High-Efficient Exploration and Development of Oil & Gas from Ocean

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Geological Oceanography".

Deadline for manuscript submissions: closed (25 September 2023) | Viewed by 20469

Special Issue Editors


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Guest Editor
1. Hubei Key Laboratory of Marine Geological Resources, China University of Geosciences, Wuhan 430074, China 2. College of Marine Science and Technology, China University of Geosciences, Wuhan 430074, China
Interests: pore structure characterization; fluid occurrence; water–rock interaction; nuclear magnetic resonance; unconventional oil/gas
Special Issues, Collections and Topics in MDPI journals
School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China
Interests: shale oil and gas geology; petroleum migration and accumulation; shale reservoir characterization; shale pore system; organic matter accumulation
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Interests: CO2 geological storage; CO2 flooding; heavy oil recovery; thermal recovery; gas hydrate
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

There are still some critical problems in developing unconventional oil and gas. First, the selection of sweet points is still challenging from a geological perspective. The explanation of geophysical data (wireline logs and seismic data) to identify the most favorable layers remains controversial. Second, prospecting well can directly recover the sample from the target layers, and detailed information about the fluid and reservoir aids selecting the best layer for development. It is also problematic to evaluate hydrocarbon occurrence, especially movability in in situ conditions. Finally, hydraulic fracturing is a basic method which is widely used to develop the most unconventional oil/gas. However, there remain unsolved problems with generating the ideal fracture network due to complex natural cracks and artificial fractures. The highly efficient development of unconventional offshore oil/gas, such as gas hydrate, is still challenging and attracts a great amount of attention. This Special Issue proposes a collection of state-of-the-art research on the exploration and development of unconventional offshore oil/gas. We sincerely invite prospective authors to submit high-quality original articles or reviews regarding how to develop unconventional oil/gas with high efficiency from both geological and engineering aspects.

Potential topics include, but are not limited to:

  • High-resolution geochemical characterization of reservoir lithofacies and diagenesis.
  • The origin, evolution, and petrophysical characterization of unconventional reservoirs.
  • High-resolution 3D reconstruction of digital cores and relevant upscaling methods.
  • In situ hydrocarbon generation, occurrence, and movability.
  • Drilling, completion, and hydraulic fracturing.
  • Rock–fluid interaction and its influence on reservoir property.
  • Natural and artificial fracture characterization.
  • CO2 flooding in oil/gas recovery and its application in carbon sequestration.
  • Enhanced gas hydrate recovery by geothermal energy.
  • Enhanced oil recovery by physical and chemical methods.

Prof. Dr. Mianmo Meng
Dr. Wenming Ji
Dr. Guodong Cui
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Marine Science and Engineering is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • gas hydrate
  • shale oil
  • shale gas
  • tight gas
  • tight oil
  • coalbed gas
  • CCUS

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Published Papers (19 papers)

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Research

15 pages, 2226 KiB  
Article
A New Approach for Production Prediction in Onshore and Offshore Tight Oil Reservoir
by Kaixuan Qiu, Kaifeng Fan, Xiaolin Chen, Gang Lei, Shiming Wei, Rahul Navik and Jia Li
J. Mar. Sci. Eng. 2023, 11(11), 2079; https://doi.org/10.3390/jmse11112079 - 30 Oct 2023
Cited by 1 | Viewed by 741
Abstract
Rapid technological advances have accelerated offshore and onshore tight oil extraction to meet growing energy demand. Reliable tools to carry out production prediction are essential for development of unconventional reservoirs. The existed tri-linear analytical solutions are verified to be versatile enough to capture [...] Read more.
Rapid technological advances have accelerated offshore and onshore tight oil extraction to meet growing energy demand. Reliable tools to carry out production prediction are essential for development of unconventional reservoirs. The existed tri-linear analytical solutions are verified to be versatile enough to capture fundamental flow mechanisms and make accurate production predictions. However, these solutions are obtained in Laplace space with the Laplace transform and numerical inversion, which may lead to uncertainty in the solution. In this paper, a general analytical solution is derived in real-time space through integral transform and average pressure substitution. Namely, the partial differential equations describing subsurface fluid flow are firstly triple-integrated and then the obtained volume average pressure are replaced with the rate-dependent expressions. Furthermore, the ordinary differential equations related to oil rate are solved analytically in real-time space. To validate our model, this derived solution is verified against two numerical models constructed with two typical physical configurations. The great match indicates the accuracy and applicability of the analytical solution. According to the developed workflow, two field cases including offshore and onshore tight oilfield data are selected for history matching and production prediction. This new approach not only makes the obtained solution more simplified, but also helps field engineers diagnose flow patterns more quickly to better optimize production schemes. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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21 pages, 5012 KiB  
Article
Sedimentary Environment Interpretation and Organic Matter Enrichment of the Lower Cambrian Shuijingtuo Shale in the Yichang Slope, South China: Insight from Sedimentary Geochemical Proxies with Major/Trace Elements
by Sile Wei, Mingyi Hu, Sheng He, Wei Yang, Qing He, Quansheng Cai and Ping Li
J. Mar. Sci. Eng. 2023, 11(10), 2018; https://doi.org/10.3390/jmse11102018 - 20 Oct 2023
Cited by 1 | Viewed by 828
Abstract
The vertical geochemical variations in total organic carbon (TOC) content and major and trace elements of the Lower Cambrian Shuijingtuo Formation from the Yichang Slope in the Upper Yangtze were investigated to assess the environmental conditions (redox conditions, water mass restriction, terrigenous input, [...] Read more.
The vertical geochemical variations in total organic carbon (TOC) content and major and trace elements of the Lower Cambrian Shuijingtuo Formation from the Yichang Slope in the Upper Yangtze were investigated to assess the environmental conditions (redox conditions, water mass restriction, terrigenous input, relative sea-level terrestrial, and paleoproductivity) and to determine the primary controlling factors for organic matter enrichment. The Shuijingtuo Shale is divided into three intervals. The lithofacies of interval I are mainly black siliceous shale with high TOC content, and interval II is mainly black siliceous shale with moderate TOC content. Interval III consists of black, clay-rich siliceous shale and dark-gray calcareous shale and is characterized by a low TOC content. The effects of diagenesis and hydrothermal activity on the elements were evaluated prior to analyzing the environmental condition. There are good positive correlations between TOC and U/Al or Mo/Al ratios, suggesting that major/trace elements still retain the geochemical signature of the sedimentary environment. Meanwhile, the geochemical proxies consisting of Al, Fe, Mn, and Ti indicate that the study area did not experience hydrothermal deposits. The redox proxies (U/Th, Corg:Ptot, and MoEF–UEF) indicate that the interval I samples were formed under a strong reducing condition. The diagram of TOC vs. Mo indicates that the water mass was moderately restricted during the deposition of interval I shales. Proxies of terrigenous input and relative sea-level (Zr/Al and Zr/Rb) suggest that the organic-rich shales at the bottom were deposited under a relatively high sea-level and experienced minimal input of terrigenous debris from the source area. Additionally, the paleoproductivity indicated by Sibio and (Ni + Cu + Zn)/Al was high for interval I samples. During the interval II period, the relative sea-level began to decline, the seawater still remained in reducing conditions, and there was no change in the productivity, but the input of terrigenous debris increased significantly. In the interval III depositional period, the relative sea-level continued to decrease, the seawater shifted to a dysoxic condition, and the paleoproductivity was also at a lower level. The evolution of the sedimentary environment indicates that the high TOC content in the interval I samples is mainly attributed to the strong reducing condition, the preservation condition and debris dilution together control the organic matter content within the interval II samples, and the low TOC content within the interval III samples is constrained by a combination of the poor preservation conditions and lower paleoproductivity. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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18 pages, 4078 KiB  
Article
Nanopore Structure and Multifractal Characteristics of Continental Shale Oil Reservoir: A Case Study from Ziliujing Shales in the Sichuan Basin
by Youzhi Wang, Wei Li, Xiandong Wang, Zhiguo Wang, Weiqi Ma, Yanping Zhu, Mengdi Sun, Bo Liu, Lijuan Cheng and Xiaofei Fu
J. Mar. Sci. Eng. 2023, 11(10), 1989; https://doi.org/10.3390/jmse11101989 - 15 Oct 2023
Viewed by 926
Abstract
Thermal maturity of the shales from the Ziliujing Formation of the Jurassic age in the Sichuan Basin is in the hydrocarbon generation window, which makes it a candidate for shale oil and gas development. The meso- and macropore characteristics and heterogeneity of shales [...] Read more.
Thermal maturity of the shales from the Ziliujing Formation of the Jurassic age in the Sichuan Basin is in the hydrocarbon generation window, which makes it a candidate for shale oil and gas development. The meso- and macropore characteristics and heterogeneity of shales are important factors affecting the occurrence and development of oil and gas. However, the meso- and macropores of the Ziliujing shales have not been systematically studied. Thus, the mineral compositions and total organic carbon (TOC) of samples from this formation, as well as its pore structure, are analyzed by low-temperature N2 adsorption technique. Moreover, the heterogeneity of the pores was determined by multifractal analysis. The results show that the Ziliujing shales can be classified into three types according to the distributions of mineral compositions of carbonate and mixed and argillaceous shales. Results revealed that the smallest meso- and macropore volume (PV), the smallest specific surface area (SSA), and the largest average pore diameter (APD) occur in the carbonate shales. However, the largest PV and SSA and the smallest APD are observed in the argillaceous shales. The porosity of carbonate shales is mainly concentrated between 5 nm and 30 nm. Compared with carbonate shales, the porosity with pore sizes less than 30 nm of mixed and argillaceous shales shows a rapid increase. Furthermore, inorganic minerals are the main factors affecting the pore distributions, while TOC shows a weak effect. Herein, clay minerals significantly increase the mesopore volume and the pore number with a size of less than 30 nm. The Dq-q curves reveal that the meso- and macropore distributions of Ziliujing shales show multifractal behavior, but the multifractal characteristics of pores of various shales are distinctly different. The information dimension D1, the Hurst exponent H, and the width of the right side D0D10 are key indicators to distinguish the local variations within the pore structure of different types of shales. The carbonate shales have the largest multifractal spectra width and the smallest D1 and H, while the opposite trend is found for the argillaceous shales. Clay minerals reduce the heterogeneity of the meso- and macropore distributions and increase the pore connectivity. Nevertheless, the carbonate minerals exhibit a reverse trend. Finally, it was found that TOC does not impact pore complexity as much. Collectively, this study supports our understanding of the occurrence of shale oil within various reservoir facies, thereby providing a guideline for future explorations in the Ziliujing Formation of the Jurassic age in the Sichuan Basin. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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26 pages, 14349 KiB  
Article
Shale Gas Exploration and Development Potential Analysis of Lower Cambrian Niutitang Formation and Lower Silurian Longmaxi Formation in Northwestern Hunan, South China, Based on Organic Matter Pore Evolution Characteristics
by Yanan Miao, Pengfei Wang, Xin Li, Haiping Huang, Can Jin and Wei Gao
J. Mar. Sci. Eng. 2023, 11(10), 1910; https://doi.org/10.3390/jmse11101910 - 02 Oct 2023
Viewed by 771
Abstract
Shale gas production is obviously higher within the Silurian Longmaxi Formation than that of the Cambrian Niutitang Formation according to the drilling test results in the northwest Hunan area. To clarify the reasons behind this variation, core samples from the two sets of [...] Read more.
Shale gas production is obviously higher within the Silurian Longmaxi Formation than that of the Cambrian Niutitang Formation according to the drilling test results in the northwest Hunan area. To clarify the reasons behind this variation, core samples from the two sets of shales were studied for a comprehensive comparison and analysis of their organic matter (OM) pore structure. Methods were used, including the total organic carbon content test, the vitrinite reflectance test, X-ray diffraction, and focused ion-beam scanning electron microscopy (FIB-SEM). The results show that these two shales have similar reservoir characteristics, both with abundant organic matter and high content of brittle minerals. However, the Longmaxi shale with 2.3% to 3.0%Ro presents lower thermal maturity than the Niutitang shale with over 3.0%Ro. In the case of pore structure associated with OM, a huge difference exists between the two shales. The OM pore shape of the Longmaxi shale is very regular, being mostly round and oval, while the OM pore shape of the Niutitang shale is irregular, being flat with a thin middle and thick and elongated ends. An important factor affecting OM pore evolution is thermal maturity. In turn, the thermal maturity is controlled by the tectonic evolution process, especially the maximum paleo-burial depth. In conclusion, the paleo-burial depth of the Lower Cambrian Niutitang shale in northwest Hunan is too large, which leads to the excessive evolution of organic matter in the shale, and the physical and chemical properties are similar to graphite, which leads to the disappearance of OM pores. Shale gas has no effective reservoir space and is largely dispersed in geological history. At the same time, due to the insufficient hydrocarbon-generation evolution time of the Lower Silurian Longmaxi Formation shale in this area, the shale could not form enough gaseous hydrocarbons and a large amount of effective reservoir space (OM pores with regular shape and large pore size), and finally failed to become a gas reservoir. Therefore, the exploration and development potential of the marine shale gas of the Lower Cambrian Niutitang Formation and the Lower Silurian Longmaxi Formation in northwest Hunan is poor. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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19 pages, 4028 KiB  
Article
Multiple Controls on Organic Matter Accumulation in the Intraplatform Basin of the Early Cambrian Yangtze Platform, South China
by Qiyang Zhang, Entao Liu, Songqi Pan, Hua Wang, Zhenhua Jing, Zhengfu Zhao and Ruiyue Zhu
J. Mar. Sci. Eng. 2023, 11(10), 1907; https://doi.org/10.3390/jmse11101907 - 02 Oct 2023
Cited by 2 | Viewed by 917
Abstract
Studying the accumulation rules of organic matter (OM) in paleo-ocean sediments can not only enhance our understanding of how OM becomes enriched in ancient oceans but also provide guidance for the exploration of shale gas in unconventional shale strata. A breakthrough has been [...] Read more.
Studying the accumulation rules of organic matter (OM) in paleo-ocean sediments can not only enhance our understanding of how OM becomes enriched in ancient oceans but also provide guidance for the exploration of shale gas in unconventional shale strata. A breakthrough has been made in shale gas exploration in the early Cambrian Qiongzhusi Formation in South China. However, less attention has been paid to the intraplatform basin of the Yangtze Platform, and the factors controlling organic matter enrichment in this special region remain unclear. This study focuses on a continuous drilling core across the full well section of the Qiongzhusi Formation in the intraplatform basin of the Yangtze Platform. Through the comprehensive analysis of total organic carbon (TOC), major and trace elements, and Mo isotopes, this study investigates the controlling factors for OM enrichment with δ98/95Mo ratios utilized to identify the existence of euxinic bottom water. The examined 240 m long core can be divided into four units, where the TOC values of the lower Units 1 and 2 (0.2–5.0 wt.%) average higher than the upper Units 3 and 4 (0.2–2.5 wt.%). Redox indicators (U/Th, Ni/Co, EF(Mo)—EF(U)) indicate an increasing oxidation of bottom waters from the bottom upwards. δ98/95Mo data further confirm the presence of weakly euxinic conditions in Units 1 and 2, addressing the ongoing controversy surrounding bottom water redox environments. Primary productivity indicators (Ni/Al, Cu/Al) suggest a relatively low average productivity level within the intraplatform basin. The upwelling indicators EF(Co) * EF(Mn) of different profiles in the Yangtze Platform suggest that low productivity within the intraplatform basin can be mainly attributed to the absence of upwelling. Consequently, this study proposes an organic matter enrichment mechanism for the Qiongzhusi Formation in the intraplatform basin, which emphasizes the significance of the redox environment in the formation of high-quality hydrocarbon source rocks in restricted environments that lack upwelling, setting it apart from the deep ocean. These findings have the potential to provide valuable insights for the exploration of high-quality hydrocarbon source rocks in other similar regions. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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24 pages, 13348 KiB  
Article
Factors Controlling the Pore Development of Low-Mature Marine–Continental Transitional Shale: A Case Study of the Upper Permian Longtan Shale, Western Guizhou, South China
by Manting Zhang, Mingyi Hu, Sile Wei, Quansheng Cai, Wei Fu, Fang Shi, Lei Zhang and Haiyan Ding
J. Mar. Sci. Eng. 2023, 11(10), 1862; https://doi.org/10.3390/jmse11101862 - 26 Sep 2023
Viewed by 636
Abstract
The Upper Permian Longtan Shale is a significant reservoir in western Guizhou. To clarify the main factors controlling the low-mature marine–continental transitional shale pore development in western Guizhou, pore types were classified with scanning electron microscopy (SEM), and the pore developmental stages and [...] Read more.
The Upper Permian Longtan Shale is a significant reservoir in western Guizhou. To clarify the main factors controlling the low-mature marine–continental transitional shale pore development in western Guizhou, pore types were classified with scanning electron microscopy (SEM), and the pore developmental stages and morphological structures were quantitatively characterized by nitrogen adsorption isotherm analyses. Additionally, the qualitative or semi-quantitative relationships between the pore developmental stages and the main controlling factors were established via geochemical analysis. The results showed that the Longtan Shale pores include intergranular pores, intragranular pores, organic pores, and microfractures. The intergranular pore structures were categorized into ink-bottle, slit, layered, and irregular types. The intragranular pores were found to be of the elliptical, nearly circular, ink-bottle, and irregular varieties. The organic pores were categorized into elliptical, bubble-like, and irregular polygonal variants. The microfractures were only of the elongated type. The clay-mineral-related intergranular pores were the predominant pore type. The organic pores were found to be poorly developed. The mesopores were predominant, followed by macropores. The shale pore diameters ranged between 1 nm and 100 nm, and they are characterized by multiple peaks. The specific surface area (SSA) was primarily provided by nanopores in the range of 5 nm to 10 nm, such that the smaller pores provided a greater contribution to the SSA, and they are more conducive to shale gas adsorption and accumulation. Clay mineral content was the dominant internal factor controlling pore development and the SSA, with the illite–smectite mixed layer being the most obvious controlling factor. While too low or too high clay mineral content is adverse to macropore development, brittle mineral content, carbonate mineral content, and total organic carbon (TOC) content are adverse to pore development and the SSA. Thermal maturity has no remarkable control effect on pore volume and the SSA of non-organic pores. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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21 pages, 5479 KiB  
Article
Experimental Characteristics of Hydrocarbon Generation from Scandinavian Alum Shale Carbonate Nodules: Implications for Hydrocarbon Generation from Majiagou Formation Marine Carbonates in China’s Ordos Basin
by Yiqing Wang, Yaohui Xu, Junping Huang, Jianglong Shi, Heng Zhao, Qingtao Wang and Qiang Meng
J. Mar. Sci. Eng. 2023, 11(8), 1616; https://doi.org/10.3390/jmse11081616 - 18 Aug 2023
Viewed by 806
Abstract
The hydrocarbon source rocks of the marine carbonates of the Ordovician Majiagou Formation in the Ordos Basin are generally in the high-overmature stage and are, therefore, not suitable for hydrocarbon thermal simulation experiments. Their hydrocarbon generation potential and hydrocarbon generation characteristics are not [...] Read more.
The hydrocarbon source rocks of the marine carbonates of the Ordovician Majiagou Formation in the Ordos Basin are generally in the high-overmature stage and are, therefore, not suitable for hydrocarbon thermal simulation experiments. Their hydrocarbon generation potential and hydrocarbon generation characteristics are not clearly understood. Meanwhile, Nordic Cambrian carbonates are similar in lithology, parent material type, and sedimentary age, and are in the low evolution stage, which is suitable for hydrocarbon thermal simulation experiments. Therefore, in this study, we selected the Nordic carbonates for the gold tube thermal simulation experiment to analyze the content and geochemical characteristics of the thermal simulation products. The experimental results are also compared and analyzed with the characteristics of thermal simulation products of Pingliang Formation mud shale (contemporaneous with the Majiagou Formation) and Shanxi Formation coal (in the upper part of the Majiagou Formation), which are similar to the Majiagou Formation in the Ordos Basin. The results showed that the Nordic carbonate has different hydrocarbon production characteristics from the mud shale of the Pingliang Formation of the same parent material type, and although the hydrocarbon production yields of the two are not very different, the carbonate still produces methane at 600 °C. The hydrocarbon production yield of the Nordic carbonates is almost equivalent to that of type-II2 kerogen, indicating that the hydrocarbon production yield is not related to lithology and only to the organic matter type; however, the Nordic carbonate can produce a large amount of H2S. The alkane carbon isotope changes are mainly controlled by the degree of thermal evolution, showing gradual heaviness with increasing temperature. No carbon isotope sequence reversal occurred during the thermal simulation, and its distribution range is roughly the same as that of the alkane carbon isotope composition of the mud shale of the Pingliang Formation. The ethane carbon isotope composition is as heavy as −21.2‰ at the high-temperature stage, showing similar coal-type gas characteristics. The addition of calcium sulphate (CaSO4) causes the TSR reaction to occur, which has a significant impact on the methane content under high maturity conditions, reducing its content by more than 50% at 600 °C. However, the addition of CaSO4 increases the yield of heavy hydrocarbon gases, such as ethane, and promotes the production of C6-14 hydrocarbons and C14+ hydrocarbons at high-temperature stages, and the addition of CaSO4 substantially increases the yield of H2, CO2, and H2S. The thermal simulation results have implications for the hydrocarbon formation mechanism of the early Paleozoic marine carbonate formation system in the stacked basins of the Ordos Basin and the Tarim Basin in China. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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25 pages, 4082 KiB  
Article
Estimating Permeability of Porous Media from 2D Digital Images
by Gang Lei, Tianle Liu, Qinzhuo Liao and Xupeng He
J. Mar. Sci. Eng. 2023, 11(8), 1614; https://doi.org/10.3390/jmse11081614 - 17 Aug 2023
Cited by 1 | Viewed by 1191
Abstract
Digital rock physics (DRP) has been widely used as an effective approach for estimating the permeability of porous media. However, conventional implementation of DRP requires the reconstruction of three-dimensional (3D) pore networks, which suffer from intensive memory and underlying uncertainties. Therefore, it is [...] Read more.
Digital rock physics (DRP) has been widely used as an effective approach for estimating the permeability of porous media. However, conventional implementation of DRP requires the reconstruction of three-dimensional (3D) pore networks, which suffer from intensive memory and underlying uncertainties. Therefore, it is highly significant to develop an approach only based on two-dimensional (2D) cross-sections of parent samples without 3D reconstruction. In this study, we present a novel approach that combines the Kozeny–Carman equation with fractal theory to derive a bridge function that links 2D cross-sectional images and 3D pore structures of parent samples in flow equivalence. Using this bridge function, we predicted the physical properties of the parent samples, including the permeability, bulk porosity, tortuosity, and pore fractal dimension. To validate our model, we performed Lattice Boltzmann (LB) simulations on nine carbonate samples and compared the LB simulation results with our model’s predictions. We also compared our predicted results with available data on various porous materials, such as sandstone, glass beads, and carbonate, in the literature. Our findings demonstrate that without reconstructing 3D pore networks, our method provides a reliable estimation of sample permeability using 2D cross-sectional images. This approach not only simplifies the determination of sample permeability in heterogeneous porous media but also sheds new light on the inherent correlations between 2D cross-sectional information and 3D pore structures of parent samples. Moreover, the derived model may be conducible to a better understanding of flow in reservoirs during the extraction of unconventional onshore and offshore oil/gas. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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15 pages, 4866 KiB  
Article
Complexity and Heterogeneity Evaluation of Pore Structures in the Deep Marine Shale Reservoirs of the Longmaxi Formation, China
by Boyuan Zhu, Jianghui Meng, Chen Song, Renfang Pan, Zhengping Zhu and Jineng Jin
J. Mar. Sci. Eng. 2023, 11(8), 1613; https://doi.org/10.3390/jmse11081613 - 17 Aug 2023
Viewed by 791
Abstract
The structural evolution and sedimentary differentiation of the Sichuan Basin in China are complex, with intricate reservoir pore structures that significantly impact shale gas production. This study examines the complexity and heterogeneity of the microscopic pore structures in the deep marine shale reservoir [...] Read more.
The structural evolution and sedimentary differentiation of the Sichuan Basin in China are complex, with intricate reservoir pore structures that significantly impact shale gas production. This study examines the complexity and heterogeneity of the microscopic pore structures in the deep marine shale reservoir in the Longmaxi Formation. Pore structure characterization techniques are used to compare deep and shallow–medium marine shales, and siliceous and silty shales. The results reveal the factors influencing pore structure and their impact on exploration and development. The key points are as follows: (1) The pore structure of deep siliceous shale is the most complex due to its diverse range of pore development patterns, pore types, and sizes. (2) The box dimension of full pore size is about 1.52 for deep marine shale and 1.46 for shallow–medium shale. Organic matter (OM) content, the degree of pore development, and inorganic mineral content all correlate positively with the complexity of the pore structure in deep marine shale, which affects the formation of high-quality reservoirs. (3) Lateral heterogeneity of pore structures shows strong regional variations in the study area. Heterogeneity is more pronounced in the deep marine shale than in the medium and shallow shale formations. OM mesopores significantly influence the overall heterogeneity of the shale pore system. The deep marine shale reservoir is situated in an area with strong regional variations. The pore structure of high-quality reservoirs is more complex than those of shallow–medium marine shales, displaying notable heterogeneity. Pore structures with fractal dimension values close to that of the shallow–medium formations (box dimensions within 1.5) offer promising targets for the exploration and development of deep marine shale gas. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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14 pages, 1629 KiB  
Article
Marine Controlled-Source Electromagnetic Data Denoising Method Using Symplectic Geometry Mode Decomposition
by Yijie Chen, Zhenwei Guo and Dawei Gao
J. Mar. Sci. Eng. 2023, 11(8), 1578; https://doi.org/10.3390/jmse11081578 - 11 Aug 2023
Viewed by 833
Abstract
The marine controlled-source electromagnetic (CSEM) method is an efficient tool for hydrocarbon exploration. The amplitudes of signals decay rapidly with the increasing offset, so signals are easily contaminated by various kinds of noise. A denoising method is critical to improve the data quality, [...] Read more.
The marine controlled-source electromagnetic (CSEM) method is an efficient tool for hydrocarbon exploration. The amplitudes of signals decay rapidly with the increasing offset, so signals are easily contaminated by various kinds of noise. A denoising method is critical to improve the data quality, but the diversity of noise makes denoising difficult. Specific frequency signals are transmitted for exploration requirements, and thus traditional filtering methods are not suitable. Symplectic geometry mode decomposition (SGMD), a new method to decompose signals, has an outstanding decomposition performance and noise robustness. Furthermore, it can reduce multiple types of noise by reconstructing the single components. In this study, we introduced SGMD to reduce the noise of marine CSEM data and improved the data quality significantly. The experiments show that SGMD is better than variational mode decomposition and the sym4 wavelet method. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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25 pages, 203904 KiB  
Article
Properties and Model of a Lacustrine Shale Oil Reservoir: A Case Study of the Upper Fourth Member and Lower Third Member of the Shahejie Formation in Dongying Sag and Zhanhua Sag, Jiyang Depression
by Cunfei Ma, Xianxu Fang, Xiaonan Ma, Xiantai Liu, Bingkun Xu and Xinmin Ge
J. Mar. Sci. Eng. 2023, 11(7), 1441; https://doi.org/10.3390/jmse11071441 - 19 Jul 2023
Cited by 1 | Viewed by 1027
Abstract
By combining thermal simulation experiments with core data, thin sections, scanning electron microscopy (SEM), source rock, and high-pressure mercury and gas adsorption analysis, this paper evaluates the properties and models of shale reservoirs in the upper fourth member and the lower third member [...] Read more.
By combining thermal simulation experiments with core data, thin sections, scanning electron microscopy (SEM), source rock, and high-pressure mercury and gas adsorption analysis, this paper evaluates the properties and models of shale reservoirs in the upper fourth member and the lower third member of the Shahejie Formation in Dongying Sag and Zhanhua Sag. The results show that the oil shale is a high-quality source rock with petroleum generation potential. Inorganic mineral pores, organic pores, and fractures have developed with petroleum storage capacity. Clay and organic-rich soft shale lithofacies are interbedded with carbonate-rich hard shale lithofacies to form sandwich-type source–reservoir–caprock assemblages with internal sealing properties. Bitumen occurs mostly in the free state, and to a lesser extent is adsorbed, and shows flow characteristics. The migration resistance of the bitumen is displacement pressure, including capillary force and adsorption resistance, and the main force is pore fluid pressure. The migration modes of the bitumen include both subcritical flow and instantaneous flow, which are controlled by pore fluid pressure, displacement pressure, and the rock’s fracture strength. Owing to the multi-scale characteristics of the shale reservoir space, a vein-type model of a multi-scale progressive transport network is developed that obeys Murray’s law with a dominant migration pathway in the shale reservoir. The shale oil reservoir is a special lithologic reservoir controlled by the sedimentary environment and has self-generation, self-storage, and self-sealing characteristics with developed pore fluid overpressure and a multi-scale transport network. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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21 pages, 25065 KiB  
Article
Sequence Stratigraphy and Implications for Shale Gas Exploration in the Southern Sichuan Basin, South China
by Lingling Xu, Jianghui Meng, Renfang Pan, Xue Yang, Qimeng Sun and Boyuan Zhu
J. Mar. Sci. Eng. 2023, 11(7), 1393; https://doi.org/10.3390/jmse11071393 - 10 Jul 2023
Cited by 1 | Viewed by 963
Abstract
In contrast to the widely used sequence stratigraphic models for passive continental margins, the stacking patterns of strata within epeiric seas, which are influenced by regional tectonic activity, may display opposing characteristics during the same geological period. These variations serve as a record [...] Read more.
In contrast to the widely used sequence stratigraphic models for passive continental margins, the stacking patterns of strata within epeiric seas, which are influenced by regional tectonic activity, may display opposing characteristics during the same geological period. These variations serve as a record of basin evolution and also affect the accumulation of hydrocarbons within the strata. Our study investigated the development potential of the deep Longmaxi Shale in the southern Sichuan Basin by examining the sequence stratigraphy and sedimentary fill patterns. Using a combination of core observation, well-logging data analysis, and 3D seismic profile interpretation, we aimed to gain an understanding of the sedimentary fill history of the Longmaxi Shale during the Early Silurian. Our analysis revealed that deglaciation and regional tectonic events affected the sequence stratigraphy, resulting in unconformities that were identifiable using seismic data and wireline logs. Through an analysis of thirty wireline logs and two seismic profiles, we identified two third-order sequences suggested in the Lower Longmaxi Formation. Within the two third-order sequences were five systems tracts, with the first exhibiting a complete cycle of sea-level change and the second cycle being incomplete due to regional tectonic events. The graptolite succession on the upper Yangtze Platform provided a temporal view of the sequence stratigraphy and sedimentation rates of the Longmaxi Shale. The thickness trends of the systems tracts reflected the interplay of short-term eustasy fluctuations, subsidence, and uplift. Our analysis suggests that regional subsidence played a significant role in the deposition of the second transgressive systems tract (TST) in the Weiyuan and Luzhou areas, which represents a promising target for shale gas exploration, in addition to the first TST. However, the Changning area experienced a relative sea-level decrease due to the intense uplift of the Qianzhogn Paleo-uplift and the increased supply of sediment and is interpreted as a highstand systems tract (HST); it is not considered to have shale gas exploration potential. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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20 pages, 13209 KiB  
Article
Contribution of Various Shale Components to Pore System: Insights from Attributes Analysis
by Lingling Xu, Renfang Pan, Haiyan Hu and Jianghui Meng
J. Mar. Sci. Eng. 2023, 11(7), 1327; https://doi.org/10.3390/jmse11071327 - 29 Jun 2023
Cited by 1 | Viewed by 766
Abstract
Shale pore systems are the result of the geological evolution of different matrix assemblages, and the composition of gas shale is considered to affect the pore systems in shale reservoirs. This study aimed to investigate the impact of both organic and inorganic constituents [...] Read more.
Shale pore systems are the result of the geological evolution of different matrix assemblages, and the composition of gas shale is considered to affect the pore systems in shale reservoirs. This study aimed to investigate the impact of both organic and inorganic constituents on the shale pore system, including specific surface area (SSA) and pore volume in Wufeng–Longmaxi Shale. Multiple linear regression (MLR) was employed to examine the contributions of different components to shale pore structure. The pore structure parameters, including pore SSA and pore volume, were obtained by gas adsorption experiments in 32 Wufeng–Longmaxi Shale (Late Ordovician–Early Silurian) samples. Both pore SSA and pore volume were calculated by the density functional theory (DFT) model on shale samples, and the pore types were determined by high-resolution field emission scanning electron microscopy (FE-SEM). The results of the X-ray diffractometer (XRD) analysis indicate that the Wufeng–Longmaxi Shale is dominated by quartz, clays, carbonates, feldspar, pyrite, and organic matter. Four models were made using SPSS software, all of which showed significant correlation between shale pore size and organic matter (OM) and clays. The content of organic matter played the biggest role in determining the size and structure of the pores. Although the content of quartz is the highest and serves as a rigid skeleton in shale reservoirs, it has complicated effects on the pore structure. In this study, most of the quartz is biogenetic and part of it is transformed from clays in deep shale. Therefore, these two parts of quartz are, respectively, related to organic matter and clays. In essence, the pores related to these two parts of quartz should be attributed to organic matter and clays, which also support the conclusion of the MLR models. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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17 pages, 8615 KiB  
Article
Exploring the Unique Characteristics of High-Pore-Volume Waterflooding and Enhanced Oil Recovery Mechanisms in Offshore Sandstone Reservoirs Using Nuclear Magnetic Resonance Technology
by Junrong Liu, Hangyu Li, Jianchun Xu, Shuyang Liu, Rongjiang Liu, Lianjie Hou and Qizhi Tan
J. Mar. Sci. Eng. 2023, 11(7), 1296; https://doi.org/10.3390/jmse11071296 - 26 Jun 2023
Cited by 3 | Viewed by 957
Abstract
A single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work. We strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a [...] Read more.
A single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work. We strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: briefly describe the main methods or treatments applied; (3) Results: summarize the article’s main findings; (4) Conclusions: indicate the main conclusions or interpretations. The abstract should be an objective representation of the article and it must not contain results that are not presented and substantiated in the main text and should not exaggerate the main conclusions. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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18 pages, 4902 KiB  
Article
Effects of Quartz Precipitation on the Abundance and Preservation of Organic Matter Pores in Cambrian Marine Shale in South China
by Sile Wei, Mingyi Hu, Sheng He, Yanbo Shu, Tian Dong, Qing He, Wei Yang and Quansheng Cai
J. Mar. Sci. Eng. 2023, 11(7), 1267; https://doi.org/10.3390/jmse11071267 - 21 Jun 2023
Cited by 2 | Viewed by 1087
Abstract
To evaluate the effects of quartz precipitation on the abundance and preservation of organic matter pores in marine shale reservoirs, the type of authigenic quartz and the source of silica, as well as the corresponding relation of the Lower Cambrian Shuijingtuo Formation shale [...] Read more.
To evaluate the effects of quartz precipitation on the abundance and preservation of organic matter pores in marine shale reservoirs, the type of authigenic quartz and the source of silica, as well as the corresponding relation of the Lower Cambrian Shuijingtuo Formation shale in South China were investigated. Quartz in the Shuijingtuo shale occurs as four different types: detrital quartz, replacement of biosiliceous debris, euhedral quartz filled in interparticle pores, and microquartz dispersed in a clay matrix. Euhedral quartz (1–5 μm) and matrix-dispersed microquartz (100–400 nm) are found to be the dominant forms of authigenic quartz. The euhedral quartz accumulates along the interparticle pores, and the porous organic matter fills the interior of the space. Microquartz is mainly wrapped in porous organic matter. Two silica sources were revealed: biogenic silica and clay-derived silica. Biogenic Si is most likely the major source for authigenic quartz in the organic-rich (total organic carbon (TOC) > 2.55 wt.%) samples, which accounts for 23–57 wt.% (average 35 wt.%) of the total Si. Based on petrographic observations, we posit that the precipitation of large-sized euhedral quartz in the interparticle pores most likely originated from biogenic silica in the early stage of diagenesis and that the silica for the clay matrix-dispersed microquartz is provided by biogenic silica and clay-derived silica. The observation of SEM images indicates that the precipitation of early diagenetic euhedral quartz in the interparticle pores enhances rock stiffness, and the buttressing effect can protect the organic matter pores from compaction during the late-stage burial diagenesis. In contrast, the precipitation of late diagenetic microquartz in the clay matrix can lead to a reduction in the capacity of the accommodation space to host retained petroleum, consequently leading to a reduction in the development of organic matter pores and the generation of shale gas. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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22 pages, 8852 KiB  
Article
Sequence Stratigraphy, Sedimentology, and Reservoir Characteristics of the Middle Cretaceous Mishrif Formation, South Iraq
by Leifu Zhang, Wenqi Zhang, Yong Li, Benbiao Song, Dawang Liu, Ya Deng, Jiacheng Xu and Yuning Wang
J. Mar. Sci. Eng. 2023, 11(6), 1255; https://doi.org/10.3390/jmse11061255 - 20 Jun 2023
Cited by 2 | Viewed by 1865
Abstract
The Cenomanian–Early Turonian Mishrif Formation is a great contributor to oil production in Iraq. Integrating petrographic, mineralogical, and wireline logging data from 52 wells, this study provides an improved understanding of the sequence stratigraphy, depositional evolution, and reservoir characteristics of the Mishrif Formation [...] Read more.
The Cenomanian–Early Turonian Mishrif Formation is a great contributor to oil production in Iraq. Integrating petrographic, mineralogical, and wireline logging data from 52 wells, this study provides an improved understanding of the sequence stratigraphy, depositional evolution, and reservoir characteristics of the Mishrif Formation in the Mesopotamian Basin, south Iraq. Five types of facies associations are classified: lagoon, shoal, rudist bioherm, shallow marine, and deep marine. Such a classification allows convenient differentiation and interpretation of wireline logs. A sequence stratigraphic framework including five third-order sequences (Mhf 1 to Mhf 5) for the Mishrif Formation is established mainly using wireline logging data of close-distance wells, with the aid of cores and thin sections. Two end-member depositional evolution stages are recognized, from clinoform-like progradational shoal complexes in Mhf 1 within a shallow marine environment, to tidal channels in Mhf 2–3 within a lagoon environment. For Mhf 4–5, abrupt changes in facies associations from north to south indicate the development of an intra-shelf basin where organic-rich mudstones directly overlie the shallow marine grainstone shoals and lagoonal wackestones. Reservoir characteristics and compartmentalization are directly controlled by the sequence stratigraphic framework. Sequence boundaries are featured by wackestones and mudstones overprinted by cementation; they are regionally correlatable and work as regional barriers. Shoal complexes in Mhf 1 and tidal channels in Mhf 2–3 are the main reservoir units. Mudstones and wackestones are intra-reservoir baffles and become more frequently developed towards the south, reflecting the increasing water depth towards south. The characterization of the tidal channels, clinoform-like shoals, and intrashelf basinal deposits in the current study could benefit later development of the Mishrif Formation. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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18 pages, 7878 KiB  
Article
Experimental Study of Mechanical Properties and Fracture Characteristics of Conglomerates Based on Mohr–Coulomb Criteria
by Pengyu Liu, Yinghao Shen, Mianmo Meng, Senlin Luo, Yi Zhong and Qiming Cen
J. Mar. Sci. Eng. 2023, 11(6), 1219; https://doi.org/10.3390/jmse11061219 - 13 Jun 2023
Cited by 1 | Viewed by 1138
Abstract
Gravel is one of the main factors affecting the mechanical properties of conglomerates, which plays a decisive role in crack propagation. In this paper, taking the conglomerate of the Baikouquan Formation in Mahu Sag of Xinjiang as the research object, a three-dimensional model [...] Read more.
Gravel is one of the main factors affecting the mechanical properties of conglomerates, which plays a decisive role in crack propagation. In this paper, taking the conglomerate of the Baikouquan Formation in Mahu Sag of Xinjiang as the research object, a three-dimensional model of the conglomerate is constructed by the discrete element numerical simulation method, and the triaxial compression experiment under different confining pressures is simulated. The mechanical properties and fracture morphology of conglomerate are analyzed with gravel content as a variable and verified by laboratory tests. In this simulation, with the increase of gravel content, the compressive strength of the conglomerate decreases, angle of internal friction decreases, and the fractures show different forms. The results show that the gravel morphology, spatial location, and gravel content have an impact on the mechanical properties of the conglomerate. The gravel content affects the formation process of the dominant fracture surface by controlling the distance between gravels so as to control the internal friction angle and it is the main controlling factor for the mechanical properties of the conglomerate. Gravel cracks initiate at the edge of gravel. Stress controls the formation of main cracks under low gravel content, and the influence of gravels under high gravel content makes cracks more discrete and complex. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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21 pages, 10069 KiB  
Article
Microscopic Analysis of Natural Fracture Properties in Organic-Rich Continental Shale Oil Reservoirs: A Case Study from the Lower Jurassic in the Sichuan Basin, China
by Xuefeng Bai, Saipeng Huang, Xiandong Wang, Zhiguo Wang, Youzhi Wang, Weiqi Ma, Yanping Zhu, Mengdi Sun, Bo Liu, Xiaofei Fu, Lijuan Cheng, Likai Cui and Yudong Hou
J. Mar. Sci. Eng. 2023, 11(5), 1036; https://doi.org/10.3390/jmse11051036 - 12 May 2023
Cited by 2 | Viewed by 1121
Abstract
Natural fractures are of paramount importance in storing carbon in shale oil reservoirs, where ultra-low porosity and permeability necessitate their essentiality for enhanced oil recovery. Therefore, comprehensively clarifying the characteristics of natural fractures in shale oil reservoirs is imperative. This paper focuses on [...] Read more.
Natural fractures are of paramount importance in storing carbon in shale oil reservoirs, where ultra-low porosity and permeability necessitate their essentiality for enhanced oil recovery. Therefore, comprehensively clarifying the characteristics of natural fractures in shale oil reservoirs is imperative. This paper focuses on investigating the microscopic features of natural fractures in organic-rich continental shale oil reservoirs that are commonly found in the Lower Jurassic strata of the Sichuan Basin, employing them as a representative example. Multiple methods were utilized, including mechanical testing, Kaiser testing, multi-scale CT scanning (at 2 mm, 25 mm, and 100 mm scales), and a numerical simulation of fluid seepage in fracture models. The results revealed that the in situ stress of the target seam displays the characteristic of σH > σv > σh, with σv and σh being particularly similar. The relatively high lateral stress coefficient (ranging from 1.020 to 1.037) indicates that the horizontal stresses are higher than the average level. Although the 2 mm CT scan provides a more detailed view of fractures and connected pores, it primarily exhibited more pore information due to the high resolution, which may not fully unveil additional information about the fractures. Thus, the 25 mm shale core is a better option for studying natural fractures. The tortuosity of the different fractures indicated that the morphology of larger fractures is more likely to remain stable, while small-scale fractures tend to exhibit diverse shapes. The simulations demonstrated that the stress sensitivity of fracture permeability is approximately comparable across different fracture scales. Therefore, our research can enhance the understanding of the properties of natural fractures, facilitate predicting favorable areas for shale oil exploration, and aid in evaluating the carbon storage potential of shale oil reservoirs. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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23 pages, 5854 KiB  
Article
The Paleoenvironment and Mechanisms of Organic Matter Enrichment of Shale in the Permian Taiyuan and Shanxi Formations in the Southern North China Basin
by Yanan Wang, Xiulei Cheng, Kai Fan, Zhipeng Huo and Lin Wei
J. Mar. Sci. Eng. 2023, 11(5), 992; https://doi.org/10.3390/jmse11050992 - 07 May 2023
Viewed by 1482
Abstract
The organic-rich shale of the Permian Taiyuan Formation (TYF) and Shanxi Formation (SXF) in the Southern North China Basin (SNCB) is considered a potential shale gas source. The shale was formed in a marine-continental transitional sedimentary environment, which has rarely been studied, with [...] Read more.
The organic-rich shale of the Permian Taiyuan Formation (TYF) and Shanxi Formation (SXF) in the Southern North China Basin (SNCB) is considered a potential shale gas source. The shale was formed in a marine-continental transitional sedimentary environment, which has rarely been studied, with the enrichment mechanisms of organic matter (OM) remaining unclear. This study investigated the controlling factors and enrichment mechanisms of OM by analyzing the total organic carbon (TOC) content, paleoclimate, paleoproductivity, sedimentation rate, redox, and paleosalinity. The TOC of the TYF ranged from 0.92 to 7.43 wt.%, with an average of 2.48 wt.%, which was higher than that of the SXF (TOC = 0.36–5.1 wt.%, average of 1.68 wt.%). These geochemical indices suggest that both the TYF and SXF were deposited in warm and humid paleoclimates, with relatively high biological productivity and sedimentation rates. During the deposition process, the TYF experienced frequent transgression and regression events, leading to an enhancement of water reducibility, a relatively high sedimentation rate, reduced OM oxidation, and rapid deposition of OM, which were conducive to the preservation of OM. Moreover, a high biological productivity increased respiratory oxygen consumption in the water column, which could lead to OM accumulation. However, the regression event experienced by the SXF reduced the paleoproductivity and sedimentation rate and increased water oxidation, leading to a decrease in OM. The main controlling factors for the enrichment of OM in the TYF and SXF were the sedimentation rate, paleoproductivity, and redox conditions, thus establishing the enrichment models for OM in the TYF and SXF. This study is conducive to understanding shale enrichment mechanisms and guiding shale gas exploration. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean)
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