Search

Gas-wetting alteration is a versatile and effective approach for alleviating liquid-blockage that occurs when the wellbore pressure of a gas-condensate reservoir drops below the dew point. Fluorochemicals are of growing interest in gas-wetting alteration because of their high density of fluorine groups and thermal stability, which can change the reservoir wettability into more favorable conditions for liquids. This review aims to integrate the overlapping research between the current knowledge in organic chemistry and enhanced oil and gas recovery. The difference between wettability alteration and gas-wetting alteration is illustrated, and the methods used to evaluate gas-wetting are summarized. Recent advances in the applications of fluorochemicals for gas-wetting alteration are highlighted. The mechanisms of self-assembling adsorption layers formed by fluorochemicals with different surface morphologies are also reviewed. The factors that affect the gas-wetting performance of fluorochemicals are summarized. Meanwhile, the impacts of gas-wetting alteration on the migration of fluids in the pore throat are elaborated. Furthermore, the Wenzel and Cassie-Baxter theories are often used to describe the wettability model, but they are limited in reflecting the wetting regime of the gas-wetting surface; therefore, a wettability model for gas-wetting is discussed. Considering the promising prospects of gas-wetting alteration, this study is expected to provide insights into the relevance of gas-wetting, surface morphology and fluorochemicals, further exploring the mechanism of flow efficiency improvement of fluids in unconventional oil and gas reservoirs.

It is well-known that shale gas production is affected by the wettability of the reservoir. In this work, two gas-wetting alteration agents were synthesized and characterized by 1H NMR and FTIR. To evaluate the effect of the gas-wetting alteration agents on the shale wettability, the contact angle for droplets on the shale surface was detected, and the results showed that the contact angles of water and n-hexadecane increased from 36° and 0° to 119° and 88° after treatment with sodium [N-propyl-N-(perfluorooctanoyl)amino]acetate (SCF-102), while the contact angles increased to 122° and 110°, respectively, after treatment with sodium [N-[[N-(perfluorooctanoyl)amino]ethyl]amino]propionate (SCF-113). The surface free energy rapidly decreased from the primeval 72 to 10.3 and 6.8 mN/m at equal concentration. These values agreed with the results of spontaneous imbibition, the capillary tube rise test, and the fluid flow test. Additionally, the analysis with energy dispersive spectroscopy and scanning electron m...

Eliminating the adverse environmental impact of chemical dispersants for oil spill has been a significant challenge since decades ago. Here, we prepared an effective and environmentally-friend dispersant with stable emulsifying capacity by the soybean lecithin and Tween 80. The mean droplet diameters of emulsions prepared by decane decreased from 11.3 to 4.1 μm, the emulsification index of emulsion climbed from 0 to 22.0% by 0.5 wt% dispersant. This dispersant exhibits favorable emulsifying capacity when the temperature ranges from 10 to 40 °C, pH within 5–7, and the concentration of inorganic cation is 30000 mg/L. Fluorescence microscopy analysis, FTIR, and the interfacial tension meter were employed to investigate the interaction between the soybean lecithin and Tween 80, a clear redshift of the hydroxyl group on the lecithin/Tween 80 dispersant and the detected surfactants over the oil-water interface confirm that there exists a synergy between the lecithin and Tween 80 due to the electrostatic attractions, which tremendously contribute to the reduction in the interfacial tension between water and oil. To further understand the influence of the dispersant on the oil hydrocarbon concentration in the water column, visualization simulation with the varying depths were performed. The results showed that the oil hydrocarbon concentration in the water column bottom was proportional to the addition of the dispersant, which facilitates spilled oil dispersing into smaller droplets, accelerates the biodegradation process. Hence, the lecithin/Tween 80 dispersant can be perceived as a promising alternative for oil spill remediation.

To investigate the mechanisms of enhancing oil recovery and the flow behaviors of foamed gel in porous media, foamed gels with characteristics of excellent strength and viscosity were prepared with polymer, crosslinking agent, foam agent, and formation water. The breakthrough-vacuum method and a rotary viscometer were used to evaluate the strength and viscosity of foamed gel. Coreflooding and pore-level visualization experiments were performed in heterogeneous reservoir models. Laboratory results illustrate that high strength and viscosity of foamed gel can be prepared by 0.15% NJ-8, 0.2% polyacrylamide solution, and 1.5% foaming agent. The strength and viscosity of the foamed gel reached 0.06 MPa and 10,000 MPa · s, respectively. The results of coreflooding experiments in heterogeneous cores show that oil recovery can be improved by approximately 36.9% after injecting 0.3 pore volume of the foamed gel, and enhanced oil recovery is mainly attributed to the improving sweep efficiency of mid- to low-permeab...

Due to the significant difference of water-in-oil emulsion and oil-in-water emulsion in viscosity, conductivity, rheology, thermal resistance, emulsion system has been widely used in the development of oil fields. The reversible phase inversion technique can enhance the performance of emulsified working liquids during the transportation of fluids in porous media. The objective of this study is to study the preparation and the application of the reversible emulsion controlled by inorganic salts. SDBS, SDS, and SPS were used as emulsifiers in this study. The white oil and deionized water were emulsified into anoil-in-water emulsion by high-speed stirring. Multivalent metal cations were added to the emulsion to control the inversion of the emulsion to water-in-oil type. Then, the multivalent metal cations were removed by anions, leading to the emulsion reversed from water-in-oil to oil-in-water type. The stability of emulsions was evaluated by the stratification time, thermal resistance, conductivity, emulsion-breaking voltage and microstructure. The results showed that emulsion's dehydration rate was 8.1% at 25°C, which increased to 14.3% as the temperature reached 90°C after 5 hours. The average diameter of droplets was about 6 μm and conductivity was about 619 μs·cm−1. The emulsion processed by CrCl3·6H2O solution inverted to water-in-oil type, and its oil separation rate was 11.9% at 25°C and 18.2% at 90°C after 5 hours. The emulsion-breaking voltage and average diameter of droplets were 153 V and 13 μm, respectively. After Cr3+ was removed by Na2CO3 solution, the type of emulsion became oil-in-water againand the dehydration rate of this emulsion increased from 3.2% to 5.8% when the temperature reached up to 90°C. Under this circumstance, the average diameter of droplets was 5 μm and conductivity was 1907 μs·cm−1. The emulsion was of high stability before and after inversion. The emulsion controlled by inorganic salts can be reversed between oil-in-water and water-in-oil type efficiently, which can be used as emulsifier within drilling fluid in the low-permeability reservoir. The characteristics of reversible emulsion drilling fluid include inhibition for shale rock, good lubricity, thermal stability, and excellent cementing quality.

Liquid condensation near the wellbore region may cause cessation of gas production in gas-condensate reservoirs when pressure drops lower than its dew point. It is believed that gas deliverability can be enhanced by altering the wettability of reservoirs to gas-wetting. In order to investigate the influence of wettability alteration on the displacement efficiency of gas-condensate, contact angle measurement and gas flood tests were conducted. Results show that core wettability can be altered from liquid-wetting to intermediate gas-wetting or preferential gas-wetting by the fluorosurfactants FG24 and FG90. The contact angles of brine and decane indicated that core wettability can be altered from liquid-wetting to preferential gas-wetting by FG24 at a concentration of 0.3%, and by FG90 at 0.5%. Surface free energy before and after core treatment was measured by Owen's two-liquid method, the results showing that core surface free energy sharply decreased from 70 to about 3 mN/m after FG24 treatment. Oil disp...

Gas condensate reservoirs often experience a sharp reduction in gas deliverability when the wellbore pressure drops under its dew point, this is known as liquid-blocking effect in gas condensate reservoir. Many solutions with limited effectiveness were proposed to figure out the problem, and wettablity alteration is proven to be one of effective measures for liquid-blocking effect. Recent investigations show that the wettability of core near wellbore region can be permanently altered from water-wet or oil-wet to intermediate gas-wetting with the fluorosurfactant treatment, and the mobility and distribution of fluids in porous media can also be significantly improved after gas-wetting alteration. The objective of this study was to find out the effect of gas-wetting alteration by fluorosurfactant modified nano-silica on the gas recovery in methane-liquid-rock system. The fluorochemicals are widely used to change the surface properties of solid to achieve a surface with a low surface free energy. In this study, gas-wetting alteration on solid surface is achieved with fluorosurfactant and fluoropolymer. In order to obtain a super gas-wetting, nano-silica particles with a size of 40 nm was functionally modified by fluorosurfactant. Contact angle measurement, Owens two-liquid method, and capillary rise in methane-liquid-core system were conducted to evaluate the effect of gas-wetting alternation on the cores wettability and gas recovery. Data of Contact angle measurement showed that the core wettability can be altered to gas-wetting or super gas-wetting after FG40, FP-2 and FG40 modified nano-silica solution treatment, the contact angles of brine and decane on core surface increased from 23° and 0° to 152° and 127° after treated by 0.5% FG40 modified nano-silica solution, respectively. The surface free energy of cores before and after treatment shows that the sueface free energy decreased from 70 mN/m to approximately 0.61 mN/m. The results of capillary rise and imbibition test verified that of the contact angle measurement and surface free energy, the liquid levels of brine and decane significantly decreased to -20 and 7 mm when the wettability of capillary atered to gas-wetting. Analysis of SEM and TEM indicated that the gas-wetting nano-silica can form a gas-wetting adsorption layer with coarse structures on core surface, which play a vital role in super gas-wetting. In summary, the cores wettability can be altered from liquid-wetting to super gas-wetting by the novel fluorosurfactant modified nano-silica, and gas deliverability can be significantly improved due to super gas-wetting alteration.

The effect of the divacancy defect on magnetic properties of Fe94V6 alloys was investigated using the first-principles calculations based on density functional theory. The model of Fe28V2 super-lattice for a divacancy in Fe94V6 alloy was established, in comparison with the perfect Fe30V2 super-lattice. For the first time, the effect of the on-site Coulomb repulsion term was considered to correct the underestimation for the bandgap. The magnetism of the Fe, V atoms, and the super-lattice were analyzed by the electron hybridization of the atoms, and the interactions between V and four different neighboring Fe atoms were also investigated. The results show that both Fe28V2 and Fe30V2 super-lattices are ferromagnetic, which is determined mainly by the strong ferromagnetism of Fe 3d electrons, and the hybridizations between Fe 3d electrons and Fe 2p and V 3d electrons account for the weak anti-ferromagnetism. When the Fe divacancy exists, the average magnetic moments of the Fe28V2 super-lattice and Fe atoms inside increase, while that of V atoms decreases due to the change of the Fe-V charges. The variation of the magnetic moments of different neighboring Fe atoms with respect to V atoms depends on the charge transfer and the Fe-V interaction.

Liquid condensation near wellbore region may kill gas production in gas-condensate reservoirs when pressure drops to lower than its dew point. One potential way to overcome this problem is to alter reservoir wettability to gas-wetting to reduce condensate accumulation in the near wellbore and maintain high productivity. It was believed that condensate accumulation can be removed by altering the wettability of reservoir from liquid-wetting to gas-wetting. The aim of this study was to investigate the effect of wettability alternation on condensate gas recovery efficiency in porous media.Different molar ratios between fluorine-containing copolymer monomer and acrylic monomers were used to synthesize a gas-wetting alternation agent. Then Contact angle measurement and Owens two-liquid method were conducted in the laboratory, meanwhile, the effects of alternation agent concentration, salt concentration, pH and temperature on the gas-wetting core were evaluated.Results showed that when the molar ratio of fluoropolymer monomer: acrylic acid was 1:2, the synthetic product could alter the wettability of core from liquid-wet to preferential gas-wetting. The contact angles of brine and oil can be altered from 23° and 0° to 137° and 90° by 1wt% FP-2 treatment, respectively, the surface free energy of core was improved from 67.52 to 1.66mN/m, the wettability of core was altered into in neutral gas wetting. And the treated cores can keep neutral gas-wetting within a condition of 100000mg/L, 120°C, pH=5~7. This novel gas-wetting alternation agent can be used to solve the problem of liquid blocking effect in gas condensate reservoirs and thus improve gas recovery.

Field trials have demonstrated that foamed gel is a very cost-effective technology for profile modification and water shut-off. However, the mechanisms of profile modification and flow behavior of foamed gel in non-homogeneous porous media are not yet well understood. In order to investigate these mechanisms and the interactions between foamed gel and oil in porous media, coreflooding and pore-scale visualization waterflooding experiments were performed in the laboratory. The results of the coreflooding experiment in non-homogeneous porous media showed that the displacement efficiency improved by approximately 30% after injecting a 0.3 pore volume of foamed gel, and was proportional to the pore volumes of the injected foamed gel. Additionally, the mid-high permeability zone can be selectively plugged by foamed gel, and then oil located in the low permeability zone will be displaced. The visualization images demonstrated that the amoeba effect and Jamin effect are the main mechanisms for enhancing oil recovery by foamed gel. Compared with conventional gel, a unique benefit of foamed gel is that it can pass through micropores by transforming into arbitrary shapes without rupturing, this phenomenon has been named the amoeba effect. Additionally, the stability of foam in the presence of crude oil also was investigated. Image and statistical analysis showed that these foams boast excellent oil resistance and elasticity, which allows them to work deep within formations.

Liquid condensation in the reservoir near a wellbore may kill gas production in gas-condensate reservoirs when pressure drops lower than the dew point. It is clear from investigations reported in the literature that gas production could be improved by altering the rock wettability from liquid-wetness to gas-wetness. In this paper, three different fluorosurfactants FG1105, FC911, and FG40 were evaluated for altering the wettability of sandstone rocks from liquid-wetting to gas-wetting using contact angle measurement. The results showed that FG40 provided the best wettability alteration effect with a concentration of 0.3% and FC911 at the concentration of 0.3%.

It is important for enterprise to innovate e-business model to gain competitive advantages. Innovation of e-business model attracts interests of academia and industry. The concept of E-business model has been ambiguous for a long times, with each researcher using it in a different meaning depending on the context of discussion. The ambiguity hinders the research on the e-business model and it is necessary to study the concept of ebusiness model for e-business model innovation. Anchored on static and dynamic perspective, a hierarchical concept framework, including role model, scale model, model organism and recipe model, is proposed. The concept framework will provide necessary bases for further research on company's innovation of E-business model.