Effect Of Supercritical CO2 Research Articles

Investigation of the Pore Characteristics and Capillary Forces in Shale before and after Reaction with Supercritical CO2 and Slickwater

CO2–slickwater hybrid fracturing technology is an essential part of shale gas recovery and CO2 geo-storage. However, the exposure to supercritical CO2 (ScCO2) and slickwater can result in potential changes of the pore structures and surface wetting behavior, which affect the gas transportation and CO2 sequestration security in shale reservoirs. Therefore, in this paper, X-ray diffraction (XRD), low-pressure nitrogen gas adsorption (N2GA), mercury intrusion porosimetry (MIP), and fractal analysis were used to describe the pore characteristics of shale before and after ScCO2–slickwater coupling treatments. Shale’s surface wettability was confirmed by contact angle measurements. After the ScCO2–slickwater treatments, the number of micropores (<3.5 nm) and mesopores (3.5–50 nm) increased, while that of macropores (>50 nm) declined based on the N2GA and MIP experiments. Combined with fractal analysis, we argue that the pore connectivity diminished and the pore structure became more complicated. By analyzing the results of XRD, shale pore changes occurring after the ScCO2–slickwater treatment can be explained by the adsorption of polyacrylamide (PAM). Contact angle measurement results showed that the shale’s surface treated by ScCO2 and slickwater was more hydrophilic than that treated by ScCO2 and water, and indirectly prove our argument above. Hence, the coupling using effect of ScCO2 and slickwater can impair the negative effect of CO2 on the shale capillary force to improve shale gas productivity, but it can negatively affect the security of CO2 sequestration in shale reservoirs.

Permeability of porous membrane polymers modified by supercritical carbon dioxide

An approach to predict the gas permeability of membrane polymers after supercritical CO2 treatment is proposed. The approach is based on the connection of the temperatures of secondary relaxation transitions with the effective sizes of mobile free volume elements in the polymers. The correlation between permeability of nitrogen and effective sizes of mobile holes for a set of polymers is established. The effect of supercritical CO2 on the nitrogen permeability of polycarbonate, polysulfone, polyvinylbutyral is analyzed by FTIR spectroscopy of low-molecular weight conformationally-inhomogeneous compounds introduced in the polymers. Membranes were exposed at 40 MPa and 333 K for 4 h through static treatment and dynamic treatment separately. For polyvinylbutyral, the nitrogen permeability did not change after supercritical CO2 modification while for polysulphone, the effective volume of mobile holes increased, but the nitrogen permeability decreased. For polycarbonate after supercritical CO2, the effective volume of mobile holes and the nitrogen permeability increased.

Study on the Influence of Supercritical CO2 with High Temperature and Pressure on Pore-Throat Structure and Minerals of Shale.

Injection of carbon dioxide offers substantial social and economic advantages for reduction of carbon emission reduction. Utilizing CO2 in shale formations can significantly enhance the extraction of shale oil or gas. Conducting fundamental research on how CO2 affects shale rock's physical properties is crucial for enhancing its porosity and permeability. Particularly for deep shale layers, the effects of supercritical CO2 on shale physical properties should be investigated at a high temperature and pressure, differing from the standard conditions applied in shallower layers. A study examined the impact of supercritical CO2 under such conditions on the pore-throat structure and mineral composition of the shale. The experimental parameters included immersing shale rock in supercritical CO2 at pressures ranging from 10 to 70 MPa and temperatures between 55 and 95 °C. This study evaluated changes in mineral composition, pore-throat structure (using scanning electron microscopy and nitrogen adsorption tests), and the porosity and permeability of the shale rocks. Findings indicated that the dissolution of CO2 altered the relative content of certain minerals. The average quartz content rose and, potassium feldspar and the average contents of plagioclase declined conversely. When increasing the pressure, an increase in the relative content of I/S mixed layer and a decrease in illite content were observed and kaolinite content experienced minor changes. When increasing the temperature, kaolinite, I/S mixed layer, and chlorite all exhibited a decreasing trend with increasing temperature, while the relative contents of illite increased. Some of the pores become rounded in a high-magnification view under the impact of CO2 dissolution. Additionally, the Brunauer-Emmett-Teller specific surface area, pore volume, porosity, and permeability generally improved with increasing pressure and temperature. With the temperature and pressure of CO2 increased, the curves of nitrogen absorption had moved first upward and then downward. However, under specific CO2 conditions, the permeability enhancement effect could diminish or even negatively impact the shale's permeability. These findings underscore the need to optimize supercritical CO2 injection parameters under high-temperature and high-pressure conditions. This research aims to provide theoretical guidance for the efficient use of CO2 in deep shale applications to increase the shale gas output.

Experimental investigation of the impacts of supercritical carbon dioxide on acid-etching fracture morphology and conductivity in tight carbonate reservoir

Carbon dioxide (CO2) as energized fluid has been used for acid-fracturing in tight carbonate reservoir. CO2 is often pumped into the wellbore in liquid phase with acid systems, and transited into supercritical state under the high-temperature formation. While the effect of supercritical CO2 (SC-CO2) on acid-etched fracture morphology and conductivity have rarely been investigated. The acid-etching and conductivity experiments were conducted on the outcrops of the Ma5 sub-member of the Ordo Basin in China. The mixed phase reaction simulation device was developed firstly. These experiments involved the mixing of SC-CO2 with various fluids, including formation water and viscoelastic surfactant (VES) acid, as well as different SC-CO2 concentrations with VES acid. The results show that 100 % SC-CO2 is easy to activate natural fractures without dissolution. After 20%SC-CO2 mixed with formation water, the dissolution ability of the mixed solution and conductivity is only 11.8 % and 1 ∼ 2 % of VES acid respectively. Roughness of the morphology created by the mixture of SC-CO2 with VES acid, exhibits a reduction compared to VES acid-etching, accompanied by the presence of wormholes. Additionally, there is a decrease in conductivity and increase in its retention rate. With the increase of SC-CO2 concentration, the roughness of acid-etching fracture decrease and the injection pressure curve becomes more stable. While the reaction rate is also retarded nearly linearly as the SC-CO2 concentration increases. Especially, when the SC-CO2 concentration is up to 40 %, the acid-rock reaction rate reaches only 55 % of that of VES acid. The conductivity of mixed-acid-etched fracture exhibits a segmented characteristic. During the low-medium closure pressure stage, the acid-etched fracture by VES acid generates high conductivity, specifically when it is below 34.5 MPa. While the higher the SC-CO2 concentration in the mixed acid is, the greater the conductivity and retention rate are at pressures above 34.5 MPa during high closure pressure stage. The conductivity of SC-CO2 acid-fracturing fracture depends on the non-uniform etching of the acid solution. The increase in SC-CO2 concentration of the mixed acid not only enhances conductivity and retention rate under high closure pressure, but also reduces the acid volume required for acid-fracturing.

Impact of supercritical CO2 exposure time on the porosity and permeability of dry and wet shale: The influence of chemo-mechanical coupling effects

CO2 storage in shale formation is a potential way to reduce CO2 emissions for carbon neutrality. The variation of permeability in shale triggered by CO2-shale interaction plays an important role in CO2 sequestration. The effect of supercritical CO2 (ScCO2) exposure times (0, 10, 20, 30, 40 days) on the porosity and permeability evolution of dry and wet shale samples was investigated herein. Results show that the porosity and permeability of both dry shale and wet shale increased first and then decreased over exposure time, and there is an inflection point. The porosity and permeability evolution of shale is controlled by the chemical-mechanical coupling effects. The dissolution of mineral induced by ScCO2 exposure increases the porosity and permeability of shale. The mechanical weakening induced by ScCO2 exposure enhances the pores compressibility of shale, makes the porosity and permeability decrease at stressed condition. In the early stage, the chemical effect is dominant, after the time of inflection point, the mechanical weakening effect is dominant. The inflection time of wet shale is earlier than that of dry shale, indicating that the chemical effect dominant stage in wet shale is shorter than that in dry shale. This can be attributed to that the water promoted the chemical reaction and enhanced the weakening of mechanical properties, then shortened the chemical corrosion dominated stage. Our findings suggest that ScCO2-shale interaction can contribute to the decrease in porosity and permeability of shale with the increase of ScCO2 exposure time, and hence adversely affecting the shale gas recovery and the continue injectivity of CO2. Thus, the time dependent chemical-mechanical coupling effects should be considered in evaluating the shale gas production and CO2 storage capacity.

The effects of supercritical CO2 on the seepage characteristics and microstructure of water-bearing bituminous coal at in-situ stress conditions

CO2 geological storage (CGS) is considered to be an important technology for achieving carbon peak and carbon neutralization goals. Injecting CO2 into deep unminable coal seams can achieve both CGS and enhance coalbed methane (ECBM) production. Therefore, the deep unminable coal seams are considered as promising geological reservoirs. CO2 exists in a supercritical CO2 (ScCO2) when it was injected into deep unminable coal seams. The injection of ScCO2 can induce changes in the seepage characteristics and microstructure of deep water-bearing coal seams. In this study, typical bituminous coal from Shenmu, Shanxi Province was used to investigate the effects of ScCO2 on seepage characteristics, pore characteristics, and mineral composition through experiments such as seepage tests, low-temperature liquid nitrogen adsorption, and X-ray diffraction (XRD). The results indicate that ScCO2 treatment of dry and saturated coal samples caused a significant increase in clay mineral content due to the dissolution of carbonates, leading to the conversion of adsorption pores to seepage pores and an improvement in seepage pore connectivity. Therefore, the Brunauer-Emmett-Teller (BET) specific surface area and pore volume of the two coal samples both decreased after ScCO2 treatment. Moreover, the permeability of dry and saturated coal samples increased by 191.53% and 231.71% at 10 MPa effective stress respectively. In semi-saturated coal samples, a large amount of dolomite dissolved, leading to the precipitation of Ca2+ and CO32- to form calcite. This caused pore throats to clog and macropores to divide. The results show that the pore volume and average pore size of coal samples decrease, while the specific surface area increases after ScCO2 treatment, providing more space for gas adsorption. However, the pore changes also reduced the permeability of the coal samples by 32.21% and 7.72% at effective stresses of 3 MPa and 10 MPa, respectively. The results enhance our understanding of carbon sequestration through ScCO2 injection into water-bearing bituminous coal seams.

Experimental Study on the Effect of Supercritical CO2 on Mechanical Properties and Fracture Characteristics of Longmaxi Shale

Conventional hydraulic fracturing techniques typically consume large amounts of water when producing shale gas. Fracking fluids may cause environmental pollution. In contrast, supercritical carbon dioxide (scCO2) (above 31.8°C, 7.29 MPa) can displace CH4 in shale reservoirs. Achieve CO2 sequestration while increasing the shale gas production. We studied the mechanical properties and fracture characteristics of a shale under the action of scCO2, nitrogen, helium, and water by comparing the triaxial compression tests of shale samples with seven coring angles. The results show that: (1) scCO2 effectively reduced compressive strength of the shale and weakened the anisotropy of shale; (2) scCO2 caused the content of dolomite, calcite, and illite to decrease by 4.7%∼13.5%, respectively; (3) scCO2 produced micropores and microfractures 10 times larger than the original size in the microstructure. These microstructures can help improve the seepage and gathering of shale gas, leading to enhanced shale gas recovery and CO2 storage.

Effects of supercritical CO2 on viscoelastic properties of shales

Laboratory uniaxial compression creep tests, with differential stress of 30 MPa hold for 3 h, were performed on Chang-7, Longmaxi (LMX) and Barnett shales to study the influence of SC-CO 2 on short-term viscoelastic properties. To this end, the wet shale samples were treated with SC-CO 2 with a pressure of 30 MPa and a temperature of 110 °C for 14 days. We analyzed the creep data using the fractional Maxwell model. To investigate microscopic structural alterations, the surface morphology of the same location, before and after SC-CO 2 -water exposure, was examined by SEM images. Compared with dry shales, dynamic and static elastic moduli decreased by up to 25.02% and 55.83%, respectively, but the creep deformation increased by 200% for LMX and Chang-7 shales, and 500% for the Barnett shale treated by SC-CO 2 . Compared to dry sample, there is an increase in calculated fractional orders of 0.02, 0.07, 0.22 for SC-CO 2 treated samples, indicating that SC-CO 2 treatment is likely to enhance shale creep. SEM investigation confirmed physicochemical mechanisms responsible for the observed elastic damage and creep enhancement, including mineral dissolution and swelling caused by SC-CO 2 . This work would further improve our current understanding of the time-dependent deformation of shale under chemical-mechanical coupling effects during CO 2 capture utilization and storage.

Effects of pore structure changes on the CH4 adsorption capacity of coal during CO2-ECBM

The effects of supercritical CO2 (scCO2) on pores in coal play a critical role in determining the CH4 adsorption and desorption characteristics and CO2 capacity of coal seams during CO2 geological storage-enhanced coalbed methane recovery (CO2-ECBM). To investigate the effects of pore structure changes caused by scCO2 on the CH4 adsorption capacity of coals, six coal samples with different ranks are exposed to scCO2 and water for 240 h at 62.5 °C and 15 MPa using a scCO2 geochemical reactor. Then, gravimetric isothermal adsorption tests, mercury intrusion porosimetry, N2 adsorption tests, and CO2 adsorption tests are performed to determine the CH4 adsorption capacity, pore volume, and pore specific surface area (SSA) of the coal samples with and without scCO2-H2O treatment. Finally, the influences of scCO2 on the pore structure and the effects of pore structure changes on the CH4 adsorption capacity of the coal samples are analyzed. The results show that the CH4 adsorption capacity of coal and its changes after scCO2-H2O treatment are strongly affected by density effects and pore selection effects. The CH4 adsorption capacity of coal is determined by the micropore volume and SSA; however, their changes only affect the CH4 adsorption capacity in the micropore filling stage when the pressure is <5 MPa with weak effects on the total CH4 adsorption capacity, which is related to their weak changes after scCO2-H2O treatment compared with macropores and mesopores. The changes in CH4 adsorption capacity mainly depend on the changes in macropore and mesopore SSAs after scCO2-H2O treatment; scCO2 mainly changes the CH4 adsorption capacity in the transitional stage, when the pressure is 5–10 MPa, and the monolayer and multilayer adsorption stage, when the pressure is >10 MPa. Meanwhile, the effect of pore structure changes on the CH4 adsorption capacity of coal with different ranks is complex. The CH4 adsorption capacity of subbituminous coal and medium-volatile bituminous coal increases after scCO2-H2O treatment due to the increases in macropore SSA, that of high-volatile bituminous coal slightly decreases, and that of semianthracite coal and anthracite coal slightly increases because of the changes in mesopore SSA after scCO2-H2O treatment. However, the CH4 adsorption capacity of low-volatile bituminous coal increases, which is the result of changes in the SSA of the mesopores and macropores due to slight changes in the micropore volume and SSA.

Effect of supercritical CO2 on limestone's pore structure based on NMR and SEM

Supercritical CO2 (SC-CO2), as a new type of energizing fluid, has been widely applied in fracturing and acidizing treatment on tight sandstone, shale and carbonate formation. However, the effect of SC-CO2 on limestone's pore structure is unclear. To explore the effect, SC-CO2 reactor featuring high-temperature and high-pressure was used to carry out soaking experiments of SC-CO2-brine-limestone and SC-CO2-limestone respectively. With the help of NMR and SEM, this paper studies the effect of SC-CO2 on limestone's pore structure when the soaking time is different. It is found that in the experiment of SC-CO2-brine-limestone, SC-CO2 will react with brine to produce carbonic acid, which would react with calcite to augment limestone's porosity and permeability. Yet at the same time, Ca2+ and Mg2+ in the brine deposit continuously, which would lessen limestone's porosity and permeability. Besides, it is the generation of large pores that leads to augmentation of porosity, and more large pores are produced as time increases. While in the experiment of SC-CO2-limestone, volume expansion caused by transforming SC-CO2 into gaseous CO2 also augments limestone's porosity, and the augmentation is due to small pores. However, the increase of porosity in experiments without brine is much lower than that with brine.

The effect of supercritical CO2 on failure mechanisms of hot dry rock

Hot dry rock is a clean, renewable resource of geothermal energy with good stability and a high utilization rate. Supercritical CO2 has shown promising results for improving the permeability and heat exchange of hot dry rock. In order to demonstrate the effect of supercritical CO2 on the failure mechanism of granite, the acoustic emission of granite during its failure process were studied in addition to X-ray diffraction, scanning electron microscopy, and optical electron microscopy investigations. The experimental results showed that for granite without supercritical CO2 treatment, as it approached failure, there were many acoustic emission events with a waiting time less than 0.0001 s, and that the power law exponent of the acoustic emission energy distribution decreased. The failure mechanisms were a combination of fracture and friction, with fracturing dominant. After immersion in supercritical CO2 , new cracks and pores appeared in the granite due to the dissolution of minerals, but friction was also a factor evidenced in particle crumbing. Generally, the acoustic emission statistical distributions of granite before and after supercritical CO2 soaking conformed to the seismic statistical distribution law. This study is conducive to increasing the understanding of artificial earthquakes induced by the development of hot dry rock. Cited as: Li, H., Jiang, X., Xu, Z., Bowden, S. The effect of supercritical CO2 on failure mechanisms of hot dry rock. Advances in Geo-Energy Research, 2022, 6(4): 324-333. https://doi.org/10.46690/ager.2022.04.07

A time-dependent Yeoh model to predict the corrosion effect of supercritical CO2 on the HNBR sealing rubber

A time-dependent Yeoh model to predict the corrosion effect of supercritical CO2 on the HNBR sealing rubber

Effects of Supercritical CO2 on Quantity and Quality of Extracted Oil from Myctophidae Fish and Comparison It with the Wet Pressing as a Commercial Method

The aim of this study was investigation the effects of different methods (wet pressing: WP and supercritical fluid extraction: SFE) of oil extraction from lantern fish (Myctophidae) in terms of quantity and quality. Results showed there was no significant difference in oil production rate (p&gt;0.05), but there was a significant difference between detected volatile components (alkanes, aldehydes, amines and acetic acid) (p&lt;0.05). Some of Neutral lipids (Wax Esters (WE), Triacylglycerol (TAG) and Free Fatty Acids (FFA)) showed significant difference (p&lt;0.05) and Cholesterol (CHOL) levels did not show significant differences between treatments (p&lt;0.05). Also, fatty acid profiles showed the level of DHA in SFE treatment was significantly higher than WP (p&lt;0.05). The acidity value (AV) did not show a significant difference (p&lt;0.05). Also, the amount of heavy metals (Mercury (Hg), arsenic (As), cadmium (Cd) and lead (Pb)) in extracted oils by SFE was lower than the other method (p&lt;0.05). Therefore, the results of this study indicate the potential of lantern fish for extraction of fish oil in human consumption and the SFE method for extracting it.

Effect of supercritical CO2 flooding on the produced water quality and performance of the scale inhibitors in a typical tight sandstone oilfield

In order to enhance oil recovery, supercritical CO2 (scCO2) flooding has been applied in many oilfields to extract oil and gas post primary recovery. However, it causes serious scaling problems in the reservoir, oil well and production tubing. In this article, the produced water quality before and after scCO2 flooding in carbonate reservoirs are analyzed. The scaling trend of produced water before and after scCO2 flooding was calculated by using the Davis-stiff saturation index and Ryznar stability index methods. Static experiments and scanning electron microscope (SEM) are used to study the scale inhibition performance and mechanism of HEDP, ATMP, MA-AA, and PAA on CaCO3 in produced water before and after scCO2 flooding. The results show that after scCO2 flooding, the quality of produced water changes obviously, thus the scaling trend of produced water increases, the growth of CaCO3 crystal is affected and the scale inhibition efficiency of conventional scale inhibitors decreases.

Study on effect of supercritical CO2 on structural ordering and charge transporting property in thiophene-based block copolymer

We reported that supercritical (sc) annealing of poly(3-hexylthiophene) (P3HT), and its block copolymers with poly(ethylene oxide) (PEO) and polystyrene (PSt) brought about improvements in the crystal structure and hole mobility, determined by the space charge limited current (SCLC) measurement. P3HT-b-PEO showed the largest increase in mobility. From the XRD profile, it was found that the treatment with scCO2 increased the crystallite size and crystallinity. UV–vis spectra showed that the effective conjugation length in the scCO2 treated films was increased, compared to the as-spun samples, suggesting that CO2 molecules are incorporated into domains of the second block domains and P3HT amorphous region, and assist to alter the characteristics of the crystalline region. Then, it was considered that the change in the crystalline structure and the improvement of P3HT chains packing led to enhanced mobility. Since PEO is known to have a higher affinity for CO2, the increase of mobility was specifically intensive.

Exfoliation and distribution behavior of graphene nanoplatelets in polystyrene-based foams fabricated by supercritical CO2 assisted microcellular foaming

The effects of supercritical CO2 (scCO2) on polymer chains’ mobility and graphene nanoplatelets (GNPs) exfoliation and distribution in a microcellular foaming process are investigated by the molecular dynamics (MD) simulations and experiments. The results of MD simulations and visualization analysis confirm that the synergistic effect of scCO2 molecules and polystyrene (PS) chains is beneficial for them to penetrate into the interlayer of GNPs during the scCO2 treatment at high saturation pressure. The scanning electron microscope images show that some cells exist in the interlayer of GNPs in the foam fabricated in the highest saturation pressure and shortest depressurization time. With foaming in different depressurization time, the growing cells facilitate the movement of GNPs after their exfoliation, leading to alignment around the cells. As compared to large diameter GNPs, the GNPs with small diameter rearrange easily and distribute more homogeneously due to lower resistance of GNPs’ movement.

Study on Temperature Feedback Effect of Supercritical CO2–Cooled Reactor

As a potential new-type reactor, the supercritical CO2 (S-CO2)–cooled reactor has several advantages, such as being a simple system, having high thermal efficiency, having a small size, and being lightweight. Due to the poor neutronics moderation performance, the S-CO2–cooled reactor shows the disadvantage of a weak temperature feedback effect on reactivity. In this article, the neutronics performance of the reactor has been focused on, and the effects of temperature feedback on fuel, coolant, and moderator studied and the method to improve temperature feedback of the S-CO2 reactor proposed.

Effect of supercritical CO2 on salt water corrosion and wear resistance of bismaleimide coating filled with organophilic montmorillonite clay

Ceramic filled polymer coatings have been shown to increase the salt water corrosion protection and wear resistance of metallic substrates. With an increase in natural and anthropogenic CO2 use as an enhanced oil recovery method paired to conventional brine-based recovery, termed ‘water after gas’ the impact of corrosion remains unknown. In this paper, we investigate the effect of salt water corrosion in a filled and unfilled coating before and after supercritical CO2 exposure. Corrosion performance is evaluated using electrochemical Tafel and impedance spectroscopy. Wear was measured using a pin on disk testing. After exposure to CO2, the corrosion performance of filled and unfilled systems were similar while the wear resistance of the filled coating was superior.

Effects of Supercritical CO2 on Matrix Permeability of Unconventional Formations

We studied the effects of supercritical carbon dioxide (scCO2) on the matrix permeability of reservoir rocks from the Eagle Ford, Utica, and Wolfcamp formations. We measured permeability using argon before exposure of the samples to scCO2 over time periods ranging from days to weeks. We measured permeability (and the change of permeability with confining pressure) when both argon and scCO2 were the pore fluids. In all three formations, we generally observe a negative correlation between initial permeability and carbonate content—the higher the carbonate content, the lower the initial permeability. In clay- and organic-rich samples, swelling of the matrix resulting from adsorption decreased the permeability by about 50% when the pore fluid was scCO2 although this permeability change is largely reversible. In carbonate-rich samples, dissolution of carbonate minerals by carbonic acid irreversibly increased matrix permeability, in some cases by more than one order of magnitude. This dissolution also increases the pressure dependence of permeability apparently due to enhanced mechanical compaction. Despite these trends, we observed no general correlation between mineralogy and the magnitude of the change in permeability with argon before and after exposure to scCO2. Flow of scCO2 through μm-scale cracks appears to play an important role in determining matrix permeability and the pressure dependence of permeability. Extended permeability measurements show that while adsorption is nearly instantaneous and reversible, dissolution is time-dependent, probably owing to reaction kinetics. Our results indicate that the composition and microstructure of matrix flow pathways control both the initial permeability and how permeability changes after interaction with scCO2. Electron microscopy images with Back-Scattered Electron (BSE) and Energy Dispersive Spectroscopy (EDS) revealed dissolution and etching of calcite minerals and precipitation of calcium sulfide resulting from exposure to scCO2.

Structural and physico-chemical properties change of polyethylene terephthalate (PET) fibers after supercritical fluid dyeing with C.I. disperse red 167

The effects of supercritical CO2 and C.I. Disperse Red 167 as media on the structural and chemical properties of polyethylene terephthalate (PET) fibers were observed in the supercritical dyeing process of these fibers using numerous methods to predict changes in their physical properties. PET samples were classified into three cases based on the sample preparation and analysis steps. When the PET fibers were treated without C.I. Disperse Red 167 under a supercritical fluid CO2 solvent at 120 °C and 25 MPa, their crystallinity, orientation, and tensile strength decreased the most among the three cases, whereas when they were treated with C.I. Disperse Red 167 under the same conditions, the three above-mentioned characteristics were relatively improved compared to the scenario without the C.I. Disperse Red 167 treatment. These experimental results provided significant information on the effects of supercritical CO2 and C.I. Disperse Red 167 on the properties of PET fiber polymers.