To investigate the rare earth element (REE) fractionation patterns, grades, and their influencing
factors in different ore blocks of the Bayan Obo REE-Nb-Fe symbiotic deposit, and to provide guidance for
research on REE patterns and directional mineral processing at Bayan Obo, elemental mass fraction was conducted
using inductively coupled plasma mass spectrometry on samples from different ore blocks of TK13-04 core in the
main orebody. Results show that two distinct REE fractionation patterns exist in the main orebody. The REE
fractionation pattern of the middle dolomite Fe-REE ores differ from that of the upper and lower dolomite REE ores.
The former exhibits an “initial upward inclination followed by rightward inclination” characteristic with increasing
from La to Nd and then decreasing from Nd to Lu. In contrast, the latter shows a “rightward inclination” pattern
with gradually decreasing from La to Lu. The middle dolomite Fe-REE ores have a lower mass fraction of total
REEs compared to the upper and lower dolomite REE ores. The total REE mass fraction is closely related to the
degree of light-to-heavy REE (LREE-HREE) fractionation, the REE fractionation pattern, and the total iron
(TFe) mass fraction. Higher degrees of LREE-HREE fractionation and higher La/ Nd ratios correlate with higher
total REE mass fraction. When the TFe is below 20%, there is no definitive correlation between TFe and the REE
mass fraction. However, when the TFe mass fraction exceeds 20%, the total REE mass fraction decreases signifi
cantly. Compared to the average proportions of individual light REEs (LREEs) in the mining area, the proportion
of Ce in the middle dolomite Fe-REE ore block of TK13-04 is significantly lower ( ~37%), while the proportion
of Nd is significantly higher ( ~40. 7%), exceeding the proportion of Ce that is typically the dominant REE in the
deposit. The proportion of La in the middle dolomite Fe-REE ore block is also reduced ( ~9%) and the proportions of
Pr and Sm are increased. Therefore, the middle dolomite Fe-REE ore blocks hold greater potential for the utilization
of Nd, Pr, and Sm elements. For the utilization of La and Ce, development of the upper and lower dolomite REE
ore block would likely yield more substantial benefits.
The exploration focus of the Junggar Basin has gradually shifted from the hydrocarbon generation
center of the sag to the peripheral uplift area. To understand the distribution characteristics of oil and gas reservoirs
in the Dabasong Uplift, the authors have conducted research on the main controlling factors and development mode
of high-quality reservoirs in the Dabasong Uplift by means of core observation, thin section identification, well
logging interpretation and various experimental analyses. It is believed that the Dabasong Uplift was in the underwater
reducing environment during the eruption period, and the carboniferous igneous rocks were mainly basic rocks,
including diabase of volcanic channel facies, crystalline tuff of the underwater sedimentary subfacies, breccia clastic
tuffs of the underwater volcaniclastic flow subfacies, basalt and andesite of underwater overflow facies, and
sedimentary tuffs of the volcanic sedimentary facies. Among them, breccia clastic tuffs of the underwater volcani
clastic flow subfacies and the diabase of volcanic channel facies are the dominant lithologic lithofacies in the study
area. The breccia clastic tuff has more concentrated pore throat distribution, good connectivity and greater contribu
tion of pore throat, while the diabase has more dispersed pore throat distribution and good connectivity. The reser
voir space of igneous rocks in the study area is dominated by intrachrystalline solution pores, matrix solution pores,
structural fractures and solution fractures. The porosity of carboniferous igneous rocks is less than 5% (51. 9%),
between 5% and 12% (29.6%), more than 12% (18.5%), the permeability is less than 1 ×10-3μm2 (81. 5%),
between (1 and 5) ×10-3μm2 (16.6%), and more than 5 ×10-3μm2 (1.9%), the whole belongs to the medium
and low porosity-low permeability reservoir. The formation of effective reservoirs is controlled by lithologic lithofacies,
dissolution and fractures, which is a weathering and dissolution modified reservoir based on lithologic lithofacies and
dominated by fractures. The results show that the favorable zone for oil and gas exploration in areas with dominant
lithological lithofacies, weathering and dissolution, active fluid dissolution and fracture development.
Recent significant breakthroughs in natural gas exploration have been achieved in the tight sandstone
reservoirs of the Bashijiqike Formation (Member 1) within the Cretaceous system of the Luntai S3 block, Tarim
Basin, which has emerged as a crucial exploration target with substantial hydrocarbon resource potential. However,
the reservoir characteristics and main controlling factors of these potential intervals remain insufficiently understood,
constraining zone evaluation and target optimization in this area. Based on physical data including mud logging,
well logging, core samples, and cuttings from existing wells, this study systematically investigated the petrological
characteristics, reservoir space types, and physical properties of the tight sandstone reservoirs through thin-section
analysis, cast thin-section observation, X-ray diffraction, mercury injection, and scanning electron microscopy.
The results revealed that: (1) The reservoirs predominantly consist of lithic arkose and feldspathic litharenite with
low compositional maturity (quartz is 59. 7%, feldspar is 23. 0%, lithic fragments is 17. 3%) and moderate tex
tural maturity. The interstitial material (predominantly calcite) accounts for an average of 7. 1%. The reservoir
space is dominated by residual primary intergranular pores (plane porosity is 2%) and intergranular dissolution
pores (average pore diameter is 109. 65 μm), exhibiting bimodal pore-throat radius distribution (main peak at
1 μm). The average displacement pressure measures 0. 27 MPa, with porosity ranging from 8. 6% to 11. 9% and
permeability between 0. 64 ×10-3 and 6. 10 ×10-3 μm2, collectively indicating low porosity and low permeability
characteristics. (2) Reservoir heterogeneity was controlled by depositional environment, with medium-coarse sand
stones in subaqueous distributary channels of braided river delta fronts (sandbody thickness proportion 42%-91%)
being identified as effective reservoir development zones, where high-energy environments promoted better sorting
and lower clay volume fractions. (3) Reservoir evolution was dominated by diagenesis: early calcite cementation
(volume fraction 7. 1% to 11. 3%) inhibited compaction and preserved residual intergranular pores (porosity
reduced to 5%-8%), while late dissolution created intergranular/ intragranular dissolution pores (maximum plane
porosity is 15%), though local re-cementation intensified heterogeneity. (4) Structural uplift (Late Cretaceous
strata exposure) enhanced epigenetic dissolution, with differential uplift causing spatial variations in dissolution
intensity. The study concluded that effective reservoir development in Member 1 was jointly controlled by sedimentology
diagenesis-tectonics coupling, with the subaqueous distributary channel sand bodies in the eastern 3-4 sand groups
being prioritized exploration targets, particularly focusing on calcite cement dissolution zones and fault-modified areas.
This study investigates members 2-3 of the Late Cretaceous Qingshankou Formation in the Gulong area
of the Songliao Basin. By integrating core data, well-logging information, magnetic susceptibility and chromaticity
measurements, wavelet transform analysis of logging curves, and cluster analysis, the coupling mechanism between
high-frequency climatic oscillations and sequence development in continental lacustrine basins was systematically
revealed. The principal findings are summarized as follows: (1) Two depositional environments lacustrine and
deltaic facies were identified in the studied interval, which were further subdivided into six microfacies: deep-lake
mud, semi-deep lake mud, shell sand, turbidite, prodelta mud, and sheet sand. A delta-lacustrine sedimentary
evolution model was established to characterize their vertical stacking patterns. (2) Two complete third-order sequences
were recognized based on lithologic associations, well-logging responses, and wavelet transform time-frequency
analysis. These sequences were divided into four system tracts, lowstand (LST), transgressive (TST), highstand
(HST), and regressive (RST). Sequence boundaries were characterized by GR curve inflection points, lithologic
abrupt changes, and energy cluster transitions in time-frequency spectrograms. (3) Paleoclimate evolution was
quantitatively reconstructed using magnetic susceptibility and chromaticity indices through SPSS cluster analysis. The
results revealed a climatic cyclicity of “cooling-warming-cooling-warming-cooling” with an anomalously warm-humid
phase during 86. 895-86. 364 Ma closely linked to lacustrine anoxic events (LAEs). This phase was attributed to
enhanced hydrological cycling-triggered terrestrial coarse clastic input and intensified reducing conditions. Overall,
paleoclimate governed sequence differentiation by regulating hydrological cycling and sediment supply. During
warm-humid phases, strengthened water circulation promoted fine-grained mudstone deposition, forming TST and
HST system tracts, whereas under relatively dry-cold conditions, weakened water circulation favored coarse-grained
gravity flow sedimentation, developing RST and LST system tracts.
To deeply reveal the paleoclimate characteristics of the Sifangtai Formation in the Songliao Basin,
infer the controlling factors of climate change, and improve the information implied by climatic evolution, magnetic
susceptibility and chromaticity tests were conducted on the core (140. 0-380. 5 m) from the ZKQA1-1 in the
Qianan area. Through Pearson correlation analysis, it was found that magnetic susceptibility and chromaticity data
were weakly correlated with stratigraphic depth. Brightness (L∗) was negatively correlated with redness (a∗) and
yellowness (b∗), while redness (a∗) was positively correlated with yellowness (b∗), indicating that the data
were minimally affected byagenesis and had reliable paleoclimate significance. Through SPSS cluster analysis,
high-frequency magnetic susceptibility, low-frequency magnetic susceptibility, frequency-dependent magnetic
susceptibility, brightness (L∗), redness (a∗), and yellowness (b∗) were filtered once, and four filtered mean
values were obtained for each dataset. The filtered values were classified into four climatic types (cold-dry, relatively
cold-dry, relatively warm-wet, and warm-wet) based on paleoclimate proxy indicators. To avoid errors caused by
semi-quantitative analysis of climatic types using magnetic susceptibility and chromaticity data, the six datasets
representing climatic types were assigned numerical values (cold-dry: 0. 5, relatively cold-dry: 1. 5, relatively
warm-wet: 2. 5, warm-wet: 3.5), averages were calculated based on depth summation, and comprehensive temporal
scale analysis was performed in combination with lithological and well-log data. The results showed that the magnetic
susceptibility and chromaticity data of the Sifangtai Formation core from the Well ZKQA1-1 indicated a relatively
cold-dry climate during the mid-Campanian (76. 08-75. 65 Ma), and the paleotemperature decrease in this stage
was associated with the migration of the intertropical convergence zone (ITCZ). A relatively warm-wet to warm-wet
climate was identified during the mid-late Campanian (75. 65-74. 32 Ma), with an extreme paleotemperature peak
observed at 75. 55 Ma, while the slight paleotemperature decline from 75. 55 to 74. 32 Ma was linked to the Campanian
Maastrichtian Boundary Event (CMBE). During the late Campanian (74. 32-73. 19 Ma), a cold-dry to relatively
cold-dry climate was recorded, with an extreme paleotemperature minimum at 74. 13 Ma, followed by a relatively
warm-wet climate from 73. 19 to 72. 86 Ma, and the paleotemperature rise from 74. 13 to 72. 86 Ma might be related
to intermittent volcanic activity prior to the late Campanian Deccan Traps eruption event. Overall, the paleoclimate
of the Sifangtai Formation was demonstrated to correspond well with global climate trends, representing a relatively
warm and dry climatic type.
Multiple wells in the carbonate gas reservoirs of the Lower Permian Qixia Formation in the central
Sichuan region of the Sichuan Basin have encountered industrial gas flows, but the anisotropy of the single well
reservoir is strong and the physical parameters are obviously different, so it is difficult to guide the well location
deployment of this type of gas reservoir by conventional geophysical means. Therefore, to clarify the main controlling
factors of the Qixia Formation gas reservoir, accurately predict the distribution of thin dolomite reservoirs, and
further improve the development efficiency of the gas reservoir, the authors combine core, logging, seismic and
other data to first determine the main controlling factors for the enrichment and high yield of the Qixia Formation gas
reservoir in the study area, and summarizes the rock physical characteristics and seismic response patterns of the
dolomite reservoir. Innovation has formed key technical processes for thin reservoir prediction, such as high-resolution
processing technology, qualitative reservoir prediction based on wavelet reconstruction, fine characterization of ancient
landforms constrained by layers, inversion technology constrained by reconstruction curves, and fracture and cave
prediction technology constrained by porosity curves. This has improved the ability to vertically resolve thin reservoirs of
1-8 m in the research area, and ultimately characterized a favorable area for the development of dolomite reservoirs
as 75 km2. The research results indicate that: (1) There is an obvious positive correlation between the thickness
of fracture-vuggy dolomite thin reservoir, fracture-cave development degree and productivity in the Qixia Formation
gas reservoir in the study area. (2) Before the sedimentation of the Qixia Formation (paleogeomorphology), reservoirs
were developed in the lower part, and the reservoir properties in the slope area during the karst period were better.
(3) The reservoirs of Qixia Formation in the study area are mainly developed in the middle and upper parts, and
the seismic profile shows the reflection characteristics of “weak peaks” in the middle and upper parts, and the more
the reservoirs are developed, the more obvious the response characteristics of “weak peaks” are. This article
combines seismic facies, paleogeomorphology, reservoir thickness, and fracture distribution parameters for the first
time to establish a series of key technologies for predicting dolomite reservoirs suitable for the study area, achieving
effective prediction of the spatial distribution of thin reservoirs in the Qixia Formation and laying the foundation for
increasing reserves and production in oil fields.
The coupled models for selecting statistical methods and machine learning models to achieve better
prediction results for geological hazard susceptibility assessment, as well as the interpretation of the contribution of
model feature factors, are further studied in this paper. Two statistical methods (information value, IV and
certainty factor, CF) and two machine learning models (support vector machine, SVM and random forest, RF) are
combined to construct four hybrid models. Taking Panshi City as an example, the study investigates the effect of
coupled models on the accuracy improvement compared to single statistical models, and selects the most accurate
model to explain the contribution of various hazard-causing factors to the prediction results. The interactive self
organization (ISO) clustering algorithm is first used to select non-harzard samples. Then, the information value
(IV) method and the certainty factor (CF) method are combined with support vector machine (SVM) and random
forest (RF) to obtain four coupled models (IV-SVM, CF-SVM, IV-RF, CF-RF) for training, respectively. The
performance of the models is evaluated using confusion matrix and receiver operating characteristic curve. The natu
ral break method is then used to generate the geological hazard susceptibility classification map (with five levels:
very low, low, moderate, high, and very high). The geological hazard intensity index is used to evaluate the clas
sification accuracy, and geological hazard susceptibility assessment is conducted. Finally, the Shapley additive ex
planations algorithm is used to explain the best-performing model. The results show that the performance of the four
coupled models is generally better than that of the single statistical models, with the CF-RF model achieving the
best accuracy evaluation results of accuracy (0. 896), precision (0. 872), F1 score (0. 899), and AUC value
(0. 959), which is an improvement of 0. 066, 0. 098, 0. 054, and 0. 059, respectively, compared to the single CF
model. Most historical geological hazard points are distributed in high and very high susceptibility zones, and the
geological hazard intensity index increases as the susceptibility level increases. Among them, the CF-RF model has
the best classification effect. The Shapley additive explanations algorithm can help understand the reasons behind
the models decisions and the occurrence patterns of geological hazards. The study indicates that land use and road
construction are the main inducing factors for geological hazard susceptibility in the study area.
When using machine learning techniques to identify lithology based on the feature vectors of each
sample in the logging dataset, it is generally imperative to first clean and preprocess the dataset to detect missing
data and outliers in it. Affected by the distortion of logging curves or the disparities in the quantity of curves
between wells, the logging dataset used for lithology identification is usually incomplete, with a large amount of
missing data and outliers. This renders it challenging for the majority of machine learning methods to be directly
applied. To tackle this problem, a K-nearest neighbors algorithm based on the partial distance strategy (PDSKNN) is
proposed. This algorithm improves the traditional K-nearest neighbors algorithm (KNN) based on a method (PDS)
that capable of computing the distance between feature vectors containing missing values, enabling the direct appli
cation to incomplete dataset. The PDSKNN algorithm was experimentally implemented and tested in the lithology
identification task of complex igneous rock reservoirs in a certain region. When the data missing rate was 2. 7%,
the lithology identification accuracy of the PDSKNN algorithm was as high as 91. 90%. This result indicates that the
PDSKNN algorithm effectively solves the problem of incomplete dataset at the algorithm level. For the purpose of
further validating the effectiveness of the PDSKNN algorithm, certain data in the dataset was randomly deleted to
elevate the missing rate, and the changes in the identification accuracy were observed. The experimental results
reveal that as the missing rate increases, the identification accuracy gradually decreases. However, even when the
missing rate attains 20%, the identification accuracy of the PDSKNN algorithm still remains above 80%. This
result proves that the PDSKNN algorithm can maintain a relatively high identification accuracy in the case of severe
data missing. Finally, by simulating the missing conditions of curves in different wells, a comparative analysis of
the changes in the identification effect of the PDSKNN algorithm was carried out. As the number of missing curves
increases, the lithology identification performance in the wells decreases to some extent, but the identification effect
of most well sections is still guaranteed. It shows that the PDSKNN algorithm has strong robustness to the missing
curves in the wells.
In order to reveal the surface deformation characteristics and fault movement mechanism of the Luding
earthquake of 5 September 2022, to mitigate the impact of seismic hazards, and to enhance disaster prevention and
mitigation capabilities, the authors extracted the coseismic deformation results by using D-InSAR technology and
inverted the geometric and kinematic parameters of the seismic faults by combining with the dislocation model. The
ascending orbit images on 26 August and 19 September 2022 and the descending orbit images on 2 September and
14 September 2022 of the Sentinel-1 satellite from the European Space Agency are selected for the study. Through
the dual-track differential interferometric processing, errors such as topographic phase and atmospheric delays are
eliminated, and the coseismic deformation results are obtained with high accuracy. The results show that the surface
deformation induced by the earthquake is significant, and the maximum uplift of 0. 16 m and 0. 13 m, and the
maximum subsidence of 0. 24 m and 0. 18 m are detected in the ascending and descending orbits, respectively, which
provide reliable observation constraints for the subsequent inversion of fault parameters. Based on the acquired
ascending and descending orbits InSAR coseismic deformation results, the Okada elastic half-space dislocation model
is used for the fault parameter inversion, and the optimal geometric parameters and kinematic characteristics of the
seismic fault are determined by the nonlinear optimisation method. The inversion results show that the seismic fault
has a strike of 169°, spreads along the NNW-SSE direction, has a dip of 72°, and a slip angle of-3°. In addition,
the total seismic moment obtained from the inversion is about 2. 46 ×1019 N·m, corresponding to a magnitude of
MW
6.8, which is basically consistent with the observation results from global earthquake monitoring and research
institutions.
To investigate the conductivity mechanism and fluid distribution characteristics of tight sandstone
reservoirs in Ordos Basin and to construct an accurate saturation model, the authors conducted a series of petrophysical
experiments, including porosity-permeability tests, resistivity measurements using the centrifuge method, and NMR
(nuclear magnetic resonance) response analysis, on 11 rock samples from the study area. Nitrogen gas was used in
the porosity-permeability experiments, revealing porosity values ranging from 5. 21% to 11. 26%, and permeability
values are (0. 132 8-1. 261 1) ×10-3 μm2. The resistivity measurements under varying centrifugation durations
provided key electrical parameters: the cementation exponent m (ranging from 2. 053 to 3. 293) and the saturation
exponent n (ranging from 0. 714 to 2. 131). The NMR technique, which leverages the relaxation time of hydrogen
nuclei within the rock, was used to characterize reservoir pore structures and fluid mobility. The T2
spectrum
obtained through NMR enabled the distinction of pore sizes and their proportions. Results indicated that the tight
sandstones in the study area exhibit similar properties and pore structures. The T2
spectrum showed a wide distribution
(0. 1-1 000. 0 ms), typically presenting a bimodal pattern with a boundary at 10 ms. Based on empirical methods,
mercury intrusion data, and NMR T2
spectrum characteristics, the T2
range for small pores was defined as 0. 01
5 ms, and for large pores as 5-10 000 ms. The findings show that fluid mobility is significantly higher in large
pores than in small ones, and water content in small pores increases during centrifugation. After converting T2
values into corresponding pore diameters, it was found that movable water is mainly distributed in the 1-10 μm
range, followed by 0. 01-0. 10 μm and 0. 10-1. 00 μm ranges. Using the fractal dimension method, a positive
correlation was established between fluid distribution and electrical conductivity, which is greater fluid presence in
large pores corresponds to smaller fractal dimensions and higher conductivity.
A novel integrated learning-based method for igneous reservoir fluid identification is proposed to
address the limitations of traditional approaches in handling complex lithological variations and heterogeneous reservoir
spaces, which are crucial for global oil and gas resource development. In this paper, the adaptive multi-objective
swarm crossover optimization (AMSCO) innovatively combined with an engineered extreme gradient boosting (XGBoost)
based on deep forest method for fluid identification in complex lithologic igneous reservoirs using conventional
logging data set. Methodologically, firstly, the AMSCO algorithm is used to optimize the imbalanced conventional
logging data set, effectively solving the problem of class imbalance in the data set, providing a more balanced data
basis for subsequent model training. Secondly, a cross-adaptive XGBoost and deep forest (CXDF) is constructed
by fully utilizing XGBoosts advantages in processing large-scale and high-dimensional data, as well as the excellent
performance of deep forest in feature extraction and classification tasks. Thus, the accurate identification of
reservoir fluids in complex lithologic igneous rocks is achieved. Then, to verify the effectiveness of this method, the
model was applied to the simulated well together with support vector machine (SVM), XGBoost and XGBoost
based deep forest for comparison. Finally, the model is applied to the actual stratum. The results show that the
evaluation index of the proposed method in the simulated well is superior to other methods, especially in the identi
fication of non-water-producing reservoir fluids. In the application to actual formations, this method maintains high
identification performance in different reservoirs with different fluid structures, and shows good generalization ability
and stability.
This study is the first to analyze the geothermal resource occurrence conditions and the formation
evolution mechanisms in the southern part of Taiyuan City, Shanxi Province, from both geothermal geophysical and
geothermal water isotope geochemical perspectives. Based on geophysical exploration data and geothermal water
isotope chemical analysis, and combined with regional geological data, a comprehensive study of the geothermal
field in southern Taiyuan is conducted. The geophysical methods primarily include gravity, magnetic, and electrical
surveys, which are used to analyze the structural characteristics and reservoir distribution of the geothermal field.
The geochemical methods mainly include hydrochemical and isotopic analyses, aimed at revealing the origin, evolution,
and water-rock interaction processes of thermal groundwater. The geophysical exploration results indicate that the
Taiyuan Basin as a whole exhibits a low gravity field and negative magnetic anomalies, reflecting a deeply buried
basement and strong tectonic activity, which provide favorable heat sources and reservoir spaces for the formation of
geothermal fields. The southern geothermal field of Taiyuan is located at the southeastern margin of the basin,
where the gravity field shows a distinct gradient zone, and the magnetic anomalies are characterized by negative
values, suggesting the presence of concealed fault structures that serve as channels for deep thermal flow upwelling.
Moreover, an apparent arcuate low-resistivity zone exists within the geothermal field, inferred to represent the
geothermal reservoir, further demonstrating the favorable conditions for geothermal resource accumulation in this
area. Geothermal water isotope geochemical analysis reveals that the thermal groundwater in the southern Taiyuan
geothermal field originates from meteoric water, undergoing processes of infiltration, leaching, and transformation
into sedimentary (semi-confined) water. During this process, water interacts with surrounding rocks through
leaching, dissolution, and cation exchange. Stable components accumulate in the groundwater, while unstable
components precipitate, thus forming the hydrogeochemical characteristics of modern geothermal water. The formation of
the geothermal field in southern Taiyuan is mainly controlled by the favorable regional geological structure, the
development of concealed faults, and the good storage capacity and permeability of the geothermal reservoir.
The Wuzhong-Lingwu area lies within the Taole-Hengshanpu thrust fault zone, characterized by
complex geological structures. Aiming to address the exploration needs for active fault development and the unclear
deep geothermal reservoir structures in the southern section of the Yinchuan Basin (Taole-Hengshanpu thrust fault
zone), this study employs the microtremor-based spatial autocorrelation method (SPAC) using background noise.
By analyzing the recorded Rayleigh wave signal data, the authors effectively inverted the high-resolution shear-wave
velocity structure of the subsurface medium in the study area, investigated the subsurface structural development in
the Wuzhong-Lingwu area, and evaluated the application of the background noise method in detecting subsurface
faults and geothermal resources. The S-wave velocity structure inversion results obtained by the SPAC technique
revealed key stratigraphic and structural features. Comparison with previous well-logging and electrical prospecting
data confirmed the reliability of the recorded observations. The results indicate that the depth range of 700-1 000 m
corresponds to the Upper Carboniferous (Ct) strata, where a slight decrease in S-wave velocity suggests the presence
of an aquifer, consistent with the distribution of geothermal water resources in the area. Between 1 000 and 1 500 m,
S-wave velocity increases again, indicating Ordovician (O) strata, with a thin, slightly lower-velocity layer at the
top interface, also inferred to be an aquifer. Based on the velocity anomalies and spatial distribution of aquifers, it
is concluded that the Upper Carboniferous aquifer (700-1 000 m) and the thin aquifer at the top of the Ordovician
strata (1 000-1 500 m) possess favorable conditions for geothermal fluid storage and migration, making them highly
promising target geothermal reservoirs. These two stratigraphic units are likely to host geothermal resources.
Founded in 1982, Quarterly Governed by: Ministry of Education of the People’s Republic of China Sponsored by: International Center for Geoscience Research and Education in Northeast Asia, Jilin University Editor-in-Chief: SUN Fengyue ISSN 1004-5589 CN 22-1111/P