Tarim Basin Research Articles

Assessment of PM2.5 pollution features and health advantages in Northwest China.

The elevated concentration of suspended particulate matter in the atmosphere is closely associated with the morbidity and mortality of human diseases. In northwest China, fine particulate matter pollution has persistently affected local health, production, and daily life due to climatic factors and economic development. This paper first examines the distribution and variation of PM2.5 concentrations in northwest China from 2013 to 2022 to understand changes in PM2.5 exposure levels, as well as their associated health and economic benefits since the implementation of the "Air Pollution Prevention and Control Action Plan." Second, we estimated the number of premature deaths in the research region under various control scenarios based on PM2.5 concentrations recorded in 2013 and 2021, utilizing existing epidemiological studies for reference. Finally, we calculated the financial benefits resulting from variations in PM2.5 concentrations within this region. Results indicated that (1) from 2013 to 2022, the Tarim Basin exhibited the highest PM2.5 concentration among all studied areas, while northern Xinjiang and Qinghai Province had notably lower levels. Additionally, wintertime concentrations were consistently higher than those observed during summer months; however, there has been a general trend toward reduced PM2.5 content over the past decade. (2) A significant inverse relationship was found between premature mortality rates and PM2.5 concentrations; specifically, fluctuations in PM2.5 levels exerted a more pronounced impact on premature deaths attributable to cardiovascular diseases compared to respiratory conditions within this northwest region. (3) Males were disproportionately affected by increases in PM2.5 concentration relative to females-experiencing two to three times more early fatalities than their female counterparts did. (4) Over a 9-year period within this research area, fiscal benefits derived from interventions targeting PM2.5 treatment increased by approximately 891 million yuan.

Characteristics of carbazole compounds in ultra-deep marine oil from Fuman oilfield, Tarim Basin: Significance for thermal maturity assessment of crude oil

Carbazoles in Ordovician ultra-deep marine oil from the FI17 fault zone in Fuman oilfield (Tarim Basin) were separated using a recently proposed silica gel column chromatographic method and the enriched fractions were analyzed by GC–MS. Biomarker and carbon isotope signatures revealed that all oil in the study area was produced from the same source rock and that compositional differences can be attributed to thermal maturation. The convergent ratios of N-H shielded isomers/N-H half shielded isomers and benzo[a]carbazole/(benzo[a]carbazole + benzo[c]carbazole) suggested that carbazoles in crude oil had not been affected by vertical migration. Therefore, thermal maturity was identified as the main controlling factor affecting chages of carbazole concentrations and ratios in crude oil. The concentrations of the total carbazole and its three isomers (N-H shielded isomers, N-H half shielded isomers and exposed isomers) in crude oil decreased sharply with increasing maturity. The 1,8-dimethylcarbazole/carbazole (1,8-MCa/Ca) and 1,8-dimethylcarbazole/2,4-dimethylcarbazole (1,8-MCa/2,4-MCa) ratios showed significant correlation with maturity expressed as %VRE (the vitrinite reflectance equivalent converted from MPI1 and MPR) when %VRE is <1.2 %. Similar trends were observed in the 1-methylcarbazole/3-methylcarbazole (1-MCa/3-MCa) as well as 1,8-dimethylcarbazole/2,6- dimethylcarbazole (1,8-DMCa/2,6-DMCa), (1,5- dimethylcarbazole + 3-ethylcarbazole)/2, 6-dimethylcarbazole ((1, 5-DMCa + 3-ECa)/2, 6-DMCa), and (1, 4-dimethylcarbazole + 4-ethylcarbazole)/2, 6-dimethylcarbazole ((1, 4-DMCa + 4-ECa)/2, 6-DMCa) when the %VRE of crude oil exceeds 1.0 %. This indicated that the concentrations and ratios of carbazole can be used to qualitatively evaluate crude oil maturity. The ratio of 1,8-dimethylcarbazole/1-ethylcarbazole (1,8-DMCa/1-ECa) showed a strict linear relationship with %VRE. The maturity of marine oil can be calculated using the formulas %Rc (the vitrinite reflectance equivalent calculated from MPI1) = −0.0335(1, 8-DMCa/1-ECa) + 1.2902 or %Rc1 (the vitrinite reflectance equivalent calculated from MPR) = −0.0405 (1, 8-DMCa/1-ECa) + 1.3418. The study can be helpful for exploring ultra-deep hydrocarbons and restoring the thermal history of source rocks in the Tarim Basin.

Sedimentary facies controlled biogeochemical process of biotic extinction and turnover across the Cambrian SPICE event

The Steptoean positive carbon isotope excursion (SPICE) event, one of the largest carbon cycle perturbations in the Cambrian, coincides with shallow-shelf-fauna extinction and plankton revolution (critical transition of plankton). The event is globally documented, but biogeochemical responses of these biotic evolutions in varying facies environments are not well understood. Here high-resolution paired δ18Ocarb, δ13Ccarb and δ13Corg datasets from varied paleodepth environments in the Tarim Basin, NW China reveal facies-dependent signatures of the event, with globally synchronous patterns but notable intra-basinal variability. Shallow marine facies record the end-Marjuman extinction with a distinct negative δ13Corg excursion prior to the event, while the transitional facies region marks twice positive δ13C excursions corresponding to an asynchronous plankton revolution from shallow and deep areas during the event. The varying isotope responses are interpreted in the context of primary productivity and redox conditions, with deeper basins recording more 13C enriched signals (i.e., higher δ13C) due to greater organic matter preservation under anoxic conditions, compared to the platform area. The biotic extinction, the planktonic revolution and the interaction of organisms along the shallow to deep marine depth gradient were reflected by the significant isotopic shifts recorded during the event, suggesting depth-dependent biogeochemical processes that shaped marine ecosystems.

Distribution and Co-Enrichment Factors of Arsenic and Fluoride in the Groundwater of the Plain Area of the Aksu River Basin, Xinjiang, PR China

The Aksu River Basin is located in the western region of the middle part of the southern foothills of the Tianshan Mountains and the northwestern edge of the Tarim Basin in Xinjiang, China. High-arsenic (As)/high-fluoride (F) groundwater is widely distributed in this area and is harmful to the life of local residents and to agricultural production. It is of great importance to understand the distribution and causes of As-F co-enrichment in the groundwater in this area. Based on the test results of 138 groundwater samples in the plain area of the Aksu River Basin, the hydrochemical characteristics of groundwater and the spatial distribution of As-F co-enrichment groundwater were analyzed under the following conditions: a single-structure phreatic aquifer (SSPA), a phreatic aquifer in a confined groundwater area (PACGA), a shallow confined aquifer (SCA), and a deep confined aquifer (DCA), all in a recharge area, transition area, and an evaporation area. The hydrogeochemical processes affecting the source, migration, and enrichment of As-F in the groundwater were revealed. The results showed that the chemical types of groundwater in the study area were mainly HCO3·SO4-Ca·Mg and SO4·Cl-Na·Mg. Horizontally, high-As-F groundwater was mainly distributed in the transition area and evaporation area in the middle and lower reaches of the Aksu River Basin. The area is close to the edge of the desert, where the groundwater runoff is sluggish and in an alkaline-reducing groundwater environment. Vertically, high-As groundwater was mainly distributed in the PACGA at a depth of 10–20 m and in the SCA at a depth of 80–100 m. High-F groundwater was mainly concentrated in the PACGA at a depth of 10–30 m and in the SCA at a depth of 80–100 m, and As-F co-enrichment groundwater was mainly concentrated in the PACGA at a depth of 10–20 m and in the SCA at a depth of 80–100 m. The hydrochemical characteristics of the groundwater in the Aksu River Basin were closely related to geological conditions, hydrogeological conditions, and the hydrochemical environment of the groundwater. As-F co-enriched groundwater was mainly affected by the combination of a small topographic gradient, a shallow groundwater burial depth, a weak reducing alkaline groundwater environment, strong evaporation and concentration, the weathering and dissolution of evaporated salt rock, and the alternating adsorption of cations.

Chromosome-scale genome assembly of Apocynum pictum, a drought-tolerant medicinal plant from the Tarim Basin.

Apocynum pictum Schrenk is a semishrub of the Apocynaceae family with a wide distribution throughout the Tarim Basin that holds significant ecological, medicinal, and economic values. Here, we report the assembly of its chromosome-level reference genome using Nanopore long-read, Illumina HiSeq paired-end, and high-throughput chromosome conformation capture sequencing. The final assembly is 225.32 Mb in length with a scaffold N50 of 19.64 Mb. It contains 23,147 protein-coding genes across 11 chromosomes, 21,148 of which (91.36%) have protein functional annotations. Comparative genomics analysis revealed that A. pictum diverged from the closely related species Apocynum venetum approximately 2.2 million years ago and has not undergone additional polyploidizations after the core eudicot WGT-γ event. Karyotype evolution analysis was used to characterize interchromosomal rearrangements in representative Apocynaceae species and revealed that several A. pictum chromosomes were derived entirely from single chromosomes of the ancestral eudicot karyotype. Finally, we identified 50 members of the well-known stress-responsive WRKY transcription factor family and used transcriptomic data to document changes in their expression at 2 stages of drought stress, identifying a number of promising candidate genes. Overall, this study provides high-quality genomic resources for evolutionary and comparative genomics of the Apocynaceae, as well as initial molecular insights into the drought adaptation of this valuable desert plant.

Influence of Gas Washing and Oil Mixing on the Phase Behavior and Physical Properties of Cambrian Light Oils in the Tazhong Uplift, Tarim Basin

Gas washing and oil mixing have been widely studied in the Tazhong area of the Tarim Basin, but their effects on Cambrian subsaltic dolomite reservoirs have not yet been adequately explored. In this study, the influence of gas washing and oil mixing on light oils from these reservoirs was investigated. Using n-alkane mass depletion (Q value) analysis, light oils from wells ZS1 and ZS5 were analyzed to quantify the intensity of gas washing and to identify possible oil mixing in the Cambrian Awataga (Є2a) and Wusongar (Є1w) reservoirs. Unaltered light oil was recovered and models of phase behavior were constructed by PVT simulation and basin modeling to compare with altered light oils. The results show that the light oil in well ZS1 experienced medium-strength gas washing (Q value = 40.88%), while the gas washing in well ZS5 was weaker (Q value &lt; 40.88%), providing evidence of oil mixing. Despite these changes, the light oils in the Cambrian reservoirs maintained a single liquid-phase state over geologic time without transitioning to condensate or gas phases. These results improve the understanding of gas washing in the Tazhong area and show that it has significantly altered the Cambrian reservoirs and affected the preservation of hydrocarbons after oil accumulation.

Dominant spring precipitation anomaly modes and circulation characteristics in the Tarim Basin, Central Asia

Recently, extreme precipitation has occurred frequently in the Tarim Basin, which has a fragile ecological environment, arousing widespread concern. Using daily precipitation observations from 42 stations in the Tarim Basin during the spring of 1980–2021 and monthly circulation reanalysis data from the European Center for Medium-Range Weather Forecasts Reanalysis v5, as well as statistical analyses and physical diagnostic methods, this study investigated the abnormal modes and the evolution characteristics and differences in atmospheric circulation. The results show that the spring precipitation anomalies in the Tarim Basin can be divided into two independent precipitation modes: the first (EOF1) is a precipitation pattern that is uniform throughout the region and the second (EOF2) is an east–west inverse pattern. Thus, there are distinct differences in the atmospheric circulation characteristics responsible for abnormal spring precipitation modes in the basin. When the precipitation across the entire basin is consistently excessive, the 500 hPa geopotential height is affected by the negative phase of the North Atlantic Oscillation related circulation, and the 700 hPa wind field is controlled by abnormal southwesterly winds. Water vapor transport is mainly driven by anomalous water vapor uplift along the terrain in the middle latitudes west of the Atlantic Ocean and south of the Arabian Sea. This leaves the Tarim Basin with a net water vapor budget and abnormally high atmospheric precipitable water. The opposite situation occurs when the precipitation across the entire basin is consistently lower than normal. When there is a west-to-east precipitation gradient, The western region of the Tarim Basin is dominated by upward airflow, whereas the eastern region is dominated by downward airflow, providing dynamic conditions for the west-to-east precipitation gradient. Under the influence of anomalous water vapor transport from the southwest and water vapor convergence, water vapor conditions favorable for precipitation can occur. The net water vapor in the basin also exhibited an abnormal west-to-east transport pattern. Moreover, the atmospheric precipitable water demonstrated an inverse phase distribution under the EOF2 atmospheric precipitation mode in the Tarim Basin.

Multi-stream encoder and multi-layer comparative learning network for fluid classification based on logging data via wavelet threshold denoising

In recent years, the importance of fluid classification in oil and gas exploration has become increasingly evident. However, the inherent complexity of logging data and noise pose significant challenges to this task. To this end, this paper proposes a wavelet threshold denoising-based multi-stream encoder combined with multi-level comparison learning (LogMEC-MCL) framework for fluid classification. The framework begins with comprehensive noise reduction, utilizing wavelet threshold denoising to preprocess the data. It then extracts global temporal features by incorporating attention gated recurrent units within the multi-stream encoder. In parallel, multi-scale convolutional neural networks capture local spatial information, ensuring a more complete understanding of the data. To further improve the discriminative power of the extracted features, the framework includes two contrastive learning modules: instance-level contrastive learning and temporal contrastive learning. These components work together to refine feature differentiation, particularly in challenging cases. Additionally, the framework introduces a custom-designed loss function that combines cross-entropy loss with contrastive loss, thereby optimizing the classification performance. The proposed model was rigorously evaluated using a real-world logging dataset from the Tarim Basin in China. The experimental results demonstrate that LogMEC-MCL consistently outperforms current state-of-the-art models on two test datasets, achieving maximum classification accuracies of 95.70% and 95.50%, respectively.

Early Oil Charging from Sinian Shales in Ordovician Carbonate of the Tabei Uplift, Tarim Basin: Evidence from Biomarkers

Early Oil Charging from Sinian Shales in Ordovician Carbonate of the Tabei Uplift, Tarim Basin: Evidence from Biomarkers

Heterogeneous Tarim Cratonic Crust Induced by a Mantle Plume and Its Effect on Later Tectonic Evolution Based on Multi‐Frequency Receiver Functions Imaging

AbstractIt remains controversial whether the interaction between a mantle plume and a craton destabilizes or reinforces the craton. The Tarim basin, with a craton core, a Permian Large Igneous Province, and internal deformation, is an ideal place to investigate this interaction. Here, we construct high‐resolution S‐wave velocity structures down to 15 km in depth using multi‐frequency receiver functions from two temporary seismic arrays that largely cover the Tarim Basin. Our results reveal a strong velocity‐increasing discontinuity across the basin and several large‐scale high‐Vs anomalies. The discontinuity is flat at about 3.5 km depth in the majority of eastern Basin but is uplifted and folded to ∼3 km depth around the Bachu Uplift in the central‐western basin and depressed to more than 6 km depth in the northwestern and southwestern basin. The high‐Vs anomalies, with an average Vs of ∼3.4 km/s, are concentrated under this discontinuity around the Bachu Uplift. Analysis with drilling data, experimental rock‐physics data and previous geophysical observations indicates that the discontinuity corresponds to the top of early Permian strata, and the high‐Vs anomalies are the magmatic intrusions from the early Permian mantle plume. There is strong deformation around the Bachu Uplift formed during Cenozoic Indian‐Eurasian collision, exhibiting a strong spatial correlation with the Permian magmatic intrusions. This suggests that the western Tarim Craton, compared to the east, may be weakened in strength by the Permian mantle plume and exhibits more localized Cenozoic deformation.

Metallogenic model of sandstone-hosted copper deposits: a case study from the Paleogene in Jiashi area, northwestern China

Sandstone-hosted copper deposits, a type of Sediment-Hosted Stratiform Copper (SSC) deposits, are widely distributed globally. While economically viable deposits of SSC are relatively scarce, they account for approximately 30 % of the world's total discovered copper resources. However, there is still a lack of comprehensive and in-depth research into the depositional and metallogenic models of these deposits. The Jiashi area of the Tarim Basin in northwestern China, known for its economically significant Paleogene SSC deposit, lacks in-depth studies on metallogenic processes. To address this, field profile observations were conducted to analyze the sedimentary evolution, sequence stratigraphy, and tectonism of the Paleogene strata in the Jiashi area. Combined with elemental geochemical analysis of samples, the provenance of sediment, and the source of metallogenic materials, a robust metallogenic model was established. The results reveal the influence of provenance for the origin of Paleogene copper-rich strata. Sedimentary evolution played a crucial role in controlling the distribution of copper and sulfur elements, as well as the spatial arrangement of metallogenic beds. Additionally, nappe movement potentially generated faults, allowing upward movement of basin fluids, which played a crucial role in the formation of copper deposits within sandstone-hosted systems. Thus, this study offers a comprehensive analysis of the metallogenic processes involved in sandstone-hosted copper deposits, thereby contributing significant insights to the broader research on SSC deposits worldwide.

Digital rock modeling of deformed multi-scale media in deep hydrocarbon reservoirs based on in-situ stress-loading CT imaging and U-Net deep learning

Deep and ultra-deep hydrocarbon reservoirs are regarded as an attractive target for onshore oil and gas exploration and development in China. The multi-scale fractures are widely distributed in this type of reservoir. The fluid-solid coupling effect is strong, which can greatly affect the fluid flow, resulting in a low hydrocarbon recovery with the average value less than 15%. To explore the underlying flow dynamics during efficient development of deep and ultra-deep hydrocarbon reservoirs, it is of great importance to characterize the multi-scale fracture-pore structure evolution of rock affected by strong geo-stress field variation. To tackle the above issues, an actual rock drilled from a typical ultra-deep reservoir in Tarim Basin are selected to conduct in-situ stress-loading computed tomography (CT) scanning experiments, and the CT gray images of rock microstructure under different dynamic loading conditions are obtained. A fully convolutional neural network (U-Net) deep learning segmentation algorithm is introduced to accurately distinguish the rock skeleton, pore space and fractures in deep rock. The three-dimensional (3-D) digital rock model of deformed multi-scale fracture-porous media under different dynamic loading conditions is ultimately established to investigate the evolution of fracture morphology and deep rock microstructure as the in-situ stress is gradually loaded. It indicates that, the U-Net deep learning semantic segmentation algorithm can accurately segment CT images of deep rocks, and the established 3D digital rock model of fractured porous media can accurately represent the pore-throat distribution, fracture morphology, and pore-scale topological connectivity. At the initial stage of stress loading, there are few micro-fractures inside the rock, and the fracture connectivity is poor. Due to effect of rock compaction, the average pore throat radius increases while pore throat ratio, coordination number and tortuosity greatly decrease. As the effective stress is gradually loaded, the micro-fractures begin to propagate, leading to stronger heterogeneity of micro-fractures’ distribution and better topological connectivity, and both the coordination number and tortuosity gradually increase. After the deep rock is fractured, micro-fractures run through a fracture network and all the above topological parameters increase greatly.

FIRST RECORD OF UPPER CRETACEOUS (CAMPANIAN?) LARGER BENTHIC FORAMINIFERA FROM THE YIGEZIYA FORMATION OF THE SOUTHWESTERN TARIM BASIN, CHINA

Larger benthic foraminifera are described for the first time from the Upper Cretaceous Yigeziya Formation of the southwestern Tarim Basin, China. They occur in middle-outer ramp carbonates with debris of rudists, coralline algae, echinoids, pithonellids, and rare dasycladalean green algae. The material allows an open taxonomic approach for a few taxa. The assemblage includes Charentia cf. cuvillieri Neumann, Cuneolina cf. parva Henson, Nezzazatinella cf. picardi (Henson), orbitolinid gen. et sp. indet., cyclamminid indet., Tetrataxiella? floriforma Schlagintweit &amp; Sanders, Suturina? sp. and the new species Dictyopselloides? tarimensis n. sp. Lacking any resilient stratigraphic data in our material, a Campanian age is tentatively assumed. The benthic association is typical for Neotethys assemblages but also shows conspicuous overlap with the Campanian Tielongtan Formation of western Tibet.

The 2024 Mw 7.0 Wushi Earthquake in Southern Tianshan Convergent Zone: Finite-Fault Model for the Coseismic Rupture and Aftershock

Abstract On 22 January 2024, an Mw 7.0 earthquake struck the oblique thrust Maidan fault (MDF) at the boundary between the Southern Tianshan and Tarim basin, making it the largest earthquake on the fault in the last 100 yr. Here, we use Interferometric Synthetic Aperture Radar (InSAR) to retrieve coseismic and aftershock deformation caused by the earthquake and then constrain fault geometry and slip distribution. Line-of-sight InSAR observations revealed a coseismic deformation area of 70 km × 60 km with a maximum value of ∼0.8 m and also captured the deformation from the aftershock event seven days after the mainshock. Our preferred two-segment coseismic fault model ruptures the MDF locked segment and deeper regions, exhibiting a homogeneous elliptical rupture with a maximum slip of ∼2.7 m on a rectangular plane with a dip angle of ∼60°, a length of ∼55 km, and a depth between 5 and 20 km. The aftershock formed a rupture plane of 10×8 km2 with the maximum slip of ∼0.3 m, causing slip in the shallow area of the fault where the coseismic ruptures were smaller, and supplementarily released the stress in the shallow part of the fault. The strong earthquake (Mw 7) return period on MDF inferred from the interseismic slip rate is 170–200 yr. Oblique thrust slip revealed by the slip distribution model is the result of long-term absorption of oblique convergence strain in the Southern Tianshan by the MDF and then concentrated release. The 2024 event resulted in a 60 km unruptured segment on the MDF being in a stress-triggering zone, increasing the potential seismic hazard, in contrast to the delayed seismicities on 100 km region of the southern Kalping fault (KPF).

Variation of CO2 concentration and its provenance in alpine on the south slope of Tomur Peak, Tianshan Mountains.

This study analyzes the characteristics of near-surface atmospheric CO2 concentrations on the southern slope of Tomur Peak from 2013 to 2022. Utilizing the Boughton two-parameter algorithm, we determined the CO2 background and non-background concentrations. Additionally, the Hysplit model was employed to investigate the potential contributing areas of the CO2 non-background concentration. Our findings that the CO2 concentration in the study area was approximately 17% lower than the global average, with an annual growth rate that was only about 47% of the global rate. The CO2 non-background concentration accounted for only 6.25% of the observed concentration, but was largely unaffected by near-ground meteorological factors. The source of the CO2 non-background was mainly controlled by the westerly belt, with potential source area mainly located in Central Asia. However, the WPSCF values in the modern ice and snow distribution area south of Tomur Peak and west of the monitoring station were significantly elevated, suggesting a strong wind transport of CO2 after accumulation under the influence of the elevated terrain. The local supplying path accounted for only 12.87%, indicating that human activities in the oasis areas of the Tarim Basin had a limited influence on the study area. Due to the blocking effect of the Baikal high-pressure system and the towering topography of the Tianshan Mountains, the influence of human emissions from higher latitudes was likely negligible.

Coupled evolution of basin structure and fluids recorded by microfractures: A case study of deep-buried ordovician in the tarim basin

The fluid activity in the deep strata of sedimentary basins is commonly related to tectonic activity, and the cements filled in fractures are a good carrier for the tectonic-fluid coupling evolution. Compared to macrofractures, microfractures have characteristics of high frequency and easy identifiable periods. Abundant microfractures infilled by carbonate cements (MCCFs) developed in carbonates of the Ordovician Yingshan and Yijianfang formations in the platform basin area of the Tarim Basin. Based on the study of petrology, U-Pb dating, and geochemical characteristics, this study determined the stages of MCCFs and clarified the tectonic-fluid coupling evolution process recorded by MCCFs in the study area. The formation order of these MCCFs is D1, C1, C2, D2, C3, and C4. The precipitation times of MCCFs have a good correspondence with orogeny around the Tarim Basin and active times of strike-slip faults in the platform basin area. The six stages of MCCFs in the Ordovician Yingshan and Yijianfang formations in the SLU recorded the tectonic-fluid coupling evolution process of concentrated seawater in the late Middle Ordovician, meteoric water at late Ordovician, organic acids during the Silurian, Mg-rich hot brine at the end Devonian-early Carboniferous, and magmatic hydrothermal fluids during the Permian. This not only indicates a close connection between fluid activity and tectonic activity in sedimentary basins, but also confirms that the formation of MCCFs in carbonate formations is closely related to regional tectonic-fluid coupling activities. This study provides a good example for studying macro scale tectonic-fluid coupling activities in basins using microfractures.

The Single-Scattering Albedo of Black Carbon Aerosols in China

Black carbon (BC) aerosols have attracted wide attention over the world due to their significant climate effects on local and global scales. BC extinction aerosol optical thickness (AOT), scattering AOT, and single scattering albedo (SSA) over China are systematically studied based on the MERRA-2 satellite reanalysis data from 1983 to 2022 in terms of the spatial, yearly, seasonal, and monthly variations. The extinction and scattering AOTs of BC show similar spatial distribution, with high values in eastern and southern China, generally as opposed to BC SSA. A decrease in BC extinction and scattering AOTs has been documented over the last decade. The mean BC extinction AOT, scattering AOT, and SSA over China are 0.0054, 0.0014, and 0.26, respectively. The BC SSA showed small variations during 1983–2022, although a high BC extinction AOT and scattering AOT have been seen in the last two decades. During different decades, the seasonal patterns of BC extinction and scattering AOTs may differ, whereas the BC SSA shows seasonal consistency. Significant monthly variations in the BC SSA are seen over four decades, which are in agreement with their seasonal patterns. The mean BC extinction AOTs are 0.037, 0.033, 0.023, and 0.0054, whereas the average BC scattering AOTs are 0.0088, 0.0082, 0.0060, and 0.0014 in the Pearl River Delta (PRD), Yangtze River Delta (YRD), Beijing–Tianjin–Hebei (BTH) region, and Tarim Basin (TB), respectively. It is interesting to see that BC SSA values in the TB region are generally higher than those over the PRD, YRD and BTH areas, whereas the reverse is true for BC extinction and scattering AOTs. This study provides references for further research on black carbon aerosols and air pollution in China.

Research on Lithofacies Paleogeography and Caprock Evaluation of the Middle Cambrian in the Tarim Basin, NW China

Research on Lithofacies Paleogeography and Caprock Evaluation of the Middle Cambrian in the Tarim Basin, NW China

Differences in the Genesis and Sources of Hydrocarbon Gas Fluid from the Eastern and Western Kuqa Depression

The Kuqa Depression is rich in oil and gas resources and serves as a key production area in the Tarim Basin. However, controversy persists over the genesis of oil and gas in the various structural zones of the Kuqa Depression. This study employs natural gas composition analysis, gas carbon isotope analysis and gold pipe thermal simulation experiments, to comprehensively analyze the differences in the genesis and sources of hydrocarbon gas fluid from the eastern and western Kuqa Depression. The results show that the Kuqa Depression is dominated by alkane gas, with an average gas drying coefficient of 95.6, with nitrogen and carbon dioxide as the primary non-hydrocarbon gases. The average of δ13C1, δ13C2 and δ13C3 values in natural gas are −27.70‰, −20.43‰ and −21.75‰, respectively. Based on comprehensive natural gas geochemical maps, the CO2 in the natural gas from the Tudong and Dabei areas, as well as the KT-1 well of the Kuqa Depression, is thought to be of organic origin. Additionally, natural gas formation in the Tudong area is relatively simple, consisting entirely of thermally generated coal gas derived from the initial cracking of kerogen. The natural gas in the KT-1 well and the Dabei area are mixed gasses, formed by the initial cracking of kerogen from highly evolved lacustrine and coal-bearing source rocks, exhibiting characteristics resembling those of crude oil cracking gas. The methane (CH4) content of natural gas in the Dabei area is high and the carbon isotopes are unusually heavy. Considering the regional geological background, potential source rock characteristics and geochemical features may be related to the large-scale invasion of dry gas contributed by CH4 from highly evolved, underlying coal-bearing source rocks. Consequently, the CH4 content in the mixed gas is generally high (Ln (C1/C2) can reach up to 5.38), while the relative content of heavy components is low, though remains relatively unchanged. Thus, the map of the relative content of heavy components still reflects the characteristics of the original gas genesis (initial cracking of kerogen). Mixed-source gas was analyzed using thermal simulation experiments and natural gas composition ratio diagrams. The contributions of natural gas from deep, highly evolved coal-bearing source rocks in the KT-1 well and the Dabei area accounted for more than 90% and approximately 60%, respectively. This analysis provides theoretical guidance for natural gas exploration in the research area.

Distribution and origin of higher diamondoids in the ultra-deep Paleozoic condensates of the Shunbei oilfield in the Tarim Basin, NW China

Higher diamondoids in the condensates of the Shunbei oilfield were analyzed using GC–MS. The findings indicate that the condensates in the Shunbei oilfield were subjected to a superimposed effect of secondary alterations, including biodegradation, hydrothermal alteration, evaporative fractionation, cracking, and TSR. High local concentrations of thiaadamantanes in oil may result from the interaction of H2S, derived from Cambrian TSR, with Ordovician hydrocarbons, influenced by hydrothermal activities. Comprehensive analysis shows that TSR is local and limited in Ordovician reservoirs in the Shunbei oilfield and has no significant impact on oil chemistry. Comparative studies indicate that the diamondoid concentrations in condensates from the Shunbei oilfield have not been significantly impacted by biodegradation and evaporative fractionation. Parameters related to diamantanes can effectively characterize their geochemical characteristics and secondary alteration. A multi-parameter correlation heat map suggests that higher diamondoids in the condensates of the Shunbei oilfield are not due to high thermal evolution but have been altered by hydrothermal activity. The hydrothermal activity promotes the formation of higher diamondoids in the condensate. The higher diamondoids that are formed by hydrothermal activity offer a new perspective for studying hydrothermal processes. Additionally, this aids in studying the organic-inorganic interactions of ultra-deep organic fluids with their mineralogical and aqueous environments.