The He 1 Member of the Ordos Basin is a key interval for tight sandstone gas exploration and development. The complex interplay between mineral fabric and pore-throat structure makes movable fluid evaluation challenging, which is a critical factor restricting the efficient development of gas reservoirs. Current research primarily analyzes fluid occurrence characteristics from the perspectives of pore-throat structure parameters and clay mineral types, yet the mechanisms by which clay minerals influence pore-throat structure and subsequently control fluid mobility under different lithological settings remain unclear. This study focuses on the tight sandstones of the He 1 Member in the Xinzhao area, Ordos Basin. Integrating thin section identification, scanning electron microscopy, X-ray diffraction, high-pressure mercury injection, and variable-speed nuclear magnetic resonance (NMR) techniques, this work classifies rock types and employs segmented fractal theory based on T2 cutoff values to elucidate the control mechanism of mineral fabric on pore-throat structure and fluid mobility under lithological constraints. The results show that the tight sandstones in the study area can be divided into four lithologies: Type Ⅰ (gravel-bearing coarse-grained lithic quartz sandstone) is dominated by intergranular/intragranular dissolution pores and kaolinite intercrystalline pores; Type Ⅱ (medium- to coarse-grained lithic quartz sandstone) is characterized by intragranular dissolution pores and clay mineral intercrystalline pores; Type Ⅲ (gravel-bearing coarse-grained lithic sandstone) mainly develops intergranular matrix dissolution pores and intragranular dissolution pores; and Type Ⅳ (coarse- to medium-grained lithic sandstone) primarily develops intragranular dissolution pores and illite intercrystalline pores. Segmented fractal analysis reveals that the pore-throat space can be divided into large and small pore systems. The fractal dimension of the large-pore system shows a significant negative correlation with movable fluid saturation, indicating that the structural complexity and connectivity of the large-pore system are key factors controlling fluid mobility. The occurrence of movable fluid is jointly controlled by mineral composition and diagenesis. Type Ⅰ and Ⅱ are characterized by high quartz content, where a rigid framework resists compaction, and dissolution pores, kaolinite intercrystalline pores, and micro-fractures constitute a well-connected large-pore system with a low fractal dimension, resulting in high movable fluid saturation (>50%). In contrast, Type Ⅲ and Ⅳ are characterized by illite and chlorite occurring in filamentous, bridging, or flaky forms, which fill the pores, leading to complex pore-throat structures, a high fractal dimension, and low movable fluid saturation (<40%). This study reveals the control mechanism of mineral fabric on pore-throat structure and movable fluid under different lithological settings, providing a theoretical basis for the efficient exploration and development of tight sandstone gas reservoirs.
Silicon drift detectors(SDDs)hold significant application value in high-precision detection tasks due to their inherent advantages of high energy resolution,low noise,and rapid response.Addressing the performance bottlenecks of domestic SDDs concerning leakage current control,readout electronics integration,and high-throughput signal processing,this study focuses on the independent research and development of core detection devices.Herein,we report for the first time the development and systematic parameter characterization of the PA150,an SDD based on a domestically produced chip.To comprehensively characterize the key physical specifications of this newly developed chip,an X-ray fluorescence spectroscopy(XRF)testing system was constructed to conduct an in-depth evaluation of its comprehensive performance,including energy resolution,count-rate linear response,and multi-element identification capabilities.The experiment investigated the synergistic modulation mechanism of operating temperature and peaking time(the signal shaping time constant that balances noise filtering bandwidth and pulse pile-up probability)on detector performance.The results indicate that the PA150 achieves an energy resolution of 143 eV at 5.9 keV,representing an improvement of approximately 25%compared to the PA200 Si-PIN detector independently developed by our institute.Furthermore,physical mechanism analysis reveals that lowering the operating temperature effectively suppresses the parallel noise and thermal noise induced by the detector's leakage current.Meanwhile,adjusting the peaking time achieves a minimum-value balance between series noise(which is inversely proportional to time)and parallel noise(which is directly proportional to time).Based on the optimal parameter combination determined by this mechanism(-23℃coupled with a 4-5 μs peaking time),the detector's energy resolution is further improved to approximately 140 eV,achieving a high-count rate of 42.99 kcps while maintaining excellent resolving capabilities.When the peaking time is reduced to 1 μs,the count rate reaches 51.39 kcps.These performance metrics are comparable to those of international commercial SDDs,demonstrating exceptional characteristic peak separation capabilities in XRF applications.The independent development of this SDD effectively resolves the reliance on imported core detectors for the rapid screening of complex matrix samples(such as heavy metals in soil)by domestic XRF equipment,providing an indigenous technological solution for geological,environmental,and industrial online inspections.The BRIEF REPORT is available for this paper at .
With the surge in industrial use of chromium(Cr)and continuous intensification of pollution emission,Cr levels in soils across numerous regions have risen significantly.X-ray fluorescence spectrometry(XRF)offers advantages including simple sample preparation,simultaneous multi-element determination,and a broad analytical concentration range.However,when determining Cr-polluted soils,this method faces multiple challenges such as insufficient concentration gradients in certified reference materials(CRMs),mineral effects,particle size effects,and absorption-enhancement effects,all of which can impact the accuracy of Cr and multi-element determinations.These limitations are addressed by preparing 24 artificial standard samples across gradient concentrations via spiking low-Cr soil CRMs(GBW series)with K2Cr2O7(Cr6+)and CrCl3·6H2O(Cr3+).Integrating these artificial standards with national soil CRMs for calibration curve development effectively compensates for the inadequate concentration coverage of existing CRMs,making the calibration range more suitable for the detection needs of high Cr-polluted soils.Experimental verification demonstrates the influence of trivalent chromium(Cr3+)and hexavalent chromium(Cr6+)on analytical results in terms of measurement angle,resolution,and sensitivity.There are slight differences in the measurement angles for Cr3+and Cr6+,but the count difference for the same sample measured at their respective characteristic peak angles is negligible.No significant differences are observed in resolution and sensitivity.When applying this method to determine CRMs,the relative error(RE)is less than 10%,and the relative standard deviation(RSD)is less than 5%.Furthermore,analysis of actual soil samples from a Cr residue site and its surrounding areas in China shows that the RE of the Cr determination results are within 10%compared to those obtained by ICP-OES.Wavelength-dispersive XRF(WDXRF)analysis reveals a distinct difference in the peak angles between Cr3+and Cr6+,corresponding to an energy shift of approximately 0.39 eV,with the peak energy of Cr6+being lower than that of Cr3+.This is consistent with the energy shift values reported in the literature,demonstrating the potential of this method for Cr speciation analysis in soils.The proposed method not only accurately determines the total Cr content in soil but also simultaneously analyzes major and minor elements such as Na,Mg,Al,and Si,thereby expanding the detection scope of soil metal elements.It is suitable for the quantitative multi-element analysis of various soil samples,especially for the accurate quantification of multiple elements in highly Cr-contaminated soils,establishing a more comprehensive methodological system for the precise multi-element determination in high-Cr soil environments.The BRIEF REPORT is available for this paper at .
Mining activities have caused severe degradation of mining soils,characterized by organic matter(OM)depletion,structural damage,and heavy metal contamination,posing significant challenges for ecological restoration.A key challenge in restoring these soils lies in insufficient OM inputs and unclear mechanisms underlying soil organic matter(SOM)stabilization,particularly the microbial-driven SOM formation and stabilization.Plant growth-promoting rhizobacteria(PGPR),as functional microorganisms,have shown great potential in promoting plant growth,enhancing SOM accumulation,and facilitating ecological rehabilitation in mining areas.The functional groups of PGPR and the main factors influencing their survival and performance in mining soils are systematically summarized in this review.The pathways and mechanisms by which PGPR mediate SOM formation and stabilization are also highlighted,including:(1)promoting plant-derived OM inputs;(2)regulating microbial metabolism;(3)facilitating the accumulation of microbial necromass carbon;and(4)promoting organo-mineral associations and soil aggregate formation.Furthermore,the potential applications of PGPR in mine site rehabilitation and SOM stabilization are discussed,such as the development of single-strain inoculants,construction of synthetic microbial consortia,combined application with organic-inorganic amendments,and the use of artificial intelligence to assist in strain selection.Overall,this review provides a theoretical and technical foundation for developing PGPR-based,green,and sustainable ecological restoration strategies in mining areas,thereby supporting ecosystem reconstruction on degraded mined lands.The BRIEF REPORT is available for this paper at .
The southern Ordos Basin is rich in tight oil resources. However, the strong heterogeneity of its main reservoir, the tight sandstone of the Yanchang Formation, limits the applicability of traditional brittleness evaluation methods based on single parameters or linear combinations, affecting the accurate identification of fracturing “sweet spots”. To more authentically characterize reservoir brittleness, this study focused on the tight sandstone of the Yanchang Formation in the southern Ordos Basin. Through high-temperature and high-pressure triaxial mechanical tests, Brazilian splitting tensile strength tests, and X-ray diffraction analysis, the controlling mechanisms of mineral composition, temperature-pressure conditions, and laminated structures on rock mechanical properties were systematically revealed. Furthermore, fractal geometry theory was introduced, and the fractal dimension of post-fracture rock surfaces was used as an index to quantitatively characterize the true brittleness. The gradient boosting decision tree (GBDT) machine learning algorithm was employed to integrate four fundamental brittleness indices based on energy, elasticity, strength, and shear mechanisms, constructing a nonlinear comprehensive brittleness index (CBI) prediction model. The results indicated the following: (1) The fracture fractal dimension can effectively quantify the complexity of rock failure and show a regular decrease with increasing confining pressure; (2) The GBDT model can effectively capture the complex nonlinear relationships among multi-source parameters, achieving a coefficient of determination (R2) of 0.9749 for the full sample set and a cross-validation root mean square error (RMSE) of 0.0467; (3) Feature importance analysis revealed that the contribution of the strength parameter (the ratio of tensile to compressive strength, 0.4584) was significantly higher than that of other parameters, indicating that the “tensile-compressive strength difference” was the dominant mechanical mechanism controlling brittleness development in the tight sandstone of this area; (4) By applying a dynamic rock mechanical parameter interpretation model established from well-logging data to the Chang-8 Member of the Yanchang Formation in Well HH26 in Honghe Oilfield on the souhern margin of the Ordos Basin, layers with higher CBI (0.70) exhibited a significantly lower on-site fracture presure gradient (1.83 MPa/100 m) compared to layers with lower CBI (0.51, 2.11 MPa/100 m), and the predicted favoable brittleness zones showed good agreement with actual fracturing responses. A quantitative brittleness evalution method for tight sandstone was established in this study, using fractal dimension as the target and machine leaning as the means, clarifying the dominant role of strength parameters in brittleness evaluation. It can provde a quantitative reference for the optimization of fracturing intervals and efficient stimulation in tight oil reservois in the southern Ordos.
