Abstract: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-(perfluorooct… Show more
“…Extensive efforts have been devoted to the synthesis and characterization of gas-wetting agents; fluorosurfactants and fluoropolymers dominate. − Fluorosurfactants typically exhibit a more pronounced performance than fluoropolymers. However, the present fluorochemicals can only achieve intermediate gas-wetting due to the inability to fabricate a multiscale adsorption layer.…”
The transformation of the liquid
menisci at pore throats is of
great importance for mitigating the liquid-blocking effect of condensate
reservoirs. Here, we reported a super gas-wetting peanut-like nanoparticle
which can facilitate the liquid menisci to transform from concave
shape to convex shape by coating a super gas-wetting adsorption with
high surface roughness. The morphology and surface chemistry of gas-wetting
nanoparticles were investigated by SEM, AFM, and XPS analysis. The
mechanism of surface modification was further explored by TEM; the
adsorption layer coated on the nanoparticle surface can be recognized
as monolayer absorption. The gas-wetting model is recommended as the
combination of the Wenzel model and Cassie–Baxter model, which
is in close agreement with the results of AFM and contact-angle measurements.
Core flooding visualization was performed to identify the effect of
gas-wetting alteration on the transformation of liquid menisci in
porous media. Results showed that the addition of gas-wetting nanoparticles
could decrease the liquid saturations by inducing the transformation
of liquid menisci in the pore throat. Additionally, a unique “amoeba
effect” and miscibility effect can synergistically improve
the mobility of the oil phase, further enhancing the oil recovery.
“…Extensive efforts have been devoted to the synthesis and characterization of gas-wetting agents; fluorosurfactants and fluoropolymers dominate. − Fluorosurfactants typically exhibit a more pronounced performance than fluoropolymers. However, the present fluorochemicals can only achieve intermediate gas-wetting due to the inability to fabricate a multiscale adsorption layer.…”
The transformation of the liquid
menisci at pore throats is of
great importance for mitigating the liquid-blocking effect of condensate
reservoirs. Here, we reported a super gas-wetting peanut-like nanoparticle
which can facilitate the liquid menisci to transform from concave
shape to convex shape by coating a super gas-wetting adsorption with
high surface roughness. The morphology and surface chemistry of gas-wetting
nanoparticles were investigated by SEM, AFM, and XPS analysis. The
mechanism of surface modification was further explored by TEM; the
adsorption layer coated on the nanoparticle surface can be recognized
as monolayer absorption. The gas-wetting model is recommended as the
combination of the Wenzel model and Cassie–Baxter model, which
is in close agreement with the results of AFM and contact-angle measurements.
Core flooding visualization was performed to identify the effect of
gas-wetting alteration on the transformation of liquid menisci in
porous media. Results showed that the addition of gas-wetting nanoparticles
could decrease the liquid saturations by inducing the transformation
of liquid menisci in the pore throat. Additionally, a unique “amoeba
effect” and miscibility effect can synergistically improve
the mobility of the oil phase, further enhancing the oil recovery.
“…Above 205 °C, the weight remains nearly unchanged. The Thermogravimetric result reveals that the decomposition of the novel fluorocarbon surfactant can proceed under relatively high-temperature 20 , 21 . Figure 5 The thermal analysis curves of the novel fluorocarbon surfactant.…”
The wettability of the formation is critical for the flow back of the fracturing fluid and can further affect the gas production. So it is very necessary to study the wettability of shale reservoir. Here, a novel fluorocarbon surfactant, N-ethyl-N-hydroxyethyl perfluorooctanoamide, was synthesized and characterized by different methods. the contact angles of water and n-decane on the shale increased from 36° and 0° to 121° and 105°, respectively, after treated by N-ethyl-N-hydroxyethyl perfluorooctanoamide (0.5 wt.%). The surface free energy reduced from 72 mN/m to 7.4 mN/m. The results agreed with that of imbibition and capillary tube rise test. Additionally, the analysis of scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) showed that the roughness of shale surface remarkably increased. These results fully proved that the shale wettability is changed to super gas-wetting. Besides, the thermal analysis revealed that the novel fluorocarbon surfactant has good thermal stability. This indicates that it can be better applied to reservoir modifications at higher temperatures.
“…Fifty milliliters of distilled water, 1.0 g of MMA (0.01 mol), and 0.1 g of OBS were added into the reaction vessel with condensation and stirring. Then, 4.0 g of F12 (0.01 mol) and 0.1 g of AIBN were dissolved in 50 mL of dimethylformamide (DMF) and added into the reaction vessel and stirred at 60 °C for 15 min under ultrasonic conditions. , Then, the reaction was heated to 80 °C and continued to react for 6 h. The emulsion with slight white fluorescence was prepared as a fluoropolymer microemulsion (Figure b). The reaction scheme is shown in Figure a.…”
Reservoir wettability is an important factor in the process of reservoir reconstruction. Especially in hydrophilic formation, it is easy to cause a water-locked phenomenon. A new type of fluoropolymer microemulsion was prepared by emulsion polymerization, and its structure and properties were characterized. The average particle size in the prepared emulsion was about 2.0 μm. The emulsion had good stability and wettability reversal performance for the storage of 30 days. After the treatment of 2.0 wt % emulsion, the contact angle between the core and water changed from 26 to 128°, the core surface free energy decreased from 66 to 2.6 mN/m, and the saturated water imbibition amount of the core decreased from 1.38 to 0.15 g. The ability of the fluoropolymer microemulsion to enhance oil recovery was evaluated by the visual displacement experiment. The fluoropolymer microemulsion can increase the displacement efficiency by more than 10%. The wettability of the core changed from hydrophilicity to hydrophobicity, and wettability reversal was achieved.
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