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Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs

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

Deadline for manuscript submissions: 31 October 2024 | Viewed by 5792

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Special Issue Editors

Dr. Hadi Jabbari

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Guest Editor

Department of Petroleum Engineering, University of North Dakota, Grand Forks, ND 58202, USA
Interests: unconventional reservoir engineering; PTA/RTA/HF; enhanced oil recovery (thermal, CO₂, surfactant); geothermal reservoir engineering
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Vamegh Rasouli

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Guest Editor

Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA
Interests: petroleum geomechanics; wellbore stability; hydraulic fracturing; sanding and sand prevention; fractured reservoir characterization; geomechanics of unconventional reservoirs

Special Issue Information

Dear Colleagues,

Over the past two decades, the increased use of hydraulic fracturing (HF) technology has led to a significant increase in the production of shale oil and natural gas in many parts of the world, including the United States. This increase in hydrocarbon production has resulted in a reduction in the use of coal for energy generation, which has contributed to cleaner environments and atmosphere. Nevertheless, new technologies and more advanced techniques are needed to improve the efficiency and cost-effectiveness to minimize the environmental footprint of hydraulic fracturing operations.

This Special Issue aims to present and disseminate the latest advancements in hydraulic fracturing technology for unconventional oil and gas reservoirs.

Topics of interest for publication include, but are not limited to:

New advances in analytical and numerical solutions to improve the accuracy of HF treatment designs: FEM, BEM, Phase Field Simulation, etc.
Well test analysis in hydraulically fractured wells: DFITs, real-time monitoring, PTA/RTA.
Optimal re-frac operations: timing and optimal treatment design; stress field; stress shadowing.
Fishbone drilling to enhance production by increasing reservoir contact.
Fracture-driven interaction to maximize estimated ultimate recovery (EUR).
Machine learning & AI techniques for optimal freshwater use management and recycling the frac-fluid: green fracturing fluids or recycle wastewater.
Advanced research on characterizing flow back fluids for optimal treatment/disposal to reduce hazards and risks.
Optimal planning and design of simul-frac vs. the traditional zipper fracs.
E-frac technology to reduce GHG emissions; economy, design, and field implementations.
Potential for hybrid stimulation methods, CO₂-frac or HF combined with chemical flooding to enhance production.
New advances in HF monitoring technology; SWPM (sealed wellbore pressure monitoring), microseismic and fiber-optic cables.

Dr. Hadi Jabbari
Prof. Dr. Vamegh Rasouli
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

hydraulic fracturing
shale oil/gas
economic factors
post-frac evaluation
fracture characterization
environmental impact
flow-back control
geomechanics
stress fields
monitoring techniques

Published Papers (7 papers)

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Research

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16 pages, 11373 KiB

Open AccessArticle

Study on the Influence of Perforating Parameters on the Flow Rate and Stress Distribution of Multi-Fracture Competitive Propagation

by Xing Zhao, Jin Zhao, Hehua Wang and Yuandong Liu

Processes 2024, 12(4), 839; https://doi.org/10.3390/pr12040839 - 21 Apr 2024

Viewed by 417

Abstract

It is of great significance to investigate the flow rate and stress distribution of multi-fracture propagation for the optimization of perforation parameters and fracture parameters. Considering the coupling of rock deformation, fracture direction and fluid flow in multi-fracture scenarios, a mathematical model and solution program for the flow and stress distribution of multiple fractures are established, and the analytical model is used for comparison and verification. The effects of perforation cluster number, cluster spacing, perforation diameter on fracture extension trajectory, fracture width, flow rate of each fracture and stress field are studied by the model. The results show that, as the number of perforating clusters increases, the inner fracture is inhibited more severely with less width, length and flow distribution, as well as lower bottom hole pressure. With the increase in cluster spacing, the stress interference between whole fractures is weakened and the flow distribution of the inner fracture is increased with lower bottom hole pressure. With the decrease in perforation diameter, the inhibition effect of inside fractures is weakened, while the inhibition effect of outside fractures, the flow distribution of inside fractures and the bottom hole pressure are increased. The uniform propagation of multiple fractures can be promoted by decreasing the perforation clusters’ number and perforation diameter or increasing fracture spacing. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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20 pages, 15511 KiB

Open AccessArticle

Experimental Investigation into the Process of Hydraulic Fracture Propagation and the Response of Acoustic Emissions in Fracture–Cavity Carbonate Reservoirs

by Hanzhi Yang, Lei Wang, Zhenhui Bi, Yintong Guo, Junchuan Gui, Guokai Zhao, Yuting He, Wuhao Guo and Guozhou Qiu

Processes 2024, 12(4), 660; https://doi.org/10.3390/pr12040660 - 26 Mar 2024

Viewed by 462

Abstract

Fracture–cavity carbonate reservoirs account for a considerable proportion of oil and gas resources. Because of the complicated relationships between cavities, fractures and pores in these reservoirs, which are defined as cavity clusters, fracturing technology is employed to enhance their hydrocarbon productivity. However, almost all previous studies have just considered the effect of a single natural cavity or fracture on the propagation of a hydraulic fracture; therefore, the mechanism by which a hydraulic fracture interacts with a cavity cluster needs to be clarified. In this study, cavity clusters with different distributions were accurately prefabricated in synthetically made samples, and large-scale simulation equipment was employed to systematically perform fracturing experiments considering different horizontal differential stress levels. Meanwhile, the hydraulic fracture propagation behaviors were comprehensively analyzed through fracture morphology, fracturing curves, the complexity of the fracture network and acoustic emission monitoring. It was found that a natural fracture with a smaller approach angle is favorable in guiding a hydraulic fracture to a cavity. The fracturing curves were divided into the following four types: frequent fluctuations with “step-like” shapes, great fluctuations with slightly lower closure pressure, fluctuations with obviously lower closure pressure, and little fluctuations with obviously lower closure pressure. And different cavity cluster distributions play a dominant role in the complexity of generated hydraulic fracture networks. In addition, AE energy was used to judge the ease of crossing the cavity. The above findings indicated that for the actual exploration and exploitation of carbonate reservoirs, the geological exploration of different fracture–cavity structures in reservoirs would be required, and targeted fracturing engineering designs need to be carried out for different fracture–cavity carbonate reservoirs. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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23 pages, 14400 KiB

Open AccessArticle

Exploring the Mechanism of Pulse Hydraulic Fracturing in Tight Reservoirs

by Zhihui Ren, Suling Wang, Kangxing Dong, Weiqiang Yu and Lu Lu

Processes 2023, 11(12), 3398; https://doi.org/10.3390/pr11123398 - 10 Dec 2023

Viewed by 793

Abstract

Pulse hydraulic fracturing is capable of creating intricate seam networks for improved reservoir recovery, but its dynamic damage mechanism remains unclear, limiting its scientific guidance for fracturing construction. This study combined the statistical damage and viscoelastic models according to the D-P criterion and fluid flow continuity equation to establish a mathematical model of the fluid–solid coupling under pulsed hydraulic pressure. The finite element approach was used to investigate the dynamic response and damage accumulation law of tight reservoirs under various pulse parameters. The model’s correctness was verified with indoor triaxial pulse hydraulic fracturing studies, and the Changqing oilfield’s pulse hydraulic fracturing parameters were optimized. The results showed that the rock body around the borehole sustained dynamic damage when exposed to pulsed fluid pressure. The impact force increases with frequency; however, when the frequency is too high, the dynamic pore pressure cannot be stabilized. Consequently, the damage to the rock mass starts to increase and then progressively decreases with higher pulse frequencies. The ideal frequency was found to be 1 Hz. The rock body steadily accumulates damage as the number of pulses rises, increasing the damage value gradually. At the same frequency, the damage is higher for larger pulse amplitudes and ground stress differences, as well as a smaller modulus of elasticity. Pulse cycling reduces the rupture pressure by up to 26% compared to conventional hydraulic fracturing. Moreover, the Sine wave is 4–20% better than the triangle wave. The pulse damage mechanism and parameter optimization in this paper provide theoretical support for improving the effect of hydraulic fracture modification. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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20 pages, 7179 KiB

Open AccessArticle

Investigation of Natural Weak Interface Properties and Their Impact on Fracture Propagation in Shale Reservoirs

by Qi Chen, Zhiqiang Huang, Xingjie Ling, Pengju Xu, Lanke Tu, Wenjing Liao, Jun Xie, Meng Wang, Yijing Chen and Lingli Li

Processes 2023, 11(9), 2697; https://doi.org/10.3390/pr11092697 - 8 Sep 2023

Viewed by 606

Abstract

Horizontal well multi-cluster fracturing technology is crucial for the economic development of fractured shale reservoirs. The abundance of natural fractures in shale reservoirs significantly influences the propagation path of hydraulic fractures and determines the formation of complex fracture networks. To investigate the impact of natural weak planes on the geometric parameters of fractures in shale reservoirs, we first conducted tests on the mechanical characteristics of core samples from outcropping shale in the Weiyuan area using the indoor three-point bending method and digital image correlation (DIC) technology, providing data validation for subsequent numerical models. Secondly, considering the interaction between hydraulic and natural weak planes in three-dimensional space, we established a three-dimensional numerical model for horizontal well fracturing to simulate the synchronous competition and expansion of fractures in multi-cluster fracturing. Based on this foundation, we analyzed the influence of formation parameters and engineering parameters on the formation patterns of complex fracture networks. The results indicate that the difference in in situ stress is a significant factor affecting the selection of fracture propagation paths. As the in situ stress difference increases, it becomes more challenging to open natural fractures, leading to a reduced probability of activation of natural weak interfaces. When the cohesive strength of natural fractures is smaller, they are more likely to open and capture hydraulic fractures, thereby increasing shear slip length and fracture network area. Each fracturing stage has an optimal perforation density combination, where a higher density of perforations leads to reduced perforation pressure drop and weaker ability to mitigate inter-cluster stress interference. To achieve a comprehensive and balanced development of multi-clusters, the inter-cluster stress interference can be alleviated by increasing the perforation pressure drop. For dense perforation clusters, higher injection rates and viscosity can be employed to ensure the uniform development of multiple perforation clusters. This study provides new insights into predicting the formation of complex fracture networks in shale reservoirs and offers valuable guidance for optimizing hydraulic fracturing designs. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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27 pages, 7639 KiB

Open AccessArticle

Applications of Differential Effective Medium (DEM)-Driven Correlations to Estimate Elastic Properties of Jafurah Tuwaiq Mountain Formation (TMF)

by Ali Shawaf, Vamegh Rasouli and Abdesselem Dehdouh

Processes 2023, 11(6), 1643; https://doi.org/10.3390/pr11061643 - 27 May 2023

Cited by 2 | Viewed by 924

Abstract

Organic-rich mud rocks are being developed on a large scale worldwide, including in the Middle East. The Jurassic Tuwaiq Mountain Formation (TMF) in the Jafurah Basin is a potential world-class unconventional play. Based on a petrophysical evaluation of the Jafurah basin, the TMF exhibits exceptional and unconventional gas characteristics, such as a high total organic content (TOC) and low clay content. Additionally, the TMF is in the appropriate maturity window, indicating that it has reached the required level of thermal maturity to generate hydrocarbons. Plans for the development of the Jafurah unconventional field use multistage hydraulic fracturing technology. The elastic properties of the shale formation, particularly its Young’s modulus and Poisson’s ratio, dictate how the rock responds to stress and deformation. These properties strongly impact the growth of hydraulic fractures in shale formations. Without a comprehensive understanding of the elastic properties, predicting the bulk mechanical response of the target zones and surrounding layers would be challenging. Therefore, this study aims to predict the elastic characteristics of the Jafurah shale play considering the variations in carbonate facies, the kerogen volume fraction, and the pore’s geometry. Petrophysical and XRD data were used to estimate the elastic properties of various tiers (geological units) of the TMF (Tiers 1, 2, and 3). Inclusion-based, differential effective medium (DEM) rock physics models were used to estimate the formation’s elastic and velocity properties as a function of the kerogen volume fraction and the pore’s geometry. The results showed that the Young’s modulus as well as the mineral and elastic brittleness indices increase as the volume fraction of calcite increases. At the same time, they decrease due to intensified clay and kerogen volumes. The effect of the TMF’s elastic parameters on the rock brittleness behavior was also investigated by considering the formation’s mineralogy, as well as clay and kerogen contents. The results led to the development of physics-based correlations of the mineral brittleness index as function of the Young’s modulus and Poisson’s ratio for various tiers of the TMF. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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25 pages, 7948 KiB

Open AccessArticle

The Impact of Formation Anisotropy and Stresses on Fractural Geometry—A Case Study in Jafurah’s Tuwaiq Mountain Formation (TMF), Saudi Arabia

by Ali Shawaf, Vamegh Rasouli and Abdesselem Dehdouh

Processes 2023, 11(5), 1545; https://doi.org/10.3390/pr11051545 - 18 May 2023

Cited by 4 | Viewed by 1027

Abstract

Multi-stage hydraulic fracturing (MsHF) is the main technology to improve hydrocarbon recovery from shale plays. Associated with their rich organic contents and laminated depositional environments, shales exhibit transverse isotropic (TI) characteristics. In several cases, the lamination planes are horizontal in shale formations with a symmetric axis that are vertical to the bedding plane; hence, shale formations are known as transverse isotropic vertical (TIV) rocks. Ignoring the TIV nature of shale formations leads to erroneous estimates of in situ stresses and consequently to inefficient designs of fractural geometry, which negatively affects the ultimate recovery. The goal of this study is to investigate the effects of TIV medium characteristics on fractural geometry, spacing, and stress shadow development in the Jurassic Tuwaiq Mountain formation (TMF) in the Jafurah basin, which is a potential unconventional world-class play. This formation is the main source for prolific Jurassic oil reservoirs in Saudi Arabia. On the basis of a petrophysical evaluation in the Jafurah basin, TMF exhibited exceptional unconventional gas characteristics, such as high total organic content (TOC) and low clay content, and it was in the proper maturity window for oil and gas generation. The unconventional Jafurah field covers a large area that is comparable to the size of the Eagle Ford shale play in South Texas, and it is planned for development through multi-stage hydraulic fracturing technology. In this study, analytical modeling was performed to estimate the fractural geometry and in situ stresses in the anisotropic medium. The results show that the Young’s modulus anisotropy had a noticeable impact on fractural width, whereas the impact of Poisson’s ratio was minimal. Moreover, we investigated the impact of stress anisotropy and other rock properties on the stress shadow, and found that a large stress anisotropy could result in fractures being positioned close to one another or theoretically without minimal fractural spacing concerns. Additionally, we estimated the fractural aspect ratio in different propagation regimes and observed that the highest aspect ratio had occurred in the fractural toughness-dominated regime. This study also compares the elastic properties and confirms that TMF exhibited greater anisotropic properties than those of Eagle Ford. These findings have practical implications for field operations, particularly with regard to the fractural geometry and proppant placement. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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22 pages, 10165 KiB

Open AccessEssay

Study on Brittleness Characteristics and Fracturing Crack Propagation Law of Deep Thin-Layer Tight Sandstone in Longdong, Changqing

by Changjing Zhou, Zhonghua Sun, Yuanxiang Xiao, Guopeng Huang, Dan Kuang and Minghui Li

Processes 2023, 11(9), 2636; https://doi.org/10.3390/pr11092636 - 4 Sep 2023

Cited by 3 | Viewed by 689

Abstract

Tight-sandstone oil and gas resources are the key areas of unconventional oil and gas resources exploration and development. Because tight-sandstone reservoirs usually have the characteristics of a low porosity and ultralow permeability, large-scale hydraulic fracturing is often required to form artificial fractures with a high conductivity to achieve efficient development. The brittleness of rock is the key mechanical factor for whether fracturing can form a complex fracture network. Previous scholars have carried out a lot of research on the brittleness characteristics of conglomerate and shale reservoirs, but there are few studies on the brittleness characteristics of sandstone with different types and different coring angles in tight-sandstone reservoirs and the fracture propagation law of sandstone with different brittleness characteristics. Based on this, this paper carried out a systematic triaxial compression and hydraulic fracturing experiment on the tight sandstone of Shan 1 and He 8 in the Longdong area of the Changqing oilfield. Combined with CT scanning cracks, the brittleness characteristics and fracturing crack propagation law of different types and different coring angles of sandstone under formation-confining pressure were clarified. The results show that there are great differences between different types of sandstone in the yield stage and the failure stage. The sandstone with a quartz content of 100% has the highest peak strength and a strong brittleness. Sandstones with a high content of natural fractures and dolomite have a lower peak strength and a weaker brittleness. There are also differences in the peak strength and fracture morphology of sandstone with different coring angles due to geological heterogeneity. The sandstone with a comprehensive brittleness index of 70.30 produces a more complex fracture network during triaxial compression and hydraulic fracturing than the sandstone with a comprehensive brittleness index of 14.15. The research results have important guiding significance for on-site fracturing construction of tight-sandstone reservoirs. Full article

(This article belongs to the Special Issue Advances in Hydraulic Fracturing Technology for Unconventional Reservoirs)

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