Accurately characterizing coal vitrinite molecular structure is crucial for understanding coalification and enabling efficient utilization. FTIR and Raman spectroscopy require separate measurements, preventing analysis of the same microregion, and conventional FTIR microscopy suffers from the Abbe diffraction limit, which restricts its lateral resolution. Here, optical photothermal infrared spectroscopy enables in situ synchronous infrared-Raman analysis and high-resolution molecular distribution imaging across six vitrinite samples of varying maturities. O-PTIR overcomes the infrared diffraction limit (∼500 nm) and acquires both infrared and Raman spectra from the same microregion with matching lateral resolution, reducing errors caused by coal heterogeneity. With increasing maturity, the infrared A-factor and C-factor decrease, suggesting progressive removal of aliphatic structures and oxygen-containing groups. Aliphatic chain length and Raman AD1/AG show variations with coal rank, implying aliphatic decomposition and reconstruction influence carbon skeleton ordering. No strong correlation between the C-factor and AD1/AG was observed, indicating oxygen functional group removal may have limited impact on the carbon skeleton. High-resolution molecular imaging generates hundreds of thousands of data points per microregion at submicron scale. Pseudo–Van Krevelen analysis shows distribution centers of the A-factor and C-factor shift toward the origin with increasing maturity, while data points progressively converge—statistically reflecting deoxygenation, decarbonization, and structural condensation, alongside microscale heterogeneous molecular evolution. This integrated approach offers a valuable tool for investigating micro- to nanoscale organic structures and provides spectroscopic insights into coalification mechanisms and heterogeneity assessment.

Predicting gas-bearing properties in tight sandstone reservoirs presents a global challenge. Traditional methods based on well log interpretation rely heavily on individual experience, which can introduce significant unknown errors. Prediction methods using seismic data and logging labels often fail to capture complex interactions between geological features, resulting in low accuracy. Furthermore, these methods typically determine only gas presence without providing quantitative results. To address these limitations, this study proposes a novel interpretable machine learning (ML) framework. Its novelty lies in: (1) directly linking well testing conclusions to logging data to provide high-resolution, semi-quantitative gas-bearing labels, eliminating intermediate interpretation errors; (2) a systematic comparison of 19 ML algorithms across different paradigms (traditional ML, deep learning, and ensemble learning) using five tailored evaluation metrics, identifying LightGBM as the optimal model for this task (Accuracy = 99.76%); and (3) integrating interpretability directly into the prediction workflow based on cooperative game theory to provide global and local explanations that align with petroleum geological knowledge, significantly enhancing the model’s transparency and credibility. Applied to the Xujiahe Formation in the Sichuan Basin, this framework achieves decimeter-level accuracy and demonstrates strong generalization capability. This work proposes a novel framework that enables semi-quantitative gas-bearing property predictions with the potential for basin-scale application, directly identifying sweet spots and offering a more streamlined and interpretable high-accuracy artificial intelligence method for oil and gas resource exploration and development.

The Sanmenxia Basin is a small to medium-sized rift lacustrine basin on the southern margin of the North China Craton. Although recent drilling (Well YXD-1) has yielded economic oil flow, the geochemistry and accumulation history of its crude oil remain largely unconstrained. This study presents the first high-resolution molecular characterization of crude oil from this basin using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC-TOFMS). The results show: (1) bimodal n-alkane distributions, C21 tricyclic terpane predominance, anomalous enrichment of long-chain alkylnaphthalenes, and C29 sterane dominance, collectively indicating mixed organic inputs from terrestrial higher plants and aquatic organisms; (2) a decoupling between conventional biomarker maturity parameters (suggesting mid-oil window maturity) and diamondoid-based indices (recording significantly higher maturity); (3) fluid inclusion homogenization temperatures with a dominant mode at 70–100°C and a subordinate mode up to 210°C; and (4) thermal history modeling showing that the maximum burial temperature of the Xiaoan Formation did not exceed ∼130°C. Integration of these four lines of evidence demonstrates that the high-maturity signal and high-temperature inclusions cannot be explained by normal burial heating. Instead, they record multi-stage hydrocarbon charging involving external high-temperature fluids, potentially derived from deeper source rocks. Owing to their limited drainage area and heightened sensitivity to climatic and provenance changes, small lacustrine basins are particularly susceptible to mixed-source inputs and multi-stage accumulation. This study provides the first geochemical evidence for complex hydrocarbon charging histories in small to medium-sized rift lacustrine basins, with direct implications for exploration in analogous basins worldwide.

Strong heterogeneity and ambiguous seismic responses hinder reliable sandstone thickness prediction when using a single seismic attribute in the lower sandstone interval of the Talang Akar Formation (hereafter abbreviated as the LTAF interval) in the B gas field, South Sumatra Basin. To address this challenge, we propose a seismic attribute fusion and reservoir sweet-spot prediction framework based on a multiscale convolutional neural network (CNN) integrated with a self-attention module. Multiple seismic attribute volumes are organized as multi-channel 2D attribute slices, and parallel convolutions with kernel sizes of 3 & times; 3, 5 & times; 5, and 7 & times; 7 are employed to capture spatial features ranging from thin-bed boundaries and channel morphology to sand-body assemblage distribution. The self-attention module explicitly models inter-attribute dependencies and performs adaptive weighted fusion to suppress noise and emphasize informative attributes. The network adopts a dual-output design, producing (i) a sandstone thickness prediction map at the same spatial resolution as the input and (ii) attribute importance scores for quantitative attribute selection and geological interpretation. Using 3D seismic data and well-constrained thickness labels, the proposed model achieves an R2 of 0.8954, outperforming linear regression (R2 = 0.8281) and random forest regression (R2 approximate to 0.8453). The learned importance scores indicate that amplitude-related attributes (e.g., RMS amplitude and maximum amplitude) contribute most to thickness prediction, whereas frequency- and energy-related attributes show relatively lower contributions, which is consistent with bandwidth-limited resolution effects. Overall, the proposed framework unifies attribute fusion, thickness prediction, and interpretability within a single model, providing practical support for fine reservoir characterization and development optimization in heterogeneous sandstone reservoirs.

Investigating the diffusion kinetics of helium is crucial for elucidating the dynamic mechanisms underlying the enrichment process of helium-rich gas reservoirs. During gas diffusion in porous media, the concentration gradient is also caused by the pressure gradient, however, the influence of gas pressure on helium diffusion remains poorly understood and lacks a unified interpretation. Moreover, due to helium's smallest molecular size, it exhibits rapid diffusion but limited diffusion mass, therefore, it requires high precision measurement to study its diffusion behavior, particularly its relationship with pressure. This study employs a self-developed "hightemperature and high-pressure gas adsorption and diffusion apparatus" to conduct gas diffusion experiments on shale, coal, and metamorphic rock samples. Diffusion data were measured at 10 pressure points from 0 to 6 MPa. The diffusion behavior was fitted using unipore and bidisperse diffusion models to investigate the diffusion laws of helium under varying gas pressures and across different rocks. Results indicate that the pore size distribution of rocks governs helium diffusion characteristics. When the pore size distribution is more concentrated, the diffusion behavior can be better described by the unipore diffusion model. The diffusion capacity of helium in different rocks decreases with increasing gas pressure, with the effective diffusivity of coal showing the highest rate of change (coal > shale > metamorphic rock). Larger pore volume and surface area in rocks lead to a more pronounced effect of gas pressure on helium diffusion capacity. Differences in helium diffusion capacity among different rocks were observed, with coal > metamorphic rock > shale. Pore volume, pore size, and fractal dimension D2 exhibit positive correlations with effective diffusivity, whereas pore surface area demonstrates a negative correlation with effective diffusivity.

Abstract Deciphering the interplay between multistage diagenetic fluids and reservoir evolution is critical for understanding pore system development in deeply buried carbonate reservoirs. This study employs an integrated multiscale approach combining petrography, cathodoluminescence, stable isotopes, trace/rare earth element geochemistry, and high-resolution micro-CT imaging to unravel the causal relationships among sedimentation, tectonic modification, and diagenetic alteration processes in Ediacaran dolomites. A case study from the Ediacaran Dengying Formation in the Sichuan Basin of China reveals: (1) Microbial dolomite and sand-debris dolomite in the Dengying Formation are high-quality reservoir rocks, with a 2D slice porosity ranging from 3.6% to 8.8%. Abundant primary algal framework pores (equivalent pore radius: 89.3–110.6 μm) and well-connected pore-throat networks (equivalent throat radius: 25.2–55.9 μm) in these dolomites provide the material foundation for reservoir development; (2) Spatiotemporal variations in dolomitizing fluids are governed by distinct diagenetic regimes, including high-salinity marine fluids during the late Ediacaran shallow marine environment, mixed freshwater and normal seawater fluids during near-surface to shallow burial stages, and acidic, reducing fluids associated with high-temperature deep fluids in the shallow to mid-burial environments; (3) The development of high-quality reservoirs is influenced by the interplay of sedimentary facies, tectonic modifications, and diagenetic fluids. Favorable sedimentary facies provide the framework, tectonic-induced fractures offer pathways for deep fluid migration, and diagenetic alteration is the key to modulating the all-important pore-throat structures. Through this tripartite mechanism, we propose a geological model of multistage dolomitization and pore evolution. These findings advance our understanding of polyphase fluid evolution in ancient carbonate systems, providing a conceptual framework applicable to hydrocarbon reservoirs in both Precambrian and Phanerozoic dolomitized successions worldwide, as well as other analogous dolomitized systems.

Climate serves as a fundamental control on source-to-sink systems. Previous studies have investigated global and regional Quaternary climatic variations—encompassing temperature, humidity, and water salinity—through geochemical and sedimentological methodologies. Newly acquired S-wave seismic data provide a novel opportunity to reconstruct facies within shallow-buried Quaternary successions dating back to 1.51 Ma. Within a wellconstrained isochronous stratigraphic framework, these seismic datasets are temporally calibrated, enabling the assessment of climate-driven sedimentological changes as recorded in facies. In the Quaternary biogenic gas-bearing Taidong area of the Sanhu Depression, Qaidam Basin, NW China, evaporite facies were delineated using seismic sedimentology techniques, supported by well-log calibration, geochemical proxies, and modern analogs. Applied seismic processing methods, including phase rotation, frequency decomposition, RGB spectral blending, and stratal slicing, facilitated the identification of linear and sub-circular geomorphic features analogous to contemporary saline pans, such as Lake Chad. Upper Pleistocene outcrop exposures of anhydrite and halite at Yanshan, coupled with lithological and paleoenvironmental records from boreholes SG-5, SG1, and SG-1b, corroborate these seismic interpretations. Seismic stratal slices derived from S-wave data illustrate a progressive increase in evaporite deposits from the K2 datum horizon (1.51 Ma) upwards, indicating a stratigraphic evolution toward heightened aridification. The vertical distribution of evaporite facies in the Taidong area aligns with regional and global paleoenvironmental transitions toward increased aridity. Facies analysis of the Quaternary succession reveals a systematic shift from a freshwater lacustrine system to brackish and saline conditions, ultimately culminating in a desiccated saline pan overlain by silt deposits. This study offers critical insights into sedimentary responses to climatic forcing and provides a framework for predicting evaporite distribution in highaltitude arid basins.

S-wave seismic data are unaffected by natural gas trapped in strata, making them a valuable tool for seismic sedimentology. In this study, S-wave seismic data were utilized to construct an isochronous framework and analyze evaporative facies in the Quaternary biogenic gas-bearing Taidong area, Sanhu Depression, Qaidam Basin, NW China, with calibration from wireline logs and modern analogs. Techniques of phase rotation, frequency decomposition, R (Red), G (Green), B (Blue) fusion, and stratal slices were integrated to reconstruct seismic geomorphological features within the isochronous framework. Linear and sub-circular morphologies, resembling those observed in modern saline pans such as Lake Chad, were identified. Observations from Upper Pleistocene outcrops of anhydrite and halite at Yanshan, east of the Taidong area, salinity measurements from Well TX1 to the north, and lithological and paleo-environmental records from boreholes SG-5, SG-1, and SG-1b to the northwest support the seismic findings. The RGB-fused slices generated from the S-wave seismic data in Taidong area indicate a progressive increase in the occurrence of evaporative features from the K2 standard zone upwards. The vertical occurrence of evaporative facies in the Taidong area mirrors the contemporary regional and global paleo-environmental changes. The interpretation of Quaternary stratal slices from seismic sedimentology—spanning K2, K1, and K0 standard zones—reveals a transition from a freshwater lake to brackish, saline, and finally, a dry saline pan, overlaid by silt. This analysis provides valuable insights into locating evaporites as cap rocks for biogenic gas accumulation and also into mining the evaporite resources in shallow layers of the Taidong area.

Geological CO2 sequestration is currently one of the main effective pathways to achieve industrial carbon reduction. The adsorption of CO2 by coal is a unique storage method for carbon sequestration in underground coal reservoirs. This study conducts isothermal adsorption experiments on high-rank coal reservoirs with strong gas adsorption capacity in the southeastern part of the Qinshui Basin, exploring the CO2 adsorption mechanism, adsorption characteristics, and adsorption capacity of coal reservoirs under different temperature and pressure conditions (especially supercritical conditions). The following conclusions are drawn: (1) The amount of CO2 sequestered by coal seams exhibits a negative temperature effect, and the overall trend of adsorption corresponds to the Langmuir adsorption potential; however, under the same temperature and pressure conditions, high-rank coal has a CO2 adsorption capacity 1.5 to 2 times that of CH4. (2) Due to the adsorption characteristics of coal for CO2, various models need to be adopted to simulate adsorption characteristics across different temperature and pressure stages. In subcritical conditions, the single-layer adsorption theory Langmuir model and the multilayer adsorption characteristic Freundlich model, along with the Tempkin model considering adsorption heat, explain the changes in adsorption characteristics during the CO2 adsorption process by coal. In supercritical conditions, an improved D-R model is used to explain the adsorption mechanism of different pores through micropore-filling effects. (3) Finally, based on actual geological data and experimental adsorption amounts, the conventional adsorption model or improved D-R model is applied to predict and assess the CO2 sequestration potential of the coal reservoirs in the study area. This study provides theoretical and practical reference significance for understanding the CO2 adsorption sequestration characteristics and quantifying sequestration amounts in deep coal reservoirs.

The Tarim Block, northwest China, was positioned on the periphery of Rodinia during the Neoproterozoic Era, and preserves a geological archive chronicling the assembly and breakup of the supercontinent. Due to its antiquity and limited exposure, sedimentary records along the margin of the Rodinia supercontinent remain sparsely documented. This study focuses on the Xifangshan and Dongqiaoenbrak formations, the oldest sedimentary units in the northwestern Tarim Block, which comprise a Neoproterozoic sedimentary record at the supercontinent margin during the transition from subduction to breakup. A comprehensive analysis employing sedimentology, petrology, elemental geochemistry, and UPb detrital zircon chronology was undertaken, to elucidate paleoenvironment, parent rocks, and tectonic-sedimentary evolution. Findings show that the Neoproterozoic witnessed the subduction of an oceanic plate beneath the Tarim Block, resulting in the formation of a continental margin magmatic arc. The Xifangshan Formation, deposited during the late phase of this arc (with the earliest sedimentary age recorded at 770 Ma), represents a submarine fan dominated by turbidity currents. Around 760 Ma, rapid crustal uplift occurred, and the tectonic setting gradually shifted from subduction to rift, giving rise to the coastal alluvial fan sedimentary system observed in the Dongqiaoenbrak Formation. Both the Xifangshan and Dongqiaoenbrak Formations record deposition in an oxic to suboxic marine environment with moderate salinity, influenced by a semiarid to semihumid palaeoclimate. The continental margin arc served as the primary source for sedimentation in both formations, and a few magmatic products linked to extension (syenite, monzonite) were also cannibalized into the sedimentary system of Dongqiaoenbrak Formation. This transition from a turbidite system to a coastal alluvial fan represents a sedimentary response to the subduction-to-breakup dynamics along the margin of the Rodinia supercontinent.

Quaternary biogas is the main natural gas resource in the Qaidam Basin, where sandstone reservoirs have traditionally been the primary producers. However, reserve growth in these reservoirs has become increasingly difficult in recent years. Mudstone gas, representing a new exploration field, has a low exploration level, and its formation, reservoir characteristics, and potential remain unknown. In this study, we utilize core data from the mudstone sections of two newly drilled wells in the study area as the object, and carry out a comprehensive study of the formation and reservoir characteristics of mudstone biogas through systematic experimental analysis, on the basis of which, favourable exploration areas for mudstone biogas are identified. The results of the study show that: (1) The Quaternary mudstone is mainly composed of dark grey mudstone in shallow and semi-deep lake, and influenced by the anoxic environment of brackish water and semi-brine water, exhibiting blocky, striped, and laminar structures. The mudstone layers frequently feature interbeds of sand and carbonate rocks. in which the mudstone is mainly concentrated in the Ⅲ, Ⅵ, and Ⅷ layer groups, characterized by large thickness and good continuity. (2) The low abundance of organic matter in the Quaternary mudstone, but a substantial proportion of organic matter suitable for microbial modification, and the large amount of different types of organic matter, such as hydrocarbons and algae, improve the biogas gas production capacity of the Quaternary system. (3) The Quaternary mudstone exhibits various pore types, including primary intergranular pores, dissolution pores, cracks, and a small number of organic pores. It is characterized by high porosity and permeability, although the pore radii of macropores, mesopores, and micropores are relatively small. (4) On-site analysis shows that mudstone layers are generally gas-bearing, with free gas being the main gas. Gas accumulation is prominent in brittle mineral developmental zones and tectonic high points within gas-bearing sections. (5) The loose Quaternary mudstone, with its high porosity and permeability, is controlled by various factors such as water content, overburden pressure, and mudstone thickness, and has the ability of self-containment and self-sealing properties. It is concluded that the Quaternary mudstone gas reservoir follows a formation model characterized by “integrated source and storage, brittle mineral content-controlled accumulation, mudstone thickness and pore sealing, and tectonic direction control”. Favorable areas for mudstone gas accumulation include the three major fields and the northern slope of the study area.

The heterogeneous cracking process of ultra-deep oil is well-studied, yet the geochemical evolution mechanisms of crude oil pyrolysis at the microscale remain unclear. This study conducts a closed-system gold-tube thermal simulation experiment on low-maturity crude oil to obtain pyrolysis residual oils and soluble asphaltenes at different thermal evolution stages. It also introduces the first application of optical photothermal infrared spectroscopy (O-PTIR) at submicron scales to analyze the molecular composition and functional group heterogeneity of residual organics during crude oil pyrolysis. The results indicate that in the early rapid pyrolysis phase, biomarkers in crude oil maintain source characteristics consistent with the original oil. By the end of this phase, aliphatic compounds are fully pyrolyzed, while aromatic biomarkers continue to effectively reflect the high-temperature thermal evolution degree of the crude oil. The two light oil samples exhibited similar molecular structural evolution patterns. At EasyRo = 1.33%, O-PTIR spectra display a marked absorption band near 1720 cm−1, with CH3 and CH2 maps showing strong infrared signals, revealing patchy and striped contours of residual asphaltene particles. Pseudo-van Krevelen analysis indicated the gradual generation or growth of short-chain hydrocarbons during the thermal cracking process. At EasyRo = 1.81%, the aromatization degree of compounds increased, with distinct peaks for CH3, CH2, C=C, and C=O functional groups. The 2D synchronous IR spectra showed a strong correlation between autocorrelation peaks and point spectra, with no regional enrichment, indicating a significant reduction in molecular structural heterogeneity. Furthermore, the overall trends in the 2D IR spectra of the asphaltenes were similar, with noticeable autocorrelation and positive cross peaks at 1600 and 1720 cm−1, indicating that the spectral intensity increased or decreased synchronously during thermal evolution. This study reveals, at the molecular scale, the evolution of organic compounds and functional groups during crude oil cracking and offers valuable insights for expanding O-PTIR applications in petroleum geology.

The growing shortage of helium reserves presents a pressing worldwide concern. However, it remains ambiguous that how, when, and which type of tectonic environment the helium source rocks were formed. Recently, several helium-enriched gas fields have been discovered in the northern Ordos Block and confirmed to be crust-derived. Why late Neoarchean-Paleoproterozoic effective helium source rocks are distributed in the northern Ordos Block are still not clear. Detailed petrological, geochemical, geochronology, Sr-Nd isotopic and in-situ EPMA of U,-Th rich minerals studies were analyzed on the outcrops and drill cores of the basement of the northern Ordos Block to investigate the helium source rocks. The results show that (1) Late Neoarchean-Paleoproterozoic A-type granite and S-type granitoids are effective helium source rock types, and a large amount of U-Th rich accessory minerals (e.g., phosphate minerals, zircon, magnetite et al.) are preserved in alkaline feldspar and quartz. (2) The helium source rocks are classified into distinct temporal intervals: 2.60-2.45 Ga, 2.45-2.30 Ga and 1.95-1.80 Ga, respectively. 2.60-2.45 Ga granitoids exhibit compositional signatures of I-type granites, consistent with magmatic arc tectonic settings linked to subduction zones. 2.45-2.30 Ga granitoids display both A-type and Itype granitic affinities, indicating long live continental magmatic arc environment characteristics.1.95-1.80 Ga granitoids exhibit both A-type and S-type characteristics, suggesting formation in an extensional tectonic regime following continental collision. (3) 2.60-2.45 Ga period is late Archean subduction-accretion and arc magmatism, followed by arc-continent collision; 2.45-2.30 Ga period is a long-time arc-continental accretion process with multiple arc magmatism; 1.95-1.80 Ga period represents continent-continent collision to post-collisional extension setting. Thus, the long-term arc-continental accretion and multistage crustal recycling of terrigenous sediments with high U and Th content, comparable to Phanerozoic subduction-accretionary orogens, explain why effective helium source rocks are enriched in the northern Ordos Block. By the comparison of Khondalite Belts in North China Craton with global Khondalite Belts, global Khondalite belts could be favorable areas for predicting the worldwide distribution of helium source rocks.

[Background]In recent years,promising helium-rich natural gas shows have been discovered in the Dong-ping gas field.However,the helium resources in the gas field exhibit lateral heterogeneity and vertical differential accu-mulation in multiple sequences,which restrict the further exploration of these resources.[Methods]By analyzing the lat-eral and vertical distribution characteristics of helium in the Dongping gas field,this study explored its origin and sources,analyzed the differences in geological backgrounds between helium-rich and helium-deficient gas reservoirs,and systematically summarized the differential enrichment pattern across different blocks within the Dongping gas field.[Results and Conclusions]In the Dongping gas field,helium-rich gas reservoirs are predominantly distributed in the shallowly buried Dongping-3 well block,where there is a significant positive correlation between helium and nitrogen concentrations.In contrast,the Dongping-1 and Dongping-17 well blocks exhibit gas reservoirs with a low helium con-centration.Helium in the Dongping gas field is typically of the crustal origin,derived primarily from ancient basement rocks including granites and granitic gneiss.The differential helium enrichment is jointly controlled by multiple factors,including source rock availability,groundwater dynamics,natural gas charging intensity,and tectonic framework.The Dongping-3 well block is characterized by U-and Th-rich ancient granites,active groundwater circulation,relatively weak natural gas charging,and traps located in structurally high parts,and the basement exhibits the highest helium gen-eration intensity of 1.02×10-12 cm3/(a·g).In this well block,small traps located in the structurally high parts were formed by the large-amplitude tectonic uplift during the Himalayan period.These traps are conducive to the upward migration of ancient formation water containing He and N2 at depth while also determining the small intensity of natural gas charging.Conversely,the Dongping-1 well block,despite its higher helium reserves,features weak groundwater hydrodynamics,intense natural gas charging,and traps in structurally low parts,which restrict helium migration and enrichment.The Dongping-17 well block shows the lowest helium concentration due to helium source rocks comprising schists,slates,and limestones with low U and Th concentrations and deeply buried traps.Based on research on differential helium en-richment in gas reservoirs with different basal lithologies and tectonic morphologies in the Dongping gas field,it is pre-dicted that the structurally high parts in the piedmont paleo-uplift and paleo-slope area of the Altun Mountain are poten-tially play fairways for helium enrichment.This prediction is expected to provide guidance for the subsequent helium ex-ploration and development work in the Qaidam Basin.

The Fengcheng Formation of Junggar Basin has been demonstrated as an essential target interval for fine-grained sedimentary rocks and shale oil exploration-exploitation in ancient alkaline lacustrine basin in China. However, the volcanic activities have influenced alkaline lacustrine environment to a large extent. Therefore, the characteristics and distributions of alkaline-volcanic lithofacies remain unclear. The cores, thin sections, scanning electron microscope (SEM) and wireline logs are employed to conduct research on the type, characteristics, distribution and evolution model of lithofacies in Fengcheng Formation. The results indicate that seven lithofacies are developed, including basalt, tuff aceous conglomerate/sandstone, massive/laminated/alkaline tuffaceous fine-grained sedimentary rocks, and alkaline rocks. Among them, basalt is mainly developed in lower part. The massive/laminated/alkaline tuffaceous fine-grained sedimentary rocks are mainly developed in middle part. The tuff aceous conglomerate/sandstone and alkaline rocks are mainly developed in upper part. The wireline responses of diff erent lithofacies/sub-lithofacies vary significantly in stacking patterns and value scope. However, the lithofacies/sub-lithofacies with similar genesis share similarity in wireline responses. The lithofacies/sub-lithofacies distribution generally show progradation in the northwest and retrogradation in the southwest. The lithofacies/sub-lithofacies scope of fine-grained sedimentary rocks are to a large extent related to tuff aceous conglomerate/sandstone distribution. In addition, the lithofacies/sublithofacies are influenced by paleo-environment (paleo-salinity, paleo-climate, paleo-water depth) changes and volcanic activities. The climate in early depositional period has turned into dry and hot. Subsequently, the scope of lacustrine basin starts to shrink, resulting in gradually-increasing salinity. The lithology during this period is dominated by dolomite and dolomitic rocks. However, the climate in late depositional period remains dry and hot. The lake level continues to fall and the salinity continues to increase. The alkaline minerals such as alkali are precipitated, marking the final formation of alkaline lakes and alkaline rocks..

Significant progress has been made in oil and gas exploration in the Tarim Basin, particularly in the Tazhong area. Exploration practices have shown that gas invasion influences the distribution of petroleum resources. This study uses geochemical analysis methods to investigate the distribution of physical properties, biomarkers, light hydrocarbon compositions, and carbon isotopic ratios in oil and gas reservoirs across different well blocks. The results reveal strong gas invasion in the crude oil in the TZ83 wellblock, while the ZG43 well block experiences weaker gas invasion. The study suggests that the intensity of gas invasion is influenced by the structural positions of the well blocks. The TZ83 well block, located in the high-position structural zone at the intersection of the Tazhong No.I fault slope fold belt and the strike-slip fault, is strongly affected by gas from underlying sources, resulting in condensate oil. In contrast, the ZG43 well block, situated on the platform zone of the Tazhong No.10 fault belt, has fewer deep and large fault systems, leading to weaker gas invasion and waxy oil formation. Additionally, reservoirs with shallow structural positions may contain undiscovered condensate oil accumulations. Future exploration should focus on areas near fault zones to enhance energy reserves.

The accurate prediction of the minimum miscibility pressure (MMP) for sour natural gas—reservoir oil is of paramount importance for the design and optimization of gas injection processes, particularly in enhanced oil recovery (EOR) and gas cycling schemes. This study introduces intelligent models that leverages machine learning algorithms to predict the MMP between reservoir oil and injected sour natural gas. The model is trained and validated using a comprehensive dataset encompassing various oil properties, reservoir temperature, and gas compositions commonly encountered in sour natural gas. The different machine learning methods are chosen to construct the MMP forecasting model with influential parameters affecting MMP, followed by the comparison of predictive accuracy of different approaches. Validation results demonstrate that the intelligent model achieves great predicting effects. The superior performance of model is attributed to its ability to capture intricate patterns and interactions within the dataset that are often overlooked by conventional methods. Furthermore, the intelligent model offers a user-friendly interface for rapid MMP prediction, enabling petroleum engineers to make informed decisions regarding gas injection strategies without the need for extensive laboratory experiments or complex simulations. This not only enhances operational efficiency but also contributes to cost savings and risk reduction in the development under the sour natural gas injection condition. In conclusion, the integration of machine learning techniques and comprehensive datasets provides a robust and accurate tool for the petroleum industry, facilitating the optimization of gas injection processes and thus enhancement of oil recovery from challenging reservoirs.