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

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

The study of fine-grained sedimentation has consistently concentrated on investigating the mechanisms and principles governing the enrichment of organic matter. However, the lack of unified stratigraphic framework has always existed as fine-grained sedimentation covers two distinct grain-size grades, namely, mud and silt, which has impeded the progress of subsequent production research. This study exemplified this issue by analyzing the first member of the Qingshankou Formation in the southern Songliao Basin. We established reconstructed gamma and density curves that mitigated filter noise interference, integrated high-resolution sequence results with astronomical cycle divisions, and created a high-frequency isochronous stratigraphic framework for clastic fine-grained sedimentation by leveraging the weak sensitivity of sandstone density curves and the robust stability in eccentricity cycle extraction. This approach addresses the inconsistencies in stratigraphic division methodologies and mismatched outcomes stemming from the use varying techniques to delineate mud and silt components within clastic fine-grained sedimentary sequences. Furthermore, it elucidates how tectonic-scale variations in sediment supply coupled with potential accommodation changes dictate macroscopic stacking patterns within strata, whereas climate fluctuations on orbital time scales govern sand-mud progradation degrees within these layers, culminating in periodic rhythmic characteristics characterized by vertical sand-mud interbedding. A model for stratigraphic development pertaining to lake delta systems constrained by a "synchronous heterotopy" paradigm is proposed for the southern Songliao Basin. The organic matter enrichment pattern aligns with its filling dynamics, indicating an "overfilling" type developmental pattern at lower strata levels where organic material predominantly originates from terrestrial plant debris external to the basin; this material accumulates primarily within silty zones along layers—with areas exhibiting heightened enrichment values slightly lagging behind short-eccentric maxima positions. In contrast, under an upper "balanced filling" type developmental framework, sources of organic matter are derived both internally and externally relative to the basin—exhibiting substantial heterogeneity—and regions marked by elevated organic matter concentrations are directly associated with locations identified as short-eccentric maxima. [ABSTRACT FROM AUTHOR]

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

The Upper Cretaceous Qingshankou Formation black shales, deposited in the late Turonian (LTB shales), are the main source rocks of the Songliao Basin. The origins of organic matter enrichment of the shales is a contentious subject fuelling many ongoing debates. This study investigates the genesis of the organic matter‐rich shale by using molecular geochemistry. The LTB shales can be divided into three sections. The Section I shales were deposited in saline, stratified and anoxic water conditions, which are related to seawater incursion events. At least three episodic and periodic seawater incursion events were recognized during Section I shale deposition. The Section II shales deposited in brackish to fresh and deep lake‐level conditions with high primary productivity, which are related to lake‐level transgression. The Section III shales were deposited under fresh and slightly oxidized water conditions, which are related to lake‐level regression. Two organic matter enrichment models for the LTB shales are identified, that is, the seawater incursion model and the maximum lake‐level transgression sedimentation model, which act on different shale sections, both playing significant roles in the enrichment of organic matter. [ABSTRACT FROM AUTHOR]

Due to the influence of terrigenous debris, the internal pore structure of continental shale is highly heterogeneous, and the controlling factors are complex. This paper studies the structure and controlling factors of shale reservoirs in the first member of the Qingshankou Formation in the Southern Songliao Basin using core data and various analytical test data. The results show that the original deposition and subsequent diagenesis comprehensively determine the shale reservoirs' pore structure characteristics and evolution law. According to the severity of terrigenous debris, the shale reservoirs in the study area are divided into four categories and six subcategories of lithofacies. By comparing the characteristics of different shale lithofacies reservoirs, the results show that the lithofacies with a high brittle mineral content have more substantial anti-compaction effects, more primary pores to promote retention and a relatively high proportion of mesopores/macropores. Controlling the organic matter content when forming high-quality reservoirs leads to two possibilities. An excessive organic matter content will fill pores and reduce the pore pressure resistance. A moderate organic matter content will make the inorganic diagenesis and organic hydrocarbon generation processes interact, and the development of organic matter mainly affects the development of dissolution pores. The comprehensive results show that A3 (silty laminated felsic shale) reservoirs underwent the pore evolution process of "two drops and two rises" of compaction, cementation and pore reduction, dissolution and pore increase, and organic matter cracking and pore increase, and they are the most favourable lithofacies of the shale reservoirs in the study area. [ABSTRACT FROM AUTHOR]

Based on sedimentary characteristics of the fine-grained rocks of the lower submember of second member of the Lower Cretaceous Shahezi Formation (K1sh2L) in the Lishu rift depression, combined with methods of organic petrology, analysis of major and trace elements as well as biological marker compound, the enrichment conditions and enrichment model of organic matter in the fine-grained sedimentary rocks in volcanic rift lacustrine basin are investigated. The change of sedimentary paleoenvironment controls the vertical distribution of different lithofacies types in the K1sh2L and divides it into the upper and lower parts. The lower part contains massive siliceous mudstone with bioclast-bearing siliceous mudstone, whereas the upper part is mostly composed of laminated siliceous shale and laminated fine-grained mixed shale. The kerogen types of organic matter in the lower and upper parts are types II2-III and types I-II1, respectively. The organic carbon content in the upper part is higher than that in the lower part generally. The enrichment of organic matter in volcanic rift lacustrine basin is subjected to three favorable conditions. First, continuous enhancement of rifting is the direct factor increasing the paleo-water depth, and the rise of base level leads to the expansion of deep-water mudstone/shale deposition range. Second, relatively strong underwater volcanic eruption and rifting are simultaneous, and such event can provide a lot of nutrients for the lake basin, which is conducive to the bloom of algae, resulting in higher productivity of types I-II1 kerogen. Third, the relatively dry paleoclimate leads to a decrease in input of fresh water and terrestrial materials, including Type III kerogen from terrestrial higher plants, resulting in a water body with higher salinity and anoxic stratification, which is more favorable for preservation of organic matter. The organic matter enrichment model of fine-grained sedimentary rocks of volcanic rift lacustrine basin is established, which is of reference significance to the understanding of the organic matter enrichment mechanism of fine-grained sedimentary rocks of Shahezi Formation in Songliao Basin and even in the northeast China. [ABSTRACT FROM AUTHOR]

Based on the observation and analysis of cores and thin sections, and combined with cathodoluminescence, laser Raman, fluid inclusions, and in-situ LA-ICP-MS U-Pb dating, the genetic mechanism and petroleum geological significance of calcite veins in shales of the Cretaceous Qingshankou Formation in the Songliao Basin were investigated. Macroscopically, the calcite veins are bedding parallel, and show lenticular, S-shaped, cone-in-cone and pinnate structures. Microscopically, they can be divided into syntaxial blocky or columnar calcite veins and antitaxial fibrous calcite veins. The aqueous fluid inclusions in blocky calcite veins have a homogenization temperature of 132.5-145.1 °C, the in-situ U-Pb dating age of blocky calcite veins is (69.9±5.2) Ma, suggesting that the middle maturity period of source rocks and the conventional oil formation period in the Qingshankou Formation are the sedimentary period of Mingshui Formation in Late Cretaceous. The aqueous fluid inclusions in fibrous calcite veins with the homogenization temperature of 141.2-157.4 °C, yields the U-Pb age of (44.7±6.9) Ma, indicating that the middle-high maturity period of source rocks and the Gulong shale oil formation period in the Qingshankou Formation are the sedimentary period of Paleocene Yi'an Formaiton. The syntaxial blocky or columnar calcite veins were formed sensitively to the diagenetic evolution and hydrocarbon generation, mainly in three stages (fracture opening, vein-forming fluid filling, and vein growth). Tectonic extrusion activities and fluid overpressure are induction factors for the formation of fractures, and vein-forming fluid flows mainly as diffusion in a short distance. These veins generally follow a competitive growth mode. The antitaxial fibrous calcite veins were formed under the driving of the force of crystallization in a non-competitive growth environment. It is considered that the calcite veins in organic-rich shale of the Qingshankou Formation in the study area has important implications for local tectonic activities, fluid overpressure, hydrocarbon generation and expulsion, and diagenesis-hydrocarbon accumulation dating of the Songliao Basin. [ABSTRACT FROM AUTHOR]

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

The extremely thick dark mudstone of the Permian Linxi Formation in the Kundu-Taohaiyingzi area of northeastern China is a promising potential area for shale gas prospecting in the periphery of the Songliao Basin. This study involved a geological field survey, outcrop sample collection, and comprehensive geochemical analysis to conduct an in-depth analysis of the organic matter enrichment and hydrocarbon generation potential of the dark mudstone of the target zone, using organic petrology and organic geochemistry. The results show that the thermal maturity of the dark mudstone of the Linxi Formation is in the mature to high-mature stage. The organic matter is dominated by type II kerogen and supplemented by type III kerogen, and the average total organic carbon content is 0.76%, classifying it as a medium-good source rock. The main peak of carbon numbers is primarily distributed between nC17 and nC19, with a smaller amount at nC21. The distribution of n-alkanes follows a pre-peak pattern characterized by medium and low carbon numbers, suggesting that the organic matter originates from aquatic plants, bacteria, and algae. Combined with the fact that the ratios of pristine and phytane (Pr/Ph) are mainly distributed in the range of 0.99-1.33, the sedimentary environment is a weakly reduced to weakly oxidized lacustrine bay. The systematic analysis of the source rocks of the Upper Permian Linxi Formation in the Kundu-Taohaiyingzi area indicates favorable prospects for shale gas exploration. Utilizing a comprehensive superposition method of geological information, this article identified the Yamen Gacha-Saihan Tala area as a potential area for shale gas exploration. [ABSTRACT FROM AUTHOR]

In the unconventional energy sector, shale oil is increasingly recognized as a crucial supplement to production. In recent years, China has made significant advancements in the development of shale oil. A unique type of pure shale reservoir in the Songliao Basin, distinct from established shale oil reservoirs worldwide, has emerged as a focal point for exploration and research endeavors. This kind of shale exhibits enhanced heterogeneity, high clay content, intricate rock electricity relationship, posing significant challenges to formation evaluation. This study introduces conversion coefficients for the elements and minerals, a decision tree model, a variable T2 cutoff value method, and 2D NMR cluster analysis, all based on the integration of microimaging, spectroscopy, and 2D NMR logging. These novel approaches facilitate a comprehensive geological quality evaluation of key parameters, including mineral composition, lithology, effective porosity, total organic carbon content, fluid composition, and saturation characteristics within pure shale formations from the Songliao Basin. The established petrophysical model has been validated by core analysis data and successfully applied in exploration wells. Through systematic petrophysical analysis, the optimal landing point for horizontal wells was identified based on the identification of the best reservoir quality interval with high movable oil and oil saturation. The subsequent drilling of horizontal wells demonstrated the reliability of petrophysical evaluation in terms of oil production. This integrated evaluation method for pure shale holds reference significance for similar shale reservoirs in other blocks in the future. [ABSTRACT FROM AUTHOR]

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

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

Based on the observation and analysis of cores and thin sections, and combined with cathodoluminescence, laser Raman, fluid inclusions, and in-situ LA-ICP-MS U-Pb dating, the genetic mechanism and petroleum geological significance of calcite veins in shales of the Cretaceous Qingshankou Formation in the Songliao Basin were investigated. Macroscopically, the calcite veins are bedding parallel, and show lenticular, S-shaped, cone-in-cone and pinnate structures. Microscopically, they can be divided into syntaxial blocky or columnar calcite veins and antitaxial fibrous calcite veins. The aqueous fluid inclusions in blocky calcite veins have a homogenization temperature of 132.5–145.1 °C, the in-situ U-Pb dating age of blocky calcite veins is (69.9±5.2) Ma, suggesting that the middle maturity period of source rocks and the conventional oil formation period in the Qingshankou Formation are the sedimentary period of Mingshui Formation in Late Cretaceous. The aqueous fluid inclusions in fibrous calcite veins with the homogenization temperature of 141.2–157.4 °C, yields the U-Pb age of (44.7±6.9) Ma, indicating that the middle-high maturity period of source rocks and the Gulong shale oil formation period in the Qingshankou Formation are the sedimentary period of Paleocene Yi'an Formaiton. The syntaxial blocky or columnar calcite veins were formed sensitively to the diagenetic evolution and hydrocarbon generation, mainly in three stages (fracture opening, vein-forming fluid filling, and vein growth). Tectonic extrusion activities and fluid overpressure are induction factors for the formation of fractures, and vein-forming fluid flows mainly as diffusion in a short distance. These veins generally follow a competitive growth mode. The antitaxial fibrous calcite veins were formed under the driving of the force of crystallization in a non-competitive growth environment. It is considered that the calcite veins in organic-rich shale of the Qingshankou Formation in the study area has important implications for local tectonic activities, fluid overpressure, hydrocarbon generation and expulsion, and diagenesis-hydrocarbon accumulation dating of the Songliao Basin.

The Upper Cretaceous Qingshankou Formation in the Songliao Basin contains thick, widespread, and organic matter-rich shale layers, offering abundant shale oil resources. Studying the sedimentary environment during shale formation and exploring the oil-bearing characteristics of shale oil enrichment intervals provide a theoretical basis for the prediction of the intervals and sweet spots. Based on previous research, the study compared organic carbon content, pyrolysis data, types of organic macerals, and major and trace elements of samples from two typical wells of different sags, well GY8HC in the Gulong Sag and well ZY1 in the Sanzhao Sag, in the central depression zone of the Songliao Basin. The analysis delved into the differences in oil-bearing characteristics and sedimentary environment of the Qingshankou Formation shales in two different sags, further analyzing the factors influencing these differences. The oil-bearing indicators of shales from the two wells in the Qingshankou Formation of the Songliao Basin showed that the total organic carbon (TOC) content in well ZY1 was significantly higher than that in well GY8HC. However, the free hydrocarbon content (S1) and oil saturation index (OSI) in well ZY1 were lower than those in well GY8HC. The geochemical environment during shale formation controlled organic matter enrichment. Comparing major and trace elements in samples from both wells, it was found that the climate in well ZY1 was more humid during its sedimentary period, the water body had stronger reducing conditions, and its paleoproductivity and paleo-water depth were significantly higher than those in well GY8HC. These conditions were favorable for the preservation of organic matter, thereby forming a higher organic matter abundance in the shale of well ZY1. In addition, it was found that the organic matter type in well GY8HC is mainly Type Ⅰ, sapropelic kerogen, at a mature to highly mature stage, whereas well ZY1 contains mainly Type Ⅱ1 kerogen, with less Type Ⅰ, at a low to mature stage. Therefore, the shale in well GY8HC possesses better oil generation potential.

A new pore type, nano-scale organo-clay complex pore-fracture was first discovered based on argon ion polishing-field emission scanning electron microscopy, energy dispersive spectroscopy and three-dimensional reconstruction by focused ion-scanning electron in combination with analysis of TOC, Ro values, X-ray diffraction etc. in the Cretaceous Qingshankou Formation shale in the Songliao Basin, NE China. Such pore characteristics and evolution study show that: (1) Organo-clay complex pore-fractures are developed in the shale matrix and in the form of spongy and reticular aggregates. Different from circular or oval organic pores discovered in other shales, a single organo-clay complex pore is square, rectangular, rhombic or slaty, with the pore diameter generally less than 200 nm. (2) With thermal maturity increasing, the elements (C, Si, Al, O, Mg, Fe, etc.) in organo-clay complex change accordingly, showing that organic matter shrinkage due to hydrocarbon generation and clay mineral transformation both affect organo-clay complex pore-fracture formation. (3) At high thermal maturity, the Qingshankou Formation shale is dominated by nano-scale organo-clay complex pore-fractures with the percentage reaching more than 70% of total pore space. The spatial connectivity of organo-clay complex pore-fractures is significantly better than that of organic pores. It is suggested that organo-complex pore-fractures are the main pore space of laminar shale at high thermal maturity and are the main oil and gas accumulation space in the core area of continental shale oil. The discovery of nano-scale organo-clay complex pore-fractures changes the conventional view that inorganic pores are the main reservoir space and has scientific significance for the study of shale oil formation and accumulation laws.

Cyclostratigraphy is widely applied in establishing high-precision sequence stratigraphic frameworks and astronomical time scales, making it an important field in the quantitative study of sedimentology. A detailed cyclostratigraphic analysis of natural gamma-ray logging data from the upper cretaceous Sifangtai formation in Qian’an area of Songliao basin was conducted in this paper. Spectral analysis results show that Sifangtai formation exhibits sedimentary cycles of 40.2, 10.6-13.1, 3.6-3.8, and 1.79-2.4 m. The ratio of these cycles is approximately the same as the ratio of Late Cretaceous astronomical orbital periods, specifically 20∶5∶2∶1, corresponding to sedimentary cycle periods of 405 ka long eccentricity, about 106 ka short eccentricity, about 38 ka obliquity, and about 21 ka precession cycles. The COCO statistical test results indicate that the sedimentation rate of the Sifangtai formation is about 9.78 cm/ka, which aligns with these astronomical periods. Filtering the sedimentary cycle corresponding to the 405 kyr long eccentricity period, eight sedimentary cycles were identified. Using the 405 kyr long eccentricity period, an astronomical tuning was performed on the GR data sequence, establishing a floating astronomical time scale. This provides a sedimentary duration of 3.23 million years for the Sifangtai formation. By referencing the chronological stratigraphic framework of the Mingshui formation and the Sifangtai formation in the Songke-1 well in the northern basin, the sedimentary duration of the uranium-bearing sand body in the study area was determined. The results show that the optimal sedimentation rate variations of the Sifangtai formation in the study area are consistent with the lithological changes, and can be divided into two high-value zones: the top and the bottom. The bottom high-value zone corresponds to the medium to coarse sandstone section of the lowstand systems tract at the early stage of the Sifangtai formation deposition, which is the main uranium mineralized sandstone layer in the Qian’an area. The top high-value zone corresponds to the regressive systems tract at the end of the Sifangtai formation, which is in conformable contact with the Mingshui formation above it. The thickness of the sandstone revealed by drilling in this section is relatively thin and its distribution is relatively limited. In addition, the sedimentation rate of the lower red mudstone and grayish-white medium to coarse sandstone section of the Sifangtai formation is significantly lower than that of the upper gray mudstone section. This indicates that during this period, under the background of a dry and hot climate, the lake basin shrank, the braided river delta prograded, and the tectonic conditions were stable. The basin accommodation space grew slowly, characterized by overcompensated infilling, and the sedimentary system was stable, favoring the formation of large-scale sand-mud combination structures. This provides favorable strata for the formation of sandstone-type uranium deposits. Uranium mineralization in sandstone in the Qian’an area develops in the lower part of the Sifangtai formation, with the sand body deposition duration estimated to be ((75.36-76.09)±0.40) Ma. The study results indicate that cyclostratigraphic analysis can be effectively applied to the exploration of sandstone-type uranium deposits. It can accurately determine the deposition period of uranium-bearing sandstone layers, making it an effective method for regional target layer identification, comparison, and exploration target area delineation.

Terrestrial sedimentary basins are influenced by rapid changes in the clay content, resulting in significant differences in the lateral sealing capacity (shale gouge ratio, SGR) of different parts of the fault. In the present study, we used a method of setting virtual wells and using seismic inversion data to accurately calculate the SGR of faults in strata composed of interbedded sandstone and mudstone calculate the clay content of the strata and to compensate for the low level of the actual well control. Optimal well spacing was determined based on the variable clay content of the formation. The planar variation of the fault throw was characterized via seismic interpretation. We also examined the lateral sealing of faults. The Putaohua oil layer in the S14 area of the Sanzhao Sag in the Songliao Basin was chosen as an case study. Based on the calculation of fault SGR values and the oil distribution, the evaluation criteria for the fault sealing capacity were determined, and the changes in the lateral sealing capacity of the faults were analyzed. This approach accurately estimates fault SGR values and predicts the effective oil-bearing area within the fault zone. It is also suitable for evaluating the lateral sealing of faults in strata composed of interbedded sandstone and mudstone. Our findings provide an in-depth understanding of the lateral sealing of faults and can aid in further research on petroleum distribution patterns. [ABSTRACT FROM AUTHOR]

Low-maturity shale oil predominates in shale oil resources. China's onshore shale oil, particularly the Cretaceous Nenjiang Formation in the Songliao Basin, holds significant potential for low-maturity shale oil, presenting promising exploration and development prospects. This study delves into the hydrocarbon generation conditions, reservoir characteristics, and oil-bearing property analysis of the mud shale from the Nen-1 and Nen-2 sub-formations of the Nenjiang Formation to pinpoint favorable intervals for shale oil exploration. Through the integration of lithology, pressure, and fracture distribution data in the study area, favorable zones were delineated. The Nen-1 sub-formation is widely distributed in the Changling Depression, with mud shale thickness ranging from 30 to 100 m and a total organic content exceeding 2.0%. Type I kerogen predominated as the source rock, while some samples contained type II kerogen. Organic microcomponents primarily comprised algal bodies, with vitrinite reflectance (Ro) ranging from 0.5% to 0.8%. Compared to Nen-1 shale, Nen-2 shale exhibited less total organic content, kerogen type, and thermal evolution degree, albeit both are conducive to low-maturity shale oil generation. The Nen-1 and Nen-2 sub-formations predominantly consist of clay, quartz, feldspar, calcite, and pyrite minerals, with minor dolomite, siderite, and anhydrite. Hydrocarbons primarily reside in microfractures and micropores, including interlayer micropores, organic matter micropores, intra-cuticle micropores, and intercrystalline microporosity, with interlayer and intra-cuticle micropores being dominant. The free oil content (S1) in Nen-1 shale ranged from 0.01 mg/g to 5.04 mg/g (average: 1.13 mg/g), while in Nen-2 shale, it ranged from 0.01 mg/g to 3.28 mg/g (average: 0.75 mg/g). The Nen-1 and Nen-2 sub-formations are identified as potential intervals for shale oil exploration. Considering total organic content, oil saturation, vitrinite reflectance, and shale formation thickness in the study area, the favorable zone for low-maturity shale oil generation is primarily situated in the Heidimiao Sub-Depression and its vicinity. The Nen-2 shale-oil-enriched zone is concentrated in the northwest part of the Heidimiao Sub-Depression, while the Nen-1 shale-oil-enriched zone lies in the northeast part. [ABSTRACT FROM AUTHOR]

Describing the organic-inorganic pore evolution influenced by mineral composition is crucial for characterizing shale oil storage capacity and flow in shale, and it also helps predict storage capacity for sequestered CO2. Using laboratory pyrolysis experiments to artificially mature shale samples at relatively high temperatures and short times, this study compares a series of natural samples with different thermal maturations, which can better reflect the real underground pore evolution. A total of 30 natural shales spanning from low to high maturity were collected from the Cretaceous Qingshankou Formation of the Songliao Basin, and the analysis results revealed four main typical shales, namely argillaceous shale, felsic shale, calcareous shale, and mixed shale. The existence of clay minerals, quartz and feldspar promote the development of > 50 nm pores, while 0-20 nm pores are mainly developed in clay minerals and organic matter. When the content of total organic carbon is less than 2.5 wt.%, it displays a positive correlation with the specific surface area, but the correlation becomes negative for samples with a content of total organic carbon greater than 2.5 wt.%. The organic pores are most developed at the peak oil maturity, while inorganic pores are most developed during the oil window, and tend to be stable at high maturity. Argillaceous shale in the high maturity stage may be favorable for petroleum exploration in the Qingshankou Formation of the Songliao Basin. Mixed shale and calcareous shale may not be conducive to the short-term storage of CO2 due to strong reactions with CO2 at the beginning. On the other hand, argillaceous shale and felsic shale may be conducive to the long-term storage of CO2. [ABSTRACT FROM AUTHOR]

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

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

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

Numerical forward modelling and laboratory experiments suggest that autogenic factors in the sediment routing system serve as long‐pass filters, preserving only orbital cycles with a period exceeding the compensation timescale, Tc, or thickness in the depth domain exceeding the compensation depth scale, Hc. For a specific orbital cycle with a certain period, this preservation in alluvial strata occurs unless it exhibits a sufficiently large amplitude. This study stratigraphically confirms, for the first time, the long‐pass filtering of autogenic dynamics using elemental data from the alluvial–lacustrine Sifangtai and Mingshui formations in the Songliao Basin. Spectral analysis of the Si and Zr series in coarse‐grained sediments reveals no cyclic signal with thicknesses below the estimated lower limits of Hc. This implies that the spatial storage threshold for orbital cycles in proxies of the coarse‐grained sediment component is equal to or less than Hc. However, cyclic signals of obliquity and precession with smaller thicknesses are identified in Ti, Fe and Al enriched in the fine‐grained sediment components of the stratigraphy. Notably, previously reported proxies preserving high‐frequency orbital cycles are derived from fine‐grained sediment components, differing from the sedimentation rate series used in the reported experimental studies. Therefore, the authors hypothesize a grain‐size component‐dependent storage threshold, suggesting that the storage threshold of orbital cycles in proxies associated with fine‐grained components is lower. This hypothesis arises from the weaker effect of autogenic dynamics on the content of fine‐grained sediment components transported to the sampling site by a suspended load compared to coarser components that are subjected to stronger autogenic dynamics within or near channels. The hypothesis and model presented propose a dynamic process elucidating the nuanced roles of autogenic dynamics in preserving orbital cycles. This perspective, considering sediment composition, inspires prioritizing proxies enriched in the fine‐grained fraction for identifying allogenic cycles in alluvial strata. [ABSTRACT FROM AUTHOR]

A new pore type, nano-scale organo-clay complex pore-fracture was first discovered based on argon ion polishing- field emission scanning electron microscopy, energy dispersive spectroscopy and three-dimensional reconstruction by focused ion-scanning electron in combination with analysis of TOC, Ro values, X-ray diffraction etc. in the Cretaceous Qingshankou Formation shale in the Songliao Basin, NE China. Such pore characteristics and evolution study show that: (1) Organo- clay complex pore-fractures are developed in the shale matrix and in the form of spongy and reticular aggregates. Different from circular or oval organic pores discovered in other shales, a single organo-clay complex pore is square, rectangular, rhombic or slaty, with the pore diameter generally less than 200 nm. (2) With thermal maturity increasing, the elements (C, Si, Al, O, Mg, Fe, etc.) in organo-clay complex change accordingly, showing that organic matter shrinkage due to hydrocarbon generation and clay mineral transformation both affect organo-clay complex pore-fracture formation. (3) At high thermal maturity, the Qingshankou Formation shale is dominated by nano-scale organo-clay complex pore-fractures with the percentage reaching more than 70% of total pore space. The spatial connectivity of organo-clay complex pore-fractures is significantly better than that of organic pores. It is suggested that organo-complex pore-fractures are the main pore space of laminar shale at high thermal maturity and are the main oil and gas accumulation space in the core area of continental shale oil. The discovery of nano-scale organo-clay complex pore-fractures changes the conventional view that inorganic pores are the main reservoir space and has scientific significance for the study of shale oil formation and accumulation laws. [ABSTRACT FROM AUTHOR]

The exploration level of tight sandstone gas reservoirs in the Denglouku Formation (DF) in the Xujiaweizi Fault Depression is low, and hydrocarbon source and accumulation process remain unclear. Through the analysis of natural gas geochemistry, X-ray diffraction, thin section observation, scanning electron microscope, physical property testing, cathodoluminescence, fluid inclusions, and basin simulation, we examine source of hydrocarbon, the period of hydrocarbon accumulation, and the evolution of physical properties of the tight sandstone gas in the DF. Additionally, the formation process of tight sandstone gas reservoirs in the DF is discussed. The results reveal the following: (1) the tight sandstone gas in the DF is categorized as III kerogen cracking gas, primarily sourced from dark mudstone of the second member of the DF, with some contribution from dark mudstone of the Shahezi Formation. (2) The tight sandstone in the DF is in stage B of middle diagenesis. Based on apparent compaction rate, apparent cementation rate, and apparent dissolution rate, it can be divided into four diagenetic facies: (1) strong compaction–medium cementation–weak dissolution facies; (2) medium compaction–strong cementation–medium dissolution facies; (3) medium compaction–strong cementation–weak dissolution facies; and (4) medium compaction–medium cementation–medium dissolution facies. The predominant diagenetic facies are the medium compaction–strong cementation–medium dissolution facies and medium compaction–medium cementation–medium dissolution facies. (3) The hydrocarbon charging period of the DF in study area ranged from 98 to 67.5 Ma. This period is earlier than the tight period of the strong compaction–medium cementation–weak dissolution facies sandstone and later than the tight period of the medium compaction–strong cementation–medium dissolution facies, medium compaction–strong cementation–weak dissolution facies, and medium compaction–medium cementation–medium dissolution facies sandstone. Consequently, two types of tight sandstone gas reservoirs exist in study area: (1) tight sandstone gas reservoir with tight first and then accumulation type and (2) composite tight sandstone gas reservoirs. Our research offers theoretical instruction for exploration of deep tight sandstone gas in northern Songliao Basin. [ABSTRACT FROM AUTHOR]

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This study addresses the unclear understanding of the primary factors controlling fluid mobility in the tuff reservoirs of the Huoshiling Formation from the Dehui Fault Depression, southeastern Songliao Basin. Through physical property analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thin section (TS), pressure-controlled porosimetry (PCP), rate-controlled porosimetry (RCP), and nuclear magnetic resonance experiments (NMR) on ten tuff samples, we conducted a comprehensive and in-depth exploration of the influencing factors that control the mobility of reservoir fluids. The results indicate: 1) The primary mineral types in the tuff reservoirs are quartz, feldspar, and clay minerals, with porosity predominantly characterized by dissolution pores and intergranular pores; 2) Based on the morphology of PCP intrusion curves, the tuff samples from the study area can be categorized into three types, with reservoir quality progressively deteriorating from Type I to Type III; 3) Compared to the movable fluids saturation (MFS), movable fluids porosity (MFP) is more suitable for characterizing fluid mobility. The mobility of fluids is influenced by various factors such as mineral composition, physical property, pore-throat connectivity, pore type and heterogeneity. MFS and MFP show a positive correlation with permeability, the content of quartz and feldspar, median pore-throat radius (R50), average throat radius (ATR), average pore-throat radius ratio (APT), T2 cutoff value (T2-C), average throat radius (RT), sorting coefficient (SC), and intergranular pore dominate space (Inter-DS), while a negative correlation with the content of calcite and clay minerals, average pore-throat radius ratio, and the fractal dimension from NMR (DNMR). This study elucidates the influencing factors of fluid mobility in tuff reservoirs, which has important reference significance for the scientific development of this type of gas reservoir.

The study of fine-grained sedimentation has consistently concentrated on investigating the mechanisms and principles governing the enrichment of organic matter. However, the lack of unified stratigraphic framework has always existed as fine-grained sedimentation covers two distinct grain-size grades, namely, mud and silt, which has impeded the progress of subsequent production research. This study exemplified this issue by analyzing the first member of the Qingshankou Formation in the southern Songliao Basin. We established reconstructed gamma and density curves that mitigated filter noise interference, integrated high-resolution sequence results with astronomical cycle divisions, and created a high-frequency isochronous stratigraphic framework for clastic fine-grained sedimentation by leveraging the weak sensitivity of sandstone density curves and the robust stability in eccentricity cycle extraction. This approach addresses the inconsistencies in stratigraphic division methodologies and mismatched outcomes stemming from the use varying techniques to delineate mud and silt components within clastic fine-grained sedimentary sequences. Furthermore, it elucidates how tectonic-scale variations in sediment supply coupled with potential accommodation changes dictate macroscopic stacking patterns within strata, whereas climate fluctuations on orbital time scales govern sand-mud progradation degrees within these layers, culminating in periodic rhythmic characteristics characterized by vertical sand-mud interbedding. A model for stratigraphic development pertaining to lake delta systems constrained by a “synchronous heterotopy” paradigm is proposed for the southern Songliao Basin. The organic matter enrichment pattern aligns with its filling dynamics, indicating an “overfilling” type developmental pattern at lower strata levels where organic material predominantly originates from terrestrial plant debris external to the basin; this material accumulates primarily within silty zones along layers—with areas exhibiting heightened enrichment values slightly lagging behind short-eccentric maxima positions. In contrast, under an upper “balanced filling” type developmental framework, sources of organic matter are derived both internally and externally relative to the basin—exhibiting substantial heterogeneity—and regions marked by elevated organic matter concentrations are directly associated with locations identified as short-eccentric maxima.

Shale oil and gas resources mainly exist in the pore and fracture system. Quantitative characterization of pore development characteristics and gas-bearing properties is crucial for shale reservoir evaluation. The pore development of shale reservoir exhibits strong complexity and heterogeneity, and research on pore development characteristics of coal measure shale lags behind that of marine shale reservoir. Hence, it is urgent to investigate the pore heterogeneity characteristics of coal-bearing shale and its influence on gas bearing properties. Therefore, the coal-bearing Cretaceous Nenjiang shales from the Songyuan area of the Songliao Basin were selected as the research object in this study. Through total organic carbon (TOC) analysis, X-ray diffraction experiments, porosity analysis, nitrogen adsorption–desorption experiments, and methane isothermal adsorption experiments, the characteristics of pore structure, heterogeneity, and gas bearing properties of coal-bearing shale were analyzed. The influence of rock and mineral components on pore structure and heterogeneity characteristics, the relationship between pore structure characteristics and fractal characteristics, and the effects of pore structure and heterogeneity on gas bearing properties were also discussed. The results show that: (1) The organic matter abundance of the shale in the Nenjiang Formation does not change significantly (the average TOC content is 2.38%). Ink bottle-shaped pores are mostly developed, and the Nenjiang shale is rich in clay minerals (average content 55.6%), with slit-shaped pores mostly developed. The pore surface of shale exhibits obvious fractal characteristics, with average fractal dimensions D1 and D2 of 2.54 and 2.74, respectively, indicating that the internal structure is more complex than the surface structure. (2) The enrichment of organic carbon increases the specific surface area by affecting the development of micropores and pores, consequently increasing the fractal dimension of pores. Similarly, the development of clay minerals increases the number of mesopores and macropores, thereby increasing the fractal dimension of pores. (3) Small pores develop larger specific surface areas, which increases the complexity and heterogeneity of the pore structure. This promotes remarkable fractal characteristics, expands the adsorption sites, and improves the adsorption capacity. This work will provide a scientific theoretical basis for the comprehensive evaluation of coal-bearing shale reservoirs and research on shale gas reservoir formation theory.

Geochemistry of noble gases has been applied to the study of deep Earth materials and celestial meteorites. With advancements in measurement technology, it is also increasingly being used in natural gas research. Using the most advanced noble gas mass spectrometer, a systematic analysis was conducted on the abundance and isotopes of noble gas samples collected from the middle and deep Songliao Basin in eastern China to elucidate the compositional characteristics of noble gases in a faulted basin. The findings reveal that the abundance of noble gases in natural gas decreases from light noble gases to heavy noble gases in a left-to-right reversed L-shaped pattern. Specifically, the isotopic ratios of noble gases are: 3He/4He at 2.64×10-6, 20Ne/22Ne at 9.94, 21Ne/22Ne at 0.029 22, and 40Ar/36Ar at 743.7, all of which are higher than atmospheric values. The isotopes 80Kr, 84Kr, 86Kr, and 131-136Xe show relative excess compared to atmospheric levels, indicating the mixing of mantle-derived gases in the natural gas. Based on the compositional characteristics of noble gases, this study suggests that the natural gas in the middle and deep Songliao Basin originated from inorganic crust and mantle mixing. Additionally, certain differences exist in the contribution of mantle-derived components across different tectonic blocks and categories of natural gas within the basin. Comparison between noble gas compositions and the types of natural gas demonstrates that light noble gases distinguish effectively between different types of natural gas, whereas the composition of heavy noble gases shows no significant differences among various types of natural gas. Noble gas isotopes, in addition to tracing the source of natural gas, can also be used to determine natural gas genesis, distinguish natural gas types and characterize tectonic settings.

The Lower Cretaceous Shahezi Formation glutenite reservoirs in the Xujiaweizi Fault Depression are important tight gas reservoirs in the deep strata of the Songliao Basin. Their complex porosity and permeability relationships pose challenges to determining reservoir boundaries and evaluating reservoir grades. For the Shahezi Formation glutenite reservoirs, the water film thickness method, charge dynamics method, gas testing productivity method, and buoyancy balance method were used to determine theoretical lower limits, gas accumulation lower limits, effective flow lower limits, and reservoir-forming upper limits. The petrophysical values of the reservoir boundaries were determined based on the porosity and permeability relationships under different diagenetic controlling factors. On this basis, reservoir types were classified according to differences in microscopic pore structures, and a grading evaluation standard for tight reservoirs was established. This standard was then applied using logging data to provide a basis for selecting sweet spots in the tight gas exploration areas. The Shahezi Formation glutenite was divided into conventional reservoirs, Class Ⅰ-Ⅳ tight glutenite reservoirs, and non-reservoirs. The reservoir boundaries and classification evaluation results were well matched. Conventional reservoirs had porosity greater than 9% and permeability greater than 0.05×10-3 μm2. Class Ⅰ tight reservoirs had porosity of 8%-9% and permeability of (0.01-0.05)×10-3 μm2. Class Ⅱ tight reservoirs had porosity of 5%-8% and permeability of (0.001-0.01)×10-3 μm2. Class Ⅲ tight reservoirs had porosity of 3.5%-5% and permeability of (0.2-1)×10-3 μm2. Class Ⅳ tight reservoirs had porosity of 2%-3.5% and permeability of (0.05-0.2)×10-6 μm2. Non-reservoirs had porosity less than 2% and permeability less than 0.05×10-6 μm2. The gas production of tight glutenite was controlled by the reservoir type. Class Ⅰ and Class Ⅱ tight reservoirs were favorable high-yield layers. The thickness of favorable reservoirs in the Anda-Songzhan area of the northern Xujiaweizi Fault Depression was large, making it a sweet spot for tight gas exploration and development.

The exploration of continental shale oil in China has made a breakthrough in many basins, but the pure shale type has only been found in the Qingshankou Formation, Gulong Sag, Songliao Basin, and the evaluation of shale oil occurrence and sweet spot faces great challenges. Using information about the total organic carbon (TOC), Rock-Eval pyrolysis, vitrinite reflectance (Ro), kerogen elemental composition, carbon isotopes, gas chromatography (GC), bitumen extraction, and component separation, this paper systematically studies the organic geochemical characteristics and shale oil occurrence at the Qingshankou Formation. The G1 well, which was cored through the entire section of the Qingshankou Formation in the Gulong Sag, was the object of this study. On this basis, the favorable sweet spots for shale oil exploration are predicted. It is concluded that the shale of the Qingshankou Formation has high organic heterogeneity in terms of organic matter features. The TOC content of the source rocks in the Qingshankou Formation is enhanced with the increase in the burial depth, and the corresponding organic matter types gradually changed from Ⅱ2 and Ⅱ1 types to the Ⅰ type. The distribution of Ro ranges from 1.09% to 1.67%, and it is the mature to high-mature evolution stage that generates a large amount of normal crude oil and gas condensate. The high-quality source rocks of good to excellent grade are mainly distributed in the Qing 1 member and the lower part of the Qing 2 member. After the recovery of light hydrocarbons and the correction of pyrolytic heavy soluble hydrocarbons, it is concluded that the occurrence state of shale oil in the Qingshankou Formation is mainly the free-state form, with an average value of 6.9 mg/g, and there is four times as much free oil as adsorbed oil. The oil saturation index (OSI), mobile hydrocarbon content, Ro, and TOC were selected to establish the geochemical evaluation criteria for shale oil sweet spots in the Qingshankou Formation. The evaluation results show that interval 3 and interval 5 of the Qingshankou Formation in the G1 well are the most favorable sections for shale oil exploration. [ABSTRACT FROM AUTHOR]

Shallow-water deltas serve as a critical area for the exploration and development of terrestrial lacustrine oil and gas reservoirs. Current research on oil and gas exploration and development in China's terrestrial lacustrine basins primarily focuses on their delta front facies zones. Despite extensive discussions on the sedimentary characteristics of shallow-water deltas by predecessors, there is a lack of comprehensive analysis on the combined effects of dynamic factors such as climate change, lake level fluctuations, and sediment supply. This paper, through a detailed examination of 12 core samples and integrating data from 493 exploratory, appraisal, and development wells in the study area, establishes a stratigraphic correlation framework using well–seismic integration techniques. It identifies two main sedimentary facies types in the southern Da'anbei area of the Songliao Basin: shallow-water deltas and lake facies, which can be further subdivided into four sub-facies and nine microfacies. Two depositional models for the shallow-water deltas of the Southern Songliao Nenjiang Formation are established: a deeper water background with channel-river mouth bar sequences forming the delta front framework and a shallower water background with channel-sheet sand sequences forming the delta front framework. This paper also discusses the controlling effects of paleoclimate, sediment supply, and lake level changes on sedimentary evolution, providing a scientific basis for the exploration of lithologic oil and gas reservoirs in the Nenjiang Formation of the study area and the deployment of horizontal wells. [ABSTRACT FROM AUTHOR]

Characterizing the microscopic pore systems in shale reservoirs is crucial for understanding their impact on shale oil and gas enrichment. Although significant strides have been made in understanding the pore structure characteristics, research on pore structures related to small-scale sedimentary structures remains limited. This study investigated the multi-scale nanopore structure characterization and its coupling relationship with sedimentary structures using comprehensive analyses of cores, field-emission scanning electron microscopy, and gas (CO2 and N2) physisorption quantification from the Upper Cretaceous Qingshankou Formation, Southern Songliao Basin, NE China. Three lithofacies were identified based on sedimentary structures: wavy laminated shale, horizontally laminated shale, and homogeneously laminated shale. Both organic and inorganic pores (interparticle pores and intraparticle pores) are generally present in shale samples. The pore size distribution displays a multi-peak pattern, with mesopores contributing to approximately 57% of the total pore volume, micropores contributing to about 31%, and macropores accounting for a small portion of the total pore volume. The pore evolution of different lithofacies shales varies due to the influence of clay minerals, quartz content, and total organic carbon (TOC) content, resulting in the substantial heterogeneity and complex pore structure characteristics of existing reservoirs. Additionally, wavy laminated shales are more favorable to lacustrine shale exploration than other lithofacies. This study offers an enhanced methodology for determining which lithofacies may be most advantageous for future shale oil exploitation. [ABSTRACT FROM AUTHOR]

The lithospheric thermal structure (LTS) not only reflects the thermal state of the Earth's interior but also controls the formation and distribution of geothermal resources. However, related research in the Songliao Basin (SB) has focused mainly on the northern or southern parts of the basin, with limited basin-scale thermal state studies. Thus, we combined published heat flow (HF) data and thermal parameters from the northern SB with new thermal information from the southern SB to study the LTS of the entire basin. The results show that the SB has a terrestrial HF (q0) of 73.89 ± 14.25 mW m−2, a temperature gradient of 41.41 ± 8.0 °C km−1, a mantle HF (qm) of 57.49 mW/m2, a crustal HF (qc) of 16.40 mW/m2, and a qm/q0 value of > 0.5, all of which indicate a typical configuration involving a hot mantle and a cold crust and high geothermal background in the SB. In addition, the thinned "thermal" lithospheric thickness in the SB is only 56.16 km. We correlate these characteristics with the westward subduction of the Pacific plate. From the proximal Kuril Trench to the distal Inner Mongolia Plateau in the subduction-influenced region, q0 generally decreases, qc increases, qm decreases, and the qm/q0 ratio gradually decreases. Thus, the present LTS in the SB might be controlled by the moderate distance of the SB from the subduction zone. Furthermore, in terms of geothermal resources in the SB, in addition to the high qm, which acts as the principal systematic heat source, deep hot partial melts act as direct heat sources and might also be controlled by the moderate distance from the subduction zone. Our results provide new insights into the relationship between the LTS and geothermal resources in similar regions. [ABSTRACT FROM AUTHOR]

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