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Advances in Unconventional Reservoir Development and CO2 Storage
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Advances in Unconventional Reservoir Development and CO2 Storage

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

Deadline for manuscript submissions: 30 January 2026 | Viewed by 3582

Special Issue Editors

Dr. Xiukun Wang

E-Mail Website
Guest Editor
Unconventional Petroleum Research Institute, China University of Petroleum-Beijing, Beijing 102249, China
Interests: unconventional reservoir development; underground hydrogen and CO2 storage; high-resolution high-performance subsurface flow simulation
Dr. Junrong Liu

E-Mail Website
Guest Editor
School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Interests: unconventional oil and gas; EOR; CO2 storage
Special Issues, Collections and Topics in MDPI journals
Dr. Kerui Liu

E-Mail Website
Guest Editor Assistant
School of Geoscience & Resource Engineering, China University of Mining & Technology, Xuzhou 221116, China
Interests: unconventional reservoir development; underground hydrogen and CO2 storage; hydrualic fracturing; fluid-rock interaction

Special Issue Information

Dear Colleagues,

As global energy consumption continues to rise rapidly, the development of unconventional reservoirs is becoming increasingly important in petroleum engineering. To mitigate greenhouse gas emissions and combat global warming and climate change, significant efforts are being directed towards CO2 storage.

Despite recent advancements and techniques, unresolved challenges persist in the development of unconventional reservoirs and CO2 storage. Hydraulic fracturing is widely used to create fractures that enhance oil recovery and facilitate CO2 distribution. The characterization and conductivity of these fractures and fracture networks are crucial for both unconventional reservoir development and CO2 spread. While large volumes of fracturing fluid are injected into reservoirs, only a fraction is recovered; the remainder can impact oil recovery and CO2 distribution. The complex phase behaviors that vary with spatial and vertical heterogeneity further influence these processes. Additionally, the mechanisms governing fluid flow within reservoirs remain unclear due to the intricate microstructures involved, complicating efforts in unconventional reservoir development and CO2 storage.

This Special Issue aims to showcase recent advances in unconventional reservoir development and CO2 storage. We welcome both research and review articles and invite prospective authors to submit high-quality original works that explore innovative approaches to promoting unconventional reservoir development and CO2 storage, particularly those that integrate geological and engineering theories and methodologies.

Potential topics include, but are not limited to the following:

  • Geochemical and geophysical characterization of unconventional reservoirs;
  • Innovative technologies for unconventional reservoirs development;
  • Numerical or experimental methods of multiphase flow in unconventional reservoirs;
  • Techno-economic analysis of unconventional resources;
  • CO2 storage and enhanced oil recovery in conventional and unconventional oil reservoir;
  • CO2 storage in deep saline aquifers and techno-economic analysis;
  • Advances in subsurface flow simulation.

Dr. Xiukun Wang
Dr. Junrong Liu
Guest Editors

Dr. Kerui Liu
Guest Editor Assistant

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

  • unconventional reservoir
  • CO2 storage
  • hydraulic fracturing
  • enhanced oil recovery
  • CO2 -EOR
  • fluid–rock interaction
  • multiphase flow mechanism

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Published Papers (6 papers)

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Research

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20 pages, 5393 KiB  
Article
Robust Optimization of Hydraulic Fracturing Design for Oil and Gas Scientists to Develop Shale Oil Resources
by Qiang Lin, Wen Fang, Li Zhang, Qiuhuan Mu, Hui Li, Lizhe Li and Bo Wang
Processes 2025, 13(6), 1920; https://doi.org/10.3390/pr13061920 - 17 Jun 2025
Viewed by 315
Abstract
Shale plays with pre-existing natural fractures can yield significant production when operating horizontal wells with multi-stage hydraulic fracturing (HWMHF). This work proposes a general, robust, and integrated framework for estimating optimal HWMHF design parameters in an unconventional naturally fractured oil reservoir. This work [...] Read more.
Shale plays with pre-existing natural fractures can yield significant production when operating horizontal wells with multi-stage hydraulic fracturing (HWMHF). This work proposes a general, robust, and integrated framework for estimating optimal HWMHF design parameters in an unconventional naturally fractured oil reservoir. This work considers uncertainty in both the distribution of the natural fractures and uncertainty in three geo-mechanical parameters: the internal friction factor, the cohesion coefficient, and the tensile strength. Because a maximum of five design variables is considered, it is appropriate to apply derivative-free algorithms. This work considers versions of the genetic algorithm (GA), particle swarm optimization (PSO), and general pattern search (GPS) algorithms. The forward model consists of two linked software programs: a geo-mechanical simulator and an unconventional shale oil simulator. The two simulators run sequentially during the optimization process without human intervention. The in-house geo-mechanical simulator model provides sufficient computational efficiency so that it is feasible to solve the robust optimization problem. An embedded discrete fracture model (EDFM) is implemented to model large-scale fractures. Two cases strongly verified the feasibility of the framework for the optimization of HWMHF, and the average comprehensive NPV increases by 35% and 102.4%, respectively. By comparison, the pattern search algorithm is more suitable for HWMHF optimization. In this way, oil and gas scientists are contributing to the energy industry more accurately and resolutely. Full article
(This article belongs to the Special Issue Advances in Unconventional Reservoir Development and CO2 Storage)
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21 pages, 5300 KiB  
Article
Micro-Pore Structure and Fractal Characteristics of Shale Reservoir in Jiyang Depression
by Qin Qian, Mingjing Lu, Anhai Zhong, Feng Yang, Wenjun He and Lei Li
Processes 2025, 13(6), 1704; https://doi.org/10.3390/pr13061704 - 29 May 2025
Viewed by 376
Abstract
In order to better understand the micropore structure of shale reservoir in Jiyang Depression, permeability damage test, low temperature nitrogen adsorption and scanning electron microscopy (SEM) were carried out on six cores in the target block. The adsorption isotherms were analyzed by Frenkel–Halsey–Hill [...] Read more.
In order to better understand the micropore structure of shale reservoir in Jiyang Depression, permeability damage test, low temperature nitrogen adsorption and scanning electron microscopy (SEM) were carried out on six cores in the target block. The adsorption isotherms were analyzed by Frenkel–Halsey–Hill (FHH) model, and the fractal dimensions of different layers were calculated. The results show that the shale pore system is mainly composed of organic nanopores, inorganic nanopores and micro-fractures. The inorganic pores are mainly distributed around or inside the mineral particles, while microcracks are commonly found between mineral particles or at the organic–mineral interface. Organic pores are located within or between organic particles. The results of nitrogen adsorption show that the shale pores are mainly H2/H3 hysteresis loops with wedge, plate or ink bottle shapes. The pore structure is highly complex, and the fractal dimension is high. The mean D1 fractal dimension, which represents pore surface roughness, is 2.3788, and the mean D2 fractal dimension, which represents pore structure complexity, is 2.7189. The fractal dimension is positively correlated with specific surface area and total pore volume and negatively correlated with average pore radius. The permeability damage rates of the N layer, B layer, and F layer are 17.39%, 20.2%, and 21.6%, respectively. The contact Angle of the core decreases with the increase in water skiing time. In this study, the micropore structure of different formations in Jiyang Depression is compared and analyzed, which provides valuable insights for the optimization and differentiated development of shale oil and gas resources. Full article
(This article belongs to the Special Issue Advances in Unconventional Reservoir Development and CO2 Storage)
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25 pages, 5915 KiB  
Article
Experimental Study on the Effect of Fractures on the Irreducible and Movable Water in Water-Bearing Tight Sandstone Gas Reservoirs
by Aiguo Hu, Li Su, Gang Cao, Zhuo Luo, Changhui Yan and Qing Chen
Processes 2025, 13(6), 1685; https://doi.org/10.3390/pr13061685 - 27 May 2025
Viewed by 342
Abstract
Hydraulic fracturing significantly impacts water production. This makes it crucial to determine whether its effects on formation water production are beneficial or detrimental in complex reservoir stimulations. This paper gives the influence that acts on pore structure variations and irreducible water transformation by [...] Read more.
Hydraulic fracturing significantly impacts water production. This makes it crucial to determine whether its effects on formation water production are beneficial or detrimental in complex reservoir stimulations. This paper gives the influence that acts on pore structure variations and irreducible water transformation by hydraulic fracturing; by using NMR and Micro-CT, pore-throat reconfiguration in core samples induced fracturing. Two main pore variation types were identified from CT images. To analyze the gas–water flow mechanisms in pre-fracturing and post-fracturing reservoir conditions, we tested quantifying changes in irreducible water transforms into movable water saturation by using a triaxial in situ flow system, thereby elucidating the impact of the hydraulic fracture on irreducible water saturation. The experiments demonstrate that pore structures are significantly modified in terms of connectivity and diameter through hydraulic fracturing. During damage zone formation, 12.4–19.2% of small pores coalesce into larger pores through integration of isolated spaces. This variation enhances fluid mobility, transforms 1.38–11.61% of irreducible water, and decreases starting pressure gradients by 1 MPa/100 m to 0.1 MPa/100 m. Modified pore structure leads to the iso-permeability point shifting toward higher water saturation. The gas-phase relative permeability at irreducible water saturation is two times as high as that of the matrix sample. Fractured zones show a 20–23% conversion efficiency of irreducible to movable water. In addition, based on the results of experimental data, hydraulic fracturing increased water production by 3607 to 9163 m3. However, this effect is only maintained during the first 3 to 6 months post-fracture. These results quantify the transformation of irreducible water into movable water in hydraulic fracturing. This study provides key performance indicators for gas reservoir applications. Full article
(This article belongs to the Special Issue Advances in Unconventional Reservoir Development and CO2 Storage)
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23 pages, 22084 KiB  
Article
Optimization of Well Spacing with an Integrated Workflow: A Case Study of the Fuyu Tight Oil Reservoir in the Daqing Oil Field, China
by Wensheng Wu, Gangxiang Song, Hui Zhang, Xiukun Wang and Zhaojie Song
Processes 2025, 13(4), 1008; https://doi.org/10.3390/pr13041008 - 27 Mar 2025
Viewed by 593
Abstract
Optimizing well spacing is crucial for enhancing the production efficiency and economic returns of tight oil development. The limited understanding of hydraulic fracture geometry and properties poses significant challenges in designing well spacing for tight oil reservoirs. In this study, we proposed an [...] Read more.
Optimizing well spacing is crucial for enhancing the production efficiency and economic returns of tight oil development. The limited understanding of hydraulic fracture geometry and properties poses significant challenges in designing well spacing for tight oil reservoirs. In this study, we proposed an integrated workflow for optimizing well spacing in tight oil reservoirs. Geological and geomechanical models were established to form the basis for numerical reservoir simulation and dynamic fracture modeling. A multi-staged, multi-clustered fracture propagation simulation of horizontal wells was conducted by a hydraulic fracturing simulator with matched actual field pumping schedules. The differences between fracture propagation simulation results and field monitoring results, including micro-seismic testing and distributed temperature sensing (DTS) monitoring, were analyzed. The geological model and fracture propagation simulation results were integrated into an efficient numerical reservoir simulator. A material balance method for fracturing fluids leak-off was proposed and utilized to equivalently calculate the actual oil–water distribution after fracturing and to complete the historical matching water cuts of all wells. Subsequently, the inter-well drainage area and pressure interference were evaluated. By employing this integrated workflow, the production performance of six wells (three well pairs) at different well spacings was simulated over a 15-year period, and their estimated ultimate recoveries (EURs) were predicted. When well spacing was less than the optimal distance, oil production dropped significantly. Ultimately, it was determined that reasonable well spacing for this block was 250 m. In future well pattern designs, well spacing smaller than the current value should be used. Full article
(This article belongs to the Special Issue Advances in Unconventional Reservoir Development and CO2 Storage)
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17 pages, 5515 KiB  
Article
Application of a Reservoir Classification Method Based on Core Data from Offshore Tight Reservoirs: A Case Study of the Liushagang Formation in the Beibu Basin
by Xinchen Gao, Liang Wang, Zihao Zeng, Qiangyu Li, Yuhang Jin and Kangliang Guo
Processes 2024, 12(11), 2510; https://doi.org/10.3390/pr12112510 - 11 Nov 2024
Viewed by 1060
Abstract
Several methods are currently used to test offshore tight reservoirs. However, the effectiveness of these applications varies among wells, and some exhibit unclear reservoir classifications. These issues lead to difficulties in decision-making during tests and result in higher testing costs. Therefore, to address [...] Read more.
Several methods are currently used to test offshore tight reservoirs. However, the effectiveness of these applications varies among wells, and some exhibit unclear reservoir classifications. These issues lead to difficulties in decision-making during tests and result in higher testing costs. Therefore, to address this issue, this study used reservoirs in the Liushagang Formation of the Beibu Basin as the research object and employed core data to apply the multi-stage FZI method. This method computes the FZI and its cumulative probability, classifying the target reservoir into seven distinct types. According to the Winland R35 method, the target reservoir was classified into five distinct types. Seven characteristic parameters were selected based on the mercury injection experimental data. The K-means clustering method was then used to classify the target reservoirs into two types. The conclusions were that, in this formation, there is predominantly low to extra-low porosity and extra-low to ultra-low permeability. According to relationship models, logged porosity can be used to calculate effective permeability. Combining the multi-stage FZI method with the K-means clustering method for reservoir classification is recommended. This integrated approach facilitates a more comprehensive analysis of the characteristics of offshore low-permeability tight reservoirs at both macro and micro scales after classification. This research provides key insights for enhancing offshore well production. Full article
(This article belongs to the Special Issue Advances in Unconventional Reservoir Development and CO2 Storage)
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Review

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17 pages, 1872 KiB  
Review
Research Progress on Optimization Methods of Platform Well Fracturing in Unconventional Reservoirs
by Li Zhang, Bo Wang, Minghao Hu, Xian Shi, Liu Yang and Fujian Zhou
Processes 2025, 13(6), 1887; https://doi.org/10.3390/pr13061887 - 14 Jun 2025
Viewed by 438
Abstract
Unconventional reservoirs are characterized by low porosity, low permeability, and limited hydrocarbon abundance, making them economically unviable for production under natural conditions. Large-scale hydraulic fracturing has emerged as a critical technology for enabling the effective development of these resources. The three-dimensional development of [...] Read more.
Unconventional reservoirs are characterized by low porosity, low permeability, and limited hydrocarbon abundance, making them economically unviable for production under natural conditions. Large-scale hydraulic fracturing has emerged as a critical technology for enabling the effective development of these resources. The three-dimensional development of platform wells employs batch drilling and batch fracturing techniques. By implementing simultaneous fracturing or zipper fracturing approaches, the process achieves well placement, fracturing, and fracture placement in a single step, thereby reducing costs and improving operational efficiency. Platform well fracturing (PWF) involves numerous parameters that require optimization, and the underlying physical processes are highly complex, presenting significant challenges to the design and control of fracturing strategies. To address these challenges, this study focuses on the following aspects: (1) identifying key parameters in PWF and reviewing prior optimization efforts that use production capacity and net present value as objective functions; (2) systematically comparing numerical simulation methods for modeling fracture propagation and simulating production performance, highlighting their role in linking fracturing parameters to objective functions; (3) evaluating the strengths and limitations of single-factor analysis, orthogonal experimental design, and intelligent automatic optimization methods, and proposing a high-dimensional intelligent optimization workflow for fracturing design; (4) examining the technological challenges of PWF and suggesting future directions for its development. This study provides valuable insights into the selection of optimization methods for PWF schemes and offers guidance for advancing the technology’s development, contributing to more efficient and effective resource recovery from unconventional reservoirs. Full article
(This article belongs to the Special Issue Advances in Unconventional Reservoir Development and CO2 Storage)
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