Search Results (1,789)

Member 2 of the Xujiahe Formation in the Anyue area of the Sichuan Basin exhibits significant resource potential for tight sandstone gas. However, its characteristic of “extensive gas presence with localized enrichment” leads to substantial variations in single-well productivity, challenges in target zone optimization, and unclear enrichment mechanisms, which hinder efficient exploration and development. This study proposes a hierarchical classification scheme of “two-level, six-type” source–reservoir structures based on the developmental characteristics of fault–fracture systems and vertical source–reservoir configurations. The gas-bearing heterogeneity is quantitatively characterized using parameters such as effective gas layer thickness, charge intensity, and effective gas layer probability, thereby revealing the differential enrichment mechanisms of tight sandstone gas controlled by source–reservoir structures. Our key findings include the following: (1) Member 2 of the Xujiahe Formation develops six subtypes of source–reservoir structures grouped into two levels, with gas-bearing capacities ranked as follows: source–reservoir separation type > source–reservoir adjacent type I > source–reservoir adjacent type II. Among these, the source–reservoir separation type (Level I) and fault–fracture conduit type (Level II) represent the most favorable structures for gas enrichment. (2) Tight sandstone gas enrichment is governed by a tripartite synergistic mechanism: hydrocarbon supply from source rocks, vertical cross-layer migration dominated by fault–fracture systems, and reservoir storage capacity determined by fracture density and reservoir thickness. (3) Three enrichment models are established: (i) a strong enrichment model characterized by “multi-layer source rocks beneath the reservoir, cross-layer migration, and thick fractured reservoirs”; (ii) a moderate enrichment model defined by “single-layer source rocks, localized migration, and medium-thick fractured reservoirs”; and (iii) a weak enrichment model featuring “single-layer hydrocarbon supply, pore-throat migration, and thin tight reservoirs.” This research provides a theoretical basis for optimizing exploration targets in Member 2 of the Xujiahe Formation in the Anyue area and offers insights applicable to analogous continental tight gas reservoirs. Full article

Sandstone-hosted uranium deposits represent one of the most critical global uranium resources suitable for in situ recovery, with their formation closely associated with organic matter (OM). We conducted a systematic literature review to synthesize over 100 published studies sourced from authoritative databases (Elsevier, Google Scholar, Web of Science, Scopus, CNKI, etc.). This study systematically summarizes the types and geological characteristics of OM in sandstone reservoirs and thoroughly analyzes the geochemical mechanisms by which OM regulates the transport and precipitation of aqueous uranium. By integrating case studies of representative sandstone uranium deposits globally, three major OM-related metallogenic models are proposed with distinct core characteristics: the humic-dominated model is driven by the complexation and direct reduction of uranium by humic substances/coal-derived OM; the roll-front model relies on reactions between oxidized uranium-bearing fluids and scattered OM, as well as microbially generated sulfides at the migration front; and the seepage-related model is fueled by upward-migrating deep hydrocarbon fluids (petroleum, methane) that act as both uranium carriers and reductants. Furthermore, this review explores the spatial coupling relationships between OM distribution and uranium mineralization in typical geological settings, evaluates the guiding significance of OM for uranium exploration, and outlines key unresolved scientific issues. The findings refine the genetic theoretical framework of sandstone-hosted uranium deposits and provide important technical support and theoretical guidance for future uranium exploration deployment and resource potential evaluation. Full article

Natural fractures in tight sandstone reservoirs are the key factors controlling hydrocarbon flow and productivity. The Bozi-1 gas reservoir in the Kuqa Depression, as a typical ultra-deep tight sandstone gas reservoir, is characterized by low-porosity and ultra-low-permeability sandstones. This study addresses the limitations of previous fracture characterization, which primarily focused on macro-structural fractures while neglecting medium- and small-scale fractures. We integrate multi-source heterogeneous data, including core, well-logging imaging, seismic, and production observations, to systematically conduct multi-scale natural fracture characterization and modeling. First, the overall geology of the study area is briefly introduced, followed by a detailed description of the development characteristics of large-scale and medium–small-scale fractures, achieving a multi-scale representation of complex curved fracture networks. Finally, the three-dimensional multi-scale fracture model is validated using static indicators, including production characteristics, water invasion features, and well leakage data. The main findings are as follows: (1) Large-scale fractures in the Bozi-1 reservoir are mainly oriented near EW, NE–SW, and NW–SE, acting as the primary hydrocarbon migration pathways. Medium–small-scale fractures predominantly develop near SN, NE–SW, NW–SE, and near EW directions, exhibiting strong heterogeneity. (2) The complex curvature of large-scale fractures was captured by the “adaptive sampling + segmented splicing + equivalent distribution of fracture flow capacity” method, while the distribution of effective medium–small-scale fractures across the study area was represented using “single-well Stoneley wave inversion + seismic machine learning prediction”, achieving an 86% match with actual single-well measurements. (3) Model reliability was further verified through static comparisons, including production characteristics (unimpeded flow vs. effective fracture density, R² = 0.92), water invasion features (fracture-dominated water invasion matching fracture distribution), and well leakage characteristics (matching rate of high fracture density zones: 84.2%). The results provide key technical support for the precise characterization of fracture systems and establish a model ready for dynamic simulation in ultra-deep tight sandstone gas reservoirs. Full article

Groundwater is one of the main sources of water supply in tropical developing countries; however, its integrated management is often constrained by limited hydrogeological information and increasing anthropogenic pressures on aquifer systems. This study presents the numerical modeling of groundwater flow in the Neogene–Quaternary aquifer system of the Middle Magdalena Valley (Colombia), focusing on the rural area of Puerto Wilches, which is characterized by strong surface–groundwater interactions, particularly with the Yarirí wetland and the Magdalena River. A three-dimensional model was implemented and calibrated in FEFLOW v.8.1 under steady-state and transient conditions, integrating both primary and secondary data. The dataset included piezometric levels measured with water level meters and automatic loggers, hydrometeorological records, 21 physicochemical and microbiological parameters analyzed in 45 samples collected during three field campaigns under contrasting hydrological conditions, 79 pumping tests, detailed lithological columns from drilled wells, and complementary geological and geophysical models. The results indicate a predominant east–west groundwater flow from the Eastern Cordillera toward the Magdalena River, with seasonal recharge and discharge patterns controlled by the bimodal rainfall regime. Microbiological contamination (total coliforms in 69% of groundwater samples) and nitrate concentrations above 10 mg/L in 21% of wells were detected, mainly due to agricultural fertilizers and domestic wastewater infiltration. Particle tracking revealed predominantly horizontal flow paths, with transit times of up to 800 years in intermediate units of the Real Group and around 60 years in shallow Quaternary deposits, highlighting the differential vulnerability of the system to contamination. These findings provide scientific foundations for strengthening integrated groundwater management in tropical regions under agroindustrial and hydrocarbon pressures and emphasize the need to consolidate monitoring networks, promote sustainable agricultural practices, and establish preventive measures to protect groundwater quality. Full article

Colorectal cancer (CRC) remains the third leading cause of mortality among cancer patients in developed countries. Each new study in this field can contribute to better detection, diagnosis, and treatment of this disease. Our study aimed to assess transcriptional activity of genes associated with the biotransformation of xenobiotics and endobiotics in all three phases in the CRC adenocarcinoma, including correlations between them, as well as the aromatic hydrocarbon receptor (AhR) pathways. Based on transcriptome analysis (1252 mRNAs) of the CRC tissue and healthy colon, the upregulation or downregulation of 46 significant mRNAs was presented. The study also revealed the downregulation of AKR7A2 and upregulation of SLC5A6 and SLC29A2, previously undistinguished and potentially therapeutically valuable in CRC. The diagnostic potential of ADH1C, GGT5, NQO2, and SLC25A5 was demonstrated. It was stated that the AHR, EPHX1, GSTP1, and SLC25A32 did not correlate in healthy intestinal tissue whereas AHCY, ALDH1A1, NNMT, GSTM4, UGT2B17, and SLCO1B3 did not correlate in CRC. The disturbed transcriptional activity of genes related to the biotransformation process at all stages of CRC suggests that this may be the cause of its occurrence; the genes ought to be taken into account in preventive strategies and the treatment of patients. Full article

The aim of this work is to implement decision tree classifiers (DTCs) capable of distinguishing bee honey by geographical origin. The case study focuses on honeys from the lowland and highland regions of Chiriquí, Panama. Characterization was conducted by analyzing their typical physicochemical and aromatic profiles using AOAC, IHC, and e-Nose methodologies, respectively. Data mining provided insights into the most relevant features, enabling the reduction of an otherwise extensive and resource-intensive dataset. The critical markers identified include reducing sugars, ash, antioxidant capacity, HMF, as well as aromatic, aliphatic, hydrocarbon, and sulfur compounds. This simplified set of features produced an intuitive classification scheme, achieving up to 86% accuracy. This proof-of-concept demonstrates that interpretable models can effectively leverage easily measurable characteristics for regional differentiation, offering a valuable tool for traceability in the Panamanian honey industry. Full article

The Hongche Fault Zone in the Junggar Basin exhibits significant spatiotemporal variations in the relationship between fault systems and hydrocarbon accumulation across different structural belts. Two key factors contribute to this phenomenon: frequent tectonic activities and well-developed Paleozoic fault systems. To date, no detailed studies have been conducted on the fault systems in the Paleozoic strata of the Hongche Fault Zone. In this study, the fault systems in the Paleozoic strata of the Hongche Fault Zone were systematically sorted out for the first time. Furthermore, the controlling effects of active faults in different geological periods on hydrocarbon charging were clarified. Firstly, basing on the 3D seismic and well-log data, the structural framework and fault activity, fault systems, source-contacting faults were characterized. Vertically, the Hongche Fault Zone experienced three major thrusting episodes followed by one weak extensional subsidence Stage, forming four principal tectonic layers: Permian (Thrusting Episode I), Triassic (Thrusting Episode II), Jurassic (Thrusting Episode III), and Cretaceous–Quaternary (Post-Thrusting Subsidence). Laterally, six fault systems are identified: Middle Permian (Stage I), Late Triassic (Stage II), Jurassic (Stage III), post-Cretaceous (Stage IV), as well as composite systems from Middle Permian–Jurassic (Stages I–III) and Late Triassic–Jurassic (Stages II–III). These reveal multi-stage, multi-directional composite structural characteristics in the study area. According to the oil–source correlation, the Carboniferous reservoir is primarily sourced by Permian Fengcheng Formation source rocks in the Shawan Sag. Hydrocarbon migration tracing shows that oil migrates along faults, progressively charging from depression zones to thrust belts and uplifted areas. In this process, fault systems exert hierarchical controls on accumulation: Stage I faults dominate trap formation, Stages II and III faults regulate hydrocarbon migration, accumulation, and adjustment, while Stage IV faults influence hydrocarbon conduction in Mesozoic–Cenozoic reservoirs. By clarifying the fault-controlled hydrocarbon accumulation mechanisms in the Hongche Fault Zone, this study provides theoretical guidance for two key aspects of the Carboniferous reservoirs in the study area: the optimization of favorable exploration zones and the development of reserves. Full article

The depositional environment of the Machów Formation in the central part of the Carpathian Foredeep is still relatively poorly understood. Although lithological variability, facies diversity, and depositional history have been described in many publications, the paleoenvironment of sedimentation and the evolution of individual segments of the sedimentary basin are still not well known. The Miocene complex is difficult to recognize using standard seismic interpretation methods due to cumulative effects of depositional, erosional, and tectonic processes. Progress in science and technology offers new opportunities for the application of high-resolution methods of seismic data interpretation, such as seismostratigraphic interpretation, seismic facies analysis, and seismic geomorphology. The results of seismostratigraphic interpretation of the Machów Formation indicate the presence of numerous depositional sequences of varying thickness and spatial range. The interpretation enabled identification of various types of paleoenvironments, typical for both deeper basin zones (e.g., slope and basin floor fans) and coastal environments. Based on the research conducted, it was concluded that high-resolution 3D seismic data play an essential role in the detection and visualization of lithostratigraphic traps for hydrocarbons, which is important both in exploration and in determining hydrocarbon migration pathways. Full article

Railway sites are characterized by the frequent occurrence of soil and groundwater pollution by oil. The primary reason for pollution is usually the handling of large volumes of fuels and lubricants and, to a lesser extent, other hazardous substances, which represent an increased likelihood of potential spills due to inattention and accidents. The second factor is spills due to inadequate (aged) process equipment. In the Slovak Republic, a network of locomotive depots, strategically located throughout the country, has been operated in the past. In 2008, a pilot project was implemented to survey groundwater quality at 45 sites, followed by monitoring of the quality status until 2014. The levels of petroleum hydrocarbons in groundwater were determined by spectrophotometric methods (NEC-IR and NEC-UV). The NEC-IR parameter documented very-high pollution at 14 sites, while the NEC-UV parameter documented the same very-high pollution degree at 23 sites. Statistical evaluation using Kruskal–Wallis test followed by Dunn’s post hoc test revealed a significant effect of the size of the site as well as activity status on the presence and intensity of pollution. The presence of light non-aqueous phase liquids (LNAPLs) was observed at almost half of the sites. Based on the evaluated data, railway sites represent a specific type of site with frequent occurrence of severe oil pollution, posing a significant environmental and health risk. Full article

This research investigates how blending ethanol with gasoline influences both gaseous and particulate emissions, as well as the toxicological characteristics of particulates emitted from a plug-in hybrid electric vehicle adapted to run on fuel mixtures containing up to 85% ethanol by volume. Testing was conducted on E10, E30, and E83 fuels, while the vehicle was exercised on a chassis dynamometer over three repetitions of the Federal Test Procedure and US06 cycles. Results showed important reductions in nitrogen oxide emissions for E30 and E83 for both cycles, along with reductions in particulate matter mass, black carbon, and solid particle number. Total hydrocarbon emissions demonstrated increases with E30 and E83 and tracked well with increases in benzene, toluene, ethylbenzene, and xylene isomers. Formaldehyde and acetaldehyde emissions trended in sympathy with higher-ethanol blending. The use of E30 and E83 blends produced more reactive emissions, which subsequently adversely affected the ozone-forming potential for these fuels compared to E10. The toxicological properties exhibited mixed results, with the higher-ethanol blends showing reduced oxidative stress compared to E10, while E83 induced a higher cytotoxic response relative to E30 and E10 fuels. Full article

The development of new approach methodologies that include human cells differentiated into organotypic formats is of high interest due to their structural and functional similarities to tissues in vivo, enabling mechanistic understanding and translation to adverse health outcomes in humans. However, these systems often fail to capture complex intercellular signaling required for processes such as pulmonary inflammation induced by polycyclic aromatic hydrocarbons (PAHs). To investigate airway epithelial–macrophage interactions in response to benzo[a]pyrene and a PAH mixture (Tox Mix), co-culture models utilizing primary human bronchial epithelial cells (HBECs) differentiated at the air–liquid interface were cultured with THP-1 macrophages either directly or indirectly, alongside HBECs alone. After 24 h of exposure, cytokine expression (IL1B, IL6, CXCL8, TNF) as well as PAH biomarkers previously identified for chemical metabolism (CYP1A1, CYP1B1), oxidative stress (ALDH3A1, HMOX1, NQO1), and barrier integrity (TJP2) were evaluated. Cytotoxicity and barrier integrity were also assessed. HBECs alone and direct co-cultures exhibited similar responses after PAH treatment, while indirect co-cultures showed lower sensitivity to induction of inflammatory cytokines and CYP1A1 and CYP1B1 biomarker expression following exposure to PAHs. The expression of other biomarkers, including ALDH3A1, HMOX1, and NQO1, remained largely consistent across all models after treatment. Overall, these findings suggest that direct co-culture systems may provide a more physiologically relevant platform for studies of PAH-induced toxicity and demonstrate that the configuration of co-culture systems can influence cellular responses to chemical exposure. Full article

Calcareous sandstones, acting as sealing layers, play a crucial role in hydrocarbon accumulation of formations with high sand content (sand content > 80%). However, the genetic mechanisms, sealing mechanisms, and effectiveness of calcareous sandstones remain unclear. This study takes the Zhuhai–Enping formations in the Panyu A Sag as an example. By comprehensively analyzing data from well logs, cores, cast thin sections, elemental geochemical analysis and carbon–oxygen isotopes, the genetic mechanisms, development patterns, and controlling effects on hydrocarbon accumulation of calcareous cement layers are investigated. The main findings are as follows: (1) The calcareous sandstone cements are mainly composed of dolomite, ankerite, and anhydrite. With increasing burial depth, dolomite transitions from micritic dolomite to silt-sized and fine-crystalline dolomite, and finally to coarse-crystalline dolomite. (2) The local transgression provided ions such as Ca²⁺ and Mg²⁺, forming the material basis for early dolomite formation. As burial depth increased, the diagenetic environment shifted from acidic to alkaline, leading to the dolomitization of early-formed calcite and the formation of ankerite. (3) The high source-reservoir displacement pressure difference effectively seals hydrocarbon accumulation. Vertically interbedded tight calcareous sandstones and thin marine transgressive mud-stones collectively control efficient hydrocarbon preservation and enrichment. This research addresses the current limits in the study of “self-sealing sandstone layers,” and provides new geological insights and predictive models for hydrocarbon exploration in sand-rich settings. Full article

Shale reservoirs contain abundant organic matter, pyrite, and clay minerals, making them highly susceptible to fluid-sensitivity damage; consequently, conventional hydraulic fracturing often yields poor stimulation performance, with low fracturing fluid flowback and rapid post-treatment production decline. Oxidative dissolution, however, can significantly alter the physical properties of shale reservoirs and improve stimulation effectiveness. In this study, nuclear magnetic resonance (NMR), contact-angle measurements, and triaxial compression tests are combined to systematically evaluate the effects of oxidative dissolution on the pore structure, wettability, and mechanical properties of Wufeng Formation shale from the Sichuan Basin. Core-flooding experiments with NaClO solutions show that, as the oxidant dosage (pore volume) increases, shale permeability rises by 66.67–266.67% and porosity by 1.79–9.58%, while the hydrophilic surface fraction increases from 5.45% to 61.73%. These changes are accompanied by a steady reduction in rock strength: the compressive strength decreases by up to 57.8%, and the elastic modulus exhibits a non-monotonic response to oxidation. Oxidative dissolution preferentially enlarges micropores, improves pore connectivity, and strengthens water wetness by consuming oil-wet organic matter and pyrite, which also enhances gel-breaking efficiency. Based on the experimental results, a series of characterization models are developed for oxidized shale reservoirs, including quantitative relationships linking porosity to compressive strength, elastic modulus, and contact angle, as well as a model relating oxidant dosage to microscopic pore structure evolution and imbibition enhancement. Overall, the coupled modifications of pore structure, wettability, and mechanical behavior produced by oxidative dissolution synergistically broaden the effective action range of fracturing fluids, promote shale gas desorption, and improve hydrocarbon seepage, providing a theoretical basis and practical guidance for oxidation-assisted stimulation in shale reservoirs. Full article

The presence of vanadium compounds in heavy oils poses a significant challenge by poisoning and deactivating refining catalysts, making their removal an essential processing step. However, this process is challenged by the competitive adsorption of abundant polycyclic aromatic hydrocarbons (PAHs) in heavy oils, due to the similar conjugated π-electron structure of PAHs and vanadyl porphyrins. In the presented study, the adsorption behaviors of vanadyl octaethylporphyrin (VOOEP) and 1-methylpyrene (1-MP) on various solid adsorbents were investigated. Among the adsorbents studied, the primary secondary amine adsorbent (PSA) demonstrated superior performance, achieving high VOOEP adsorption capacity and exceptional selectivity, even in the presence of a large excess of 1-MP. The adsorption kinetics, isotherms, and thermodynamics of VOOEP and 1-MP onto PSA were studied. Four common kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion) were used for data fitting. The adsorption isotherms were modeled using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. The adsorption kinetics for both VOOEP and 1-MP on PSA were best described by the pseudo-second-order model, while equilibrium data were well fitted by the Freundlich isotherm. Thermodynamic analysis confirmed that the adsorption of VOOEP and 1-MP on PSA is a spontaneous and exothermic process. The practical applicability of PSA was confirmed with a heavy deasphalted oil (HDAO), where it efficiently removed vanadium with high selectivity, with lower co-adsorption of desirable oil components. The results indicate that PSA is a promising adsorbent for effectively removing vanadium compounds from heavy oils. Full article

This review provides a comprehensive analysis of the petrophysical controls influencing greensand reservoirs, with an emphasis on the role of glauconite and associated clay minerals in determining porosity, permeability, and water saturation. Greensands contain iron-rich clay minerals that exert paramagnetic and conductive effects, challenging conventional well-log interpretations and often leading to biased estimates of reservoir parameters. Several challenges for petrophysical property measurements are faced in the laboratory due to clay-induced pore-throat obstruction and microporosity, which underscores the importance of tailored interpretation workflows and data integration. In this paper we highlight the necessity of integrated approaches such as combining core analysis, spectral gamma-ray, and nuclear magnetic resonance (NMR) logging with conventional well logs to calibrate petrophysical models using shale–sand water saturation models, such as Waxman–Smits and Simandoux, to better characterise economical pay zones. Finally, future research directions are indicated, which include refining the calibration of saturation and permeability models, advancing rock-typing methodologies, and understanding mineralogical influences on reservoir quality to optimise hydrocarbon recovery from greensand reservoirs. Full article