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Processes
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Phase Behavior Modeling in Unconventional Resources
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Phase Behavior Modeling in Unconventional Resources

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

Deadline for manuscript submissions: 31 August 2026 | Viewed by 1471

Special Issue Editors

Dr. Yanjun Meng

E-Mail Website
Guest Editor
College of Geological and Surveying Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Interests: coalbed methane development geology; adsorption/desorption; coal reservoir damage; oxidation fracturing modification technology; reservoir characterization and modeling
Special Issues, Collections and Topics in MDPI journals
Dr. Yue Chen

E-Mail Website
Guest Editor
College of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China
Interests: coalbed methane geology; coalbed methane development technology; unconventional oil and gas reservoir evaluation; coalfield geology
Dr. Xinlu Yan

E-Mail Website
Guest Editor
College of Geological and Surveying Engineering, Taiyuan University of Technology, Taiyuan 030006, China
Interests: coalbed methane; numerical simulation; coal reservoir evaluation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In recent years, the exploration and development of unconventional oil and gas (including coalbed methane, shale gas, tight sandstone gas, shale oil, tight oil, natural gas hydrates, etc.) have become hotspots in the energy industry. However, unconventional oil and gas reservoirs usually have dense reservoir structures, low porosity and low permeability, and complex fluid phases, which greatly restrict the improvement of unconventional oil and gas recovery rates. The transport properties and mechanisms as well as phase behaviors of unconventional storage under nanoscale constraints show significant deviations from their macroscopic reservoir behaviors. This is due to the significant influence of molecular–wall interactions and molecular–molecule interactions in reservoirs characterized mainly by nanopores. Therefore, conducting phase behavior modeling in unconventional resources is of great significance in the field of geological research for oil and gas development.

For this Special Issue, titled “Phase Behavior Modeling in Unconventional Resources”, we seek high quality works focusing on fluid–structure coupling and phase state modeling. Topics include, but are not limited to, the following:

  1. Simulation and prediction of unconventional oil and gas phases;
  2. Analysis of fluid–structure coupling characteristics of unconventional oil and gas reservoirs;
  3. Characterization of full-scale pore and fracture structures in unconventional oil and gas reservoirs;
  4. Characteristics of surface wettability of unconventional oil and gas reservoirs and methods for enhancing oil recovery;
  5. Physical properties and petrophysical responses of unconventional oil and gas reservoirs;
  6. Dynamic analysis of unconventional oil and gas reservoir modification and development.

Dr. Yanjun Meng
Dr. Yue Chen
Dr. Xinlu Yan
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 250 words) can be sent to the Editorial Office for assessment.

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 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 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

  • phase behavior modeling
  • unconventional resources
  • coalbed methane
  • shale gas
  • bauxite natural gas
  • tight oil
  • tight gas
  • fluid–structure coupling characteristics

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Published Papers (3 papers)

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Research

23 pages, 7628 KB  
Article
Geological Controls and Geochemical Responses Governing CBM Well Productivity in the Sigong River Block of the Southern Junggar Basin, China
by Lexin Xu, Shuling Tang, Yuanhao Zhi, Weiwei Guo, Tuanfei Liu and Jiamin Zhang
Processes 2026, 14(6), 936; https://doi.org/10.3390/pr14060936 - 16 Mar 2026
Viewed by 327
Abstract
The southern Junggar Basin in Xinjiang is rich in coalbed methane (CBM) resources. Large-scale development is underway in the Sigong River block (SGR block) of the Fukang West Block. Based on an integrated analysis of geological and hydrogeochemical characteristics, this study clarifies the [...] Read more.
The southern Junggar Basin in Xinjiang is rich in coalbed methane (CBM) resources. Large-scale development is underway in the Sigong River block (SGR block) of the Fukang West Block. Based on an integrated analysis of geological and hydrogeochemical characteristics, this study clarifies the key factors affecting CBM well productivity in the SGR block. Based on gas and water production performance, four distinct productivity types of CBM wells are identified, which are jointly controlled by burial depth, local structural and hydraulic disturbance, and also governed by synergistic interplay between gas content and permeability. The optimal geological combination—comprising the 700–1000 m burial depth, syncline core structure, stagnant hydrodynamic conditions, relatively high gas content, and favorable permeability—collectively contributes to the high-productivity Type I wells with low water production. In contrast, deep coal seams (>1400 m), characterized by reduced gas content and extremely low permeability, correspond to Type IV wells, which exhibit low gas and water production. Type II wells, located in the 1000–1400 m interval, exhibit moderate and variable productivity controlled by the interplay between high gas content and a wide range of permeability. Shallow margins (<700 m) affected by coal combustion and surface water influx produce high-water and low-gas wells (Type III). Geochemical signatures effectively differentiate between these types: closed, stagnant environments (Types I/II) are marked by a Na-Cl-HCO3/Na-HCO3-Cl water type, moderate total dissolved solids, and low sodium chloride coefficients, while open hydrodynamic conditions (Type III) are indicated by Na-SO4-HCO3 water with high sodium chloride coefficients. A δD-H2O/δ18O-H2O ratio of 7–9, combined with favorable TDS and water type, is identified as a key indicator of high productivity. Based on these relationships, a productivity response index model incorporating critical geological and geochemical parameters was developed. This model provides a practical tool for predicting CBM well performance and targeting sweet spots, offering significant value for exploring geologically and hydrologically complex basins. Full article
(This article belongs to the Special Issue Phase Behavior Modeling in Unconventional Resources)
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18 pages, 6816 KB  
Article
Coalbed Methane Enrichment and Production Potential in Multiple Coal Seams in Yanjiao Composite Syncline, Western Guizhou Province, South China
by Lihua Wang, Guoxiao Zhou, Cunyou Liu and Shida Chen
Processes 2026, 14(5), 842; https://doi.org/10.3390/pr14050842 - 5 Mar 2026
Viewed by 407
Abstract
Coalbed methane (CBM) hosted by multiple (>20) thin (<2 m) seams in South China represents an important unconventional gas supplement. In the Yanjiao composite syncline, high-frequency sea-level fluctuations produced widely distributed thin seams (20–60 layers), with tidal-flat coal groups I (No. 2–No. 9) [...] Read more.
Coalbed methane (CBM) hosted by multiple (>20) thin (<2 m) seams in South China represents an important unconventional gas supplement. In the Yanjiao composite syncline, high-frequency sea-level fluctuations produced widely distributed thin seams (20–60 layers), with tidal-flat coal groups I (No. 2–No. 9) and III (No. 20–No. 35) as primary targets. Variable magma intrusion drives the present coal-rank partitioning (1.8–4.3% Ro) and pronounced reservoir heterogeneity. A basalt floor (>200 m) and the Lower Triassic Feixianguan caprock (~100 m) confine the Longtan strata into an independent hydrodynamic unit. Groundwater migrates from syncline wings to the axial domain and seals CBM in stagnant zones, resulting in higher gas contents toward the axis. Deep CBM is constrained by high in situ stress and low permeability (typically <0.1 mD below 600 m) and a relatively uniform and low-abnormal pressure system. The syncline is divided into four parts: Part I is the most favorable, where staged fracturing of closely spaced (<60 m) coal group III achieved a maximum production rate of 2400 m3/d and a stabilized rate of 2100 m3/d, whereas Part IV (depth > 1000 m) records a peak daily gas rate of 512–654 m3/d and shows no stabilized-production stage. Full article
(This article belongs to the Special Issue Phase Behavior Modeling in Unconventional Resources)
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19 pages, 7768 KB  
Article
The Evolution Law of Molecular Structure of Vitrain and Durain During Low–Medium Coalification
by Yue Chen, Zan Liu, Huaichang Wang, Changjiang Ji, Liya Wang, Pengpeng Guan, Peilin Wang, Kai Ma and Liyuan Dang
Processes 2026, 14(3), 401; https://doi.org/10.3390/pr14030401 - 23 Jan 2026
Viewed by 336
Abstract
Molecular structural disparities between maceral components are intrinsic factors governing their reactivity and physicochemical behaviors during storage and transportation. To investigate the molecular structural differentiation between vitrain and durain in low- to medium-rank coals (Ro,max = 0.65–1.71%), this study selected samples [...] Read more.
Molecular structural disparities between maceral components are intrinsic factors governing their reactivity and physicochemical behaviors during storage and transportation. To investigate the molecular structural differentiation between vitrain and durain in low- to medium-rank coals (Ro,max = 0.65–1.71%), this study selected samples of long-flame coal and gas coal from the Huanglong Coalfield, coking coal from the Hedong Coalfield, and fat coal from the Weibei Coalfield. The microstructural variations in macroscopic coal components during coalification were analyzed using Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (13C-NMR), and X-ray photoelectron spectroscopy (XPS). The results indicated that the aromatic structures of vitrain are predominantly trisubstituted, with their proportion consistently exceeding that in durain. In contrast, durain exhibits a progressive transition from trisubstituted to pentasubstituted aromatics with increasing coal rank, accompanied by higher aromaticity, condensation degree, and aromatic carbon content. The d002 size of the vitrain decreased from 3.82 to 3.47, while that of the durain decreased from 3.52 to 3.40. Both values showed a gradual decline, with the vitrain exhibiting a larger reduction than the durain. This indicates that the lateral extension of the microcrystalline structure in the durain is more developed, resulting in tighter molecular connections. 13C-NMR analysis further reveals that durain possesses higher falH/fal* and bridge carbon ratios (XBP), along with a lower faS/fa’ ratio, reflecting a greater degree of aromatic ring condensation. XPS analysis revealed that durain generally contains a higher oxygen-functional group content but lower C-C/C-H content compared to vitrain. Collectively, these findings confirm significant structural divergence between vitrain and durain during coalification, with durain exhibiting more developed aromaticity, structural condensation, and organizational order. Full article
(This article belongs to the Special Issue Phase Behavior Modeling in Unconventional Resources)
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