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Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research
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Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "H1: Petroleum Engineering".

Deadline for manuscript submissions: 1 July 2024 | Viewed by 5651

Special Issue Editors

Dr. Qing Li

E-Mail Website
Guest Editor
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China
Interests: characterization and evaluation of tight oil and gas reservoirs (including shale oil and gas reservoirs); sedimentation and diagenesis of fine-grained sedimentary rocks; genetic mechanism and dolomitization of dolomite reservoirs
Dr. Haitao Sun

E-Mail Website
Guest Editor
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Interests: sedimentary petrology; reservoir geology; applied sedimentology

Special Issue Information

Dear Colleagues,

We are pleased to invite you to submit papers to the journal Energies for a Special Issue that will be entirely devoted to “Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research”.

The Special Issue will expand on reservoir characterization technology, the formation mechanism of the high-quality reservoirs, and the accumulation mechanism of unconventional oil and gas reservoirs for improving the understanding of unconventional oil and gas reservoirs. This Special Issue will serve as an excellent channel for sharing information and lessons learned, collected from different plays.

In the last few decades, unconventional resources have gained significant attention from the petroleum industry, and unconventional oil and gas have evolved into an important resource play worldwide. The potential for unconventional oil and gas exploration is huge and has broad implications. Although extensive studies have been conducted on unconventional oil and gas reservoirs in recent years, the formation mechanism of high-quality reservoirs and accumulation mechanism of unconventional oil and gas are still unclear.

Potential topics of interest include but are not limited to:

  • Novel technologies to characterize shale/tight reservoir pore structure;
  • Organic-inorganic interaction in shale diagenesis;
  • Formation mechanism of the high-quality reservoir;
  • Advanced methods for shale oil mobility evaluation;
  • Mechanisms of accumulation of shale/tight oil.

Dr. Qing Li
Dr. Haitao Sun
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Energies is an international peer-reviewed open access semimonthly 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

  • unconventional resources
  • shale oil and gas
  • tight oil
  • reservoir evaluation
  • accumulation mechanism

Published Papers (5 papers)

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Research

16 pages, 6852 KiB  
Article
Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China
by Qing Li, Xuelian You, Jiangshan Li, Yuan Zhou, Hao Lu, Shenghe Wu, Dali Yue and Houmin Zhang
Energies 2024, 17(5), 1140; https://doi.org/10.3390/en17051140 - 28 Feb 2024
Viewed by 455
Abstract
The lithofacies types, pore structure differences, and main controlling factors on the shale reservoirs are vital problems that need to be addressed in the process of shale oil exploration and development. This study explores the Luohe oilfield in the southern Ordos Basin, which [...] Read more.
The lithofacies types, pore structure differences, and main controlling factors on the shale reservoirs are vital problems that need to be addressed in the process of shale oil exploration and development. This study explores the Luohe oilfield in the southern Ordos Basin, which is composed of organic-rich shale in the Chang 7 member, to clarify the reservoir properties and analyze major factors affecting the reservoir quality. The shale reservoir can be divided into five lithofacies using ternary diagrams of TOC, argillaceous minerals, and siliceous minerals: high organic-rich siliceous shale (HOSS), high organic-rich argillaceous shale (HOAS), medium organic-rich siliceous shale (MOSS), medium organic-rich argillaceous shale (MOAS), and low organic-rich shale (LOS). The type of organic matter in the studied samples is mainly Type I kerogen and Type II kerogen, predominantly Type II1 kerogen. The kerogen mostly lie within the mature zone in the study area. Various types of pores have been identified in the studied shale: intergranular pores, intragranular pores, intercrystalline pores, organic matter pores, and seams around organic matter. The pores are commonly nanoscale to micrometer in scale, with diameters ranging from 10 nm to several microns. The S1 content in shale is positively correlated with the macropore content, indicating that macropores in shale are the main effective oil storage spaces and are important for oil-bearing reservoirs. There is a good positive relationship between the macropore volume of shale and the content of organic matter. Organic matter in the shale can be beneficial for generating organic matter pores, dissolution pores, and seams at organic matter edge, resulting in better physical properties of shale reservoirs. There is a negative relationship between the quartz/feldspar content and macropores content, indicating that quartz and feldspar are detrimental for the macropore volume development. The lithofacies type is one of the important factors controlling the macropore volume. MOAS and HOAS are favorable lithofacies for the development of macropores. The findings of this study can be utilized for hydrocarbon exploration and development in the lacustrine shale formation of the Ordos Basin and other similar basins. Full article
(This article belongs to the Special Issue Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research)
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20 pages, 11878 KiB  
Article
Reservoir Characteristics and Influencing Factors of Organic-Rich Siliceous Shale of the Upper Permian Dalong Formation in Western Hubei
by Yang Wang, Luheng Bai, Yanlin Zhang, Xiaoming Zhang, Bowei Yang, Ke Duan, Yi Wang and Tong Xie
Energies 2023, 16(13), 5130; https://doi.org/10.3390/en16135130 - 3 Jul 2023
Cited by 3 | Viewed by 1046
Abstract
To elucidate the reservoir characteristics of organic-rich siliceous shale of the Upper Permian Dalong Formation in western Hubei, this study focused on the drilling cores of Well ED-2. Various techniques, including a mineral composition analysis, an organic carbon content analysis, a vitrinite reflectance [...] Read more.
To elucidate the reservoir characteristics of organic-rich siliceous shale of the Upper Permian Dalong Formation in western Hubei, this study focused on the drilling cores of Well ED-2. Various techniques, including a mineral composition analysis, an organic carbon content analysis, a vitrinite reflectance measurement, a total porosity determination, field emission scanning electron microscopy (FE-SEM), and low-pressure CO2 and N2 physical adsorption tests, were employed to analyze the mineralogy, organic geochemistry, total porosity, and pore structure characteristics. Additionally, the factors influencing the reservoir performance of the Dalong Formation shale were investigated. The results indicated that the Dalong Formation’s shale was characterized as an organic-rich siliceous shale. Organic matter was mainly of sapropelic type, with a relatively high thermal evolution degree and Ro ranging from 2.59% to 2.76%. The total porosity of the Dalong Formation’s siliceous shale was low, indicating poor reservoir properties. Organic matter pores were highly developed, mainly the ones formed after the hydrocarbon generation of solid asphalt. Micropores and mesopores were the dominant pore types in the shale, with macropores being significantly less abundant. The study further revealed that the pore volume and specific surface area exhibited a significantly positive correlation with total organic carbon (TOC) content and clay minerals, while demonstrating a weak negative correlation with quartz content. The comprehensive analysis revealed that there were two factors contributing to the poor physical properties of organic-rich siliceous shale in the Dalong Formation. Firstly, in siliceous shale with a high quartz content, the siliceous component was partly derived from the siliceous cementation of hydrothermal fluids. This process led to the formation of secondary quartz that filled intergranular pores, resulting in a decrease in macropore volume, total porosity, and a weak negative correlation with quartz content. Secondly, in siliceous shale with a relatively high clay mineral content, the organic matter was subjected to stronger compaction due to the relatively low content of brittle minerals. This compaction caused the destruction of most macropores, leaving behind primarily micropores and mesopores. Consequently, the average pore size decreased, leading to poor physical properties. Full article
(This article belongs to the Special Issue Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research)
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18 pages, 8380 KiB  
Article
Control Effect of Deposition Processes on Shale Lithofacies and Reservoirs Characteristics in the Eocene Shahejie Formation (Es4s), Dongying Depression, China
by Yepeng Yang, Zaixing Jiang, Jianguo Zhang, Zongxuan Zhang and Chun Yang
Energies 2023, 16(5), 2200; https://doi.org/10.3390/en16052200 - 24 Feb 2023
Viewed by 1125
Abstract
The lacustrine fine-grained sedimentary rocks in the upper interval of the fourth member of the Eocene Shahejie Formation (Es4s) in the Dongying Depression are important shale oil exploration targets in Bohai Bay Basin. They are widely distributed and rich in organic matter. In [...] Read more.
The lacustrine fine-grained sedimentary rocks in the upper interval of the fourth member of the Eocene Shahejie Formation (Es4s) in the Dongying Depression are important shale oil exploration targets in Bohai Bay Basin. They are widely distributed and rich in organic matter. In this study, samples were observed under the optical microscope and FESEM, combined with geochemical test and physical property analysis to study the sedimentary characteristics and reservoir characteristics of them. Nine lithofacies are recognized based on the mineral composition, the content of organic matter and the beddings. The middle-high organic laminated calcareous fine-grained sedimentary rocks (LF1) and the middle-high organic laminated mixed fine-grained sedimentary rocks (LF2) resulted from seasonal sediment variations and settled by suspension in the deep lake. The middle-high organic flaggy mixed fine-grained sedimentary rocks (LF3), the middle-high organic flaggy calcareous fine-grained sedimentary rocks (LF4), the middle-high organic massive calcareous fine-grained sedimentary rocks (LF5) and the middle organic massive mixed fine-grained sedimentary rocks (LF6) were formed by redeposition. The low organic massive argillaceous fine-grained sedimentary rocks (LF7), the low organic massive felsic fine-grained sedimentary rocks (LF8) and the low organic massive mixed fine-grained sedimentary rocks (LF9) are affected by the terrigenous input events. The pore structures vary in different beddings which are influenced by the kinds and arrangement of minerals and particles. In the laminated lithofacies, the ink-bottle-shaped pores are dominant. In the flaggy and massive lithofacies, the ink-bottle-shaped pores and the slit-shaped pores coexist. LF1 and LF2 are the best target for shale oil exploration and the LF3, LF4, LF5 and LF6 are the second. The deposition processes control the lithofacies and reservoir characteristics of the fined-grained sedimentary rocks. Full article
(This article belongs to the Special Issue Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research)
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20 pages, 5277 KiB  
Article
Evaluation of Shale Oil Mobility for the Eocene Shahejie Formation in Liutun Sag, Dongpu Depression, Bohai Bay Basin
by Qiang Yan, Hongwei Ping, Xin Yang, Honglin Liu and Honghan Chen
Energies 2023, 16(5), 2101; https://doi.org/10.3390/en16052101 - 21 Feb 2023
Cited by 1 | Viewed by 1041
Abstract
Previous studies have shown that shale oil mobility depends on the relative content of free oil and adsorbed oil. However, the research on how to establish a shale oil mobility evaluation is relatively insufficient. This study aims to use pyrolysis data before and [...] Read more.
Previous studies have shown that shale oil mobility depends on the relative content of free oil and adsorbed oil. However, the research on how to establish a shale oil mobility evaluation is relatively insufficient. This study aims to use pyrolysis data before and after extraction to accurately identify the content of free oil and adsorbed oil, analyze the influencing factors of shale oil mobility, characterize the hydrocarbon generation and expulsion process, and evaluate shale oil mobility. We utilized an integrated mineralogical and geochemical dataset from the PS18-1 well in the Liutun Sag, Dongpu Depression, Bohai Bay Basin. The results show that the adsorption capacity of type I organic matter (OM) on shale oil is greater than that of type II OM, the OM abundance is of great significance to shale oil mobility, and that quartz and feldspar can promote shale oil mobility. The Tmax corresponding to the threshold of hydrocarbon expulsion is 438~440 °C, and the oil saturation index (OSI) is about 158 mg/g TOC. There are four small intervals: a (3257 m~3260 m), b (3262 m~3267 m), c (3273 m~3278 m), and d (3281 m~3282 m) meeting the conditions of hydrocarbon expulsion. Large-scale hydrocarbon expulsion occurred in interval a, a small amount of hydrocarbon expulsion in interval b, a large amount of hydrocarbon expulsion in interval c, and almost no hydrocarbon expulsion in interval d. Based on the crossplot of S1 and TOC, combined with other parameters such as OSI, hydrocarbon generation potential (HGP), and free and adsorbed oil, we established an evaluation chart of shale oil mobility and divided it into five categories: A, B, C, D, and E. While categories A and C have good mobility and great resource potential, categories B and D have relatively poor mobility and medium resource potential, and category E has little mobility and is an invalid resource. Full article
(This article belongs to the Special Issue Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research)
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24 pages, 10197 KiB  
Article
Pore Structure and Fractal Characteristics of Tight Sandstone: A Case Study for Huagang Formation in the Xihu Sag, East China Sea Basin, China
by Jin Dong, Zhilong Huang, Jinlong Chen, Tianjun Li, Jing Zhao, Yongshuai Pan and Tong Qu
Energies 2023, 16(4), 2013; https://doi.org/10.3390/en16042013 - 17 Feb 2023
Cited by 3 | Viewed by 1226
Abstract
Various experiments, including routine petrophysical measurements, thin section and scanning electronic microscope (SEM), high-pressure mercury intrusion (HPMI), and nuclear magnetic resonance (NMR), were performed to characterize the microscopic pore structure of tight sandstone in the Huagang Formation (E3h), Xihu Sag, East [...] Read more.
Various experiments, including routine petrophysical measurements, thin section and scanning electronic microscope (SEM), high-pressure mercury intrusion (HPMI), and nuclear magnetic resonance (NMR), were performed to characterize the microscopic pore structure of tight sandstone in the Huagang Formation (E3h), Xihu Sag, East China Sea Basin, China. Specifically, NMR was used to investigate the dynamic variation of fractal dimensions during centrifugation, and the comparison of HPMI and NMR were used to clarify the difference of fractal dimensions. The results showed that there were four types of pores observed in thin section and SEM images: primary intergranular pores, intergranular dissolution pores, intragranular dissolution pores, and micropores within clay aggregates. The geometric shape and pore size of different pore types showed huge differences, indicating the formation of complex and diverse pore structures in the E3h formation. The flow capability of the reservoir was dominated by large pores, while the storage capacity was determined by small pores. The dynamic variation of fractal dimensions calculated by NMR data showed the water residing in the pore structure with low fractal dimensions was removed preferentially, and the pore structure of the resided water was always more complicated than the pore structure of removed water, which indicated the flow capability of the reservoir was affected by the complexity of the pore structure. Based on the comparison of the fractal dimension data from HPMI and NMR, it was found that the variation trends of the fractal dimensions were consistent, as the radius of the pore throat increased, the fractal dimensions increased, and the pore structure became more complicated. Both fractal dimensions of macropores (Dmac) and movable-fluid pores (Dmov) can reflect the flow capability of reservoir effectively, but the correlations between fractal dimensions from HMPI and NMR were poor, which could be due to the different working mechanism in these methods. Full article
(This article belongs to the Special Issue Unconventional Oil and Gas: Reservoir Evaluation and Accumulation Mechanism Research)
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