Effectively improving the mechanical properties and thermal resistance of epoxy shape-memory polymers (ESMPs) without affecting their shape-memory performance is necessary to expand these polymers in practical applications. In this article, modified multi-walled carbon nanotubes (MWCNTs) were prepared and used as efficient reinforcement for enhancing the comprehensive properties of ESMPs. Increases of nearly 289% to 444% for impact strength and 112% to 184% for tensile force were obtained by adding only 0.1 to 1 wt% epoxy-modified MWCNTs. The addition of unmodified and carboxyl-modified MWCNTs was also investigated but showed less impact on the mechanical properties of the ESMPs than epoxy-modified MWCNTs. Thermogravimetry analysis (TGA) and dynamic mechanical analyses (DMA) showed that less than 1 wt% modified MWCNTs can enhance the heat resistance of ESMPs greatly. Although the shape recovery time for composite materials increased upon adding the MWCNTs, the entire recovery time was still less than 1 minute, and the shape recovery rate was relatively high, nearly 100%.
It
is well-known that the production of gas-condensate reservoirs
is significantly affected by the liquid condensation near the wellbore
region. Gas-wetting alteration can be one of the most effective approaches
to alleviate condensate accumulation and improve liquid distribution.
However, gas well deliverability is still limited because the wettability
of cores is altered only from liquid-wetting to intermediate gas-wetting
by using traditional chemical stimulation. To solve this bottleneck
problem, herein, we developed a fluorine-functionalized nanosilica
to achieve super gas-wetting alteration, increasing the contact angles
of water and n-hexadecane on the treated core surface from 23 and
0° to 157 and 145°, respectively. The surface free energy
reduces rapidly from 67.97 to 0.23 mN/m. The super gas-wetting adsorption
layer on the core surface formed by functionalized nanosilica not
only increases the surface roughness but also reduces the surface
free energy. The core flooding confirms that the required pressure
for displacement is apparently reduced. Meanwhile, the core permeability
can be dramatically restored after the super gas-wetting alteration.
The microscopic visualization is employed to further understand the
impact of fluorine-functionalized nanosilica on the fluid flow behavior
and mechanism in porous media. The oil saturation in the micromodel
decreases sharply from 48.75 to 7.84%, eliminating the “water
locking effect” and “Jiamin effect”, which indicates
that the added functional nanosilica effectively improves fluid flow
capacity and may contribute to production in the gas condensate reservoirs.
In addition, this work reveals the fluid flow behavior and mechanism
in the reservoir in detail, which will expand the better application
of this material to many oilfields and other mining engineering systems.
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 microscopy revealed that the fluorine-containing
adsorption layer was formed and the roughness of the shale surface
was significantly increased. This indicated that the gas-wetting surface
can be achieved by using the gas-wetting alteration agents. The above
results confirmed that the wettability of the shale surface is altered
from the original water-wetting or oil-wetting to gas-wetting. Furthermore,
the thermal analysis exhibited that the two gas-wetting alteration
agents have good thermal stability under 165 and 216 °C, respectively.
It demonstrated that they have greater potential to be applied to
high-temperature reservoirs.
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