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Advances in Theory and Technology of Unconventional Oil and Gas...
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Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Energy Systems".

Deadline for manuscript submissions: 25 December 2025 | Viewed by 2397

Special Issue Editors

Prof. Dr. Hui Han

E-Mail Website
Guest Editor
School of Geoscience and Technology, Southwest Petroleum University (SWPU), Chengdu 610500, China
Interests: geochemistry; shale oil and gas evaluation; hydrocarbon accumulation mechanism
Special Issues, Collections and Topics in MDPI journals
Dr. Haifeng Gai

E-Mail Website
Guest Editor
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Interests: petroleum geochemistry; hydrocarbon generation kinetics; hydrocarbon accumulation process
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Unconventional oil and gas resources have garnered increasing attention over the past few years. The differences between unconventional and conventional reservoirs are abundant. For instance, unconventional oil and gas reservoirs serve as both source rocks and storage space, and they possess low porosity and permeability. Therefore, numerous unconventional technologies and methods have been developed to examine unconventional reservoirs, such as SEM, TEM, and gas (CO2 and N2) adsorption. In addition, many novel theories abound that can facilitate the exploration and production unconventional oil and gas reservoirs. These advancements in the theory and technology of unconventional oil and gas reservoirs have stimulated a rapid increase in oil and gas production. This Special Issue, “Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs”, aims to cover novel advances in the geological theories and experimental methods used in the exploration and exploitation of unconventional oil and gas reservoirs. Relevant themes include, but are not limited to, the following:

  • The exploration and production of unconventional oil and gas reservoirs;
  • The characterization of unconventional reservoirs;
  • The mechanisms of unconventional oil and gas accumulation;
  • The processes of unconventional oil and gas reservoir formation;
  • The evaluation of unconventional oil and gas resources.

Prof. Dr. Hui Han
Dr. Haifeng Gai
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. Processes 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 2400 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

  • shale oil and shale gas
  • coalbed methane
  • oil shale
  • tight oil and tight gas
  • gas hydrate

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Published Papers (5 papers)

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Research

16 pages, 3614 KB  
Article
Molecular Simulation Study on the Competitive Adsorption and Diffusion of CH4 and CO2 in Coal Nanopores with Different Pore Sizes
by Guangli Huang, Qinghua Zhang and Fujin Lin
Processes 2025, 13(9), 2990; https://doi.org/10.3390/pr13092990 - 19 Sep 2025
Viewed by 207
Abstract
Coalbed methane (CBM), mainly composed of methane (CH4) and carbon dioxide (CO2), has attracted increasing attention due to its dual significance as a clean energy resource and its role in greenhouse gas management. This research systematically examines the adsorption, [...] Read more.
Coalbed methane (CBM), mainly composed of methane (CH4) and carbon dioxide (CO2), has attracted increasing attention due to its dual significance as a clean energy resource and its role in greenhouse gas management. This research systematically examines the adsorption, desorption, diffusion, and bubble evolution dynamics of methane (CH4) and carbon dioxide (CO2) in graphene nanopores with diameters of 4 nm, 6 nm, and 8 nm by molecular dynamics simulations. Radial distribution function (RDF) analyses reveal strong solvation of both gases by water, with CO2 exhibiting slightly stronger interactions. Adsorption and desorption dynamics indicate that CO2 molecules display shorter residence times on the graphene surface (0.044–0.057 ns) compared with CH4 (0.055–0.062 ns), reflecting faster surface exchange. Gas-phase molecular number analysis demonstrates that CH4 accumulates more significantly in the vapor phase, while CO2 is more prone to adsorption and re-dissolution. Mean square displacement (MSD) results confirm enhanced molecular mobility in larger pores, with CH4 showing greater overall diffusivity. Structural evolution of the 8 nm system highlights asymmetric bubble dynamics, where large bubbles merge with the upper adsorption layer to form a thicker layer, while smaller bubbles contribute to a thinner layer near the lower surface. CH4 and CO2 follow similar pathways, though CO2 diffuses farther post-desorption due to its weaker surface retention. These results provide fundamental insights into confinement-dependent gas behavior in graphene systems, offering guidance for gas separation and storage applications. Full article
(This article belongs to the Special Issue Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs)
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21 pages, 2133 KB  
Article
The Supercritical Adsorption Potential Equation for Shale Gas and Its Application: A Case Study of Methane Adsorption in Danish Bornholm Shale
by Pei Xue, Quansheng Liang, Chao Gao, Jintao Yin, Cheng Huang and Yushan Ma
Processes 2025, 13(9), 2918; https://doi.org/10.3390/pr13092918 - 12 Sep 2025
Viewed by 240
Abstract
Since shale gas adsorption belongs to supercritical gas adsorption, the ideal gas adsorption potential equation is not suitable for calculating the adsorption potential of shale gas. In this study, the supercritical gas adsorption potential equation is proposed based on the assumption that the [...] Read more.
Since shale gas adsorption belongs to supercritical gas adsorption, the ideal gas adsorption potential equation is not suitable for calculating the adsorption potential of shale gas. In this study, the supercritical gas adsorption potential equation is proposed based on the assumption that the adsorbed phase is a real gas. The adsorbed phase pressure, as the parameter in the adsorption potential equation, was calculated using the Amankwah equation. For the unknown parameter K in the Amankwah equation, a method for determining the optimal value of K based on the consistency of the adsorption characteristic curve and the accuracy of the predicted isothermal adsorption curve is proposed, thus obtaining the adsorbed phase pressure. Simultaneously, based on a comparison of the ideal gas and supercritical gas adsorption potential, a simplified equation for the supercritical gas adsorption potential is proposed. In this paper, the isothermal adsorption curve of CH4 adsorbed by Holm shale is used to carry out practical calculations. This study revealed that the optimal value of K for the CH4 adsorption system in Holm shale is 2.9, with the adsorbed phase pressure ranging from 17.11 to 32.19 MPa within the temperature range of 300–373 K. The supercritical gas adsorption characteristic curves exhibited excellent consistency, and the average relative error of the predicted ascending segment of the excess adsorption isotherm at 373 K was merely 1.77%, thereby substantiating the rationality of the supercritical gas adsorption potential equation. The simplified equation for supercritical gas adsorption potential is straightforward in form, facilitating its widespread application and promotion. Full article
(This article belongs to the Special Issue Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs)
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23 pages, 11598 KB  
Article
Characteristics of Load-Bearing Rupture of Rock–Coal Assemblages with Different Height Ratios and Multivariate Energy Spatiotemporal Evolution Laws
by Bo Wang, Guilin Wu, Guorui Feng, Zhuocheng Yu and Yingshi Gu
Processes 2025, 13(8), 2588; https://doi.org/10.3390/pr13082588 - 15 Aug 2025
Viewed by 508
Abstract
The destabilizing damage of rock structures in coal beds engineering is greatly influenced by the bearing rupture features and energy evolution laws of rock–coal assemblages with varying height ratios. In this study, we used PFC3D to create rock–coal assemblages with rock–coal height ratios [...] Read more.
The destabilizing damage of rock structures in coal beds engineering is greatly influenced by the bearing rupture features and energy evolution laws of rock–coal assemblages with varying height ratios. In this study, we used PFC3D to create rock–coal assemblages with rock–coal height ratios of 2:8, 4:6, 6:4, and 8:2. Uniaxial compression simulation was then performed, revealing the expansion properties and damage crack dispersion pattern at various bearing phases. The dispersion and migration law of cemented strain energy zoning; the size and location of the destructive energy level and its spatiotemporal evolution characteristics; and the impact of height ratio on the load-bearing characteristics, crack extension, and evolution of multiple energies (strain, destructive, and kinetic energies) were all clarified with the aid of a self-developed destructive energy and strain energy capture and tracking Fish program. The findings indicate that the assemblage’s elasticity modulus and compressive strength slightly increase as the height ratio increases, that the assemblage’s cracks begin in the coal body, and that the number of crack bands inside the coal body increases as the height ratio increases. Also, the phenomenon of crack bands penetrating the rock through the interface between the coal and rock becomes increasingly apparent. The total number of cracks, including both tensile and shear cracks, decreases as the height ratio increases. Among these, tensile cracks are consistently more abundant than shear cracks, and the proportion between the two types remains relatively stable regardless of changes in the height ratio. The acoustic emission ringing counts of the assemblage were not synchronized with the development of bearing stress, and the ringing counts started to increase from the yield stage and reached a peak at the damage stage (0.8σc) after the peak of bearing stress. The larger the rock–coal height ratio, the smaller the peak and the earlier the timing of its appearance. The main body of strain energy accumulation was transferred from the coal body to the rock body when the height ratio exceeded 1.5. The peak values of the assemblage’s strain energy, destructive energy, and kinetic energy curves decreased as the height ratio increased, particularly the energy amplitude of the largest destructive energy event. In order to prevent and mitigate engineering disasters during deep mining of coal resources, the research findings could serve as a helpful reference for the destabilizing properties of rock–coal assemblages. Full article
(This article belongs to the Special Issue Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs)
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19 pages, 7491 KB  
Article
A Model and the Characteristics of Gas Generation of the Longmaxi Shale in the Sichuan Basin
by Xuewen Shi, Yi Li, Yuqiang Jiang, Ye Zhang, Wei Wu, Zhiping Zhang, Zhanlei Wang, Xingping Yin, Yonghong Fu and Yifan Gu
Processes 2025, 13(7), 2294; https://doi.org/10.3390/pr13072294 - 18 Jul 2025
Viewed by 399
Abstract
Currently, the Longmaxi shale in the Sichuan Basin is the most successful stratum of shale gas production in China. However, because Longmaxi shale mostly has high over-maturity, a low-maturity sample cannot be obtained for gas generation thermal simulations, and as a result, a [...] Read more.
Currently, the Longmaxi shale in the Sichuan Basin is the most successful stratum of shale gas production in China. However, because Longmaxi shale mostly has high over-maturity, a low-maturity sample cannot be obtained for gas generation thermal simulations, and as a result, a gas generation model has not yet been established for it. Therefore, models of other shales are usually used to calculate the amount of gas generated from Longmaxi shale, but they may produce inaccurate results. In this study, a Longmaxi shale sample with an equivalent vitrinite reflectance calculated from Raman spectroscopy (EqVRo) of 1.26% was obtained from Well Yucan 1 in the Chengkou area, northeast Sichuan Province. This Longmaxi shale may have the lowest maturity in nature. Pyrolysis simulations based on gold tubes were performed on this sample, and the gas generation line was obtained. The amount of gas generated during the low-maturity stage was compensated by referring to gas generation data obtained from Lower Silurian black shale in western Lithuania. Thus, a gas generation model of the Longmaxi shale was built. The model showed that the gas generation process of Longmaxi shale could be divided into three stages: (1) First, there is the quick generation stage (EqVRo 0.5–3.0%), where hydrocarbon gases were generated quickly and constantly, and the generation rate was steady. A maximum of 458 mL/g TOC was reached at a maturity of 3.0% EqVRo. (2) Second, there is the stable stage (EqVRo 3.0–3.25%), where the amount of generated gas reached a plateau of 453–458 mL/g TOC. (3) Third, there is the rapid descent stage (EqVRo > 3.25%), where the amount of generated gas started to decrease, and it was 393 mL/g TOC at an EqVRo of 3.34%. This model allows us to more accurately calculate the amount of gas generated from the Longmaxi shale in the Sichuan Basin. Full article
(This article belongs to the Special Issue Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs)
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21 pages, 2074 KB  
Article
Influence of Clay Content on the Compaction and Permeability Characteristics of Sandstone Reservoirs
by Jin Pang, Tongtong Wu, Chunxi Zhou, Haotian Chen, Jiaao Gao and Xinan Yu
Processes 2025, 13(6), 1835; https://doi.org/10.3390/pr13061835 - 10 Jun 2025
Viewed by 665
Abstract
Clay content is a critical geological parameter influencing the pore structure, compaction sensitivity, and flow capacity of sandstone reservoirs. In this study, representative Tertiary sandstones from a major sedimentary basin in western China were selected, covering natural and synthetic core samples with clay [...] Read more.
Clay content is a critical geological parameter influencing the pore structure, compaction sensitivity, and flow capacity of sandstone reservoirs. In this study, representative Tertiary sandstones from a major sedimentary basin in western China were selected, covering natural and synthetic core samples with clay contents ranging from 20% to 70%. Utilizing a self-developed apparatus capable of both static and dynamic compaction experiments, we systematically performed staged static loading and gas–water two-phase displacement tests. This enabled us to obtain comprehensive datasets on porosity, permeability, pressure response, and two-phase flow characteristics under various clay content, confining pressure, and gas drive rate conditions. Results demonstrate that high clay content leads to pronounced pore structure compaction and substantially greater permeability reductions compared to low-clay reservoirs, indicating heightened stress sensitivity. The synergy between gas drive rate and confining pressure regulates intralayer water production efficiency: initially, increased gas drive enhances mobile water production, but efficiency drops sharply at late stages due to pore contraction and increased bound water. As confining pressure increases, the mixed-flow region for two-phase flow shrinks, with water permeability decreasing sharply and gas permeability increasing, revealing the dynamic fluid transport and productivity decline mechanisms controlled by effective stress. The research deepens understanding of compaction–flow mechanisms in clay-rich sandstones, offering bases for evaluating reservoir stress sensitivity and supporting efficient, sustainable gas reservoir development, which increasingly helps offset global energy shortages. Full article
(This article belongs to the Special Issue Advances in Theory and Technology of Unconventional Oil and Gas Reservoirs)
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