Search Results (88)

Against the backdrop of global energy transition and strict environmental regulations, supercritical carbon dioxide (scCO₂) fracturing and oil displacement technologies have emerged as pivotal green approaches in shale gas exploitation, offering the dual advantages of zero water consumption and carbon sequestration. However, the inherent low viscosity of scCO₂ severely restricts its sand-carrying capacity, fracture propagation efficiency, and oil recovery rate, necessitating the urgent development of high-performance thickeners. The current research on scCO₂ thickeners faces a critical trade-off: traditional fluorinated polymers exhibit excellent philicity CO₂, but suffer from high costs and environmental hazards, while non-fluorinated systems often struggle to balance solubility and thickening performance. The development of new thickeners primarily involves two directions. On one hand, efforts focus on modifying non-fluorinated polymers, driven by environmental protection needs—traditional fluorinated thickeners may cause environmental pollution, and improving non-fluorinated polymers can maintain good thickening performance while reducing environmental impacts. On the other hand, there is a commitment to developing non-noble metal-catalyzed siloxane modification and synthesis processes, aiming to enhance the technical and economic feasibility of scCO₂ thickeners. Compared with noble metal catalysts like platinum, non-noble metal catalysts can reduce production costs, making the synthesis process more economically viable for large-scale industrial applications. These studies are crucial for promoting the practical application of scCO₂ technology in unconventional oil and gas development, including improving fracturing efficiency and oil displacement efficiency, and providing new technical support for the sustainable development of the energy industry. This study innovatively designed an amphiphilic modified amino silicone oil polymer (MA-co-MPEGA-AS) by combining maleic anhydride (MA), methoxy polyethylene glycol acrylate (MPEGA), and amino silicone oil (AS) through a molecular bridge strategy. The synthesis process involved three key steps: radical polymerization of MA and MPEGA, amidation with AS, and in situ network formation. Fourier transform infrared spectroscopy (FT-IR) confirmed the successful introduction of ether-based CO₂-philic groups. Rheological tests conducted under scCO₂ conditions demonstrated a 114-fold increase in viscosity for MA-co-MPEGA-AS. Mechanistic studies revealed that the ether oxygen atoms (Lewis base) in MPEGA formed dipole–quadrupole interactions with CO₂ (Lewis acid), enhancing solubility by 47%. Simultaneously, the self-assembly of siloxane chains into a three-dimensional network suppressed interlayer sliding in scCO₂ and maintained over 90% viscosity retention at 80 °C. This fluorine-free design eliminates the need for platinum-based catalysts and reduces production costs compared to fluorinated polymers. The hierarchical interactions (coordination bonds and hydrogen bonds) within the system provide a novel synthetic paradigm for scCO₂ thickeners. This research lays the foundation for green CO₂-based energy extraction technologies. Full article

Based on a detailed investigation of the geological setting of coalbed methane by previous work in the Xiangzhong Depression, Hunan Province, numerical simulation methods were used to simulate the geological storage of carbon dioxide and displacement gas production in this area. In this simulation, a 400 m × 400 m square well group was constructed for coalbed methane production, and a carbon dioxide injection well was arranged in the center of the well group. Injection storage and displacement gas production simulations were carried out under the conditions of original permeability and 1 mD permeability. At the initial permeability (0.01 mD), carbon dioxide is difficult to inject, and the production of displaced and non-displaced coalbed methane is low. During the 25-year injection process, the reservoir pressure only increased by 7 MPa, and it is difficult to reach the formation fracture pressure. When the permeability reaches 1 mD, the carbon dioxide injection displacement rate can reach 4000 m³/d; the cumulative production of displaced and non-displaced coalbed methane is 7.83 × 10⁶ m³ and 9.56 × 10⁵ m³, respectively, and the average daily production is 1430 m³/d and 175 m³/d. The displacement effect is significantly improved compared to the original permeability. In the later storage stage, the carbon dioxide injection rate can reach 8000 m³/d, reaching the formation rupture pressure after 3 years, and the cumulative carbon dioxide injection volume is 1.17 × 10⁷ m³. This research indicates that permeability has a great impact on carbon dioxide geological storage. During the carbon dioxide injection process, selecting areas with high permeability and choosing appropriate reservoir transformation measures to enhance permeability are key factors in increasing the amount of carbon dioxide injected into the area. Full article

The coal reservoir in the Ordos Mizhi block is buried at a depth of over 2000 m. This study aims to obtain the characteristics of the coal reservoir in the Mizhi block through various experimental methods and combine the gas-bearing characteristics obtained from on-site desorption experiments to analyze the gas content and logging response characteristics of the study area. On this basis, a reservoir parameter interpretation model for the study area is established. This provides a reference for the exploration and development of coal-rock gas in the Mizhi block. The research results show that: (1) The study area is characterized by the development of the No. 8 coal reservoirs of the Benxi Formation, with a thickness ranging from 2 to 11.6 m, averaging 7.2 m. The thicker coal reservoirs provide favorable conditions for the formation and storage of coal-rock gas. The lithotypes are mainly semi-bright and semi-dark. The coal maceral is dominated by the content of the vitrinite, followed by the inertinite, and the exinite is the least. The degree of metamorphism is high, making it a high-grade coal. In the proximate analysis, the moisture ranges from 0.36 to 1.09%, averaging 0.65%. The ash ranges from 2.34 to 42.17%, averaging 16.57%. The volatile ranges from 9.18 to 15.7%, averaging 11.50%. The fixed carbon ranges from 45.24 to 87.51%, averaging 71.28%. (2) According to the results of scanning electron microscopy (SEM), the coal samples in the Mizhi block have developed fractures and pores. Based on the results of the carbon dioxide adsorption experiment, the micropore adsorption capacity is 7.8728–20.3395 cm³/g, with an average of 15.2621 cm³/g. The pore volume is 0.02492–0.063 cm³/g, with an average of 0.04799 cm³/g. The specific surface area of micropores is 79.514–202.3744 m²/g, with an average of 153.5118 m²/g. The micropore parameters are of great significance for the occurrence of coal-rock gas. Based on the results of the desorption experiment, the gas content of the coal rock samples in the study area is 12.97–33.96 m³/t, with an average of 21.8229 m³/t, which is relatively high. (3) Through the correlation analysis of the logging parameters of the coal reservoir, the main logging response parameters of the reservoir are obtained. Based on the results of the logging sensitivity analysis of the coal reservoir, the interpretation model of the reservoir parameters is constructed and verified. Logging interpretation models for parameters such as industrial components, microscopic components, micropore pore parameters, and gas content are obtained. The interpretation models have interpretation effects on the reservoir parameters in the study area. Full article

This study systematically investigates the pore–fracture architecture of deep coal seams in the JiaTan (JT) block of the Ordos Basin using an integrated suite of advanced techniques, including nuclear magnetic resonance (NMR), high-pressure mercury intrusion, low-temperature nitrogen adsorption, low-pressure carbon dioxide adsorption, and micro-computed tomography (micro-CT). These complementary methods enable a quantitative assessment of pore structures spanning nano- to microscale dimensions. The results reveal a pore system overwhelmingly dominated by micropores—accounting for more than 98% of the total pore volume—which play a central role in coalbed methane (CBM) storage. Microfractures, although limited in volumetric proportion, markedly enhance permeability by forming critical flow pathways. Together, these features establish a dual-porosity system that governs methane transport and recovery in deep coal reservoirs. The multiscale characterization employed here proves essential for resolving reservoir heterogeneity and designing effective stimulation strategies. Notably, enhancing methane desorption in micropore-rich matrices and improving fracture connectivity are identified as key levers for optimizing deep CBM extraction. These insights offer a valuable foundation for the development of deep coalbed methane (DCBM) resources in the Ordos Basin and similar geological settings. Full article

Heterogeneity of pore and fracture structures has become an important factor affecting the migration of methane and water in coal reservoirs. However, controlling factors of pore and fracture structure collected from coal seam 10 in Taliqike Formation, Kubai Coalfield, Xinjiang need to be studied. In this paper, carbon dioxide adsorption, cryogenic liquid nitrogen, and high-pressure mercury intrusion, as well as coal microscopic components, were used to study pore volumes and characterize pore diameter distribution heterogeneity. By the theory of single weight and multiple fractal formations, the heterogeneity of the pore fracture structure of coal reservoir is expressed, and the influencing factors of the heterogeneity of the pore fracture structure and the pore volume are also discussed. The results are as follows. (1) Micro-pore distribution presents a distinct bidirectional state, with the main peak at approximately 0.6 nm and 0.85 nm. R_o,max has an obvious influence on micro-pore volume. The single-fractal dimension of micro-pore is not affected by a micro-pore volume but is influenced by other factors such as R_o,max and microscopic composition. The heterogeneity of the low-value area controls the heterogeneity of micro-pore diameter distribution. (2) For lower R_o,max samples, mesopores of these samples are ink bottle-shaped pores, and the pore connectivity is poor. In contrast, meso-pore of higher thermal evolution coal samples are mostly simple pores, such as parallel plates. The main mesopores are 10–100 nm pores, accounting for 75% of the total meso-pore volume. For the single fractal dimension, D₁ is greater than D₂, which also shows that the heterogeneity of a pore structure greater than 4 nm is much stronger than that of a pore structure less than 4 nm in these samples. (3) For lower R_o,max samples, double S-shaped curves with distinct hysteresis loop are obtained, while samples of higher R_o,max samples show parallel curves, suggesting that macro-pore of this type of sample develops parallel plate-like pore. There is a positive relationship between D₋₁₀–D₀ and D₋₁₀–D₁₀, while D₀–D₁₀ and D₋₁₀–D₀ have a weak correlation. With the increase of 2–10 nm pore volume, pore distribution heterogeneity of lower value area (D₋₁₀–D₀) weakens. This indicates that pore volume is an important factor affecting the multifractal variation. Full article

This article provides an overview of low-permeability reservoir development technologies, including carbon dioxide injection, nitrogen injection, air injection, natural gas injection, water injection (unstable water injection, advanced water injection), water–gas alternating injection, and hydraulic fracturing (hydraulic fracturing, repeated fracturing). These technologies have their own strengths and weaknesses in improving crude oil recovery and are significantly constrained by reservoir characteristics. This article uses specific cases such as the increase in CO₂ injection pressure in Yaoyingtai oilfield, which significantly improves recovery rate, nitrogen injection in Zhongyuan oilfield, which increases adjacent well production and single-well recovery rate, air injection in a certain block of Changqing oilfield, natural gas injection in Yushulin oilfield, which has the best effect under specific pressure, as well as the effects and problems of water injection technology, the increasing production effect, and potential risks of hydraulic fracturing, to deeply analyze the application effectiveness and influencing factors of various technologies. Through comparative analysis, it can be concluded that CO₂ injection has corrosion and gas channeling problems, nitrogen injection is limited by solubility, oxygen consumption in air injection is affected by temperature and pressure, natural gas injection is constrained by reservoir structure, water injection technology is unstable and difficult to determine timings, and fracturing technology faces difficulties in energy replenishment and time determination. Therefore, optimizing and applying these technologies rationally is of great significance for the efficient development of low-permeability reservoirs. Full article

Many studies have shown that the thermal evolution degree is the main factor affecting the micropore structure of coal reservoirs. However, within the same thick coal seam, the R_o,max of the entire coal seam is not much different, which affects the determination of the main controlling factors of pore structure heterogeneity. Therefore, No. 8 coal collected from Benxi Formation in the eastern margin of Ordos was taken as an example, and 16 samples were selected for low-temperature liquid nitrogen, carbon dioxide adsorption, and industrial component tests. Based on heterogeneity differences of R_o,max, industrial components and pore volume distribution of adsorption pores (pore diameter is less than 100 nm), the main controlling factors affecting the micropore structure of ultra-thick coal seams, were discussed. Then, the surface free energy theory was used to study the influencing factors affecting surface free energy variations during coal adsorption. First of all, R_o,max is not the main controlling factor affecting the micropore-fracture structure, as the effects of industrial components on the micropore structure are obvious, which indicates that industrial components are the main factors affecting vertical differences in the micropore structure within the same thick coal seam. Second of all, R_o,max and industrial components affect the adsorption process. When the adsorption pressure is lower, the adsorption volume and adsorption potential increase rapidly. When the adsorption pressure is higher (pressure is larger than 15 Mpa), the adsorption capacity and potential tend to be stable. Moreover, the maximum surface free energy increases with the increase in coal rank, which indicates that the degree of thermal evolution is the core factor affecting the adsorption free energy, but it is also controlled by the influence of industrial components (ash content). Lastly, micropores affect the adsorption capacity, and mesopores have little effect on the adsorption capacity, since micropores restrict the adsorption capacity and change the adsorption process by affecting surface free energy variations. The refined characterization of pore-fracture structures in deep coal reservoirs plays a crucial role in the occurrence and seepage of coalbed gas. This research can provide a theoretical basis for the efficient development of deep coalbed gas in the target area. This study aims to identify the primary factors controlling micropore structures in No. 8 coal from the Benxi Formation and to analyze the role of industrial components, which has been overlooked in previous research. Full article

CO₂ fracturing technology has been widely used to develop unconventional oil and gas reservoirs such as shale oil and gas and tight sandstone reservoirs. To mitigate the issues of low viscosity and high friction associated with traditional CO₂ fracturing technology, this paper proposes CO₂ quasi-dry fracturing technology. Taking the low permeability tight sandstone reservoir in Block X of T oilfield as the research object, indoor experiments were conducted to optimize the ratio of CO₂ quasi-dry fracturing fluid. Numerical simulation was used to select the optimal construction displacement using FracproPT, and the temperature and pressure changes in the reservoir and the grid after CO₂ injection were analyzed using CMG to lay a foundation for the production practice. The results show that the fracturing fluid formulation system is 70% liquid CO₂ + 30% water with 1.2% water-based thickener APQD-6 and 1.2% CO₂ thickener APFR-2; the optimal construction displacement is 3 m³/min, and the fracture half-length is 206.2 m; the reservoir temperature responds to the CO₂ injection volume more rapidly than the pressure, which indicates that CO₂ has a more significant effect on the temperature. The field application results show that the reservoir temperature responds more rapidly to the CO₂ injection volume than the pressure, indicating that CO₂ has a more significant effect on temperature. The field application results are remarkable. This operation successfully achieved the key parameter indicators of the highest sand ratio of 10% and the average sand ratio of 6%. The daily liquid production of the well was stable at 1.6 t, the daily gas production jumped by 820 m³, and the daily oil production also increased by 0.7 t. The effect of single-well stimulation is very prominent, which strongly verifies the feasibility and effectiveness of CO₂ quasi-dry fracturing technology exploiting low-porosity and low-permeability reservoirs. This practical result provides valuable practical guidance for developing similar reservoirs. It is expected to promote the further development and application of low porosity and low permeability reservoir development technology. Full article

Liquid carbon dioxide (L-CO₂) phase transition blasting technology, known for its high efficiency, environmental friendliness, and controllable energy output, has been widely applied in mine safety fields such as coal roadway pressure relief and coal seam permeability enhancement. However, the synergistic control mechanism between L-CO₂ blasting loads and in situ stress conditions on coal seam fracturing and permeability enhancement remains unclear. This study systematically investigates the key process parameters of L-CO₂ phase transition blasting in deep coal seams using response surface methodology and numerical simulation. First, three commonly used L-CO₂ blasting tubes with the overpressure of 150 MPa, 210 MPa, and 270 MPa were selected, and the corresponding material parameters and state equations were established. A dynamic mechanical constitutive model for a typical low-permeability, high-gas coal seam was then developed. A numerical model of L-CO₂ phase transition blasting, considering fluid–solid coupling effects, was then constructed. Multiple experiments were designed based on response surface methodology to evaluate the effects of blasting pressure, in situ stress, and stress difference on L-CO₂ fracturing performance. The results indicate that the overpressures of the three simulated blasting loads were 156 MPa, 215 MPa, and 279 MPa, respectively, and the load model closely matches the actual phase blasting load. L-CO₂ blasting creates a plastic deformation zone and a pulverized zone around the borehole within 500 μs to 800 μs after detonation, with a tensile fracture zone appearing at 2000 μs. By analyzing radial and tangential stresses at different distances from the explosion center, the mechanical mechanisms of fracture formation in different blast zones were revealed. Under the in situ stress conditions of this study, the number of primary fractures generated by the explosion ranged from 0 to 12, the size of the pulverized zone varied from 1170 cm² to 2875 cm², and the total fracture length ranged from 44.4 cm to 1730.2 cm. In cases of unequal stress, the stresses display axial symmetry, and the differential stress drives the fractures to expand along the direction of the maximum principal stress. This caused the aspect ratio of the external ellipse of the explosion fracture zone to range between 1.00 and 1.72. The study establishes and validates a response model for the effects of blasting load, in situ stress, and stress difference on fracturing performance. A single-factor analysis reveals that the blasting load positively impacts fracture generation, while in situ stress and differential stress have negative effects. The three-factor interaction model shows that as the in situ stress and stress difference increase, their inhibitory effects become stronger, while the enhancement effect of the blasting load continues to grow. This research provides a theoretical basis for blasting design and fracture propagation prediction using L-CO₂ phase transition blasting in the coal seam under varying in situ stress conditions, offering valuable data support for optimizing the process of L-CO₂ phase transition fracturing technology. Full article

In deep brine oil and gas injection–production operations, the combined long-term effects of brine and carbon dioxide on rock mechanical properties are not clear. In order to solve this problem, the influence of long-term salt–CO₂ environment on the mechanical properties of sandstone is discussed. The mechanism of interaction evolution and fracture propagation was studied in detail by NMR, the triaxial compression test and a CT scan. The results show that the triaxial compressive strength and mass of sandstone decrease first and then increase with the prolonging of soaking time. The proportion of micropores first decreased and then increased, while the proportion of medium and large pores first increased and then decreased. The pores obtained by Avizo’s segmentation of the threshold value of CT sections first increased and then decreased, and the fractal dimensions obtained first increased and then decreased. In particular, the calcium ions in the immersion solution increased first and then decreased. The reaction rate was obtained and verified according to the changes in calcium carbonate mass and calcium ion mineralization at different times. The failure mode of the sample gradually changed from /-shaped failure to V-shaped composite failure, then to local /-shaped failure, and finally to X-shaped composite failure. On this basis, the process of sandstone was divided into the dissolution stage, precipitation stage and secondary dissolution stage, and the rock microstructure change model under a salt–CO₂ environment was established. The mechanics, temperature, chemical interaction mechanism and fracture propagation mechanism of sandstone under a salt–CO₂ environment are discussed. Full article

The medium development characteristics and controlling factors of the karst peak forest plain water system constitute the core of analyzing the complex and variable hydrogeological environment, especially in revealing the controlling factors between the hydrological system and karst development characteristics, which is crucial for a deeper understanding of karst hydrogeological environments. This study takes Zengpiyan in Guilin as an example and conducts a dynamic clustering analysis on the advantageous occurrence of fracture development in three sampling areas. A total of 3472 karst channels and fractures were identified and measured. Our research reveals the following: (1) The high degree of development of fissures on surface rock outcrops is mainly formed by the expansion of shear joints through dissolution and erosion. The dip angles of fissures are mainly characterized by low angles, with fissures with dip angles between 18° and 80° accounting for 65.44% of the total observed fissures. The linear density of fissures is 3.64 per meter. (2) There are significant differences in the line density of cracks and fissures in different areas of the research area. For example, the line density in Sampling Area 1 is 0.99 lines per meter, while the line density in Sampling Area 3 reaches 5.02 lines per meter. In addition, the extension length of cracks is generally long, with joints with extension lengths exceeding 1.5 m accounting for 77.46% of the total observed joints and through cracks with extension lengths exceeding 5 m accounting for 23.33%. (3) The development characteristics of underground karst reveal that underground karst caves are mainly distributed at elevations of 120 to 160 m, with a drilling encounter rate of about 43.3%. It is also noted that geological structures control the horizontal distribution of karst, and geological lithology, hydrodynamic conditions, and water carbon dioxide concentrations are key factors affecting the vertical zoning of karst. This study provides an important scientific basis for understanding the development characteristics and controlling factors of karst water system media in peak forest plains and has important guiding significance for water resource management in karst areas and disaster prevention during tunnel excavation. Full article

Disuse osteoporosis occurs due to rest and reduced mechanical stimulation. Under these conditions, bone resorption exceeds bone formation, leading to a decrease in bone density. Vector potential (VP) generators have been developed, and their ability to maintain cartilage thickness has been reported. However, their effects on bone tissue remain unstudied. In this study, experiments were conducted to test the effects of VP on bones that had undergone weight reduction due to hindlimb suspension as a model of disuse osteoporosis. Methods: In this study, 7-week-old male Wistar rats (N = 6 each) were classified into control (CO), hindlimb suspension (HS), and VP energization intervention groups. The tail was used to suspend the HS and VP to remove the load applied to the hindlimbs. The VP conditions were as follows: voltage, 67 mV; frequency, 20 kHz, 0.12 mA; experimental intervention, 30 min/day, 5 days/week, for 3 weeks. At the end of the experimental period, the rats were euthanized with carbon dioxide gas, and histological specimens were fixed in 4% paraformaldehyde (PFA) in the femur and analyzed by electron microscopy, bone morphometry, immunohistology, bone fracture testing, and gene expression analysis. Results: HS decreased trabecular bone density and strength. However, VP maintained a significantly higher bone mass than HS, and VP did not differ from CO in bone strength; more osteoclasts were observed on the bone surface in HS, but they were suppressed in VP, and gene expression of CTSK and MMP-9 was decreased. Conclusions: VP suppressed bone resorption by osteoclasts, suggesting that VP is useful in the treatment of disuse osteoporosis. Full article

The pore fracture structure of deep coal reservoirs is crucial for evaluating the potential of deep coalbed methane resources, conducting exploration and development, and controlling coal mine gas disasters. Mercury intrusion porosimetry, the liquid nitrogen method, and the low-temperature carbon dioxide adsorption method were used to study the full pore size structure and pore fractal characteristics of different coal grades in deep coal and comprehensively characterize the pore structure of kilometer-level coal mining. The sponge, Frenkel–Halsey–Hill (FHH), and density function models were applied to comprehensively analyze the pore complexity of coal, and the influence of metamorphic degree on pore size structure was evaluated. The distribution relationship of pore volume in different stages of coal samples was macropore→mesopore→micropore, and macropores had the best connectivity. Micropores and mesopores had the largest specific surface area, and the development of micropores and microcracks controlled the deep gas adsorption performance. The micropore volume and specific surface area both revealed a nonlinear decreasing trend with the increase in volatile matter, and coal metamorphism promoted the development of micropores. The pore volume and specific surface area of mesopores and macropores decreased first and then increased in a “U” shape with increasing volatile matter. In contrast, the fractal dimension D₁ revealed an inverted U shape with increasing volatile matter, followed by a decrease. The D₂ value decreased nonlinearly with increasing volatile matter, whereas the D₃ value increased nonlinearly with increasing volatile matter. The degree of metamorphism increased, and the microporous structure became more regular. Full article

Diagenesis has been demonstrated to significantly affect porosity development in shale reservoirs, however, the effect of diagenetic modifications on shale pore structures is still unclear. For clarifying this issue, this paper focuses on the Upper Ordovician to Lower Silurian Wufeng and Longmaxi shales, which are the only commercially gas-produced shale plays in China. This study aims to reveal the influence of diagenetic alterations on the WF-LMX shale reservoir quality by integrating total organic carbon (TOC) content, X-ray diffraction (XRD), low-temperature gas (N₂) and carbon dioxide (CO₂) adsorption experiments, field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS), and cathodoluminescence (CL) analyses. Three major shale lithofacies were identified, mainly including siliceous, siliceous–argillaceous mixed, and argillaceous shale; the siliceous shale has a relatively high TOC content. The organic pores, intergranular pores, intragranular pores, and fractures are generally developed in the WF-LMX shales. The pore volume (PV) and specific surface area (SSA) of micropores, mesopores, and macropores of siliceous shales are higher than those of mixed shales and argillaceous shales. The TOC content has a strongly positive correlation with PV and SSA for micropores and mesopores. After combustion, the PV and SSA of micropores and mesopores were decreased, whereas the PV and SSA of macropore were significantly increased. In the siliceous shale, organic pore is the dominant pore type due to the fact that a large amount of authigenic microcrystalline quartz aggregates can protect organic pores from compaction. The argillaceous shale has high clay and low TOC content, and the dominant pore type is pores between clay flakes. The siliceous shale has a relatively high TOC content, large PV and SSA, and so are the dessert lithofacies for shale gas exploration. Full article

The application of carbon dioxide (CO₂) in enhanced oil recovery (EOR) projects is becoming increasingly more interesting in the petroleum industry because it can boost oil production rates while potentially reducing greenhouse gas emissions. The injected CO₂ causes oil swelling and viscosity reduction, making it easier to flow through the reservoir fractures. This article studies the performance of the first EOR CO₂ project in Croatia, which started operations in 2014 with a capacity of 0.41 million tons per year (Mtpa). The CO₂ source is a natural gas processing plant, which released the CO₂ into the atmosphere prior to the EOR project. Now, this CO₂ is continuously captured, compressed, transported, liquefied, and injected into the EOR fields of Ivanić and Žutica. Tertiary (EOR) oil recovery at these two oil fields is expected to raise the oil recovery factors up to 55% from the previously achieved 9% in the primary stage and 36% in the secondary stage. Besides the EOR project, this article reviews other carbon capture, utilization, and storage (CCUS) projects in Croatia, for the cement industry, power generation, and biofuel production. All these projects combined could bring the total CCUS capacity up to 1.843 Mtpa by 2030. Full article