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Engineering Problems in the Development of Unconventional Oil and Gas...
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Engineering Problems in the Development 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: 30 April 2026 | Viewed by 2322

Special Issue Editors

Dr. Junliang Zhao

E-Mail Website
Guest Editor
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Interests: microscale rock mechanics
Prof. Dr. Huiying Tang

E-Mail Website
Guest Editor
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Interests: hydraulic fracturing simulation; geomechanical modeling; machine-learning-assisted fracturing optimization; integrated simulation of fracturing and production; gas storage stability analysis
Special Issues, Collections and Topics in MDPI journals
Dr. Haibin Chang

E-Mail Website
Guest Editor
School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
Interests: subsurface flow simulation; production optimization; data assimilation; machine learning; underground gas storage

Special Issue Information

Dear Colleagues,

Unconventional hydrocarbon accounts for approximately 80% of the total oil and gas resources all over the world. The development of unconventional reservoirs constitutes a significant guarantee for realizing the transformation of the global energy mix. Due to its low porosity and low permeability, multiscale structure spanning nanometers to kilometers, strong heterogeneity, and complex geological conditions, unconventional oil and gas extraction involves numerous engineering challenges. The representative engineering problems include cross-scale reservoir characterization and evaluation, stress field and natural fracture description and evolution, prediction and real-time tracking of artificial fracture network propagation, rapid and safe drilling, and dynamic optimization of fracturing stimulation methods. 

This Special Issue aims to assemble original research works attempting to solve aforementioned problems. Relevant aspects include, but are not limited to, the following:

  1. Laboratory experiments involving advanced techniques;
  2. Simulation coupling multi-physical fields;
  3. Machine learning used for enhancing unconventional reservoirs;
  4. Correlations among multiple scales;
  5. Filed applications of new theories and methodologies.

Dr. Junliang Zhao
Prof. Dr. Huiying Tang
Dr. Haibin Chang
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

  • unconventional reservoir
  • engineering problem
  • laboratory experiment
  • multi-physical simulation
  • machine learning
  • cross-scale characterization
  • field application

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Further information on MDPI's Special Issue policies can be found here.

Published Papers (4 papers)

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Research

26 pages, 6759 KB  
Article
Nonlinear Stress Sensitivity of Multiple Continua in Shale and Its Impact on Production: An Experimental Study on Longmaxi Formation, Southern Sichuan Basin, China
by Xue-Feng Yang, Hai-Peng Liang, Yue Chen, Shan Huang, Dong-Chen Liu, Yuan-Han He, Xue-Lun Zhang, Chong-Jiu Qu, Lie-Yan Cao and Kai-Xiang Di
Processes 2026, 14(2), 325; https://doi.org/10.3390/pr14020325 - 16 Jan 2026
Viewed by 290
Abstract
Based on a nonlinear effective stress coefficient calculation method, this study investigates the nonlinear stress sensitivity of permeability in deep shale gas reservoirs through high-temperature, high-pressure experiments on matrix, unpropped fracture, and propped fracture samples. Furthermore, the influence of different effective stress models [...] Read more.
Based on a nonlinear effective stress coefficient calculation method, this study investigates the nonlinear stress sensitivity of permeability in deep shale gas reservoirs through high-temperature, high-pressure experiments on matrix, unpropped fracture, and propped fracture samples. Furthermore, the influence of different effective stress models on production performance in deep shale gas wells was investigated using the PETREL integrated fracturing production simulation module. Results reveal significant nonlinearity in the effective stress behavior of all media, with matrix samples showing much stronger permeability stress sensitivity than fracture samples. Numerical simulations revealed that horizontal well productivity under the nonlinear effective stress model was lower than predictions from the net stress model, providing critical theoretical and technical foundations for the large-scale and efficient development of deep marine shale gas reservoirs in the Sichuan Basin and emphasizing the importance of accurate stress models for production performance forecasting. Full article
(This article belongs to the Special Issue Engineering Problems in the Development of Unconventional Oil and Gas Reservoirs)
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16 pages, 2859 KB  
Article
Production Dynamics of Hydraulic Fractured Horizontal Wells in Shale Gas Reservoirs Based on Fractal Fracture Networks and the EDFM
by Hongsha Xiao, Man Chen, Shuang Li, Jianying Yang, Siliang He and Ruihan Zhang
Processes 2026, 14(1), 114; https://doi.org/10.3390/pr14010114 - 29 Dec 2025
Viewed by 347
Abstract
The development of shale gas reservoirs relies on complex fracture networks created via multistage hydraulic fracturing, yet most existing models still use oversimplified fracture geometries and therefore cannot fully capture the coupled effects of multiscale fracture topology on flow and production. To address [...] Read more.
The development of shale gas reservoirs relies on complex fracture networks created via multistage hydraulic fracturing, yet most existing models still use oversimplified fracture geometries and therefore cannot fully capture the coupled effects of multiscale fracture topology on flow and production. To address this gap, in this study, we combine fractal geometry with the Embedded Discrete Fracture Model (EDFM) to analyze the production dynamics of hydraulically fractured horizontal wells in shale gas reservoirs. A tree-like fractal fracture network is first generated using a stochastic fractal growth algorithm, where the iteration number, branching number, scale factor, and deviation angle control the self-similar hierarchical structure and spatial distribution of fractures. The resulting fracture network is then embedded into an EDFM-based, fully implicit finite-volume simulator with Non-Neighboring Connections (NNCs) to represent multiscale fracture–matrix flow. A synthetic shale gas reservoir model, constructed using representative geological and engineering parameters and calibrated against field production data, is used for all numerical experiments. The results show that increasing the initial water saturation from 0.20 to 0.35 leads to a 26.4% reduction in cumulative gas production due to enhanced water trapping. Optimizing hydraulic fracture spacing to 200 m increases cumulative production by 3.71% compared with a 100 m spacing, while longer fracture half-lengths significantly improve both early-time and stabilized gas rates. Increasing the fractal iteration number from 1 to 3 yields a 36.4% increase in cumulative production and markedly enlarges the pressure disturbance region. The proposed fractal–EDFM framework provides a synthetic yet field-calibrated tool for quantifying the impact of fracture complexity and design parameters on shale gas well productivity and for guiding fracture network optimization. Full article
(This article belongs to the Special Issue Engineering Problems in the Development of Unconventional Oil and Gas Reservoirs)
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15 pages, 5802 KB  
Article
Experimental Study on the Mechanical Damage and Permeability Evolution of Tight Sandstone Reservoir Under Triaxial Loading
by Mingnan Xu, Yintong Guo, Haijun Mao, Yinping Li, Xilin Shi, Hongling Ma, Yuting He and Jiangyu Fang
Processes 2025, 13(12), 3919; https://doi.org/10.3390/pr13123919 - 4 Dec 2025
Cited by 2 | Viewed by 582
Abstract
This study systematically investigates the evolution of mechanical damage and the permeability response of tight sandstone under triaxial compression and alternating load conditions, with a focus on the safety and stability of deep underground tight sandstone gas storage reservoirs in China subjected to [...] Read more.
This study systematically investigates the evolution of mechanical damage and the permeability response of tight sandstone under triaxial compression and alternating load conditions, with a focus on the safety and stability of deep underground tight sandstone gas storage reservoirs in China subjected to complex geological environments and alternating stress conditions. By integrating conventional triaxial testing, cyclic loading experiments, CT scanning, and fractal dimension analysis, this study elucidates the enhancement effects and transformation mechanisms of confining pressure on the strength behavior and failure patterns of sandstone. It identifies the influence mechanisms of fault roughness on permeability and its convergence behavior under high-stress conditions and comprehensively characterizes the three-stage evolution of sandstone damage at the microscale under cyclic loading. Experimental results showed that with increasing confining pressure, both the peak strength and elastic modulus of sandstone displayed an increasing trend. With confining pressure increasing from 10 MPa to 40 MPa, the peak deviatoric stress increased from 98.42 MPa to 171.00 MPa and the elastic modulus rose from 8.70 GPa to 12.65 GPa. The failure mode transitioned from brittle shear failure under low confining pressure to a ductile-plastic failure pattern under high confining pressure. Alternating loading resulted in a 17.23% reduction in sandstone strength (from 98.42 MPa to 81.46 MPa at 10 MPa confining pressure). At confining pressures > 25 MPa, the permeability differences among faults with different roughness converged to within 10%. These research findings offer a robust experimental foundation and theoretical framework for evaluating the long-term stability and predicting the sealing performance of deep underground gas storage reservoirs. Full article
(This article belongs to the Special Issue Engineering Problems in the Development of Unconventional Oil and Gas Reservoirs)
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16 pages, 3548 KB  
Article
Modeling Transient Vaporous Cavitating Flow in Pipelines by a Two-Phase Homogeneous Flow Model
by Jie He, Changjun Li and Yuying Guo
Processes 2025, 13(11), 3510; https://doi.org/10.3390/pr13113510 - 1 Nov 2025
Cited by 2 | Viewed by 709
Abstract
Vaporous cavitating flow may occur in pipelines when a water hammer causes pressure to drop to saturated vapor pressure. This paper presents a two-phase homogeneous flow model for transient vaporous cavitating flows. The homogeneous flow model consists of continuity and momentum balance equations [...] Read more.
Vaporous cavitating flow may occur in pipelines when a water hammer causes pressure to drop to saturated vapor pressure. This paper presents a two-phase homogeneous flow model for transient vaporous cavitating flows. The homogeneous flow model consists of continuity and momentum balance equations and an equation describing the volume fraction of vapor. A two-step finite difference MacCormack scheme is used to solve the model. The calculated results obtained from the model are compared with those of the classical discrete gas cavity model (DGCM) and with experimental data from the literature. For all test cases, the model converged at a similar number of grids. The numerical results indicate that the model can reproduce cavitation events well, especially for the prediction of the first maximum pressure peak after cavity collapse. The model also provides direct access to the vapor volume fraction at each location as a function of time. Through numerical analyses, the initial vapor volume fraction in the model is selected as 10−7; with this selection, the numerical results are in good agreement with experimental data. The model also exhibits comparable predictive capability with respect to the DGCM and superior performance under some operating conditions. Nevertheless, neither of these two models can appropriately estimate the pressure phase in severe cavitation events. Full article
(This article belongs to the Special Issue Engineering Problems in the Development of Unconventional Oil and Gas Reservoirs)
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