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- 摘要：To facilitate the implementation of the "dual carbon" goals, explore the market application potential and low-carbon benefits of green ammonia as a new type of clean energy fuel, and conduct a study on the cost and carbon reduction value assessment from the production to the application of green ammonia fuel. Focusing on the entire process of green ammonia production through water electrolysis, synthesis, storage and transportation, as well as its combustion applications, with carbon pricing and electricity pricing as the core variables, we quantify the costs and carbon reduction benefits of green ammonia fuel under different scenarios, and complete a comprehensive economic evaluation of green ammonia fuel. The results indicate that, based on the carbon price at the end of 2024, when the electricity price is below 0.10 yuan/(kW·h), the cost of green ammonia can be on par with that of gray ammonia. When it drops below 0.08 yuan/(kW·h), it can become more competitive than natural gas. However, if the grid electricity price is set at 0.60 yuan/(kW·h), green ammonia will not possess a competitive edge until 2050. The coupled effect of carbon price fluctuations and carbon emission intensity has significantly reshaped the economic landscape of ammonia fuel applications. The northwest electricity curtailment production model,leveraging its advantages of low-cost green electricity and low emissions, has already demonstrated carbon emission reduction benefits in 2020. Its cost advantage is expected to continue to increase in 2030, and it is projected that by 2050, carbon revenues will fully cover production, storage, and transportation costs. In summary, as the cost of wind and solar renewable energy generation continues to decline, green ammonia possesses excellent low-carbon economic benefits and broad application prospects, making it a viable clean energy alternative to important fossil fuels.关键词：green ammonia;Fuel;cost;carbon reduction benefits1|0|0更新时间：2026-08-06
- 摘要：To reduce the cost of organic solar cells (OSCs), a simple diester-based electron-deficient unit (2,5-bis(5-bromothiazol-2-yl)thiophene-3,4-dicarboxylic acid bis(2-ethylhexyl) ester, 2ETT z-2Br) was designed and synthesized. By copolymeri zing it with the easily synthesized (4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo [1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane) (BDT-2Sn) donor unit, a novel wide-bandgap polymer donor material, PBT zT2E, was successfully prepared. Studies have demonstrated that this polymer exhibits excellent thermal stability, a broad spectral absorption range, and a deep HOMO energy level (5.72eV). Meanwhile, the non-covalent interactions of O…S and N…S within the molecular skeleton effectively enhance the backbone planarity and the ordering of aggregated structures. The device based on the blend of PBTzT2E and L8-BO achieved a high open-circuit voltage ( OC) of 0.98 V, with a short-circuit current density ( SC) of 12.95 mA/ cm2 and a fill factor (FF) of 40.99%, ultimately yielding a power conversion efficiency (PCE) of 5.20%. The above results confirm that the synergistic electron-withdrawing effect of the carboxylate ester and the thiazole 仔-bridge significantly lowers the HOMO energy level, achieving a high OC of nearly 1 V. However, the HOMO energy-level offset of －0.04 eV between the donor and acceptor materials weakens the charge-separation driving force, which to some extent limits efficient charge transport. Therefore, finely regulating the energy-level offset between donor and acceptor through molecular engineering to achieve an optimal balance between OC and SC is the key to enhancing the photovoltaic performance of devices.关键词：wide-bandgap polymer;high voltage;negative energy level offset;organic solar cells (OSCs)3|0|0更新时间：2026-08-06
- 摘要：Under the dual influences of global climate change and human activities, the runoff dynamics in the Dongjiang River Basin have undergone significant changes, posing new challenges to water resource security. Based on measured runoff sequences from 1956 to 2023 at four hydrological stations (Longchuan, Heyuan, Lingxia, and Boluo) along the main stream of the Dongjiang River, along with precipitation data above the gauging sections, this study employs a hydrological variability diagnostic system to identify the variability characteristics of runoff and precipitation. Using an attribution analysis method based on the rainfall-runoff relationship, the contributions of climate change and human activities to runoff variability were quantitatively separated. Results indicate that runoff variability exhibits distinct seasonal distribution patterns. During the dry season, runoff generally shows a jumping upward trend, with variability points concentrated between 1968 and 1974, aligning with the operational water replenishment scheduling of the Three Major Reservoirs (Xinfengjiang, Fengshuba, and Bai Puzhu) in the basin during the dry season. In contrast, runoff during the wet season mostly exhibits a jumping downward trend, with variability points concentrated in 2008 and 2019, reflecting the combined effects of reservoir flood regulation and drought control. For annual runoff sequences, the Heyuan and Lingxia stations experienced a jumping downward variability in 2019, with significant reductions in annual runoff, reflecting the regulatory role of comprehensive basin management on runoff processes. Precipitation variability primarily occurs in May, June, and October, with consistent variability years across all sections, all showing a jumping downward trend, while the annual pan-precipitation sequence did not exhibit significant variability. Human activities are the dominant driver of runoff evolution, with contribution rates exceeding 90% during the dry season and reaching over 80% in most months during the wet season. The contribution rate of climate change significantly increased in March and April, closely related to the high variability of the pre-monsoon rainfall in South China and the strong modulation effects of ENSO events. These findings reveal the spatiotemporal differentiation patterns and driving mechanisms of runoff evolution in the Dongjiang River Basin, providing a scientific basis for optimized water resource management, water supply security, and climate change adaptation in the region.关键词：runoff evolution;hydrological alteration diagnosis;climate change;human activities;rainfall-runoff relationship;attribution analysis;Dongjiang River Basin4|0|0更新时间：2026-08-05
- 摘要：Accurate evaluation of geological reserves is a core prerequisite for understanding the development potential of shale oil reservoirs and formulating scientific development plans. Aiming at the problems of strong heterogeneity of shale oil reservoirs, prominent non-uniqueness of parameter prediction, conventional volumetric method masking reservoir heterogeneity, traditional probabilistic method underestimating the inherent correlation of parameters, and difficulty in accurately quantifying reserve scale and uncertainty, this study takes the QY1 shale oil well group in the Second Member of Funing Formation, Qintong Sag, Subei Basin as the research object, adopts a stochastic modeling approach to conduct a systematic analysis of the entire reserve evaluation process, and focuses on completing the identification of sensitive factors, formulation of desensitization countermeasures, and application of reserve evaluation. The results show that: depth deviation in seismic interpretation, primary and secondary range parameters of porosity and oil saturation modeling, and model grid cell step size are medium-to-high sensitive factors affecting reserve uncertainty, with their relative impact on reserves ranging from 4.1 to 12.2%; through three major desensitization countermeasures — constrained data mining in structural modeling, facies-controlled constraint in property modeling, and optimization of model grid step size — the relative impact of medium-to-high sensitive factors on reserves can be reduced to 2.4% to 3.5%; after desensitization, the value range of evaluated reserve distribution narrows by 38.5%, the slope of the cumulative probability curve increases by 114.7%, uncertainty decreases by 10.7%, and reserve prediction accuracy is significantly improved. Based on the desensitized stochastic modeling method, the quantitative evaluation of reserves by formation in the well group was further completed, confirming that the interval from Lower Member Ⅰ to Upper Member Ⅱ is the core area of reserve distribution, followed by Member Ⅲ, and Submembers Ⅳ to Ⅴ with extremely low abundance; combined with the relationship between P50 reserve abundance and single-well internal rate of return, suggestions for optimization of well spacing by formation and improvement of reservoir stimulation were proposed.关键词：stochastic modeling;shale oil;reserve evaluation;sensitive factor;uncertainty desensitization;Qintong Sag;Subei Basin7|0|0更新时间：2026-08-04
- 摘要：Water diversion projects represent critical engineering interventions for mitigating the spatiotemporal mismatch of water resources in densely populated deltaic regions. However, long-distance raw water conveyance inevitably reshapes nutrient concentrations and trophic states in receiving reservoirs, triggering complex non-stationary shifts in aquatic water quality regimes. To systematically assess the temporal dynamics and spatial gradients of water quality across successive diversion nodes along the Pearl River Delta Water Resources Allocation Project, this study conducted year-round continuous monthly monitoring of key physicochemical water quality parameters in 2025 at four representative monitoring sites. These sites cover the full diversion cascade, including the Liyuzhou Pumping Station (the Xijiang River source water intake), Gaoxinsha Reservoir, Luotian Reservoir, and Gongming Reservoir (the terminal impoundment of this diversion corridor).Based on the field monitoring dataset, the Carlson trophic state index (TSI) was quantified for each sampling month to classify the eutrophication risk of each water body. Two multivariate statistical approaches, principal component analysis (PCA) and permutational multivariate analysis of variance (PERMANOVA), were further applied to disentangle the dominant environmental drivers of water quality differentiation and test the statistical disparities of nutrient regimes across different reservoir sites.The results showed that the water quality status of Gaoxinsha Reservoir, the first receiving impoundment downstream of the intake, was predominantly constrained by the nutrient loads carried by diverted inflow from Liyuzhou Pumping Station. Following the sequential water diversion gradient from Liyuzhou Pumping Station through Gaoxinsha Reservoir and Luotian Reservoir to Gongming Reservoir, the concentrations of total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3-N), as well as water electrical conductivity exhibited a steady declining trend, whereas underwater transparency continuously rose along the flow path. Correspondingly, the calculated TSI values dropped significantly at Gongming Reservoir, the terminal section of the entire project. Compared with the raw Xijiang River inflow at Liyuzhou Pumping Station, the three cascaded reservoirs achieved substantial nutrient retention and purification effects after sequential water storage and transport, which led to remarkable reductions in dissolved and particulate nutrient concentrations and obvious overall improvements in water quality.From a seasonal perspective, TN, chlorophyll-a (Chl.a) and TSI shared identical seasonal fluctuation patterns: their concentrations and index values peaked in summer and autumn, while decreasing to relatively low levels during spring and winter. In stark contrast, total phosphorus exhibited pronounced spatial heterogeneity, with divergent concentration magnitudes across the four monitoring nodes throughout the entire hydrological year. The outputs from PCA and PERMANOVA collectively corroborated that nitrogen nutrients, phosphorus nutrients, and integrated trophic status constituted the primary drivers governing spatial water quality variations. Statistically significant differences in the full suite of measured environmental variables were further confirmed among the three downstream cascade reservoirs.This study confirms that all water bodies along the Pearl River Delta Diversion Project currently stay in the oligotrophic to mesotrophic trophic state, with no severe eutrophication outbreaks recorded. However, significant spatial heterogeneity in nitrogen-phosphorus nutrient stoichiometric ratios was observed across the entire diversion corridor. Given the concurrent rise in chlorophyll-a (Chl.a) levels and Trophic State Index (TSI) values during the high-temperature summer–autumn transition, we recommend that targeted monitoring and precision water operation management prioritize key environmental drivers governing algal proliferation and nutrient retention in hot seasons. This proactive strategy mitigates latent algal bloom risks and sustains stable raw water quality to underpin regional water supply security.关键词：water quality;nitrogen and phosphorus nutrients;trophic state;temporal and spatial distribution;Pearl River Delta Water Resources Allocation Project5|1|0更新时间：2026-08-03
- 摘要：Rainwater harvesting is an important strategy for alleviating urban water shortages, reducing drainage pressure, and improving the resilience of urban stormwater management systems. Accurate land-cover recognition is essential for estimating surface runoff and rainwater harvesting potential, particularly in highly urbanized areas where impervious surfaces, vegetated land, roads, rooftops, and water bodies are spatially mixed. In this study, an urban rainwater harvesting potential assessment framework was developed by integrating high-resolution remote sensing interpretation, a U-Net land-cover recognition model, and hydrological estimation methods. The six urban districts of Xi'an, China, were selected as the study area. Five major land-cover types, including water bodies, bare land, vegetated land, building rooftops, and roads, were identified from remote sensing imagery. The U-Net model was constructed using ArcGIS Learn with a ResNet-34 backbone, and a support vector machine (SVM) model was introduced as a traditional supervised classification method for comparison. Classification performance was evaluated using overall accuracy, Kappa coefficient, precision, recall, F1-score, and confusion matrices. Based on the land-cover recognition results, runoff coefficients were estimated using both the composite runoff coefficient method and the Soil Conservation Service Curve Number (SCS-CN) model. The composite runoff coefficient method assigns empirical runoff coefficients according to land-cover types, whereas the SCS-CN model further incorporates hydrological soil groups and antecedent moisture conditions to represent differences in infiltration and retention capacity. A slope correction factor was also introduced to adjust runoff coefficients under different terrain conditions. Precipitation records from 1961 to 2023 were analyzed to establish rainfall scenarios corresponding to 10%, 50%, and 90% frequency levels, as well as the long-term mean annual rainfall. In addition, classification error propagation was considered using the U-Net confusion matrix to evaluate the influence of land-cover recognition uncertainty on rainwater harvesting potential estimates. The results show that the U-Net model achieved an overall accuracy of 0.780 and a Kappa coefficient of 0.725, outperforming the SVM model, which achieved an overall accuracy of 0.430 and a Kappa coefficient of 0.276. The U-Net model showed relatively good recognition performance for building rooftops and roads, while some confusion remained among water bodies, bare land, and vegetated land. Compared with the composite runoff coefficient method, the SCS-CN model produced higher runoff coefficients and stronger spatial heterogeneity, indicating that it can better reflect the effects of land-cover types and hydrological soil conditions on runoff generation. Under rainfall scenarios corresponding to the 10%, 50%, and 90% frequency levels and the long-term mean annual rainfall, the corrected rainwater harvesting potentials were estimated as 285, 220, 173, and 226 million m³·yr⁻¹, respectively. Building rooftops and roads were identified as the dominant contributors to rainwater harvesting potential. The proposed framework provides a technical reference for urban rainwater resource assessment and resilient stormwater management.关键词：rainwater harvesting;U-Net model;land-cover recognition;runoff coefficient;geographic information system;Xi'an4|1|0更新时间：2026-07-31
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Monthly Runoff Prediction Based on Two-Stage CEEMDAN-VMD Decomposition and CPO-Transformer-BiLSTM AI导读
摘要：Monthly runoff series are widely recognized to exhibit pronounced nonlinearity, non-stationarity, and multi-scale fluctuation characteristics, which pose notable challenges to accurate single-station monthly runoff forecasting. Even after primary decomposition processing, the reconstructed high-frequency sub-components often retain intricate local fluctuating patterns, rendering them difficult to predict directly with satisfactory performance. To further enhance the prediction accuracy and operational stability for single-station monthly runoff series, this study proposes a novel hybrid forecasting framework that integrates secondary decomposition, intelligent parameter optimization, and deep learning techniques. The proposed hybrid model couples complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), variational mode decomposition (VMD), the crested porcupine optimizer (CPO), Transformer, and bidirectional long short-term memory (BiLSTM) into an integrated forecasting workflow. Monthly runoff records from the Gongshang Hydrological Station in the upper Xihe River Basin were adopted as the experimental dataset, covering a total of 552 consecutive months from 1975 to 2020. The full time series was chronologically partitioned into a training subset spanning 442 months (1975–2011) and a test subset covering 110 months (2012–2020). During the training phase, CEEMDAN was first implemented on the runoff series in the training set to generate a set of intrinsic mode functions (IMFs) and one residual term. Sample entropy was subsequently employed to quantify the complexity of each decomposed sub-component, and K-means clustering was adopted to reconstruct these sub-components into three grouped components: high-frequency, medium-frequency, and low-frequency. The reconstructed high-frequency component was further processed via secondary decomposition using VMD. All VMD-derived sub-modes, together with the pre-obtained medium- and low-frequency reconstructed components, were assembled into the final component set for subsequent component-wise forecasting. The CPO algorithm was introduced to automatically tune the critical hyperparameters of the Transformer-BiLSTM architecture, including the input time step, number of BiLSTM hidden units, initial learning rate, and number of attention heads. In the testing phase, a rolling forecasting strategy was applied to generate predictions for each individual component, and the final monthly runoff forecast was derived by summing the predicted values of all sub-components. The proposed hybrid CEEMDAN-VMD-CPO-Transformer-BiLSTM model demonstrates excellent forecasting performance on the test dataset. The corresponding determination coefficient (𝑅R), Nash-Sutcliffe Efficiency (NSE), root mean square error (RMSE), and mean absolute error (MAE) are quantified as 0.960, 0.951, 0.226 m³/s, and 0.171 m³/s, respectively. Compared with four benchmark models (Transformer-BiLSTM, CNN-BiLSTM, BiLSTM, and LSTM), the proposed model achieves RMSE reductions of 47.36%, 53.69%, 56.47%, and 59.59%, along with MAE reductions of 49.93%, 52.61%, 56.68%, and 57.65%, respectively. Over 20 independent repeated runs, the full proposed model yields a stable RMSE of 0.226±0.006. The Wilcoxon signed-rank tests between the full model and its corresponding ablation variants return p-values below 0.0001, confirming that the observed performance improvements are statistically significant. The proposed hybrid framework effectively enhances the forecasting accuracy and operational stability of monthly runoff at the Gongshang Hydrological Station. The results demonstrate that the integrated performance improvement stems from the synergistic effects of the CEEMDAN-VMD decomposition-reconstruction scheme, secondary VMD decomposition, CPO-driven parameter optimization, and the adopted Transformer-BiLSTM forecasting architecture. This developed model can serve as a reliable reference for analogous single-station monthly runoff forecasting investigations.关键词：monthly runoff prediction;two-stage CEEMDAN-VMD decomposition;crested porcupine optimizer;Transformer-BiLSTM;upper Xihe River Basin5|2|0更新时间：2026-07-30 - 摘要：Against the backdrop of intensifying global climate change, the evolutionary dynamics of flood characteristics in small- and medium-sized watersheds have grown increasingly intricate. Accurately identifying these spatiotemporal patterns carries critical practical implications for the formal review and updating of design flood standards. Taking the Liuxihe Reservoir as the study case, this paper systematically investigates the evolutionary behaviors of its inflow flood peak discharge and flood volume series from three complementary dimensions: long-term trend, abrupt change point detection, and multi-timescale periodicity, followed by a quantitative assessment of how hydrological record extension influences the reassessment outcomes of design flood values.Using a 66-year flood record (1959–2024) of the Liuxihe Reservoir, this study applied the Mann–Kendall test and Sen's slope estimator to identify the trends and rates of change in the inflow flood peak and volume series. The Pettitt test was then employed to detect change points and their statistical significance. The Morlet wavelet transform was used to reveal the time-scale periodic characteristics of the flood series. Finally, based on these identified evolution patterns, the impact of extending the data series on the reassessment of design floods and characteristic water levels was quantitatively evaluated.The results showed that the annual maximum peak discharge, 24-hour flood volume, and 3-day flood volume series all exhibited slight decreasing trends, but none were statistically significant. The Sen's slope estimates were -2.33 m³/s per year, -0.001 1×10⁸ m³ per year, and -0.0007×10⁸ m³ per year, respectively, with 95% confidence intervals included zero, suggesting considerable uncertainty in the trends. The Pettitt test showed that the p-values were all above 0.05, indicating no statistically significant abrupt changes, thus satisfying the hydrological consistency assumption. The Morlet wavelet analysis revealed two distinct periodic components in the flood variables: a long period of approximately 33 years and a short period of 5–7 years. The peak discharge and 24-hour flood volume were dominated by the long period, while the 3-day flood volume was governed by the short period. This discrepancy reflects the differential responses of flood events with varying durations to multi-decadal atmospheric circulation regimes and interannual climate anomalies. Extending the series to 2024 effectively covers multiple cycles of the dominant periods, thereby improving the reliability of design flood parameter estimation. The reassessed design flood peak discharge and flood volumes were generally comparable to the 1999 results but slightly lower, which is expected because no larger flood events occurred in the extended period, and the reduction in frequency estimates follows statistical principles. Flood routing showed that the 100-year and 1 000-year maximum water levels were 237.24 m and 238.42 m, both below the original design values, thus meeting the regulatory requirements.The annual maximum flood series of Liuxihe Reservoir exhibits overall statistical stationarity, with well-defined multi-timescale periodic oscillations and no statistically significant monotonic long-term trend. These empirical findings deviate substantially from the widely documented rising tendencies of extreme flood events in small- and medium-sized watersheds under ongoing climate change, which underscores the regional specificity of flood regime evolution in this catchment. Follow-up investigations based on extended observational datasets and cross-watershed comparative analyses are warranted to fully disentangle the intricate hydrological response mechanisms behind such atypical flood behaviors. The outcomes of this study provide a robust scientific reference for design flood reassessment and reservoir operational management under the non-stationary background of a changing climate.关键词：trend analysis;abrupt change analysis;periodicity analysis;design flood review;Liuxihe Reservoir3|1|0更新时间：2026-07-30
- 摘要：Gaoxinsha Reservoir receives water diverted from the Liyuzhou section of the Xijiang River, functioning as a pivotal water storage and regulation node within the major water resource allocation project serving the entire Pearl River Delta region. The reservoir was officially put into full operational use at the end of 2024, and its aquatic ecosystem remains in the early succession phase following initial impoundment, with unstable hydrological conditions and gradually reshaped biological assemblages. Cladocerans are at a central trophic position as key primary consumers grazing on phytoplankton; their population directly controls algal growth, mitigates eutrophication risks, and sustains the structural balance and functional integrity of freshwater aquatic ecosystems. To systematically reveal the structural characteristics and seasonal differentiation of cladoceran assemblages under early reservoir operation, field investigations covering cladoceran sampling, morphological species identification, and individual body length measurement were carried out across the dry and wet seasons throughout 2025. Synchronous monitoring of physicochemical and biological environmental variables was implemented, including water temperature, turbidity, total nitrogen, total phosphorus and chlorophyll-a. Multiple statistical approaches were adopted for comprehensive data analyses: one-way ANOVA tested seasonal disparities in community metrics; PCA sorted core environmental gradients; NMDS visualized community compositional dissimilarity; RDA quantified the linkage between biotic assemblages and ambient variables; and multiple linear regression clarified dominant drivers of diversity indices. Ten cladoceran taxa were taxonomically identified in total. Species richness was eight in the wet season versus six in the dry season, yet seasonal differences in total abundance, biomass, and overall diversity indices were non-significant. Turbidity and copepod biomass exerted significant constraints on species richness, whereas water temperature, total nitrogen, rainfall, and rotifer biomass jointly determined the true Simpson diversity. A significant seasonal shift occurred in abundance-weighted community structure, accompanied by a clear turnover of dominant taxa from Bosmina fatalis in the dry season to Diaphanosoma dubium in the wet season. Water temperature, turbidity, and chlorophyll-a acted as the primary environmental filters structuring cladoceran assemblages. Collectively, small-bodied cladocerans prevail in this newly built reservoir. Pronounced seasonal shifts in community composition are co-regulated by thermal conditions, water transparency, and algal biomass during the early succession stage.关键词：cladocera;community structure;seasonal variation;diversity5|1|0更新时间：2026-07-30
- 摘要：Based on physical model experiments on sediment deposition behind a pile-supported wharf in a wave basin, this study proposes a sediment dredging design and site selection scheme for an offshore groin. The results show that sediment deposition behind the wharf increases towards the pile foundations beneath the wharf, and the most severe deposition area is located near the central part of the second berth. After the groin is installed in the most severe sediment deposition area, mean sediment deposition is reduced by about 29%, indicating that the groin can enhance the local flow velocity and improve the sediment dredging behind the wharf. Subsequently, a field demonstration is conducted in the basin behind a pile-supported wharf on the southeastern coast of China to evaluate the flow-diversion and sediment dredging potential of the device under realistic tidal current conditions. The offshore groin is designed as a movable flow-diversion structure composed of floating platforms, anchoring chains, diversion curtains, etc., which makes it be deployed fast in the restricted water area behind the wharf. Detailed flow measurements are conducted to examine the spatial distributions of the velocities as well as their dredging potential behind the wharf under the influence of the groin. The results of continuous 48 h field demonstration show that, the effective accelerating region exceeds 130% of the device characteristic length and the scouring-related velocity increases by at least 50% in 67% of the observation periods. The number of effective periods during ebb tide is 28% higher than that during flood tide. The area with enhanced dredging is also found to be more closer to the pile foundations due to the groin's orientation inclined to the wharf. Meanwhile, within 43% of the ebb-tide periods, the presence of the offshore groin enables local flow velocities to reach or exceed the critical velocity for sediment incipient motion, indicating its favorable flow diversion and sediment dredging capability under the tidal forcing. The findings provide a technical basis for the design and deployment of those devices in flow diversion and dredging activity behind the pile-supported wharves, with both benefits of reducing the dredging costs using mechanical equipment and improving the personnel safety with less operation on sea.关键词：offshore groin;tidal current;pile-supported wharf;field demonstration;dredging velocity3|1|0更新时间：2026-07-30
- 摘要：Continental mixed shale reservoirs commonly exhibit complex pore-fracture architectures and strong heterogeneity, which are key geological factors restricting sweet-spot prediction and efficient shale-oil development. To clarify reservoir-space types, pore-fracture system architecture, and their main controlling factors in mixed shale, this study focuses on the Permian Fengcheng Formation in the Mahu Sag, Junggar Basin, and integrates core observation, thin-section analysis, microscopic characterization, low-temperature N₂ adsorption, and high-pressure mercury intrusion to conduct a comprehensive characterization of the reservoir space system and an analysis of its controlling factors.Resultsshow that the reservoir space system is dominated by inorganic pores, organic matter pores, and microfractures. Inorganic pores include intergranular pores, intragranular dissolution pores, and intercrystalline pores, among which intergranular pores are dominant and mainly occur between felsic mineral grains. Microfractures are primarily bedding-parallel fractures and tectonic microfractures, with apertures predominantly in the 10-30μm range, and they contribute significantly to pore-microfracture connectivity and seepage capacity. Full-scale pore characterization indicates a distinct bimodal pore size distribution (<100 nm and >2 000 nm), and an average total pore volume of about 0.0085 cm³/g. Reservoir quality varies systematically among lithofacies, generally following the order: felsic shale > mixed shale > clay-rich shale. Mineral composition and lamination collectively exert strong controls on the pore-fracture system, mainly through pore enhancement by dissolution, pore reduction by cementation, and fracture promotion by brittleness: dissolution of quartz and plagioclase generates secondary pores; intercrystalline pores associated with clay minerals contribute substantially to micropore volume; whereas carbonate cementation reduces pore-throat connectivity but may facilitate fracture development under tectonic stress. Interbedded felsic-mixed laminae promote the development of bedding-parallel fractures, and organo-inorganic complexes within clay-rich laminae enhance pore-network connectivity. Overall, pore-fracture coupling is a key mechanism governing reservoir effectiveness and heterogeneity, and provides an important basis for constructing reservoir evaluation schemes and optimizing sweet-spot intervals in continental mixed shale oil systems.关键词：reservoir space;development characteristics;controlling factors;mixed shale;Fengcheng Formation;Mahu Sag4|5|0更新时间：2026-07-30
- 摘要：Fractal theory is an important method for quantitatively characterizing the heterogeneity of shale reservoir pore structures. Taking the Longmaxi Formation shale reservoir as an example, this study systematically compares the monofractal and multifractal characteristics of seven shale samples from this formation in the Sichuan Basin, based on N2 adsorption experiments, with particular emphasis on the advantages of multifractals in representing complex pore structures. The results indicate that: ① The pore structure of Longmaxi Formation shale is complex, dominated by slit-like pores, and also includes composite features such as conical pores, conical parallel-plate pores, and ink-bottle pores. The pore volume is mainly contributed by pores with diameters around 35 nm, whereas the specific surface area is predominantly provided by pores with diameters of approximately 3 nm; ② Using three monofractal models, namely the Frenkel-Halsey-Hill (FHH), Neimark, and Wang-Li models, different fractal dimensions are obtained (DFHH: 2.610 0~2.814 9, DNeimark: 2.875 1~2.984 6, DWang-Li: 2.606 1~2.778 7). Among them, the Wang-Li model exhibits the highest goodness of fit (R2>0.999). However, all models are limited by their theoretical assumptions and applicable scale ranges, making it difficult to fully capture the complexity of shale pores across different scales; ③ All samples exhibit pronounced multifractal behavior, with stronger heterogeneity in low-probability regions (moment order q ≤ -1) and relatively uniform structure in high-probability regions (q ≥ 1). Multifractal parameters (D-q/Dq, D-q-Dq, αmin-αmax, and αmin/αmax) are negatively correlated with specific surface area and positively correlated with mean pore diameter, indicating that this approach effectively characterizes pore heterogeneity across scales. By systematically comparing monofractal and multifractal methods for Longmaxi Formation shale, this study highlights the advantages of multifractals in quantifying complex shale pore networks and provides new analytical perspectives and theoretical references for N2 adsorption-based fractal characterization.关键词：fractal;N2 adsorption;pore structure;Longmaxi Formation;shale24|19|0更新时间：2026-07-30
- 摘要：The deep tight sandstone gas reservoirs (3 680~4 250 m) in the Shaximiao Formation of the Zitong Block, Sichuan Basin, exhibit distinctive geological features: nanopore-throat dominance, strong compaction and cementation, and coupled wettability hysteresis and clay swelling. These features cause severe fracturing fluid invasion, low flowback efficiency (typically<20%), and compounded damage from water blocking and clay swelling, significantly hindering efficient reservoir development. To address these challenges, this study conducted full-cycle core-flooding experiments on natural samples from the first member of the Shaximiao Formation. Using a high-temperature high-pressure dynamic capillary pressure testing system under simulated reservoir conditions (82 °C, 40 MPa confining pressure), we simulated water-flooding-gas (fracturing fluid injection) and gas-flooding-water (flowback). Fifteen core samples with gas permeability ranging from 0.071×10-3 μm2 to 1.158×10-3 μm2 were divided into three groups: ultra-low permeability (K≤0.1×10-3 μm2), low permeability (0.1×10-3 μm2<K≤1.0×10-3 μm2), and relatively high permeability (K>1.0×10-3 μm2 ). The results reveal three key findings. First, during water flooding, dynamic capillary pressure transitions from a driving force to flow resistance as water saturation increases, with a critical transition at approximately 37% saturation. This resistance growth is more pronounced in lower-permeability cores (K≤0.1×10-3 μm2). Second, during gas flooding, capillary pressure consistently acts as a resistance that intensifies with decreasing water saturation; ultra-low permeability cores exhibit resistance 1.5 to 4.0 times greater than high-permeability cores. Third, a quantitative relationship was established, revealing the synergistic amplification mechanism of high nanopore-throat proportion (>70%) and illite-dominated wettability hysteresis (dynamic contact angle deviation of 30°~45°). Based on these findings, we propose an optimized flowback strategy comprising “rate-controlled injection, staged gentle flowback, clay stabilization, and real-time adjustment,” with differentiated engineering measures integrating permeability zonation and geological characteristics. This research provides experimental and theoretical support for refining fracturing design and optimizing flowback regimes in the Zitong Block, and offers valuable guidance for developing analogous deep tight sandstone gas reservoirs in the Sichuan Basin and beyond.关键词：deep tight sandstone gas reservoirs;dynamic capillary pressure;wettability hysteresis;fracturing fluid flowback;permeability zoning26|19|0更新时间：2026-07-30
- 摘要：As an important type of continental shale oil and gas resources, shale oil in saline lacustrine basins is subject to multiple controls such as sedimentation and diagenesis during its hydrocarbon generation process, showing remarkable complexity and heterogeneity. Based on data investigation of the geological characteristics of shales in typical saline lacustrine basins in China, combined with research results from experimental techniques including closed-system and semi-open-system hydrocarbon generation simulations and organic sulfur analysis, this study systematically discusses the genetic mechanism of differential hydrocarbon generation of shales in saline lacustrine basins in China. The results show that shales in saline lacustrine basins are rich in lithofacies and organic facies types with strong heterogeneity, and the major source rock intervals generally have moderate to high organic matter abundance, kerogen types dominated by Type Ⅰ-Ⅱ2, and thermal maturity ranging from 0.7% to 1.3% vitrinite reflectance (Ro). Some typical shales exhibit a bimodal oil generation characteristic during hydrocarbon generation: bimodal distribution of low-mature oil and mature oil for shales in sulfate-type lacustrine basins, and bimodal distribution of mature oil and high-mature oil for shales in alkaline carbonate-type lacustrine basins. The types of hydrocarbon-generating organisms controlled by sedimentary environments dominate the material basis and hydrocarbon generation process of source rocks. Organic sulfur reduces the hydrocarbon generation activation energy of kerogen through low-bond-energy C-S bonds, leading to an earlier hydrocarbon generation threshold of shales. Salt minerals, clay minerals, volcanic minerals and alkaline minerals regulate hydrocarbon generation pathways and product compositions through organo-mineral interactions such as catalytic reactions, hydrogen supply and saponification. Through innovative experimental techniques and in-depth mechanism analysis, dynamic simulation of hydrocarbon generation from microscopic compounds to macroscopic geological processes has been realized, providing key technical support for kinetic modeling of hydrocarbon generation, resource potential evaluation and “sweet spot” interval prediction of shales in saline lacustrine basins. This study is of great significance for improving the theory of continental shale hydrocarbon generation and guiding the efficient exploration and development of continental shale oil and gas.关键词：saline lacustrine basin;shale oil;hydrocarbon generation mechanism;organic sulfur;organic-inorganic interactions112|480|0更新时间：2026-07-30
- 摘要：To clarify the effects of Cu/Zn molar ratio on the catalytic performance and reaction mechanism of pure Cu-Zn catalysts for CO2hydrogenation to methanol, this study focuses on the intrinsic synergistic effect of Cu and Zn by eliminating the interference of supports and additives to conduct performance regulation analysis. Pure Cu-Zn catalysts with Cu/Zn molar ratios of 0.5, 1.0, 1.5, 2.0 and 2.5 were synthesized via the co-precipitation method. Their catalytic performances were evaluated in a fixed-bed reactor, reaction intermediates and pathways were identified by in-situ diffuse reflectance infrared fourier transform spectroscopy (in-situ DRIFTS), and long-term stability tests were also carried out. The results indicate that,the catalyst with a Cu/Zn molar ratio of 1.5 exhibits the optimal catalytic performance, achieving a CO2 conversion of 29.8%,methanol selectivity of 93.8% and methanol yield of 28.0%. It also possesses excellent long-term stability with low sintering degree of Cu nanoparticles. In-situ DRIFTS results confirm that this catalyst can efficiently generate HCOO active intermediates, which facilitates methanol formation and suppresses the production of CO by-products. For the first time, this work establishes a complete correlation among Cu/Zn molar ratio, catalyst structure, catalytic performance, reaction mechanism and stabilityin the carrier-free Cu-Zn system, and clarifies the quantitative regulation effect of Cu/Zn molar ratio in pure Cu-Zn systems. This study provides experimental guidance for the rational design and optimization of simplified catalysts.关键词：Cu-Zn binary catalyst;Cu/Zn molar ratio;CO2 hydrogenation to methanol;HCOO intermediate species;reaction21|6|0更新时间：2026-07-29
- 摘要：The Dongjiang River Basin serves as a critical water supply source for the Guangdong-Hong Kong-Macao Greater Bay Area, and its water resources conditions have direct implications for regional sustainable development. To identify the key constraints limiting water resources carrying capacity (WRCC) in this basin and ensure long-term water supply stability for the Greater Bay Area, a comprehensive evaluation covering the period from 2007 to 2020 was conducted, with the aim of providing an empirical basis for long-term water resources management strategies in the watershed. Using annual data spanning 2007–2020, this study comprehensively evaluated and analyzed the WRCC of the Dongjiang River Basin by integrating the DPSIR (Driver-Pressure-State-Impact-Response) conceptual framework with an entropy-weighted TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) approach. The DPSIR framework was adopted to systematically organize evaluation indicators across five interrelated subsystems, thereby capturing the complex interactions between anthropogenic activities and natural hydrological processes. The entropy weighting method was employed to objectively determine indicator weights based on the information content of observed data, minimizing subjective bias in the composite scoring process. The TOPSIS procedure subsequently assessed annual WRCC performance by calculating each year's relative closeness to an ideal solution. To further diagnose the dominant restricting factors, an obstacle degree model was applied for each year under review, enabling in-depth exploration of the temporal evolution of major constraining factors over the study period. The WRCC index of the Dongjiang River Basin ranged from 0.38 to 0.58 throughout the study period, exhibiting an overall fluctuating upward trend, but with relatively weak stability. Comprehensive analysis revealed an improving trend in human water use as represented by the P subsystem; however, the deterioration of the R subsystem indicated significant negative ecological effects associated with the continued expansion of human activities, while the D, S, and I subsystems associated with natural factors exhibited pronounced unstable fluctuations. Combined obstacle degree analysis found that the primary constraints on carrying capacity development shifted markedly over time — from early dominance by water use intensity indicators toward a pattern of instability driven by three compounding factors: the contraction of wetland coverage, the expansion of population scale, and heightened interannual variability in precipitation.These findings suggest that future water resources governance in the Dongjiang River Basin should strategically reorient its focus from conventional water-saving and demand-side control measures toward an integrated paradigm encompassing ecological restoration and dynamic demand–supply balance regulation, in order to rehabilitate degraded ecosystems, strengthen the basin's natural hydrological buffering capacity, and sustain a stable and reliable long-term water supply under mounting socioeconomic and climatic pressures.关键词：DPSIR;water resources carrying capacity;Entropy-weighted TOPSIS;Obstacle degree model3|4|0更新时间：2026-07-29
- 摘要：Conducting CCUS parameter optimization research targeting high-temperature oil reservoirs, it is possible to both product oil and gas resources from the reservoirs and develop unused geothermal resources, while achieving CO2 geological storage, enhancing the utilization value of the reservoirs, and prolonging their economic lifespan. In the current CCUS injection production parameter optimization project for high-temperature oil reservoirs, the use of reservoir numerical simulators to manually set parameter value limits is time-consuming, labor-intensive, and low calculation accuracy. The paper takes high-temperature oil reservoirs as the research target and establishes the comprehensive numerical model for CCUS that simultaneously considers three mechanisms: CO2 geological storage, oil displacement, and heat production. In order to maximize the economic benefits of CO2 oil displacement, heat production, and storage, constructing a high-temperature reservoir CCUS injection production optimization model with CO2 injection rate and liquid production rate as optimization variables and economic net present value as the objective function, and using the improved ant colony algorithm to solve. To address the issues of low computational efficiency and susceptibility to local optima in standard ant colony algorithms, an improved ant colony optimization algorithm is proposed. The improved ant colony optimization algorithm introduces ant direct communication learning mechanism and global optimal solution optimization method, improves path selection probability, ensures population diversity to escape local optima, and enhances algorithm accuracy and robustness. The results show that for the CCUS injection production optimization model of high-temperature oil reservoirs, the improved ant colony algorithm can obtain the optimal solution after 435 iterations, with an optimal economic net present value of 369 million yuan, which is 7 million yuan higher than the standard ant colony algorithm. Corresponding to the optimal gas injection rate of 40879 m ³/day and liquid production rate of 3370 m ³/day; Compared with the standard ant colony algorithm, the improved ant colony optimization algorithm has higher efficiency and better results. It can quickly and accurately optimize and adjust the CO2 oil recovery and storage plan, which is of great significance for improving the economic benefits of reservoir development.关键词：High-temperature oil reservoir;CCUS;Improved ant colony algorithm;Direct communication learning mechanism;Optimization of injection and procurement parameters;Net present value of economy10|7|0更新时间：2026-07-27
- 摘要：Continental mixed shale reservoirs commonly exhibit complex pore–fracture architectures and strong heterogeneity, which are key geological factors restricting sweet-spot prediction and efficient shale-oil development. To clarify reservoir-space types, pore–fracture system architecture, and their main controlling factors in mixed shale, this study focuses on the Permian Fengcheng Formation in the Mahu Sag, Junggar Basin, and integrates core observation, thin-section analysis, microscopic characterization, low-temperature N₂ adsorption, and high-pressure mercury intrusion to conduct a comprehensive characterization of the reservoir space system and an analysis of its controlling factors. Results show that the reservoir space system is dominated by inorganic pores, organic matter pores, and microfractures. Inorganic pores include intergranular pores, intragranular dissolution pores, and intercrystalline pores, among which intergranular pores are dominant and mainly occur between felsic mineral grains. Microfractures are primarily bedding-parallel fractures and tectonic microfractures, with apertures predominantly in the 10–30μm range, and they contribute significantly to pore–microfracture connectivity and seepage capacity. Full-scale pore characterization indicates a distinct bimodal pore size distribution (<100 nm and >2000 nm), and an average total pore volume of about 0.0085 cm³/g. Reservoir quality varies systematically among lithofacies, generally following the order: felsic shale > mixed shale > clay-rich shale. Mineral composition and lamination collectively exert strong controls on the pore–fracture system, mainly through pore enhancement by dissolution, pore reduction by cementation, and fracture promotion by brittleness: dissolution of quartz and plagioclase generates secondary pores; intercrystalline pores associated with clay minerals contribute substantially to micropore volume; whereas carbonate cementation reduces pore-throat connectivity but may facilitate fracture development under tectonic stress. Interbedded felsic–mixed laminae promote the development of bedding-parallel fractures, and organo–inorganic complexes within clay-rich laminae enhance pore-network connectivity. Overall, pore–fracture coupling is a key mechanism governing reservoir effectiveness and heterogeneity, and provides an important basis for constructing reservoir evaluation schemes and optimizing sweet-spot intervals in continental mixed shale oil systems.关键词：reservoir space;development characteristics;controlling factors;mixed shale;Fengcheng Formation;Mahu Sag10|6|0更新时间：2026-07-23
- 摘要：To address the difficulties in identifying gas channeling during CO2 flooding in low-permeability oil reservoirs and the high global warming potential and environmental burden of conventional gas tracers, this study evaluates the performance and applicability of gas-phase tracers. The objective is to provide low-carbon and environmentally friendly alternative tracer media for dynamic field monitoring of gas channeling and to meet the field requirements of coordinated monitoring across large reservoir blocks and multiple well groups. Four gas-phase tracers, namely SF6, C2F6, C4F8 and C2HF5, were selected for static retention experiments and dynamic displacement experiments. The results show that: ①All four gas-phase tracers exhibit good stability within the experimental temperature and pressure ranges. The retention rates of the non-polar tracers C2F6 and C4F8 remain above 90% throughout the tested range, while the retention rate of the polar tracer C2HF5 remains above 87%. ②The dynamic production characteristics of the four tracers exhibit clear transport equivalence and functional differentiation in different types of cores. In high-permeability cores, the tracer response curves are highly consistent, with relative differences in breakthrough time of less than 5%. All tracers respond sensitively to preferential flow channels and exhibit broad, flat-topped slug characteristics. In contrast, in low-permeability and fractured cores, the tracers show differentiated transport behaviors due to differences in molecular polarity. The non-polar tracers C2F6 and C4F8 migrate more rapidly with the gas phase and break through earlier, whereas the polar tracer C2HF5 shows a significantly delayed production front in the low-permeability matrix because of interphase partitioning and adsorption, and exhibits a lower secondary-peak mole fraction in fractured cores. All four tracers demonstrate good feasibility for field monitoring and can provide a wider range of options for field tracer selection. Among them, C2F6 and C4F8 can serve as environmentally friendly alternatives to conventional SF6 and are suitable for reliable characterization of preferential flow channels, whereas the polar tracer C2HF5, which exhibits a sensitive transport-retardation response to the fluid environment, is more suitable for differential evaluation of matrix sweep characteristics.关键词：CO2 flooding;low-permeability reservoir;gas-phase tracers;preferential flow channel;displacement experiment10|12|0更新时间：2026-07-23
- 摘要：ObjectivesUnder the background of the development of new power systems, a system efficiency measurement framework considering photovoltaic cluster ancillary services (CAS) is designed to clarify the support mechanism of CAS on the system electricity-carbon operational efficiency.MethodsBased on the power grid carbon flow theory, a system carbon flow calculation method under the CAS mode and a cluster classification approach integrating carbon flow indicators are proposed. An efficiency evaluation model is developed with photovoltaic power output as the input indicator and electrical quantities and carbon flow as the output indicators, to analyze the coupling mechanism among multi-dimensional indicators of the system, and simulation verification is carried out on the improved IEEE 14-bus system.ResultsCAS can optimize the system electricity-carbon indicators. The all-time line loss rate is 4.220%-4.955%, the maximum voltage deviation is 6.000%-6.200%, the frequency deviation during peak and valley periods of the system is controlled within ±0.080 Hz, the carbon emission factor is reduced by about 16.500%, and the average node carbon potential fluctuation is reduced.ConclusionsCAS can improve key system electro-carbon indicators, reduce the system line loss rate, voltage deviation, and frequency deviation, lower the carbon emission factor and the average node carbon potential fluctuation, thus improving the energy-saving and carbon-reduction effect of the system. The findings can provide references for the formulation of low-carbon operation optimization strategies of new power systems and the allocation of new energy ancillary service resources.关键词：photovoltaic cluster;ancillary services;carbon emission flow;cluster partitioning;energy saving and carbon reduction;low-carbon operation4|10|0更新时间：2026-07-20
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