Search Results (125)

Tests during methane hydrate (MH) production in Japan have shown that excessive water production is a primary challenge in MH development. It can lead to sand production, inhibit effective reservoir depressurization, and hinder gas production. This study investigated the ability of a reactive grout, produced by the in situ reaction of CO₂ with sodium silicate (SS), to inhibit water generation from unconsolidated sand layers by forming a water-blocking gel barrier. The performance of this grout was evaluated through laboratory experiments using silica sand as a porous medium. Under controlled conditions, diluted SS and CO₂ were sequentially injected. The injection and gelation processes were monitored in real time using CT scanning, and SEM was employed to analyze the microstructure of the reaction products. The results indicated that SS exhibited piston-like flow, with elevated concentrations increasing viscosity and promoting more uniform injection. CO₂ injection resulted in successful in situ gel formation. A homogeneous gel distribution decreased permeability by ~98% when the SS concentration was 25 wt%. However, at 50 wt%, rapid localized gelation caused preferential flow paths and reduced sealing efficiency. These findings highlight the potential of CO₂ reactive grouting for water management in MH exploitation and the importance of optimizing injection parameters. Full article

Gas hydrate-bearing sediments in marine environments represent both a future energy source and a geohazard risk, prompting increasing international research attention. In the Shenhu area of the South China Sea, a large volume of drilling and laboratory data has been acquired in recent years, yet a comprehensive framework for evaluating the characteristics of key reservoir parameters remains underdeveloped. This study presents a spatially integrated and statistically grounded framework that captures regional-scale heterogeneity using multi-source in situ datasets. It incorporates semi-variogram modeling to assess spatial variability and provides statistical reference values for geological and geotechnical properties across the Shenhu Area. By synthesizing core sampling results, acoustic logging, and triaxial testing data, representative probability distributions and variability scales of hydrate saturation, porosity, permeability, and mechanical strength are derived, which are essential for numerical simulations of gas production and slope stability. Our results support the development of site-specific reservoir models and improve the reliability of early-phase hydrate exploitation assessments. This work facilitates the rapid screening of hydrate reservoirs, contributing to the efficient selection of potential production zones in hydrate-rich continental margins. Full article

In comparison to shallow coal seams, deep coal seams exhibit characteristics of high temperature, pressure, and in-situ stress, leading to significant differences in reservoir properties that constrain the effective development of deep coalbed methane (CBM). This study takes the Carboniferous deep 8# coal seam in the Yulin area of Ordos basin as the research subject. Based on the test results from core drilling wells, a comprehensive analysis of the characteristics and variation patterns of coal reservoir properties and a comparative analysis of the exploration and development potential of deep CBM are conducted, aiming to provide guidance for the development of deep CBM in the Ordos basin. The research results indicate that the coal seams are primarily composed of primary structure coal, with semi-bright to bright being the dominant macroscopic coal types. The maximum vitrinite reflectance (R_o,max) ranges between 1.99% and 2.24%, the organic is type III, and the high Vitrinite content provides a substantial material basis for the generation of CBM. Longitudinally, influenced by sedimentary environment and plant types, the lower part of the coal seam exhibits higher Vitrinite content and fixed carbon (FC_ad). The pore morphology is mainly characterized by wedge-shaped/parallel plate-shaped pores and open ventilation pores, with good connectivity, which is favorable for the storage and output of CBM. Micropores (<2 nm) have the highest volume proportion, showing an increasing trend with burial depth, and due to interlayer sliding and capillary condensation, the pore size (<2 nm) distribution follows an N shape. The full-scale pore heterogeneity (fractal dimension) gradually increases with increasing buried depth. Macroscopic fractures are mostly found in bright coal bands, while microscopic fractures are more developed in Vitrinite, showing a positive correlation between fracture density and Vitrinite content. The porosity and permeability conditions of reservoirs are comparable to the Daning–Jixian block, mostly constituting oversaturated gas reservoirs with a critical depth of 2400–2600 m and a high proportion of free gas, exhibiting promising development prospects, and the middle and upper coal seams are favorable intervals. In terms of resource conditions, preservation conditions, and reservoir alterability, the development potential of CBM from the Carboniferous deep 8# coal seam is comparable to the Linxing block but inferior to the Daning–Jixian block and Baijiahai uplift. Full article

Type IV hydrogen storage cylinders are pivotal for high-pressure hydrogen storage and transportation, offering advantages such as lightweight design, high hydrogen storage density, and cost efficiency. Polyamide 6 (PA6) has emerged as a promising liner material due to its excellent mechanical strength, chemical resistance, and gas barrier properties. However, challenges remain, including high hydrogen permeability and insufficient mechanical performance under extreme temperature and pressure conditions. This review systematically summarizes recent advances in modification strategies to enhance PA6’s suitability for Type IV hydrogen storage cylinders. Incorporating nanofillers (e.g., graphene, montmorillonite, and carbon nanotubes) significantly reduces hydrogen permeability. In situ polymerization and polymer blending techniques improve toughness and interfacial adhesion (e.g., ternary blends achieve a special increase in impact strength). Multiscale structural design (e.g., biaxial stretching) and process optimization further enhance PA6’s overall performance. Future research should focus on interdisciplinary innovation, standardized testing protocols, and industry–academia collaboration to accelerate the commercialization of PA6-based composites for hydrogen storage applications. This review provides theoretical insights and engineering guidelines for developing high-performance liner materials. Full article

Mobilisation of in situ fine particles within oil sands reservoirs plays a critical role in permeability reduction and pore throat blockage, ultimately impairing reservoir performance and diminishing well productivity during thermal recovery operations. Variations in reservoir fluid conditions, such as changes in salinity and temperature, trigger the detachment, transport, and redeposition of fines within porous media. This study introduces a novel high-pressure high-temperature (HP-HT) sand retention testing (SRT) facility designed for evaluating formation damage by fines migration in SAGD producer wells, under salinity change and elevated temperature conditions. Such an integrated approach accounting for conditions closer to near-wellbore SAGD producers has not been explored in previous SRT methodologies. Laboratory tests were conducted on synthetic sand mixtures replicating the particle size distribution (PSD) and sand composition of the McMurray Formation, packed over a slotted liner coupon as a common sand control device used in SAGD producer wells. Produced fines concentration analysis, permeability measurements, and post-mortem retention profile analysis were employed to explain the fines transport mechanisms. The results highlighted the influence of repulsive electrostatic forces in mobilising, transport mechanisms and retention of fine particles at elevated temperature and low salinity conditions. The findings of this paper provide a deeper understanding of fines migration in SAGD reservoirs, delivering insights for optimising field strategies to mitigate fines-related flow restrictions and enhance bitumen recovery efficiency. Full article

Water injection is the most widely used secondary recovery method, but its low viscosity limits sweep efficiency in heterogeneous carbonate reservoirs, especially when displacing heavy crude oils. Polymer flooding overcomes this by increasing the viscosity of the injected fluid and improving the mobility ratio. In this work, we compare three biopolymers (i.e., Xanthan Gum, Scleroglucan, and Guar Gum) using a core flood test on Indiana Limestone with 16–19% porosity and 180–220 mD permeability at 60 °C and 30,905 mg/L of salinity. We injected solutions at 100–1500 ppm and 0.5–6 cm³/min to measure the Resistance Factor (RF), Residual Resistance Factor (RRF), in situ viscosity, and relative injectivity. All polymers behaved as pseudoplastic fluids with no shear thickening. The RF rose from ~1.1 in the dilute regime to 5–16 in the semi-dilute regime, and the RRF spanned 1.2–5.8, indicating moderate, reversible permeability impairment. In-site viscosity reached up to eight times that of brine, while relative injectivity remained 0.5. Xanthan Gum delivered the highest viscosity boost and strongest shear thinning, Scleroglucan offered a balance of stable viscosity and a moderate RF, and Guar Gum gave predictable but lower viscosity enhancement. These results establish practical guidelines for selecting polymer types, concentration, and flow rate in reservoir-condition polymer flood designs. Full article

The distribution of leachate in landfill systems significantly influences landfill stability, pollutant migration, and gas transport. However, existing methods for measuring leachate levels in landfills with multiple intermediate cover layers remain insufficient. This study introduces a novel in situ testing method to determine multi-layer leachate levels. Field experiments at a landfill site in northwestern China successfully quantified leachate levels on each intermediate cover layer. Seepage analysis simulated the leachate level recovery test method used in field investigations, enabling examination of the formation mechanisms and drainage characteristics of multi-layer leachate systems. Measurement results demonstrated that each intermediate cover layer retained a corresponding perched leachate level. Variations in perched water head across waste layers arise from differences in drainage capacity between waste strata. Differential settlement of the intermediate cover layers in localized areas generated adverse hydraulic gradients, contributing to spatial heterogeneity in perched leachate distribution. Back analysis yields an in situ saturated hydraulic conductivity ranging from 1 × 10⁻⁴ to 3.3 × 10⁻³ cm/s. Low-permeability intermediate cover layers were identified as the primary factors contributing to multi-layer leachate formation. The implementation of effective horizontal drainage can reduce perched leachate accumulation above intermediate layers. Full article

Hydraulic fracturing significantly impacts water production. This makes it crucial to determine whether its effects on formation water production are beneficial or detrimental in complex reservoir stimulations. This paper gives the influence that acts on pore structure variations and irreducible water transformation by hydraulic fracturing; by using NMR and Micro-CT, pore-throat reconfiguration in core samples induced fracturing. Two main pore variation types were identified from CT images. To analyze the gas–water flow mechanisms in pre-fracturing and post-fracturing reservoir conditions, we tested quantifying changes in irreducible water transforms into movable water saturation by using a triaxial in situ flow system, thereby elucidating the impact of the hydraulic fracture on irreducible water saturation. The experiments demonstrate that pore structures are significantly modified in terms of connectivity and diameter through hydraulic fracturing. During damage zone formation, 12.4–19.2% of small pores coalesce into larger pores through integration of isolated spaces. This variation enhances fluid mobility, transforms 1.38–11.61% of irreducible water, and decreases starting pressure gradients by 1 MPa/100 m to 0.1 MPa/100 m. Modified pore structure leads to the iso-permeability point shifting toward higher water saturation. The gas-phase relative permeability at irreducible water saturation is two times as high as that of the matrix sample. Fractured zones show a 20–23% conversion efficiency of irreducible to movable water. In addition, based on the results of experimental data, hydraulic fracturing increased water production by 3607 to 9163 m³. However, this effect is only maintained during the first 3 to 6 months post-fracture. These results quantify the transformation of irreducible water into movable water in hydraulic fracturing. This study provides key performance indicators for gas reservoir applications. Full article

A novel cost-effective, rapid, and eco-friendly method was described for the removal of carbon dioxide (CO₂) from the gaseous emissions of gasoline engines. This involved the use of a sandwich filter (~10 cm diameter) made of a nonwoven poly (m-phenylene isophthalamide) (Nomex) fabric loaded with a thin layer of activated carbon. The optimized filter, with an activated carbon mass of 2.89 mg/cm², a thickness of 4.8 mm, and an air permeability of 0.5 cm³/cm²/s, was tested. A simple homemade sampling device equipped with solid-state electrochemical sensors to monitor the concentration levels of CO₂ before and after filtration of the emissions was utilized. The data were transmitted via a General Packet Radio Service (GPRS) link to an Internet of Things (IoT)-based gas monitoring system for remote management, and real-time data visualization. The proposed device achieved a 70 ± 3.4% CO₂-removal efficiency within 7 min of operation. Characterization of the filter was conducted using a high-resolution scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Brunauer–Emmett–Teller (BET) analysis. The effects of loaded activated carbon mass, fabric type, filter porosity, gaseous removal time, and adsorption kinetics were also examined. The proposed filter displayed several advantages, including simplicity, compactness, dry design, ease of regeneration, scalability, durability, low cost, and good efficiency. Heat resistance, fire retardancy, mechanical stability, and the ability to remove other gasoline combustion products such as CO, SO_x, NO_x, VOCs, and particulates were also offered. The filtration system enabled both in situ and on-line CO₂ real-time continuous emission monitoring. Full article

Wastewater reinjection is an important measure for balancing the sustainable development of petroleum resources with environmental protection. However, the polymer-containing wastewater generated after polymer injection presents challenges such as reservoir damage and waterflooded zone identification in oilfields. To address this, this study systematically examined the impact of injection water with varying salinities on the flow characteristics and electrical responses of low-permeability reservoirs, based on rock-electrical and multiphase displacement experiments. Additionally, this study analyzed the factors influencing the damage to reservoirs during polymer-containing wastewater reinjection. Mass spectrometry, chemical compatibility tests, and SEM-based micro-characterization techniques were employed to reveal the micro-mechanisms of reservoir damage during the reinjection process, and corresponding protective measures were proposed. The results indicated the following: (1) The salinity of injected water significantly influences the electrical response characteristics of the reservoir. When low-salinity wastewater is injected, the resistivity–saturation curve exhibits a concave shape, whereas high-salinity wastewater results in a linear and monotonically increasing trend. (2) Significant changes were observed in the pore-throat radius distribution before and after displacement experiments. The average frequency of throats within the 0.5–2.5 µm range increased by 1.894%, while that for the 2.5–5.5 µm range decreased by 2.073%. In contrast, changes in the pore radius distribution were relatively minor. Both the experimental and characterization results suggest that pore-throat damage is the primary form of reservoir impairment following wastewater reinjection. (3) To mitigate formation damage during wastewater reinjection, a combined physical–chemical deblocking strategy was proposed. First, multi-stage precision filtration would be employed to remove suspended solids and oil contaminants. Then, a mildly acidic organic-acid-based compound would be used to inhibit the precipitation of metal ions and dissolve the in situ blockage within the core. This integrated approach would effectively alleviate the reservoir damage associated with wastewater reinjection. Full article

Compared with traditional gas reservoirs, ultra-deep and ultra-high-pressure tight sandstone gas reservoirs are characterized by well-developed faults and fractures, strong heterogeneity and stress sensitivity, and complex in situ stress distribution. Traditional three-dimensional geological models and numerical models ignore the variation characteristics of reservoir in situ stress during the production process, it affects the accuracy of the subsequent fracturing modification design and development plan formulation. Therefore, based on the integrated method of geological engineering, this article first carried out high-temperature and high-pressure stress sensitivity tests on reservoir rock samples and fitted the stress-sensitive mathematical model to clarify the influence of high temperature and high pressure on permeability. Then, aiming at the problem of four-dimensional in situ stress variation caused by the coupling of the seepage field and stress field during the exploitation of tight sandstone gas reservoirs, combined with the results of well logging interpretation, rock physical property analysis, and mechanical experiments, based on the three-dimensional geological model and geomechanical model of the gas reservoir and coupled with the stress-sensitive characteristics of the reservoir, a four-dimensional in situ stress model for the reservoir of tight sandstone gas reservoirs was established. The prediction of the variation law of four-dimensional in situ stress during the production process was carried out. Finally, the influence of considering stress sensitivity on reservoir production was simulated. The results show the following: ① The production process has a significant impact on the magnitude and distribution of four-dimensional in situ stress. With the decrease in pore pressure, both the maximum horizontal principal stress and the minimum horizontal principal stress decrease. ② In the area near the production well, the direction of in situ stress will significantly deflect over time. ③ In an ultra-deep and ultra-high-pressure environment, the gas reservoir is affected by the stress-sensitive effect. The stable production time of the gas well is reduced by two years, and the cumulative gas production decreases by 5.01 × 10⁸ m³. The research results provide the temporal stress field distribution results for the simulation and prediction of the secondary fracturing of old wells and the commissioning fracturing of new wells in the target well area. Full article

In in situ leaching, fine particles can be stripped and transported with the leach solution, significantly altering the particle size distribution and pore structure of each layer of the rare earth ore body. In this study, water and magnesium sulfate were used as leaching agents. Based on indoor column leaching experiments, particle gradation experiments, and pore structure tests, this study investigates and analyzes the patterns of particle migration and changes in pore structure in rare earth ores with varying fine particle contents under leaching conditions. The results indicate that during the leaching process, the degree of change in particle gradation follows the order of upper layer > middle layer > lower layer. As the depth increases, the soil becomes denser, leading to reduced permeability, a slower seepage rate of the leaching solution, and a higher fine particle content, making the effect more pronounced. During magnesium sulfate leaching, the overall trend of porosity in the rare earth ore structure initially increases and then decreases. Additionally, a higher fine particle content corresponds to higher porosity. In the early and late stages of leaching, pore size changes involve the transformation of larger pores into smaller ones, followed by the conversion of smaller pores into larger ones. Moreover, the higher the fine particle content, the greater the degree of transformation between the pore sizes. Full article

Bitumen extraction using Steam-Assisted Gravity Drainage (SAGD) in northern Alberta oilsands has been crucial for recovery; however, the thermal effects on formation damage still require significant attention. This thermal recovery method causes substantial changes in temperature and pressure, which are critical thermodynamic factors in the rock-fluid system of a reservoir. Those changes, both directly and indirectly, impact the flow of oil and water within the porous medium, changing fluid properties and physicochemical interactions that affect rock and fluid behaviour. Coreflooding experiments confirm the accumulation of in situ migratory particles within the pore spaces can lead to pore throat plugging and fines accumulation on the sand control screen. This disturbance within the near-wellbore region triggers permeability reduction and, subsequently, skin buildup. At the same time, changes in pressure drop may trigger the precipitation of organic and inorganic scaling and, finally, wettability alterations. This paper combines field observations and experimental tests to assess the formation damage mechanisms. While the literature has identified factors influencing the formation damage mechanisms, the interaction between these mechanisms, as well as the interplay between the wellbore completion and the surrounding sand from the perspective of formation damage, has not been thoroughly investigated. Current laboratory tests do not adequately account for the effects of high pressure and high temperature on formation damage mechanisms and their interaction in the near-wellbore region. Following the introduction of current experimental and theoretical methods related to formation damage mechanisms around SAGD wellbores, this paper introduces a comprehensive and integrated methodology for designing, testing, and evaluating formation damage mechanisms in SAGD producer wells, addressing the gaps identified in this review. This approach aims to bridge identified gaps from the literature review, advance formation damage assessment, and support the reduction of induced formation damage in thermal recovery operations. Full article

Engineers, geomorphologists, and ecologists acknowledge the need for temporally and spatially resolved measurements of sediment clogging (also known as colmation) in permeable gravel-bed rivers due to its adverse impacts on water and habitat quality. In this paper, we present a novel method for non-destructive, real-time measurements of pore-scale sediment deposition and monitoring of clogging by using wire-mesh sensors (WMSs) embedded in spheres, forming a smart gravel bed (GravelSens). The measuring principle is based on one-by-one voltage excitation of transmitter electrodes, followed by simultaneous measurements of the resulting current by receiver electrodes at each crossing measuring pores. The currents are then linked to the conductive component of fluid impedance. The measurement performance of the developed sensor is validated by applying the Maxwell Garnett and parallel models to sensor data and comparing the results to data obtained by gamma ray computed tomography (CT). GravelSens is tested and validated under varying filling conditions of different particle sizes ranging from sand to fine gravel. The close agreement between GravelSens and CT measurements indicates the technology’s applicability in sediment–water research while also suggesting its potential for other solid–liquid two-phase flows. This pore-scale measurement and visualization system offers the capability to monitor clogging and de-clogging dynamics within pore spaces up to 10,000 Hz, making it the first laboratory equipment capable of performing such in situ measurements without radiation. Thus, GravelSens is a major improvement over existing methods and holds promise for advancing the understanding of flow–sediment–ecology interactions. Full article

Cytarabine (CTR) is a hydrophilic anticancer drug used to treat leukemia. It suffers from poor permeability and intestinal metabolism, diminishing its oral bioavailability. Background/Objectives: The objective was to develop and evaluate niosomes and bilosomes for enhanced intestinal absorption; hence, oral bioavailability. Results: CTR-loaded niosomes and bilosomes with vesicle sizes of 152 and 204.3 nm were successfully prepared with acceptable properties. The presence of bile salts increased the zeta potential of bilosomes. The recorded entrapment efficiency of cytarabine was acceptable for such a hydrophilic drug. CTR-bilosomes showed a pH-dependent drug release pattern with preferred release in pH 6.8. Intestinal absorption behavior indicated a site-dependent CTR absorption pattern with unfavorable absorption in the distal intestine. Niosomal and bilosomal formulations enhanced intestinal absorption parameters with evidence for a predominant paracellular absorption mechanism that bypasses intestinal barriers. The investigation of the anti-leukemic effect of niosomal and bilosomal formulations indicated that both formulations ameliorated the blood parameters, reflecting significant improvement in leukemia treatment compared with the drug solution. Pathological examination of blood films revealed decreased blast cells in peripheral blood in groups treated with tested formulations. Methods: Tested formulations were prepared according to the pro-concentrate method and characterized for particle size, zeta potential, entrapment efficiency, and in vitro release. CTR-loaded niosomes and bilosomes were evaluated for enhanced intestinal absorption utilizing the single-pass in situ intestinal perfusion method in rabbits, and the anti-leukemic effect was assessed using the benzene-induced leukemia model in rats. Conclusions: This study introduced surfactant vesicles for enhanced oral bioavailability of CTR. Full article