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Arid zone grassland is a crucial component of terrestrial ecosystems and plays a significant role in ecosystem protection and soil erosion prevention. However, accurately mapping grassland spatial information in arid zones presents a great challenge. The accuracy of remote sensing grassland mapping in arid zones is affected by spectral variability caused by the highly diverse landscapes. In this study, we explored the potential of a rectangular tile classification model, constructed using the random forest algorithm and integrated images from Sentinel-1A (synthetic aperture radar imagery) and Sentinel-2 (optical imagery), to enhance the accuracy of grassland mapping in the semiarid to arid regions of Ordos, China. Monthly Sentinel-1A median value images were synthesised, and four MODIS vegetation index mean value curves (NDVI, MSAVI, NDWI and NDBI) were used to determine the optimal synthesis time window for Sentinel-2 images. Seven experimental groups, including 14 experimental schemes based on the rectangular tile classification model and the traditional global classification model, were designed. By applying the rectangular tile classification model and Sentinel-integrated images, we successfully identified and extracted grasslands. The results showed the integration of vegetation index features and texture features improved the accuracy of grassland mapping. The overall accuracy of the Sentinel-integrated images from EXP7-2 was 88.23%, which was higher than the accuracy of the single sensor Sentinel-1A (53.52%) in EXP2-2 and Sentinel-2 (86.53%) in EXP5-2. In all seven experimental groups, the rectangular tile classification model was found to improve overall accuracy (OA) by 1.20% to 13.99% compared to the traditional global classification model. This paper presents novel perspectives and guidance for improving the accuracy of remote sensing mapping for land cover classification in arid zones with highly diverse landscapes. The study presents a flexible and scalable model within the Google Earth Engine framework, which can be readily customized and implemented in various geographical locations and time periods. [ABSTRACT FROM AUTHOR]

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The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and adjacent basins remain unclear. To better assess the connections between the temporal and structural activity in HTB, apatite fission-track (AFT) and zircon fission-track (ZFT) analyses were conducted in this study. The lack of adequate FT data from the HTB is a source of contention and dispute. This paper collected samples for AFT and ZFT techniques from the central and southern HTB, trying to improve the research. The ZFT and AFT ages could be divided into the following 7 groups: 279 Ma, 222–213 Ma, 193–169 Ma, 151–147 Ma, 130–109 Ma, 92–77 Ma, and 65–50 Ma. The inverse modeling results of AFT indicate 4 fast cooling episodes of 170–120 Ma, 120–95 Ma, 66–60 Ma, and ~10–8 Ma to the present. Combining the results of FT analysis with radial plot and inverse modeling of AFT, the following eight age groups are believed to reveal the distinct tectonic activities in HTB: the first age group of 279 Ma mainly represented the back-arc extension of the southern HTB; the age group of 222–213 Ma was bounded with NNE-SSE trending contraction between the South China block and North China Craton; the event of 193–169 Ma responded to the post-orogenic collapse followed after the second event; the 151–147 Ma group was interpreted as the eastward extrusion induced by the subduction between Qiangtang and Lhasa blocks; the Early Cretaceous (130–109 Ma) group was not only affected by the rollback of the Pacific Plate, but also denoted the collapse of the thickened lithosphere formed in the Late Jurassic; the Late Cretaceous (92–77 Ma) group was attributed to long-distance impact from the subduction of the Pacific Plate beneath the Eurasian Plate; the event during 65–50 Ma was a correspondence to far-field effect of the onset collision between the Eurasian and Indian Plates; and from 10–8 Ma to the present, the progressive collision of the Indian and Eurasian Plates have a significant impact on the HTB and the northeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Urban carbon emissions are one of the most important areas contributing to the growth of carbon emissions, and resource-dependent cities with natural resource extraction and processing as their leading industries tend to have higher carbon emissions. Ordos is the city with the highest coal production in China, and its economic development is dominated by coal, oil and gas, and other resource extraction and processing industries, with industrial activities making a large contribution to carbon emissions. At the same time, Ordos has undergone rapid industrialization in recent years, but still faces the problem of environmental pollution, epitomizing a typical resource-dependent city in China. Therefore, this paper takes Ordos as an example and uses the Generalized Divisa Index Method (GDIM) to study the drivers of industrial carbon emissions in Ordos from 2005–2020, a typical resource-dependent city in China, and further analyzes are conducted in relation to the three phases of development. Based on the key drivers, the Monte Carlo method is used to forecast industrial carbon emissions from 2021 to 2030. The results show that the most important factors driving the growth of industrial carbon emissions are the scale of industrial output and industrial energy consumption, while the intensity of industrial energy investment is the most important factor mitigating industrial carbon emissions, and that energy efficiency and carbon intensity of energy consumption can also mitigate carbon emissions after economic transformation. At the same time, investment is the factor with the greatest potential for optimization on the path to emissions reduction. [ABSTRACT FROM AUTHOR]

This study investigates the spatial-temporal evolution and the interconnectedness of land use/cover change (LUCC) and ecosystem service value (ESV). Such analysis can offer theoretical guidance and support decision-making for sustainable land resource development and ecological preservation in ecologically vulnerable cities within the Loess Plateau-Maowusu Desert transition zone. Utilizing Landsat data spanning 2000–2020, the paper examines the synergistic relationship between ESV and land use intensity in Shenmu City through bivariate spatial autocorrelation and the coupled coordination degree (CCD) model. Our findings indicate that the area of construction land in Shenmu City experienced the most significant change between 2000 and 2020, with a dynamism rate of 76.8%. This shift resulted in a decrease in the total ESV, from RMB 10.059 billion in 2000 to RMB 9.906 billion in 2020. The bivariate spatial autocorrelation analysis reveals a significant positive spatial correlation between ESV and land use intensity, while the CCD levels for both demonstrate a fluctuating yet overall upward trend over the 20-year period. The paper uncovers the spatial-temporal evolution of LUCC and ESV in Shenmu City along with their interconnected dynamics. The research outcomes can contribute valuable insights for reinforcing land resource utilization and promoting sustainable regional development within cities in the Loess Plateau-Maowusu Desert transition zone. [ABSTRACT FROM AUTHOR]

In this paper, production system (PS) of shale oil is optimized according to production data and indoor experiments, including core and fluid tests. Results showed that: ① Pressure drop rate at wellhead is a reasonable reference for the determination of post-fracture shut-in duration (PFSID). When pressure at a wellhead of horizontal well is relatively stable and the pressure drop less than 0.1 MPa per day for three consecutive days, PFSID ends; ② Flowback intensity of fracturing fluid affects the effectiveness of proppant underground, thus flowback intensity can be determined by the critical flow rate and safety factor of each proppant; ③ Flowback intensity should be varied during different development stages, which could be divided into four according to production gas and oil ratio(GOR) of a shale oil horizontal well: low, medium–high, high and high-low production GOR. During the stage of low production GOR, ratio of flow pressure and saturation pressure should be maintained greater than 1.0, and the initial daily liquid productivity for a hundred-meter oil-bearing lateral length in a horizontal well is 2.4 ~ 2.9 m3/d; and during the medium–high production GOR, high production GOR and high-low production GOR stages, the responding initial daily liquid productivity should be maintained between 0.8 ~ 1.0 or less than 0.8 respectively. [ABSTRACT FROM AUTHOR]

Underground coal mining leads to land subsidence, which, in turn, results in damage to buildings and infrastructure, disturbs the original ecological environment, and hinders the sustainable development of coal mining cities. A reasonable estimation of land subsidence, on the other hand, is the foundation for building protection, land reclamation, and ecological environment reconstruction. However, when we applied the existing land subsidence estimation theory to the deep mining areas of the Ordos coalfield in western China, there was a significant deviation between the estimations and the measurements. To explain such unusual case, we propose using the overburden's average GSI (Geological Strength Index) value instead of the compressive strength (UCS) of rock specimens for a better representation of the overburden's overall properties. By using on-site subsidence monitoring results and historical data, we provided evidence which supports that the overburden's average GSI value has a much greater impact on subsidence rates than the UCS. Subsequently, we investigated the relationship between three typical overburden's GSI values and the subsidence rates via a calibrated numerical model, revealing the variation patterns of maximum surface subsidence when the overburden's average GSI value is set at 30, 50, and 75, respectively. Finally, on the basis of the measured and simulated results, we discussed a non-conventional strip mining method for mining subsidence control in the deep mining areas of the Ordos coalfield in western China, and explained why it is possible and what are the significant advantages behind. The proposed methods, findings, and suggestions in this paper are therefore quite helpful for researchers and engineers who wish to estimate and control the mining-induced land subsidence, as well as for those who are particularly interested in the study of environment science related to land subsidence. [ABSTRACT FROM AUTHOR]

Among so many fault basins around Ordos presenting good geothermal background, Yinchuan Plain is the key development and protection area of the Ecological and Economic Belt along the Yellow River in Ningxia and Yinchuan Metropolitan Area. The study of geothermal resources in this region is of great significance to the sustainable economic development of Yinchuan Plain. Most scholars suggested that Yinchuan Plain geothermal resources are low-to-medium temperature geothermal resources and have high value in terms of development and utilization due to their large reserves, good water quality conditions, and wide distribution. However, there is much controversy over the geothermal mechanism of this region. As an effective means to study geothermal mechanism, geophysical methods can be used to study regional basement uplift and structural distribution characteristics. Based on the discussion of regional geothermal geology background, this paper studies the distribution rules of Moho and Curie depths in the region by applying different geophysical data. The results show that the western margin of Yinchuan Plain is obviously uplifted. As inferred from the epicentral distribution of Yinchuan Plain section, there is a significant difference of the seismic bottom interface on the east and west sides of the Yellow River fault in Yinchuan Plain. The three-dimensional gravity inversion confirms basement uplift in this region. By referring to results obtained by the inversion of gravity and magnetic data and deep seismic exploration, the paper presents a comprehensive analysis of the regional geothermal geology conditions and proposes a geothermal conceptual model of Yinchuan Plain. The heat source comes from the earth heat flow and migrates to the thermal reservoir through the fault or fissure convection. The deep-large active faults provide a channel for deep heat flow to the shallow part, and the thermal fluid accumulates in the uplift area to form the high geothermal anomaly area. There should be two large-scale geological activities in the geotropics around Ordos. One is the basement uplift of the basins around Ordos platform, which provide the heat source. The other is the uplift of Ordos, which places the surrounding basin in an extensional environment and provides a channel for the heat source upwelling. [ABSTRACT FROM AUTHOR]

Considering China's goal of achieving peak carbon emissions in 2030 and carbon neutrality in 2060, this paper analyzes carbon emissions, carbon emission intensity, the decoupling of carbon emissions and economic development, and associated influencing factors using data from Ordos City from 2009 to 2020. The methods employed are the IPCC carbon emission calculation method, Tapio decoupling model, and logarithmic average Dickens index decomposition. The results show the following: (1) During the study period, Ordos City carbon emissions showed an increasing trend, and the total carbon emissions increased from 5.634 billion tons in 2009 to 204.734 million tons in 2020, with an average annual growth rate of 13.77%. (2) The decoupling elasticity of Ordos City from 2009 to 2016 was 1.26, which is the expansion negative decoupling state. From 2016 to 2020, the decoupling elasticity was -3.2657, showing a strong negative decoupling state. (3) The increase in population and per capita GDP in Ordos are the main factors contributing to the increase of carbon emissions, and the main negative growth driver is the increase in energy intensity. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic gneiss domes are important structures of the Khondalite Belt in the northwestern North China Craton. However, less attention has been paid to their formation and evolution, and it thus hampers a better understanding of the deformation history of the Khondalite Belt. In this paper, we conducted structural and geochronological studies on the Qianlishan gneiss domes of the Khondalite Belt. The field observations and zircon U–Pb dating results show that the Qianlishan gneiss domes consist of 2.06–2.01 Ga granitoid plutons in the core, rimmed by granulite facies metasedimentary rocks (khondalites) of the Qianlishan Group. Both of them were subjected to two major phases of deformation (D1–D2) in the late Paleoproterozoic. Of these, D1 deformation mainly generated overturned to recumbent isoclinal folds F1 and penetrative transposed foliations/gneissosities S1 at ~1.95 Ga. Subsequently, D2 deformation produced the NW(W)–SE(E)-trending doubly plunging upright folds F2 at 1.93–1.90 Ga, and they have strongly re-oriented S1 gneissosities, giving rise to the Qianlishan gneiss domes. Combined with previous studies, we argue that the Qianlishan gneiss domes were the products of the Paleoproterozoic collisional orogenesis between the Yinshan and Ordos Blocks. Additionally, the development of doubly plunging antiforms is considered an important dome-forming mechanism in the Khondalite Belt. [ABSTRACT FROM AUTHOR]

A set of low-grade clastic metamorphic and carbonate rocks, and greenschists outcropping in the southwestern (SW) margin of the North China Craton (NCC), was originally classified as the Paleoproterozoic Xiong'er Group according to stratigraphic correlation. To verify the age, this paper carried out detrital zircon U–Pb LA-ICP-MS dating of low-grade clastic metamorphic rocks exposed in the Changqing area at the SW margin of the Ordos Block in the SW part of the NCC. Results from detrital zircon dating indicate that the metamorphic and carbonate rocks can be classified into the Neoproterozoic Nanhua System, which is the only Nanhua System stratum in this block so far, and it probably could provide new clues to Rodinia break-up and Snowball Earth of the NCC. The nine peak ages of the low-grade clastic metamorphic rocks reflected its relatively complex provenance, and almost all major geological events experienced by the NCC basement since the Neoarchean, but some age peaks were difficult to correspond to that of the NCC, indicating that the southwestern part of the Ordos Block was also affected by the Qinling and Qiliang orogenic belts during Nanhua System of Neoproterozoic. Combined with provenance analysis, it was revealed that the current southwest boundary of the Ordos Block was the previous southwest boundary of the Ordos Block during the Qingbaikou-Nanhua Period of the Neoproterozoic. [ABSTRACT FROM AUTHOR]

This research paper focuses on the laminated shale oil reservoir in the third sub-member of the seventh member of Yanchang Formation (Chang 73 sub-member) in the Ordos Basin. The study aims to comprehensively analyze the lithofacies type, micro qualitative and quantitative pore structure parameters, and the main controlling factors of the pore structure in laminated shale. The analysis involves various techniques, including a comprehensive analysis of TOC, rock-eval, X-ray diffraction, polarized light and fluorescence microscope observation, field emission scanning electron microscope observation, and low-pressure N2 adsorption analysis. Based on the sedimentation characteristics, geochemistry, and mineral composition differences, the Chang 73 laminated shale can be classified into three lithofacies types: tuffaceous-organic matter binary laminated shale, clayey-organic matter binary laminated shale, and felsic-clayey binary laminated shale. The pore network consists primarily of organic hydrocarbon generation pressurization fractures, clay mineral felsic intergranular composite pores, and felsic plasmid intergranular pore fracture systems. Mesopores are the most developed pore type. The pore volume and specific surface area increase in the order of “tuffaceousorganic matter”, “clayey-organic matter”, and “felsic-clay”, while the heterogeneity of the pore network gradually weakens, and the roughness of the pore surface enhances. The overall development of organic matter pores is limited, with organic matter-pyrite-clay mineral composite pores being the main components of micropores. The primary intergranular pore system, associated with rigid quartz particles, dominates the mesopores and macropores, and acts as the main framework of the entire pore network. The development of feldspar dissolution pores is limited and contributes minimally to the pore network. [ABSTRACT FROM AUTHOR]

As an essential unconventional natural gas resource, China's coalbed methane resources are only commercially exploited in a few areas, such as the Qinshui Basin and the Ordos. The rise of coalbed methane bioengineering makes it possible to realize the conversion and utilization of carbon dioxide through microbial action and the carbon cycle. According to the metabolic behavior of the underground microbial community, if the coal reservoir is modified, it may stimulate the microorganism to continuously produce biomethane to prolong the production life of depleted coalbed methane wells. This paper systematically discusses the microbial response to promoting microbial metabolism by nutrients (microbial stimulation), introducing exogenous microorganisms or domestication of in situ microorganisms (microbial enhancement), pretreating coal to change its physical or chemical properties to improve bioavailability, and improving environmental conditions. However, many problems must be solved before commercialization. The whole coal reservoir is regarded as a giant anaerobic fermentation system. Some issues still need to be solved during the implementation of coalbed methane bioengineering. Firstly, the metabolic mechanism of methanogenic microorganisms should be clarified. Secondly, it is urgent to study the optimization of high-efficiency hydrolysis bacteria and nutrient solutions in coal seams. Finally, the research on the underground microbial community ecosystem and biogeochemical cycle mechanism must be improved. The study provides a unique theory for the sustainable development of unconventional natural gas resources. Furthermore, it provides a scientific basis for realizing the carbon dioxide reuse and carbon element cycle in coalbed methane reservoirs. [ABSTRACT FROM AUTHOR]

Ordos Basin is a multicycle superimposed cratonic basin in northern China with a simple internal structure and a gentle stratigraphic slope. It is characterized by extensive development, numerous oil and gas-bearing layers, and complete source-reservoir-caprock assemblages. However, the research on continental shale reservoirs and gas-bearing characteristics in the southern part of the basin is not in-depth enough, which restricts the further exploration and development of shale gas in this area. In this paper, the development characteristics of pores and fractures in shale reservoirs and the gas-bearing characteristics of Yanchang Formation shale in the study area are summarized by the comprehensive use of field outcrop, core, and logging, combined with common thin section observation, scanning electron microscope observation, X-ray diffraction analysis, and other methods and techniques. Research indicates that the cement content of the sandstone in the Yanchang Formation reservoir in the south of Ordos is generally 5%-25%. The reservoir also has a large number of primary pores, secondary pores, and microfractures. The gas content of the Yanchang Formation shale represented by Chang 7 is related to both organic matter and pore structure. [ABSTRACT FROM AUTHOR]

High-resolution satellite images have recently been widely used for change detection of mineral resources and mining area environments. However, with their increasing resolution and number of feature sub-categories, traditional machine learning methods have become sensitive to pseudo-changes and intra-class changes, which are prone to producing misclassifications. To address these problems, a novel fully convolutional network, the Hybrid Dilated Convolutional Siamese Network (HDC-Siam) was proposed. This model combines the modular dilated convolution network with the fully convolutional Siamese networks structure, in order to reduce the commission rate. In this paper, pairs of Sentinel-2 images with an interval of about two years was used as the experimental data. The HDC-Siam model was used to detect changes, where we evaluated the accuracy in the Dongsheng coalfield in Ordos, China and the Kuznetsk coalfield in Kemerovo, Russia. We obtained F1-scores of 85% and 75% for these respective locations. In addition, we conducted comparative experiments using two other methods – Fully Convolutional Siamese – Difference (FC-Siam-diff) and Fully Convolutional Early Fusion (FC-EF) – in order to verify that the HDC-Siam works. [ABSTRACT FROM AUTHOR]

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Weakly cemented medium-grained sandstone in Ordos mining area of China is widely distributed under phreatic water. The creep behavior of saturated rock is important for the stability of water-resisting strata. In this paper, creep mechanical properties of saturated medium-grained sandstone were studied by triaxial rheological test. The results showed that medium-grained sandstone only shows attenuation creep and stable creep under low stress level, and accelerated creep occurs when axial load reaches about 75% of instantaneous compressive strength. The rock samples exhibit volume dilatancy under most loading levels and finally shear fracture. The failure mechanism is the dislocation separation of mineral particles. Based on the energy dissipation theory, the damage evolution equation was modified and introduced into the Burgers model, which can accurately describe the rheological behavior of saturated medium-grained sandstone. The modified model was used to predict the crack initiation time under different deviatoric stresses, which can provide guidance for early warning of water-resisting rock stability. [ABSTRACT FROM AUTHOR]

In common with other important coal bases in northwestern China, the hydrology and ecology and environment of Ordos, northern Shaanxi (Shanbei), and Shanxi Provinces have much. Terrestrial water storage anomaly (TWSA), soil moisture anomaly (SMA), and groundwater storage anomaly (GWSA), are important water storage qualities that play a critical role in the distribution and growth of vegetation. In this paper, multi‐source remote sensing data were used to analyze the spatial–temporal changes and relationships of water storage, ecology and environment from 2002 to 2020. The numerical results showed the TWSA and GWSA in the study area had a declining trend and the rates were −7.512 mm yr‐1 and −8.268 mm yr‐1, respectively. On the contrary, the SMS showed an increasing trend, and the rate was 0.840 mm yr‐1. By trend variation and correlation analysis, we found GWSA is the main part in the variation of TWSA. By further analysis, it was found that the climate factors are not the major factors causing the variation of GWSA, but coal mining and artificial irrigation activities, which are especially clear in the Taihang Mountains in eastern Shanxi Province. The ecology and environment have been improving, and water storage and climate factors have played a different role in different regions. The warm climate conditions and the increased 0–40 cm of soil water have promoted the growth of vegetation and the improvement of the ecology and environment. The research results are helpful to understand the impacts of water storage on the ecology and environment in high‐intensity coal mining areas. [ABSTRACT FROM AUTHOR]

Total organic carbon content (TOC) is an important parameter for shale gas resource evaluation. Among the existing TOC prediction methods, ΔlgR method is the most widely used. There are two main problems in this method: 1) assuming a linear relationship between ΔlgR and TOC; 2) manually determining the baseline and introducing human error. Due to the frequent alternating changes in the sedimentary environments of continental shale, the heterogeneity of it is strong. In this case, the relationship between well logs and TOC is complex and nonlinear, which leads to incorrect results for predicted TOC using ΔlgR method. The objective of this paper is to develop a new empirical method to determine the TOC of continental shale using support vector regression (SVR) based on grid search cross-validation. The optimized SVR method can fit the nonlinear relationships between log data and TOC well, and it is suitable for TOC estimation in strong heterogeneity case such as continental shale. Three hundred sixty-four measured TOC samples of Zhangjiatan shale and the corresponding GR, DEN, AC, U logs data were used to construct the SVR model. Compared with the ΔlgR method, the accuracy of the SVR model to calculate TOC is obviously higher. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Phytogenic mounds (nebkhas) formed by shrubs are a common phenomenon in arid and semi-arid areas. The formation of nebkhas is accompanied by the appearance of the fertile island effect. Quantitative evaluation of the shrub sand compost island effect is a key link in preventing soil erosion and nutrient loss. This study took the typical shrub Tetraena mongolica in desert areas as the research object and quantified the sand-trapping capacity of the shrub. We revealed the influence of sediment texture and volumetric soil water content on fertile islands during the development of T. mongolica nebkhas. The results showed that (1) the single shrub intercepted large amounts of sediments due to the high density of branches of T. mongolica, forming nebkhas that were positively correlated with the shrub size. (2) The overall soil nutrient content below the shrub was greater than the soil nutrient content outside the shrub, forming a typical fertile island effect. The soil organic carbon (SOC), alkaline hydrolytic nitrogen (AHN), available phosphorus (AP), and available K (AK) content all increased gradually with increasing nebkha volume. Compared with the deep soil of nebkhas, the nutrient content of the surface soil was generally higher. (3) There was a positive correlation between the volumetric water content and nutrient content in nebkhas. (4) The semi-ellipsoid shape of T. mongolica enabled it to intercept large amounts of coarse-grained material. Fine sand (100–250 µm) was the main particle size in the sediment aggregates inside the nebkhas. The fine sand content generally increased with increasing shrub size. Redundancy analysis (RDA) revealed that the fine sand content of the nebkha sediments had a strong positive correlation with the soil nutrient content. This paper provides an example for evaluating the fertile island effect during the deposition process of nebkhas in the desert transition zone. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the last 50 Ma, the eastern Eurasian continent has experienced widespread crustal and lithospheric deformation. However, mechanisms in creating such widespread intra‐continental deformation are still not well understood. Here, we present a 3‐D S‐wave velocity model of the northeastern Tibetan Plateau and adjacent regions by jointly inverting teleseismic body and surface waves. The resulting model clearly suggests that lateral extrusion of asthenosphere from northern Tibet is being blocked by the thick cratonic keels of Ordos and Sichuan, and therefore the asthenosphere is channeled into a strong eastward flow beneath the northern Qinglin between these two cratonic keels. Our results also demonstrate that continental deformation in eastern Eurasia is likely influenced by the small‐scale convection when the lateral asthenospheric flow from NE Tibet encounters preexisting continental lithospheric steps to the east of Ordos. Plain Language Summary: In this paper, we present a 3‐D S‐wave velocity model of the northeastern Tibetan Plateau and adjacent regions by jointly inverting teleseismic body and surface waves. The resulting model clearly suggests that lateral extrusion of asthenosphere from northeastern Tibet is being blocked by the thick cratonic keels of Ordos and Sichuan, and therefore, the Tibetan asthenosphere can only be extruded into a narrow eastward flow channel beneath the northern Qinglin between these two cratonic keels. Our results provide solid evidence for eastward extrusion of Tibetan mantle and indicate that the asthenospheric flow from NE Tibet could play an important role in lithospheric reworking, rifting, and intraplate volcanism around the Ordos in east China. Key Points: We obtain a high resolution 3‐D velocity model of NE Tibet by joint inversion of teleseismic body wave and surface waveThe joint inversion model reveals mantle flow from NE Tibet that is extruded through a narrow channel beneath the northern QinlingThe asthenospheric flow from NE Tibet played an important role in lithospheric reworking and intraplating volcanism around the Ordos [ABSTRACT FROM AUTHOR]

Receiver function (RF) analysis is an indispensable method that is widely utilized to image the deep structure of the crust and upper mantle. Although the P -wave receiver function (PRF) has the advantages of a higher signal-to-noise ratio and higher resolution than S -wave receiver function, the information about P -to- S converted (Ps) phases from velocity discontinuities of the crust and upper mantle is usually obstructed by multiples from shallower crustal interfaces. Sometimes it is difficult to identify useful information about lithospheric discontinuities. In this paper, we propose a method for suppressing multiples and isolating the Ps phases of RFs. This task is accomplished by exploiting the differences in arrival times resulting from the slowness between the conversion and the multiples that occur at the same interface in the PRFs and by separating them in the Radon domain, which enables removal of crustal and sedimentary multiples. This method can effectively remove multiples and isolate the useful signals of Ps phases contained in the PRFs. We test the method on synthetic PRFs and demonstrate that crustal multiples can be effectively eliminated or suppressed and that the Ps phase of lithospheric discontinuities can be coherently traced. Next, we apply the method to real PRF data collected from the seismic station of the China Array seismic experiment (Phase II and Phase III) in the Ordos block and its adjacent area, and successfully obtain an improved common conversion point stacking image of lithospheric discontinuity structures in the depth domain, particularly for detecting the lithosphere–asthenosphere boundary. [ABSTRACT FROM AUTHOR]

The mechanical behavior of coal is significantly influenced by the loading rate and bedding plane. In this paper, the uniaxial compression tests at different loading rates were conducted on coal specimens with vertical bedding (CSVB) and coal specimens with parallel bedding (CSPB), which were prepared by the coal with bursting liability from the Ordos deep mining areas, China. The results show that the uniaxial compressive strengths of CSVB and CSPB are positively correlated with the loading rate. The peak values of acoustic emission (AE) counts and accumulated absolute AE energy of CSVB and CSPB increase with the loading rate, and the AE parameters of CSVB are larger than those of CSPB. The variation rules of input energy density and elastic energy density are similar for CSVB and CSPB, but the variation rules of dissipated energy density in stage IV are different. As the axial load increases, the energy storage rate and energy dissipation rate of both coal specimen types increase and decrease, respectively. The bedding planes of coal and the loading conditions in the field should be fully considered when identifying the bursting liability of coal and forecasting coal burst. This study can provide a reference for coal burst warning and prevention under similar geological conditions in Ordos deep mining areas. [ABSTRACT FROM AUTHOR]

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In order to speed up the development and utilization of hydrothermal energy, it is essential to assess the potential of geothermal resources in petroliferous basins. In this paper, the distribution of reservoirs (aquifers) and the characteristics of geothermal fields have been studied systematically based on geological, geophysical, well drilling, temperature, and sample test data obtained from the major petroliferous basins of China. It has been found that some of the porous sandstone formations in these petroliferous basins are major geothermal reservoirs and are extensively thick and widely distributed. In general, the geothermal gradient in China is higher in the eastern basins and lower in the western basins. On average, the geothermal gradient is above 30 °C/km in the Bohai Bay, Songliao, and Subei basins. The geothermal resource abundance is also higher in eastern China and in the Beibuwan basin in southern China, and the geothermal source forming condition is better, followed by the Ordos, Qaidam, and Sichuan basins in Central China. Other potential basins include the Tarim and Junggar basins in western China, where the geothermal gradient ranges between 21 and 22 °C/km, on average. In this paper, three methods, stochastic simulation, unit volumetric, and analogy, were used for the assessment of geothermal resources. Using the stochastic simulation and unit volumetric methods, the geothermal resources, annual recovered geothermal resources, geothermal water resources, and thermal energy of water in 11 basins or blocks of up to 4000 m deep were calculated. Grading evaluation criteria were established by considering the heterogeneity of geothermal reservoirs. The results showed that the petroliferous basins are very rich in geothermal resources. The annual recoverable resources reach 1626.8 × 106 tons of standard coal, in which grade I, grade II, and grade III resources are 641.9 × 106, 298.6 × 106, and 686.3 × 106 tons of standard coal, respectively. The results demonstrate that the development and utilization of geothermal energy in oilfields has a huge potential for industrial production and family use, and a great significance for the development of green oilfields. With the high demand of heat, the eastern oilfields with high geothermal resource abundance should be the first to be considered for the production and utilization of geothermal energy, followed by the central and western oilfields. [ABSTRACT FROM AUTHOR]

This paper applies the perspective of informality to examine the nexus between informal housing finance and housing markets in China. The study explores the causes, formation, influences and consequences of informal housing financing mechanisms in Ordos. It argues that informal housing finance contributes to the local property market boom and becomes an instrument of wealth building through homeownership, but classifies and reinforces social classes based on their gains from the property market. The study discusses the possibilities of institutionalizing informal housing finance and diversifying economic structures, with special consideration of resource-based frontier cities. [ABSTRACT FROM AUTHOR]

CO2 geological storage (CGS) is a crucial strategy for meeting CO2 emission reduction targets. However, the effect of microbial action on CGS in deep saline aquifer is unclear. In this paper, numerical simulations based on previous experimental data were conducted to investigate CO2 solubility-trapping and mineral-trapping by microbial-mediated process in CGS demonstration base in Ordos, north of China. The simulation results reveal that the presence of a microbial community has a positive influence on CGS, mainly in terms of the amount of CO2 that can be injected and the manner by which it is stored. With the effect of microbial action, the amount of injected CO2 was increased by 23.33% and the CO2 mineral sequestration increased from 1.12 to 2.05%. In addition, microbial action plays different roles at different stages of CGS. In the initial stage of CO2 injection, the microbial action promotes dissolution of calcite, oligoclase and clay minerals such as chlorite and kaolinite, providing a favorable condition (more K+, Ca2+, Na+, Mg2+, Fe2+ and HCO3−) for CO2 mineral-trapping. In the following stage of CGS, microbial action accelerates the precipitation of carbon-fixing minerals such as calcite and siderite, enhancing the CO2 storage security in deep saline aquifer. As such, secondary minerals such as ferroan dolomite and dawsonite were observed in advance in microbially mediated CO2–saline–sandstone interactions, further indicating that microbes play a positive role in CO2 mineral-trapping. Consequently, the microbial action can promote mineral capture of CO2 and increase the CO2 storage security in deep saline aquifer. These conclusions can provide a reference and basis for the suitability assessment of CGS in such deep saline aquifer like Erdos, China. [ABSTRACT FROM AUTHOR]

Summary: Extraction residue (ER) is, in this study, considered as an insoluble portion derived from a novel extraction process with direct coal liquefaction residue, which is the byproduct from 1000 kton/y direct coal liquefaction and oil production process in Ordos, China. ER mostly consists of unreacted coal and minerals, spent catalyst, and solvent. It is considered as a hazardous waste in China. Gasification is a promising way to employ ER, as the carbon resource contained in it could be adequately utilized, so strongly reducing the environmental impact of this material. In this paper, a kinetic study is carried out concerning CO2 gasification (in thermobalance) of ER char, coal char, and their blends. The results show that, at temperatures ranging from 1123 to 1323 K, the reactivity of ER char is much larger than that of coal char, and the reactivity of ER/coal char blends increases when the ER fraction increases, consistently resulting in between the reactivities shown by ER char and coal char alone. The partial pressure of CO2 promotes the reactivity of all samples. BET surface area resulted three times larger for ER char vs coal char, while pore surface area and pore volume were four times larger. Moreover, the relevant parameters of the random pore model for CO2 gasification of ER char, coal char, and their blend #2 (with 20% ER) were obtained; the activation energy resulted 210.6, 240.5, and 232.8 kJ/mol, and the reaction order 0.30, 0.45, and 0.40, respectively. [ABSTRACT FROM AUTHOR]

Understanding existing fractures is critical to achieving high and stable yields in low‐permeability reservoirs, tight sandstones, and shale reservoirs. When multiple fracture sets are present in a reservoir, accurately determining the seepage direction of fluids is critical for the deployment of the well network, fracture reformation, and the design of horizontal wells. In this paper, based on conventional logging data calculations and rock triaxial mechanical experiments, a heterogeneous finite element model was established using the finite element software. The densities and the occurrence of the natural fractures were calculated by numerical simulation of the paleostress field; the fracture apertures were calculated numerically by a current in situ stress simulation. Using a combined static coordinate system and dynamic coordinate system approach, a model suitable for determining the 3D permeability tensor of multiple fractures is established, and the formula of the permeability tensor is given. In addition, by adjusting the rotation angle and flip angle in the dynamic coordinate system, the permeability of elements is predicted for different directions. The results show that fractures mainly trend in the NE (45°) and ESE (120°) directions. Additionally, the results of differential strain, microseismic monitoring, stress relief, and regional borehole collapse observations indicate that the dominant direction of the in situ stress field is ENE (70°). The principal values of maximum permeability in the reservoirs in the Chang 71 layer mainly range from 0.05 to 2 × 10−3 μm2, and in the horizontal plane, the direction of maximum principal permeability ranges from 56 to 124°. [ABSTRACT FROM AUTHOR]

The rapid acquisition of soil water content (SWC) in field crop root zone is significant for drought supervision and precision irrigation. The UAV multispectral remote sensing system has the advantages of obtaining high spatial-temporal resolution of crop phenotype data, and has a wide application prospect in soil moisture monitoring. In order to obtain SWC accurately and timely at a farm scale, in this paper, the field maize with different water treatments is taken as the research object, and the multispectral remote sensing monitoring of summer maize is carried out by using the UAV remote sensing platform, and the soil water content of different soil depth in maize root zone is collected synchronously. Based on the UAV multispectral remote sensing image data sets of jointing stage, tasseling-silking stage and milky-maturity stage of summer maize in 2018, the soil background is removed by support vector machine classification, the spectral reflection of maize canopy is extracted, and the 10 vegetation indices are calculated, then the sensitivity analysis of soil water content in different depth is carried out by using full subset screening method for different wave bands and vegetation indices, and the soil water content in different depth is analyzed respectively, ridge regression and extreme learning machine are used to construct quantitative estimation models of soil water content at 0-20, 20-45 and 45-60 cm soil depth after full subset selection. The test area is located in Zhaojun Town, Dalate Banner, Ordos, Inner Mongolia, China(40°26'0.29" N, 109°36'25.99" E, elevation 1 010 m). The sowing time of maize is on May 11, 2018, the emergence time is on May 18, and the harvest time is on September 8, 2018. The total growth period is 114 days. The UAV multispectral remote sensing images and ground data collection dates are July 8, July 12, July 17, July 21, July 26, August 2, August 28 and September 7, 2018. It is collected once a day and tested 8 times in the whole growth period. July 8-21 is the jointing stage, July 26-August 2 is the tasseling-silking stage, August 28-september 7 is the milk-maturity stage. The flight altitude of the UAV is 70 m, and the flight time is 11:00-13:00 local time (11:44-13:44 Beijing time). Firstly, the UAV multispectral canopy images of field maize with 5 different irrigation treatments (TRTs) are acquired through the six-rotor UAV equipped with a RedEdge multispectral camera ( MicaSense, USA), and the multispectral images of diffuse reflector (reflectivity 58%, size 3×3 m) are collected at the same height to perform radiometric correction in the meantime, and then the spectral reflectances of the field maize are acquired. Secondly, the support vector machine (SVM) is used to eliminate the multispectral image of soil background in ENVI and ArcGIS software, then the maize canopy spectral reflectance is extracted and 10 vegetation indices (VIs), such as Normalized Difference Vegetation Index (NDVI), Normalized Green Difference Vegetation Index (GNDVI) and Transformed Chlorophyll Absorption In Reflectance Index(TCARI), etc, are calculated. Finally, the full subset selection method based on Bayesian Information Criterion (BIC) is used to analyze the sensitivity of SWC at different depths for different spectra bands and vegetation indices in R3.5.1 software, and then Ridge Regression (RR) as well as Extreme Learning Machine (ELM) are used to construct a quantitative estimation model of SWC at soil depths of 0-20, 20-45 and 45-60 cm at different growth stages, respectively. The results show that the full subset selection method based on BIC can effectively select the optimal spectral subset, and the selected variables generally pass the significance test and the independent variables number is small; the effects of the ELM model outperformed the RR model almost under all the same conditions; the optimal monitoring soil depth of maize at jointing stage, tasseling-silking stage is 0-20 cm, and the optimal monitoring soil depth of milk-maturity stage is 20-45 cm; the ELM inversion model at 20-45 cm soil depth at milk-maturity stage has the best effect, the decision coefficients of modeling set and verification set are 0.825 and 0.750, respectively, the root mean square error are 1.00% and 1.32%, respectively, and the normalized root mean square error are 10.85% and 13.55%, respectively. The combination of full subset selection method and machine learning can improve the inversion accuracy and robustness of SWC. This study provides a new way for rapid and accurate monitoring of SWC in farmland and precise irrigation. [ABSTRACT FROM AUTHOR]

Copyright of China Harbour Engineering is the property of Editorial Office of China Harbour Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sensitivity analysis of model parameters and inputs is an important research method to improve model accuracy and calibration efficiency. The purpose of this paper is to explore the sensitivity of model parameters and model inputs in arid areas, and then to study the linear or nonlinear relationship of model sensitivity taking Erjiama small watershed in Jungar banner, Ordos, Inner Mongolia, China as the research object. Based on the calibration of CASC2D-SED model, four model parameters, including hydraulic conductivity, Manning coefficient, Suction head and vegetation interception, and one model input-river network were perturbed at a variation rate of 25%. The hydrological process is simulated by using the combination of 20 model parameters and model inputs after perturbation, and then the sensitivity analysis of model parameters and inputs is studied. The results show that: 1) The sensitivity of Manning coefficient to peak discharge and peak arrival time is non-linear, while the sensitivity of hydraulic conductivity, Suction head and vegetation interception to peak discharge, peak arrival time, simulated total discharge and infiltration amount is linear; 2) With the increase of hydraulic conductivity, Suction head and vegetation interception, the peak discharge and simulated total discharge decrease gradually, while the peak arrival time and infiltration amount increase gradually; 3) With the increase of Manning coefficient, the simulated total flow decreases gradually, while the infiltration rate increases gradually; 4) With the increase of the number of tributaries, the peak discharge, the simulated total discharge and the total amount of infiltration gradually decrease, while the flood peak arrival time presents a U-shaped change; 5) With the increase of Manning coefficient, hydraulic conductivity, Interception and Suction head, the simulated sediment flow decreases. Manning coefficient is more sensitive to the simulated amount of clay than the other three model parameters. Sensitivity analysis of parameters and inputs of CASC2D-SED model plays a guiding role in model calibration and accurate modeling. This method can be applied to the calibration, structural uncertainty and model application of hydrological models, and has a wide range of application. [ABSTRACT FROM AUTHOR]

This paper takes the Linxing area of the eastern margin of Ordos Basin as an example. Based on the data of reservoir fluid inclusions (FI) and combined with the history of buried thermal history in Linxing area, the main effects of magmatism on the gas accumulation time, accumulation period, gas accumulation dynamics and accumulation pattern are studied. The vitrinite reflectance (Ro) in source rocks of Zijinshan tectonic area is higher than that in gentle tectonic area. The closer to Zijinshan pluton, the more it tends to single period natural gas charging, the earlier time of gas charging. The characteristics of natural gas accumulation are evidently regional and zonal. Gas accumulation in gentle tectonic area conforms to the law of "gas accumulation in near source reservoir is earlier than remote source reservoir". The gas generated from the source rocks in the lower formation of the Zijinshan tectonic area reached the upper formation rapidly through the faults and fractures caused by the uplift of the Zijinshan pluton, and the accumulation interval time between the near source and remote source formation is relatively short. The Zijinshan tectonic area is the long-term high-pressure area and high-fluid potential area. The fluid potential in gentle tectonic area is low, and the fluid potential difference between the north and south is the motive force to promote the long distance lateral migration of gas. Zijinshan tectonic area is the hydrocarbon generation center and driving force source area, and gas accumulated rapidly from bottom to top. The features of gas accumulation in gentle tectonic area are dominated by vertical accumulation, supplemented by lateral supplementation. Since the Late Cretaceous, a large number of deep faults have been caused by the strong uplift of Zijinshan pluton, and a large number of natural gas are scattered through the faults and the reservoirs are destroyed. The faults in gentle tectonic area are not developed, and the natural gas preservation conditions are good, with good exploration prospects. • Although the role of Zijinshan pluton control of natural gas accumulation in the Linxing area has been noticed, it is limited to the representational description of the present phenomenon. It does not clarify the specific influence process and mechanism. In this paper, the inclusion analysis technique is mainly used to solve a series of problems of natural gas accumulation in the Linxing area under the action of magmatism. After studying the gas accumulation period, accumulation dynamics, and accumulation process, the characteristics of natural gas reservoir-forming in Linxing area are obviously regional and can be divided into the magmatic control area, the transition area, and the normal burial control area. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigated the porosity controlling factors for tight sandstone reservoir in the Daniudi gas field, Ordos Basin based on an integrated petrographic, petrophysical and geostatistical analyses, and proposed a comprehensive prediction model for reservoir porosity. Compaction was found to be a key factor for causing reservoir densification. The degree of sandstone compaction appears to be affected by grain sizes and sorting. Under normal compaction conditions (e.g., cement content less than 6%, and with no dissolution), the variation in reservoir porosity with burial depth can be well correlated with grain compositions, grain sizes, and sorting. Based on qualitative examination of the controlling factors for reservoir porosities, geostatistics were used to quantify the effects of various geological parameters on reservoir porosities. A statistical model for comprehensive prediction of porosity was then established, on the assumption that the present reservoir porosity directly relates to both normal compaction and diagenesis. This model is easy to use, and has been validated with measured porosity data. The porosity controlling factors and the comprehensive porosity prediction can be used to quantify effects of the main controlling factors and their interaction on reservoir property evolution, and may provide a reference model for log interpretation. [ABSTRACT FROM AUTHOR]

Water rights trading volume (WRTV) is an integral part of an effective transaction. At present, in China, WRTV is mostly based on the water demand of the transferee, not the transferor. Some transactions last for a long time, yet lack proper measures to adjust trading volume, making theoretical and quantitative studies on WRTV necessary and essential. Therefore, based on the theory of property rights, this study first analyzed the concept of WRTV, and proposed that WRTV must consider the tradable water volume (TWV) of the transaction parties. For that, this paper divided water rights trading into two stages: initial stage and operation stage, to analyze how to measure WRTV in different stages. Second, currently, industry or sector is a major player of water rights trading. TWV of industry is, hence, the difference between the initial water rights volume (IWRV) and water demand of industry, significant for calculating WRTV in different stages. For that, this study employed the ratio method to calculate the IWRV of industry, and the Grey Model—GM (1,1) to predict the water demand of industry. Last, this paper carried out a case study on the inter-league and inter-city water rights trading between Bayannur city and Ordos city in Inner Mongolia, China. Results show that the TWV of industry of Bayannur and Ordos in 2030 are – 904.966 million m3 and − 87.135 million m3 respectively, implying insufficient TWV for the transferee, which may lead to transaction breakdown. The theory and calculation method of WRTV proposed in this study lay a theoretical foundation for WRTV measurement, and can help facilitate the orderly development of water rights trading in China. [Display omitted] • The volume of water rights should be considered the tradable water volume of the transaction subjects at the same time. • The impact of the change of the tradable water volume on the water rights transaction volume is analyzed. • The change of water rights trading volume has a great impact on trading, and even leads to the transaction rupture. • Forecasting the trading volume of water rights between Bayannur city and Ordos city in Inner Mongolia of China in 2030. [ABSTRACT FROM AUTHOR]

China's new town and ghost city phenomenon has attracted interest from academics and the media since the 2010s. There is, however, little research on the lived experiences of people in new towns, or of the transformation of these new towns. This paper uses Lefebvre's spatial triad to examine how the spaces of the new town are produced and transformed by interactions between multiple actors. Using an analytical framework based on the spatial triad, we explore the interactive mechanisms and the dialectical relationships within the triad. Taking Kangbashi, a new town in Ordos, Inner Mongolia, as a case study, we explore how the spatial production of a new town is co-created by multiple actors, and local government-led conceived space plays a dominant role in that creation. Through interactions in the dynamic nexus of conceived-perceived-lived space, the new town space is in the process of transformation from an empty "ghost city" to a comfortable habitable city. This research deepens our understanding of new towns and production of space by connecting state-led and capital-driven urban construction with the lived practices of residents. Moreover, this empirical Chinese study contributes to knowledge and understanding across diverse global urban contexts. • An analytical framework based on the spatial triad is proposed. • The mechanisms for the transformation of a new town space from a ghost city to a more habitable city is examined. • The local government dominates both the production of space and its transformation in the new town. [ABSTRACT FROM AUTHOR]

Nature reserves play an important role in the protection of biological habitats and the maintenance of biodiversity, but the performance and mechanisms of desert steppe nature reserves in improving plant community productivity, biodiversity and soil nutrient content are still largely unknown. To investigate the conservation effects of desert steppe nature reserve management on plant productivity and biodiversity, we compared the plant biomass, diversity and soil nutrient content inside and outside the West Ordos National Nature Reserve through sample survey, biomass determination, diversity index calculation and soil nutrient content determination. We found the following: (1) The aboveground biomass and belowground biomass of plant communities in the nature reserve were significantly larger than those outside the reserve; and the aboveground biomass of plant communities in shrub–steppe was significantly larger than that of herb grassland in both the nature reserve and the outside of the reserve. (2) The Margalef richness index, Shannon–Wiener index and Simpson index were significantly greater in the reserve than outside the nature reserve. In the desert steppe, the establishment of the nature reserve increased the α-diversity of the plant community. (3) The soil organic carbon (SOC) and soil total nitrogen (STN) were greater in the nature reserve than outside the reserve, and for the 10–20 cm and 20–40 cm soil layers, the SOC and STN were significantly greater in the core protected zone of the reserve than outside the reserve. The reserve significantly increased the nutrient content of the deeper soil layers. (4) The aboveground biomass of the plant community had a significant positive linear relationship with the species richness index, the Shannon index, and the Simpson index. There was a positive correlation between the diversity of the plant community and the soil nutrients. In summary, the nature reserve improved local plant productivity, biodiversity and the soil nutrient content, and the soil nutrient content in deeper soil layers may be the driving factor for the increase in productivity and biodiversity, which deepens our understanding of the conservation effectiveness of the nature reserve and its mechanisms. [ABSTRACT FROM AUTHOR]

General characteristics and biomarker distributions of Lower Permian coal-measure source rocks in northeastern Ordos Bsain have been analyzed in this paper. The results show that the source rocks are type III kerogen, thermally mature, with high content of total organic carbon. The extracts of the source rock samples with different lithologies from Well Su 27 feature high Pr/Ph ratios, high CTT and CTe, high rearranged hopanes, a predominance of C sterane in regular steranes, and the absence of C 4-methylsteranes. These data suggest that the source rocks were deposited in suboxic to oxic conditions with dominantly terrigenous higher plant input. In contrast, the source rocks from wells Shuang 1 and Yu 20, are characterized by low Pr/Ph ratios, low CTT and CTe, high CTT, similar content of C sterane and C sterane, and the presence of C 4-methylsteranes, showing that the source rocks were deposited in reducing environment with algae and/or microorganisms and terrigenous higher plant input. [ABSTRACT FROM AUTHOR]

Deep saline aquifers still remain a significant option for the disposal of large amounts of CO from the atmosphere as a means of mitigating global climate change. The small scale Carbon Capture and Sequestration demonstration project in Ordos Basin, China, operated by the Shenhua Group, is the only one of its kind in Asia, to put the multilayer injection technology into practice. This paper aims at studying the influence of temperature, injection rate and horizontal boundary effects on CO plume transport in saline formation layers at different depths and thicknesses, focusing on the variations in CO gas saturation and mass fraction of dissolved CO in the formation of brine in the plume's radial three-dimensional field around the injection point, and interlayer communication between the aquifer and its confining beds of relatively lower permeability. The study uses the ECO2N module of TOUGH2 to simulate flow and pressure configurations in response to small-scale CO injection into multilayer saline aquifers. The modelling domain involves a complex multilayer reservoir-caprock system, comprising of a sequence of sandstone aquifers and sealing units of mudstone and siltstone layers extending from the Permian Shanxi to the Upper Triassic Liujiagou formation systems in the Ordos Basin. Simulation results indicate that CO injected for storage into deep saline aquifers cause a significant pressure perturbation in the geological system that may require a long duration in the post-injection period to establish new pressure equilibrium. The multilayer simultaneous injection scheme exhibits mutual interference with the intervening sealing layers, especially when the injection layers are very close to each other and the corresponding sealing layers are thin. The study further reveals that injection rate and temperature are the most significant factors for determining the lateral and vertical extent that the CO plume reaches and which phase and amount will exist at a particular time during and after the injection. In general, a large number of factors may influence the CO-water fluid flow system considering the complexity in the real geologic sequence and structural configurations. Therefore, optimization of a CO injection scheme still requires pursuance of further studies. [ABSTRACT FROM AUTHOR]

In the lower parts of oil reservoirs Chang 9 and Chang 10 of the Yanchang Formation are oil-bearing layers newly found in oil exploration in the Ordos Basin. Based on GC, GC-MS analyses of saturated hydrocarbons from crude oils and source rocks, reservoir fluid inclusions and BasinMod, the origin of crude oils, accumulation period and accumulation models are discussed in combination with other petroleum geology data in this paper. The result shows that (1) there are two different types of crude oils in oil reservoir Chang 9 in the Longdong and Jiyuan regions: crude oils of type I(Well D86, Well A44, Well A75, Well B227, Well X62 and Well Z150) are mainly derived from the Chang 7 source rocks (including mudstones and shales) and distributed in the Jiyuan and Longdong regions; those of type II(Well Z14 and Well Y427), are distributed in the Longdong region, which are derived from the Chang 9 source rocks. Crude oils from oil reservoir Chang 10 in the Shanbei region are mainly derived from the Chang-9 source rocks; (2) there are two phases of hydrocarbon filling in oil reservoir Chang 9 in the Jiyuan and Longdong regions and oil reservoir Chang 10 in the Shanbei region: The first phase started at the early stage of Jz. The process of hydrocarbon filling was discontinuous in the Late Jurassic, because of the tectonic-thermal event in the Ordos Basin. The second phase was the main accumulation period, and hydrocarbons began to accumulate from the late stage of Ja to the middle-late of K, mainly at the middle-late stage of K; (3) there exist two types of accumulation models in oil reservoirs Chang 9 and Chang 10 of the Yanchang Formation: source rocks of the reservoirs in oil reservoir Chang 9 in the Jiyuan region and oil reservoir Chang 10 in the Shanbei region, the mixed type of reservoirs on the lateral side of source rocks and source rocks of the reservoirs in oil reservoir Chang 9 in the Longdong region. [ABSTRACT FROM AUTHOR]

• The partial normalized sandy barren index (PNSBI) is proposed for differentiating sandy barren land from barren land. • PNSBI outperformed six conventional barren indexes in the identification of sandy barren areas in both TM and OMI images. • Spectral measurement and analysis enable rapid and effective discrimination of barren sandy pixels in multi-source images. • The spectral mixture analysis and bandwidth effectiveness should be considered in future work. Sandification is a serious global environmental problem. The spatiotemporal dynamics of sandy barren land is an important indicator in monitoring its ecological restoration. Such monitoring requires fast and accurate identification of sandy barren land. Although several bare indexes have been developed for the mapping of barren land, these have not proven effective in the mapping of sandy barren land. In this paper, the partial normalized sandy barren index (PNSBI), a new barren index based on spectrum reflectance measurement and analysis, is proposed. The efficiency and enhanced accuracy of PNSBI at retrieving sandy barren land was validated using Landsat Thematic Mapper (TM) and Operational Land Imager (OLI) images of the Poyang Lake and Ordos regions of China. These results suggest that the proposed PNSBI achieved higher accuracy than the other bare indexes in retrieving sandy barren land from the other types of bare land. And it is benefit for the study of the spatiotemporal dynamics of sandification, water distribution, soil erosion, etc. [ABSTRACT FROM AUTHOR]

• Resource-Richness Analogy Approach used in less explored reservoirs is proposed. • Genesis-Statistics Assessment Approach for heterogeneous tight oil is proposed. • The parameter criteria of lacustrine tight oil resource assessment are established. • In-place tight oil resources in China's major basins are estimated of 12.6 × 109 t. • 15 most favorable plays are outlined with in-place resources of 5.3 × 109 t. Large-scale commercial development of shale gas and tight oil resources in North American and continuous discoveries of tight oil in China lead to the recognition of the importance of assessment on tight oil resources. Based on the characteristics of China's tight oil reservoirs and exploration status, this paper discusses a workflow focusing on in-place resource evaluation. In the workflow, a Resource-Richness Analogy Approach (RR-AA) is proposed for assessment of tight oil resources in less explored areas, a Genesis-Statistics Assessment Approach (GS-AA) for lacustrine tight oil resources with strong heterogeneity and regions where more delicate assessment is required, and an EUR Analogy Approach (EUR-AA) for assessment on recoverable tight oil by fully using available EUR data of production wells. After analyzing the geological characteristics of the formation of tight oil in the Ordos, Bohai Bay, Songliao, Junggar, Sichuan and other major Basins, the distributions of essential parameters such as reservoir thickness, area and porosity have been defined, and the parameter evaluation criteria have been established. Finally, the tight oil resource potentials in the major basins in China have been evaluated using one of the three methods and the prospective areas of high resource abundance are outlined in each of basins. The results from this study show that China's tight oil resources have a large potential and good exploration future. The estimated in-place tight oil resources are 12.580 × 109 tons, mainly distributed in the Ordos, Songliao, Bohai Bay and Junggar Basins. 15 most favorable zones are proposed having in-place resources of 5.296 × 109 tons. [ABSTRACT FROM AUTHOR]

This paper presents new field observations that assist in further defining the extent of Last Permafrost Maximum (LPM) permafrost and frozen ground in north China. In that respect, this region is specific by its arid environment and continental position. Bedrock exposures and sand and gravel pits were examined along a south-north transect from southern Ordos as far as the vicinity of Dongsheng District, Ordos City on the Ordos Plateau (North China). Attention focussed upon the recognition of sand-wedge remains and possible cryoturbations. Two types of wedge structures were recognized: type A wedges extend to depths in excess of 3.0 m and are thought to have formed under conditions of continuous permafrost. Type B wedges are restricted to the upper 1.5 m and are thought to reflect discontinuous permafrost and/or deep seasonal frost. OSL dating of wedge infills indicates that type A wedges formed between 23–19 ka and younger type B wedges formed until the early Holocene. It is now possible to delineate a more exact position of the boundary between continuous permafrost and discontinuous permafrost and/or deep seasonal frost on the Ordos Plateau during the LPM. This boundaries occur between Dongsheng and Jinbian at 37°-39°N. • Precise location of southern limit of continuous permafrost during the Last Permafrost Maximum (c.19-23 ka) in north China. • Narrow zone of discontinuous/sporadic permafrost during the Last Permafrost Maximum (c.19-23 ka) in north China. • Permafrost extent in N China at LPM was specific by its aridity, continentality and proximity to the Siberian High Pressure. [ABSTRACT FROM AUTHOR]

Yushenfu coal field is located in the Maowusu Desert and the Loess Plateau convergence zone in China, where ecological environment is fragile and ecological water resources are scarce. The heterogeneous distribution of main aquifers and mine water inflow influence the safe production of coal mines. Thus, the protection and uti-lization of water resources are of significance to coal mine production and ecological construction. After analyzing the distribution and water abundance of the main aquifers, such as Salawusu Formation, burnt rock and weathering bedrock, combining the thickness of overlying bedrock and water inflow on field, the operating coal mines and unplanned areas could be divided into four types which are the areas of water scarcity, water richness, water abundance and surface water source. The study area has been divided into sub-regions according to the classification and their distribution. Based on the classification, the concrete measures for water preservation and mine water utilization have been proposed such as storage and purification in goaf area, industrial utilization, agricultural irrigation, wetlands construction and artificial lakes. In the paper, the scientific content of water-preserved mining has been extended and interpreted as that both preserving shallow main aquifers and effectively utilizing coal mine water resource should be taken simultaneously. It proposes that mining damage and ecological self-repair should be considered before coal mine construction. It also proposes that the idea of using economic benefits to repay the local ecosystem and green economy which provides certain references for mining area planning and construction. [ABSTRACT FROM AUTHOR]

The first successful sand-control was achieved in the Mu Us Desert by local people in the 1950–1960s, and their experience and approach have been extended to the whole Ordos and Northern China since then. The objective of this paper is to assess comprehensively the effectiveness of sand-control in 15 counties in and around Mu Us using multitemporal satellite images and socioeconomic data. After atmospheric correction, Landsat TM and OLI images were harnessed for land cover classification based on the ground-truth data and for derivation of the GDVI (generalized difference vegetation index) to extract the biophysical changes of the managed desert and desertification. Climatic, socioeconomic, environmental and spatial factors were selected for coupling analysis by multiple linear and logistic regression models to reveal the driving forces of desertification and their spatial determinants. The results show that from 1991 to 2020, 8712 km2 or 63% of the desert has been converted into pastures and shrublands with a greenness increase of 0.3509 in GDVI; the effectiveness of sand-control is favored by the rational agropastoral activities and policies; though desertification occurs locally, it is associated with both climatic and socioeconomic factors, such as wind speed, precipitation, water availability, distance to roads and animal husbandry. [ABSTRACT FROM AUTHOR]

A total of six giant gasfields each with proven reserves of more than 100 billion cubic metres are present in the Ordos and Tarim Basins, China. The gasfields are Sulige, Yulin, Wushenqi, Da'niudi and Jingbian in the Ordos Basin, and Kela 2 in the Tarim Basin. In this paper, we report on the geochemical characteristics of the natural gas at these fields based on studies of gas composition (150 samples), together with stable isotope data (143 samples) and helium isotope data (21 samples). Results show that the gases have high contents of C1-4 alkanes (generally over 90%) and minor contents of CO2 (below 3%). The generally high δ13C values of C1-C4 hydrocarbons indicates a significant contribution from humic source rocks such as Permian-Carboniferous and Mid-Lower Jurassic coal measures. δ13 C1, δ13C2, δ13C3 and δ13C4 values for gases in Upper Palaeozoic reservoirs were -35 to -32‰, -28 to -24‰, -27 to -24‰, and -23.5 to -22‰, respectively. The δ13CiC4 value is higher than that of the δ13CnC4• He3/He4 ratios vary from 10-7 to 10-8, indicating that the helium is of crustal (as opposed to mantle) origin. The CH4/ He3 ratio is 1010 - 1011, indicating that the CH4 is of biogenic origin. None of the data is consistent with an abiogenic origin for gas in the Ordos Basin. [ABSTRACT FROM AUTHOR]

The delineation of the southern boundary of the latitudinal permafrost in the north of China in the period of late Pleistocene, i.e. the last glaciation maximum (LGM), has been hampered for two reasons. Firstly, previous studies were limited to the eastern part of the north of China, and, secondly, the ages of the permafrost had not been determined systematically. In this paper, we suggest that the southern boundary of the high latitudinal permafrost in the north of China is bounded by approximately 38-40°N (eastern part) and 37-39°N (western part) lines of latitude based on our interpretation of periglacial phenomena and their implication to the environment during the late Pleistocene, and this southern boundary is plotted for the first time. Also, we reconstrnct the migration of the southern latitudinal permafrost boundary and the environment after LGM. It is proposed that two cold stages occurred in the LGM at 26 kaBP and 23-13 kaBP, when the annual mean temperature was 8 -12°C lower than at present. [ABSTRACT FROM AUTHOR]