Mineralogy, Geochemistry, and Sedimentary Geology of Lacustrine Basins

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: closed (1 December 2023) | Viewed by 11978

Special Issue Editors


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Guest Editor
Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Interests: sedimentary geology; sedimentary geochemistry

E-Mail Website
Guest Editor
Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Interests: event sedimentary geology; sedimentary geology

E-Mail Website
Guest Editor
School of Earth Science and Engineering, Xi’an Shiyou University, Xi’an 710065, China
Interests: sedimentary geology; reservoir sedimentary geology

Special Issue Information

Dear Colleagues,

In recent years, with the development of shale oil and gas on both the domestic and international levels, unconventional oil and gas have gradually become new hotspots in the energy industry. As convergence systems in the terrestrial source sink system, lacustrine basins can mainly be divided into fault depression type, depression type, and foreland type. Due to their unique fine-grained sedimentary system and low-energy environment, a variety of lithologic tight reservoirs, including tight sandstone, tuff and carbonate rocks, are developed for such purposes. At the same time, the lake basin is vulnerable to the impact of climate and the environment, and a variety of chemical evaporites are developed. These will tend to damage the reservoir porosity and permeability conditions and further lead to reservoir densification. The sedimentary environment and sedimentary models of lake basins are relatively complex, with diverse types and evolutionary processes of diagenesis. The characteristics of tight sandstone reservoirs in lake basins are variable, making the process of developing lake shale oil and gas difficult.

Therefore, the characteristics of lake basin mineralogy, geochemistry and sedimentary geology are in urgent need of clarification, which is of great significance to the exploration and development of global continental lake basins. Thus, this Special Issue will focus on primary progress, innovative research, and system improvement in the field of lake basin sedimentology, including research into and discussions of the following topics:

  • Advanced technologies and methods for studying lacustrine sedimentary environment;
  • Advanced technologies and methods for studying lacustrine tight sandstone;
  • Practical application of high-resolution sequence stratigraphy in lacustrine equivalent.

We look forward to receiving your contributions.

Prof. Dr. Jingchun Tian
Dr. Qingshao Liang
Prof. Dr. Qinlian Wei
Guest Editors

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Keywords

  • sedimentary environment and sedimentary model
  • diagenesis types and diagenetic evolution
  • shale oil and gas in lacustrine basins
  • characteristics of tight sandstone reservoirs in lacustrine basins
  • high-resolution sequence stratigraphy of lacustrine basins

Published Papers (12 papers)

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Research

32 pages, 16140 KiB  
Article
Mineralogy and Geochemistry of the Paleocene–Eocene Palana Formation in Western Rajasthan, India: Insights for Sedimentary Paleoenvironmental Conditions and Volcanic Activity
by Mohammed Hail Hakimi, Alok Kumar, Abdullah M. Alqubalee, Alok K. Singh, Mohammed Almobarky, Afikah Rahim, Mohammad Alqudah, Aref Lashin, Khairul Azlan Mustapha and Waqas Naseem
Minerals 2024, 14(2), 126; https://doi.org/10.3390/min14020126 - 24 Jan 2024
Viewed by 1075
Abstract
Organic-rich shale rocks from the Paleocene–Eocene Palana Formation in western Rajasthan, India, were systematically investigated based on inorganic and organic geochemistry combined with microscopic examinations to evaluate the sedimentary paleoenvironmental conditions and volcanic activity and their impact on the high organic carbon accumulation. [...] Read more.
Organic-rich shale rocks from the Paleocene–Eocene Palana Formation in western Rajasthan, India, were systematically investigated based on inorganic and organic geochemistry combined with microscopic examinations to evaluate the sedimentary paleoenvironmental conditions and volcanic activity and their impact on the high organic carbon accumulation. The Palana shales are categorized by high organic matter (OM) and sulfur contents, with total values up to 36.23 wt.% and 2.24 wt.%, respectively. The richness of phytoplankton algae (i.e., telalginite and lamalginite) together with redox-sensitive trace elements further suggests a marine setting and anoxic environmental conditions during the Paleocene–Eocene. The significant low oxygen conditions may contribute to enhancing the preservation of organic matter during deposition. The mineralogical and inorganic geochemical indicators demonstrate that the Palana organic-rich shale facies was accumulated in a warm and humid climate with moderate salinity stratification conditions in the water columns, thereby contributing to the high bioproductivity of the phytoplankton algae blooms within the photic zone. The presence of significant contents of zeolite derived from volcanic material together with silica minerals such as apophyllite and tridymite in most of the Palana organic-rich shales indicates a volcanic origin and supports hydrothermal activities during the Paleocene–Eocene period. These volcanic activities in this case are considered the influx of large masses of nutrients into the photic zone due to the ash accumulation, as indicated by the presence of the zeolites in the Palana shales. Therefore, the high bio-productivity associated with effective OM preservation led to the organic carbon accumulation in the Palana Formation during the Paleocene–Eocene. Full article
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21 pages, 12429 KiB  
Article
High-Frequency Lacustrine Lithological and Geochemical Variations in the Eocene Qaidam Basin: Implications for Paleoenvironment Reconstruction
by Kunyu Wu, Xiucheng Tan, Xiangjun Liu, Peng Pang, Songtao Wu, Shituan Xue, Haoting Xing, Ying Xiong, Yafeng Li, Menglin Zhang, Wei Deng and Juan Wang
Minerals 2024, 14(1), 79; https://doi.org/10.3390/min14010079 - 10 Jan 2024
Viewed by 797
Abstract
Lacustrine sedimentary processes exhibit high sensitivity to paleoenvironmental changes, often manifesting as high-frequency sedimentary cycles that control the complex variations in sedimentary structure, mineral composition, and element distribution. However, the intricate co-variation mechanism among paleoclimate and paleowater properties at a high precision level [...] Read more.
Lacustrine sedimentary processes exhibit high sensitivity to paleoenvironmental changes, often manifesting as high-frequency sedimentary cycles that control the complex variations in sedimentary structure, mineral composition, and element distribution. However, the intricate co-variation mechanism among paleoclimate and paleowater properties at a high precision level (centimeter to meter scale) is still controversial. This study focuses on conducting a high-frequency cycle analysis of lacustrine mixed rocks from the Eocene Lower Ganchaigou Formation (LGCG) in the Qaidam Basin, employing petrology, mineralogy, organic geochemistry, and elemental geochemistry techniques. The lithological variation was characterized by the superposition of three lithofacies types from the bottom to the top with a single sequence: massive sandstone, laminated silty shale, and bedded calcareous dolostone. Geochemical data revealed cyclical variations in the paleoenvironment in the vertical profile, which conformed to the high-frequency lithofacies cycles. Based on the reconstruction of the lake level and paleowater properties, a synthesized paleoclimate–sedimentary model that comprised three consecutive periods within an individual sequence was established. From the bottom to the top of each cycle, the Eocene paleoenvironment varied from reduction and desalination to oxidation and salinization, which was controlled by a decline in the lake level resulting from a transformation of the paleoclimate from warm and humid to cold and arid. The variations in petrology and geochemistry observed in the Eocene Qaidam Basin play a crucial role in comprehending the sedimentary response to paleoenvironmental changes at high precision levels within lacustrine settings. Full article
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25 pages, 28317 KiB  
Article
Provenance of the Upper Carboniferous Yanghugou Formation in the Western Margin of the Ordos Basin, China: Constraints on Paleogeography and Basin Development
by Tao Zhang, Rong Chen, Feng Wang, Jianling Hu, Min Zhang, Qian Li, Jingyi Wu and Lei Liu
Minerals 2024, 14(1), 78; https://doi.org/10.3390/min14010078 - 10 Jan 2024
Viewed by 764
Abstract
The Carboniferous Yanghugou Formation in the western margin of the Ordos Basin exhibits significant potential for oil and gas exploration. However, due to the influence of complex tectonic activities, there are substantial variations in stratigraphic thickness and depositional environments across the formation. The [...] Read more.
The Carboniferous Yanghugou Formation in the western margin of the Ordos Basin exhibits significant potential for oil and gas exploration. However, due to the influence of complex tectonic activities, there are substantial variations in stratigraphic thickness and depositional environments across the formation. The lack of a systematic source–sink comparative study has resulted in an unclear understanding of sediment sources and paleogeographic patterns, impacting the exploration for hydrocarbon accumulations. We conducted a comprehensive study of the source–sink system characteristics and paleogeography in the research area through field outcrop observations and drilling core sampling. By utilizing detrital zircon U–Pb geochronology and geochemistry, paleocurrent directions, lithofacies types, and sedimentary features, we delve into the understanding of the source–sink systems. Four major source–sink regions in the research area were identified: the Alxa, Yinshan, Alxa–Yinshan mixed and Qilian source–sink regions. The Alxa source–sink region formed a transitional delta-barrier-island sedimentary system. The northern part of the Yinshan source–sink region developed a transitional tidal-controlled delta-tidal-flat sedimentary system, while the southern deep-water area developed a shallow marine to semi-deep marine shelf sedimentary systems. The sediments of Alxa–Yinshan mixed source–sink region were deposited in a transitional tidal-controlled delta-tidal-flat barrier-island system. The Qilian source–sink region is characterized by small tidal-controlled delta-barrier-island system. From the analysis of the source–sink systems, it is inferred that the Alxa Block and the North China Craton had already merged before deposition of the late Carboniferous Yanghugou Formation. The delta sand bodies in the Alxa–Yinshan mixed source–sink region have the highest compositional and structural maturity, the best reservoir performance, and the great exploration potential. Full article
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17 pages, 17193 KiB  
Article
Quantitative Evaluation of Paleocene Reservoir Diagenetic Facies by Logging in Lishui West Sag, East China Sea Basin
by Ji Teng, Qiang Fu, Jun Qin, Wenrui Ma, Guanyu Zhang and Kailong Feng
Minerals 2024, 14(1), 28; https://doi.org/10.3390/min14010028 - 26 Dec 2023
Viewed by 684
Abstract
Exploration in the Lishui West Sag of the East China Sea Basin is limited by the scarcity of offshore drilling sites, and the prediction of deep, high-quality reservoirs is challenging using only geophysical methods. This study introduces a quantitative approach to diagenetic facies [...] Read more.
Exploration in the Lishui West Sag of the East China Sea Basin is limited by the scarcity of offshore drilling sites, and the prediction of deep, high-quality reservoirs is challenging using only geophysical methods. This study introduces a quantitative approach to diagenetic facies division in individual wells based on logging data, providing a new method and perspective for the prediction of deep, high-quality reservoirs. We employed comprehensive data from core, logging, thin-section casting, cathodoluminescence, scanning electron microscopy, and X-ray diffraction analyses from five wells to study the petrology, physical properties, diagenetic types and strength, and diagenetic minerals of the Paleocene sandstone reservoirs in the Lishui West Sag. Apparent compaction rate, apparent cementation rate, and other quantitative characterization parameters were used to calculate the comprehensive diagenetic coefficient (Cg), and the diagenetic facies were divided into compaction, cementation, and dissolution facies. A logging calculation model for the comprehensive diagenetic coefficient (Cg) and a quantitative identification method for diagenetic facies in individual well reservoirs were established through a fitting analysis between Cg and logging curve parameters. Continuous quantitative identification of vertical diagenetic facies in the five wells in the study area showed that the high-quality reservoirs in wells L1, L2, and L3 within the L1 gas field are characterized by extensive development of dissolution facies, while wells L4 and L5 are dominated by compaction and cementation facies, with poor reservoir properties and no industrial gas flow output. The results demonstrate the reliability of the model method. The establishment of this quantitative characterization method for diagenetic facies using logging data provides guidance for the prediction of favorable reservoirs. Full article
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19 pages, 13718 KiB  
Article
Sedimentary Facies, Paleogeography, and Depositional Models of the Middle–Late Permian in the Sichuan Basin, Southwest China
by Mo Deng, Guowei Zhao, Xiaobing Lin, Chunyu Chen, Longlong Li and Qingshao Liang
Minerals 2023, 13(11), 1406; https://doi.org/10.3390/min13111406 - 01 Nov 2023
Cited by 1 | Viewed by 1286
Abstract
This study focuses on the analysis of the sedimentary facies of the Middle–Late Permian, including the Qixia, Maokou, Wujiaoping/Longtan, and Changxing/Dalong Formations, in the Sichuan Basin, southwest China. Integrating drilling data and field outcrop data, various sedimentary facies indicators were employed to define [...] Read more.
This study focuses on the analysis of the sedimentary facies of the Middle–Late Permian, including the Qixia, Maokou, Wujiaoping/Longtan, and Changxing/Dalong Formations, in the Sichuan Basin, southwest China. Integrating drilling data and field outcrop data, various sedimentary facies indicators were employed to define eight sedimentary facies types in the Sichuan Basin during the Middle–Late Permian, namely, mixed tidal flat, tidal flat, restricted platform, open platform, platform margin, slope, basin, and volcanic facies. Detailed facies analysis was conducted on selected well logs, and sedimentary facies distribution maps were compiled for different time intervals, establishing depositional models. During the Qixia to Maokou stages, an extensive open platform was developed in the Sichuan Basin, accompanied by shallow intra-platform shoals. Towards the west along the Dayi–Ya’an line, platform margins were developed, followed by slope facies and basin facies in a northwest direction. During the Changxing stage, the Kaijiang–Liangping fault block subsided, forming the “Kaijiang-Liangping” paleochannel, which controls reef–shoal deposition in the region. This study provides comprehensive insights into the sedimentary facies characteristics and depositional environments of the Middle–Late Permian in the Sichuan Basin, contributing to the understanding of the regional sedimentary history and geological evolution. Full article
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17 pages, 4342 KiB  
Article
Reservoir Characteristics and Controlling Factors of Large-Scale Mono-Block Gas Field Developed in Delta-Front Sandstone—A Case Study from Zhongqiu 1 Gas Field in the Tarim Basin
by Songbai Zhu, Quanwei Du, Chen Dong, Xue Yan, Yong Wang, Yanli Wang, Zhuangsheng Wang and Xiaobing Lin
Minerals 2023, 13(10), 1326; https://doi.org/10.3390/min13101326 - 13 Oct 2023
Viewed by 730
Abstract
Taking the Zhongqiu 1 Gas Field in the Tarim Basin as an example, the heterogeneity of large-scale mono-block gas fields and their primary controlling factors have been analyzed. Based on drilling core data, well log data, scanning electron microscopy, thin-section analysis, and mercury [...] Read more.
Taking the Zhongqiu 1 Gas Field in the Tarim Basin as an example, the heterogeneity of large-scale mono-block gas fields and their primary controlling factors have been analyzed. Based on drilling core data, well log data, scanning electron microscopy, thin-section analysis, and mercury injection experiments, combining sedimentological interpretation, research on the reservoir characteristics and variability was carried out. The results showed that: (1) The lithologic characteristics showed obvious variations among wells in the Zhongqiu 1 gas field. Specifically, the main lithology developed in the Zhongqiu 1 well is feldspar lithic sandstone, while the remaining wells predominantly consist of lithic feldspar sandstone. These differences in rock composition maturity reveal that a higher proportion of stable mineral components leads to poorer reservoir properties; (2) the main factors controlling oil and gas productivity include the variations in petrology, mineralogy, and diagenetic process characteristics. The high content of unstable mineral components and constructive diagenesis could increase reservoir porosity together. (3) Sedimentary facies of the Bashijiqike Formation in the Zhongqiu 1 Gas Field played a dominant role in the reservoir distribution. The division of sedimentary facies zones reflects variations in material composition and grain size, serving as the main material basis for reservoirs. Differences in mineral composition reflect the sedimentary environment of the reservoir. Additionally, mineral composition indicates the relationship between diagenetic processes and reservoir evolution. The high feldspar content in well ZQ1 corresponded to relatively favorable reservoir properties. The dominant feldspar type was plagioclase, suggesting that early-stage chemical weathering had undergone significant alteration. The above conclusions provided a microscopic perspective to explain the differences in oil and gas production capacity of large delta-front gas fields, serving as a geological basis for the exploration and exploitation of similar fields. Full article
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19 pages, 12906 KiB  
Article
Diagenetic Evolution and Petrophysical Characteristics of Paleogene Sandstone Reservoirs in the Southwest Baiyun Sag, Northern South China Sea
by Guanyu Zhang, Qiang Fu, Guangrong Peng, Xudong Wang, Lili Zhang, Xuhong Xiang and Zhiwei Zhu
Minerals 2023, 13(10), 1265; https://doi.org/10.3390/min13101265 - 28 Sep 2023
Viewed by 657
Abstract
In addressing the critical need to understand the geological and diagenetic factors affecting Paleogene sandstone reservoirs in the Baiyun Sag—a region vital for oil and gas exploration—this study delves into the Paleogene Zhuhai and Enping formations. Advanced methodologies, including petrographic thin-section analysis, scanning [...] Read more.
In addressing the critical need to understand the geological and diagenetic factors affecting Paleogene sandstone reservoirs in the Baiyun Sag—a region vital for oil and gas exploration—this study delves into the Paleogene Zhuhai and Enping formations. Advanced methodologies, including petrographic thin-section analysis, scanning electron microscopy, wavelet analysis, and carbon and oxygen isotope analysis, were employed to evaluate their petrological characteristics, pore structures, physical properties, and key diagenetic processes. The results indicate that the Zhuhai Formation is primarily composed of feldspathic quartz sandstones with prevalent intergranular dissolution pores, while the Enping Formation consists mainly of feldspathic sandstones with intragranular solution pores. The diagenetic temperatures across both formations ranged from 42.6 to 116.3 °C. The studied reservoirs have experienced porosity alterations due to mechanical compaction (23.07% reduction), carbonate cementation (9.02% reduction), and dissolution (5.09% enhancement). Notably, feldspar dissolution emerged as a significant contributor to high-quality reservoirs, particularly in the upper Enping Formation. These findings offer invaluable insights into the diagenetic evolution of sandstone reservoirs in the Baiyun Sag and hold significant implications for guiding future oil and gas exploration efforts in the region. Full article
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22 pages, 11464 KiB  
Article
Research on Fractal Characteristics and Influencing Factors of Pore-Throats in Tight Sandstone Reservoirs: A Case Study of Chang 6 of the Upper Triassic Yanchang Formation in Huaqing Area, Ordos Basin, China
by Fanchi Nan, Liangbiao Lin, Yating Lai, Chao Wang, Yu Yu and Zhaobing Chen
Minerals 2023, 13(9), 1137; https://doi.org/10.3390/min13091137 - 28 Aug 2023
Viewed by 813
Abstract
In recent years, tight sandstone oil and gas have been an important area for unconventional oil and gas exploration and development in China. It is of great significance to clarify the pore-throat structure characteristics of tight sandstone reservoirs to guide production practices. This [...] Read more.
In recent years, tight sandstone oil and gas have been an important area for unconventional oil and gas exploration and development in China. It is of great significance to clarify the pore-throat structure characteristics of tight sandstone reservoirs to guide production practices. This study takes the tight sandstone of the sixth member of the Yanchang Formation in the Huaqing area, Ordos Basin, as an example, based on experimental methods such as high-pressure mercury intrusion, cast thin sections and scanning electron microscopy. At the same time, the pore-throat structure of tight sandstone reservoirs is divided into three types using the tube-bundle and spherical fractal models. The corresponding pore and throat radius distribution, pore-throat combination mode and influencing factors of various pore-throats are studied. The results show that the fractal dimension of type I pore-throats is the smallest, and the distribution of their pore-throat radii is the most uniform. They are dominated by intercrystalline pores and dissolution pores with tube-bundle throats and small pores with small throats. Type II pore-throats have the largest fractal dimension and the worst pore-throat uniformity. They are dominated by residual primary intergranular pores with necked throats and large pores with small throats. The type III pore-throat fractal dimension is in the middle, mainly composed of residual dissolved intergranular pores with pore-reduced throats, sheet-like and curved sheet-like throats, and large pores with large throats. The influence of different pore-throat combinations on the reservoir is reflected in the different characteristics of mercury injection parameters. The main influencing factors for the differences in the fractal dimensions of different pore-throats are diagenesis, rock composition and pore-throat combination type. Diagenesis and rock composition, in turn, affect the type and development degree of pore-throats, as well as the combination of pore-throats. The purpose of this study was to clarify the internal connection modes of different homogeneous pore-throats and their influencing factors, enrich the theoretical basis for the study of tight sandstone reservoirs and provide theoretical guidance for their exploration and development. Full article
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16 pages, 5224 KiB  
Article
Microscopic Pore Structure Characteristics and Fluid Mobility in Tight Reservoirs: A Case Study of the Chang 7 Member in the Western Xin’anbian Area of the Ordos Basin, China
by Qinlian Wei, Huifang Zhang, Yonglin Han, Wenjie Guo and Ling Xiao
Minerals 2023, 13(8), 1063; https://doi.org/10.3390/min13081063 - 11 Aug 2023
Cited by 1 | Viewed by 676
Abstract
This research addresses the limited understanding of movable fluid occurrence characteristics in the Chang 7 reservoir by employing mercury injection capillary pressure, constant-rate mercury injections, and nuclear magnetic resonance methods. This study investigates the microscopic pore structure characteristics and movable fluids in the [...] Read more.
This research addresses the limited understanding of movable fluid occurrence characteristics in the Chang 7 reservoir by employing mercury injection capillary pressure, constant-rate mercury injections, and nuclear magnetic resonance methods. This study investigates the microscopic pore structure characteristics and movable fluids in the tight reservoir of the western Xin’an region, located in the Ordos Basin. The finding reveals that as permeability decreases, the distribution of the throat radius becomes more concentrated in the low-value area, resulting in a narrow distribution range with high curve peaks. Conversely, with an increasing permeability, the distribution range expands towards the high-value area while the curve peak decreases. This research underscores the significance of the throat radius, especially the main flow throat radius, in constraining the permeability of rock samples. Furthermore, this study highlights a stronger correlation between permeability and movable fluid saturation than porosity. This finding emphasizes the importance of considering movable fluid saturation when assessing reservoir characteristics. Notably, the throat radius plays a crucial role in influencing the occurrence characteristics of movable fluids, with a smaller throat radii posing hindrances to fluid flow in the reservoir. Additionally, the presence of clay minerals in the reservoir leads to pore segmentation and increased fluid flow resistance, ultimately reducing the saturation of movable fluids. I must be understood that these factors are essential for developing and producing reservoirs with similar characteristics. In conclusion, the insights gained from this study hold considerable theoretical value and provide essential references for developing and producing reservoirs with tight characteristics, particularly in the western Xin’an region of the Ordos Basin. Full article
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17 pages, 33260 KiB  
Article
Coupling Relationships between Sedimentary Microfacies, Sand Bodies, and Tectonic Fracture Characteristics in Braided River Deltas: A Case Study of the Bashijiqike Formation in the Keshen 2 Area
by Zhuangsheng Wang, Xiaobing Lin, Songbai Zhu, Junming Fan and Yuchao Zheng
Minerals 2023, 13(8), 1020; https://doi.org/10.3390/min13081020 - 30 Jul 2023
Cited by 1 | Viewed by 1148
Abstract
Fractures are crucial as main natural gas transport channels in tight sandstone reservoirs. In order to reveal the correlation between the combination of fractures in Block Keshen 2 and sandstone, we have collected drilling core data, logging curve data, imaging logging data, and [...] Read more.
Fractures are crucial as main natural gas transport channels in tight sandstone reservoirs. In order to reveal the correlation between the combination of fractures in Block Keshen 2 and sandstone, we have collected drilling core data, logging curve data, imaging logging data, and rock thin-section data from the Bashjiqike Formation in the Keshen 2 area, and by classifying and statistically analyzing the different influencing factors of fractures, we have established a correlation between the development of fractures and sandstone thickness, lithology, and sedimentary microfacies. The results reveal the following: (1) frequent vertical superposition and lateral migration occur in the sedimentary sand bodies of the Bashijiqike Formation. Three types of patterns of sand bodies have been identified according to the changes in microfacies. Type I refers to the patterns of sand bodies developed in main subaqueous distributary channels, type II refers to the patterns of sand bodies developed in secondary subaqueous distributary channels or mouth bars, and type III refers to the patterns of sand bodies developed in isolated subaqueous distributary channels; (2) three types of fracture patterns have been described in the various sand bodies of the Bashijiqike Formation in the Keshen area, including high–medium-angle branch-like fracture patterns, medium-angle reticular fracture patterns, and isolated fractures; (3) the coupling relationship among sedimentary microfacies, sand body patterns, and fracture patterns has been established. The high–medium-angle branch-like fracture patterns mainly develop in the main underwater distributary channel and the type I sand body patterns. The medium-angle reticular fracture patterns mainly develop in the secondary underwater distributary channel and mouth bars, as well as the type II sand body patterns. Isolated fractures can occur in all sedimentary microfacies but are sporadically distributed within the three types of sand body patterns. The research results present the regularity of fracture development in fractured reservoirs, which can be applied to oil and gas fields with the same background, providing certain geological evidence for exploration and development. Full article
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18 pages, 5526 KiB  
Article
Densification Mechanisms and Pore Evolution Analysis of a Tight Reservoir: A Case Study of Shan-1 Member of Upper Paleozoic Shanxi Formation in SW Ordos Basin, China
by Ling Xiao, Leilei Yang, Xuwen Zhang, Xijuan Guan and Qinlian Wei
Minerals 2023, 13(7), 960; https://doi.org/10.3390/min13070960 - 19 Jul 2023
Cited by 2 | Viewed by 1013
Abstract
This comprehensive analysis investigated the causes of formation densification in the Shan-1 Member tight reservoir in the southwestern Ordos Basin. The study aimed to mitigate exploration and development risks by examining petrological characteristics, reservoir performance, pore characteristics, and pore evolution. Various techniques were [...] Read more.
This comprehensive analysis investigated the causes of formation densification in the Shan-1 Member tight reservoir in the southwestern Ordos Basin. The study aimed to mitigate exploration and development risks by examining petrological characteristics, reservoir performance, pore characteristics, and pore evolution. Various techniques were employed, including thin-section casting, scanning electron microscopy, and analysis of porosity and permeability. By establishing the relationship between visualized reservoir porosity and thin slice porosity, along with employing mechanical compaction correction methods and the principle of “back stripping by inversion,” the recovery of paleophysical properties in tight sandstone reservoirs was conducted. Additionally, the research integrated diagenetic evolution sequences and the recovery of paleophysical properties to analyze the origins of reservoir densification and pore evolution in the Shan-1 Member. The results suggest that compaction is the primary factor contributing to reservoir densification, with burial depth playing a crucial role in determining the intensity of compaction. Cementation, particularly associated with illite, emerged as a significant influence on reservoir densification, while low dissolution also contributed to the densification process. The densification of the Shan-1 reservoir in the study area was estimated to have occurred during the Early Jurassic, approximately 195 Ma. These research findings not only enhance the understanding of the Shan-1 reservoir but also provide valuable insights for predicting tight reservoirs and improving the efficiency of oil and gas production. Full article
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20 pages, 13006 KiB  
Article
Characteristics and Geological Significance of High-Frequency Cycles in Salinized Lake Basins: The Paleogene Kumugeliemu Group in the Xinhe Area, Northern Tarim Basin
by Yanru Yang, Jingchun Tian, Xiang Zhang, Yingxu Li, Yue Zhang and Qiaoyi Xia
Minerals 2023, 13(6), 824; https://doi.org/10.3390/min13060824 - 16 Jun 2023
Viewed by 887
Abstract
Salinized lake basins have distinctive sedimentary response characteristics, similar to marine shallow-water carbonate platforms. High-frequency cycles can also be used to reveal more sedimentological information, such as relative lake-level fluctuations, lithofacies sequence combinations, and paleogeographic evolution. In this article, a comprehensive study on [...] Read more.
Salinized lake basins have distinctive sedimentary response characteristics, similar to marine shallow-water carbonate platforms. High-frequency cycles can also be used to reveal more sedimentological information, such as relative lake-level fluctuations, lithofacies sequence combinations, and paleogeographic evolution. In this article, a comprehensive study on the stratigraphic shelf delineation and high-frequency cycles of the Paleozoic Kumugeliemu Group in Xinhe area, northern Tarim Basin, was performed using drilling cores, logging curves, and seismic analyses. As a result of the study, the following data were obtained: the three sets of marker beds in the Kumugeliemu Group in the study area could be divided into a bottom sandstone component (E1-2 km1), a lower gypsum mudstone component (E1-2 km2), a salt rock component (E1-2 km3), and an upper gypsum mudstone component (E1-2 km4) by petrology vertical overlay combination and isochronous tracking correlation, which constituted two third-order cycles (ESQ1, ESQ2). They were further divided into seven fourth-order cycles (Esq1–Esq7). Due to the droughty and saline lacustrine depositional system background, the internal rock fabric changed frequently and showed a periodic vertical overlay pattern. Stratified gypsum salt, gypsum mud (sand) rock, and gypsum rock were used as the cycle interface. A single cycle was mainly characterized by an upward shallower depositional sequence of rapid lake transgression followed by a slow lake regression, composed of massive sandstone–lamellar mudstone–lime dolomite–gypsum rock, massive sandstone–lamellar mudstone–gypsum rock (gypsum salt), massive sandstone–massive gypsum mud (sand) rock–gypsum rock, and other cycle structure types. The complete sedimentary cycle was superposed by a single cycle and compared by the inter-well thickness difference, indicating that the study area had a paleogeomorphology pattern of “West-Low–East-High”. The thickness of the cycles decreased gradually from bottom to top vertically, and five sedimentary stages were determined, i.e., freshwater, brackish, brackish water, salt lake, and semi-saltwater, reflecting the evolutionary process of increasing salinity, lake basin filling, and gradual salinization and shrinkage. Full article
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