential of low salinity effect in reservoirs with high acidic components (acid number = 4.0 mg KOH/g and base number = 1.3 mg KOH/g) with a combination of approaches (e.g., contact angle and zeta potential measurements, and surface complexation modeling). We measured the contact angles of oil on calcite surfaces in presence of aqueous ionic solutions at different pH (3 and 8), salinity (0.01 and 1 mol/L), ion type (CaCl 2 and Na 2 SO 4) and temperatures (25-100 o C). Our results show that both salinity and ion type significantly affect contact angle at pH=8. However, at low pH (pH 3), the oil-brine-calcite system becomes strongly water-wet with minor effect from salinity, ion type, and temperature. Lowing salinity drives the zeta potential of both
Experimental study of combined low salinity and surfactant flooding effect on oil recovery
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles
A new generation improved oil recovery methods comes from combining techniques to make the overall process of oil recovery more efficient. One of the most promising methods is combined Low Salinity Surfactant (LSS) flooding. Low salinity brine injection has proven by numerous laboratory core flood experiments to give a moderate increase in oil recovery. Current research shows that this method may be further enhanced by introduction of surfactants optimized for lowsal environment by reducing the interfacial tension. Researchers have suggested different mechanisms in the literature such as pH variation, fines migration, multi-component ionic exchange, interfacial tension reduction and wettability alteration for improved oil recovery during lowsal injection. In this study, surfactant solubility in lowsal brine was examined by bottle test experiments. A series of core displacement experiments was conducted on nine crude oil aged Berea core plugs that were designed to determine the impac...
2017
The effect of injection brine salinity on the displacement efficiency of low water salinity flooding was investigated using sea water at 35,000 ppm, and two field injection waters, namely, Um-Eradhuma (UER) at 171,585 ppm and simsima (SIM) at 243,155 ppm. The salinity of the employed waters was varied from original salinity to 1,000 ppm and used in the displacement of oil in selected core samples. The results of this set of experiments revealed that UER salinity of 5,000 ppm is the optimum system for the candidate reservoir. UER original water and its optimum water were then used in this project as the high and low salinity waters in the CO 2-WAG flooding experiments. Displacement efficiencies were evaluated under three injection modes: carbon dioxide WAG miscible flooding (CO 2-WAG, 1:1, 2:1, and 1:2), continuous CO 2 injection, and waterflood. The WAG performance parameters, such as secondary and tertiary displacement efficiencies, CO 2 flood utilization factor, and CO 2 performance during different WAG flood cycles were determined. To insure miscibility condition between the injected gas and the employed oil, all of the flooding experiments were conducted at 3,200 psia (which is 300 psia above the minimum miscibility pressure of CO 2 and used oil) and 250°F. Experimental results indicated that core length is a critical parameter in determining the optimum WAG process, and that a minimum core length of 29 cm is required to insure the generation of miscibility before breakthrough in CO2-WAG flooding experiments. On the other hand, core length had no effect on the performance of the low salinity flooding experiments. Using single core flooding low salinity CO 2-WAG of 1:2 flooding produced an improvement in the displacement efficiency of 29 % over the high salinity system. Also, composite core flooding experiments showed that the high salinity CO 2-2:1 WAG achieved a displacement efficiency of 98 %. These results indicate that achieving miscibility at the reservoir conditions is the dominant mechanism and that low salinity will have no major effect on the displacement efficiency of CO 2-Miscible WAG flooding. Results also indicate that oil recovery during different CO2-WAG cycles is a function of WAG ratios.
Low Salinity as New Technique of Enhanced Oil Recovery
International Journal of Chemical Engineering and Applications, 2017
Low salinity water flooding is a very promising EOR method in recent years in which chemistry play major role in improving oil recovery. Several studies shown that oil recovery significantly increase by low salinity water flooding (LSWF) in sandstone. However, the mechanisms of oil recovery improvement are still controversial, its considered to be decrease of residual oil saturation and alteration of rock wettability, the solution and surface chemistry as well as rock/fluid interactions have important roles that can be attributed to reservoir minerals being sensitive to small changes in solution properties. This paper provides a comprehensive review of low salinity water flooding. Attempt is made to cover all aspects and features of low salinity water flooding to shed light on critical and challengeable features and clear the gaps and deficiencies of conducted studies. The proposed mechanisms are discussed and their success and failure are explained. Analytical and numerical modeling of low salinity water flooding is presented. Secondary and tertiary low salinity water flooding are compared in the term of additional oil recovered. Surfaces forces and rock/fluid/brine interaction and its relationship to wettability are discussed. Results of combined low salinity and EOR methods are described which includes simultaneous use of low salinity with polymer flooding, surfactant flooding. Accordingly, low salinity water flooding EOR methods have great potential for enhanced oil recovery in the future.
Effect of salinity degree of injected water on oil recovery from carbonate reservoir
Indian Journal of Geo-Marine Sciences, 2019
Water injection is considered the most successful and widespread secondary recovery method. Low salinity water injections is a well-established and proved technique for water flooding application in sandstone rocks to enhance the recovery efficiency; where the water salinity is adapted to a certain degree to extract the highest amount of oil from a reservoir. Reserve-estimation statistics show the significance of oil reserves in carbonate reservoirs, hence this work deals with the carbonate rocks where water flooding may fail due to many reasons, and the most common one is fractures existence in the carbonate rocks. This work applied the water injection for six carbonate (limestone) core samples from Belayim Formation of Middle Miocene age that extracted from an Egyptian offshore oil field in the Gulf of Suez. This carbonate facies is hard, vuggy, fragmented, dolomitic, and highly saturated with oil and considered a good reservoir. Relative permeability test was carried out to inves...