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Environmentally Friendly Production of Energy from Natural Gas Hydrates
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Environmentally Friendly Production of Energy from Natural Gas Hydrates

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

Deadline for manuscript submissions: 31 December 2025 | Viewed by 5054

Special Issue Editors

Dr. Qingchao Li

E-Mail Website
Guest Editor
School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454000, China.
Interests: Natural gas hydrate; CCUS; Wellbore stability; Sand Production
Dr. Qiang Li

E-Mail Website
Guest Editor
College of Engineering, China University of Petroleum-Beijing at Karamay, Karamay, 834000, China.
Interests: CCU; Natural gas hydrate; Shale gas; Hydraulic Fracturing

Special Issue Information

Dear Colleagues,

Natural gas is considered a clean energy source that enables human society to transition from a fossil fuel-dominated phase to a sustainable and renewable energy-dominated phase. Fortunately, natural gas hydrates could become an important source of natural gas in the near future. It was estimated that the global reserves of natural gas hydrates are as high as 3 × 1015 m3, which is about double the reserves of conventional fossil fuels (such as oil, gas, and coal). In the stable structure of gas hydrate, natural gas is firmly fixed in the center of the cage structure that is composed of water molecules. Once its stable state is disturbed, natural gas escapes from the cage structure, allowing it to be extracted and utilized. At present, the commonly used development strategies mainly include depressurization, thermal stimulation, inhibitor injection, and CO2 replacement. Unfortunately, there will be many environmental challenges during its long-term development process using these strategies. For example, inhibitors injected into hydrate-bearing sediments can contaminate pore fluids and cause damage to the reservoir. Therefore, exploring strategies for producing energy from natural gas hydrates in an environmentally friendly and efficient manner has become particularly important.

This Special Issue on “Environmentally Friendly Production of Energy from Natural Gas Hydrates” seeks high-quality research focusing on environmentally friendly production strategies for natural gas hydrates. Topics include, but are not limited to, the following:

(1) Impact of hydrate development on the environment and ecology, including analysis of engineering geological issues, methane leakage, reservoir damage, and contamination by chemical reagents.
(2) Development of environmentally friendly chemicals for hydrate development, such as drilling fluid additives, fracturing fluid additives, and various inhibitors.
(3) Application of industrial waste (such as power plant flue gas and waste heat) or low-quality energy (such as geothermal energy) in the efficient development of hydrates.
(4) Economic and technical evaluation of various environmentally friendly production strategies for natural gas hydrates.

Dr. Qingchao Li
Dr. Qiang Li
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

  • natural gas hydrate
  • production strategy
  • additives
  • inhibitors
  • wellbore stability
  • sand production
  • reservoir damage
  • geothermal
  • economic and technical evaluation

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Published Papers (7 papers)

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21 pages, 12715 KiB  
Article
Effect of Twisted Tapes on Swirling Flow Dynamics in Gas–Solid Two-Phase Flows for Natural Gas Hydrate Transportation
by Yongchao Rao, Zijia Gong, Shuli Wang, Chenglong Zhang, Yunxiao Wang and Chuang Wen
Processes 2025, 13(3), 781; https://doi.org/10.3390/pr13030781 - 7 Mar 2025
Viewed by 190
Abstract
The discrete phase model (DPM) and the RNG k-ε turbulence model were employed to simulate the swirl flow behavior of hydrate transport in pipelines equipped with twisted tapes. The study analyzed the effects of various twisted tape parameters on the velocity [...] Read more.
The discrete phase model (DPM) and the RNG k-ε turbulence model were employed to simulate the swirl flow behavior of hydrate transport in pipelines equipped with twisted tapes. The study analyzed the effects of various twisted tape parameters on the velocity field, turbulent dissipation, turbulent kinetic energy, and pressure distribution of hydrate particles. The results indicate that increasing the placement angle of the twisted tape enhances the tangential velocity near the pipe axis while reducing the axial velocity. Similarly, higher twisted tape configurations result in a further decrease in axial velocity. An increase in the number of twisted tapes leads to reductions in both tangential and axial velocities, and maximum speed increased by 18.2%. Larger placement angles of twisted tapes also intensify turbulence dissipation, with a more pronounced decay in turbulence intensity observed from the pipe wall to the axis. At section 8D, the turbulent kinetic energy increases by 60% with the increase in the height of the twisted tapes. Furthermore, as the number of twisted tapes increases, the disparity in turbulence strength between regions near the twisted tape and the pipe axis diminishes. The inner pipe pressure distribution is 360°/n rotation symmetrical distribution, and the twist tape is more, and the high pressure area is greater on the pipe section. The minimum pressure area is gradually close from the lee plane of the diversion strip to the position of the pipe axis. At section 65D, the pressure drop increases gradually with the increase in the orientation angle, and it increases by 36.8%. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
►▼ Show Figures

Figure 1

Figure 1
<p>Velocity and velocity vector distribution map of twist tape pipes at different sections.</p> Full article ">Figure 2
<p>Influence of the placement angle of twist tape on different sections on tangential and axial velocities: (<b>a</b>) Tangential velocity (<span class="html-italic">Z</span> = 10 <span class="html-italic">D</span>), (<b>b</b>) Axial velocity (<span class="html-italic">Z</span> = 10 <span class="html-italic">D</span>), (<b>c</b>) Tangential velocity (Z = 30 D), (<b>d</b>) Axial velocity (<span class="html-italic">Z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) Tangential velocity (<span class="html-italic">Z</span> = 50 <span class="html-italic">D</span>) and (<b>f</b>) Axial velocity (<span class="html-italic">Z</span> = 50 <span class="html-italic">D</span>).</p> Full article ">Figure 2 Cont.
<p>Influence of the placement angle of twist tape on different sections on tangential and axial velocities: (<b>a</b>) Tangential velocity (<span class="html-italic">Z</span> = 10 <span class="html-italic">D</span>), (<b>b</b>) Axial velocity (<span class="html-italic">Z</span> = 10 <span class="html-italic">D</span>), (<b>c</b>) Tangential velocity (Z = 30 D), (<b>d</b>) Axial velocity (<span class="html-italic">Z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) Tangential velocity (<span class="html-italic">Z</span> = 50 <span class="html-italic">D</span>) and (<b>f</b>) Axial velocity (<span class="html-italic">Z</span> = 50 <span class="html-italic">D</span>).</p> Full article ">Figure 3
<p>Influence of the placement angle of the twist tape at different cross-sections on the turbulent dissipation and turbulent flow energy: (<b>a</b>) Turbulent dissipation (<span class="html-italic">Z</span> = 10 <span class="html-italic">D</span>), (<b>b</b>) Turbulent kinetic energy (<span class="html-italic">Z</span> = 10 <span class="html-italic">D</span>), (<b>c</b>) Turbulent dissipation (Z = 30 D), (<b>d</b>) Turbulent kinetic energy (<span class="html-italic">Z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) Turbulent dissipation (<span class="html-italic">Z</span> = 50 <span class="html-italic">D</span>) and (<b>f</b>) Turbulent kinetic energy (<span class="html-italic">Z</span> = 50 <span class="html-italic">D</span>).</p> Full article ">Figure 4
<p>Influence of the height of twist tape on different sections on tangential and axial velocities: (<b>a</b>) Tangential velocity (<span class="html-italic">Z</span> = 8 <span class="html-italic">D</span>), (<b>b</b>) Axial velocity (<span class="html-italic">Z</span> = 8 <span class="html-italic">D</span>), (<b>c</b>) Tangential velocity (Z = 30 D), (<b>d</b>) Axial velocity (<span class="html-italic">Z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) Tangential velocity (<span class="html-italic">Z</span> = 47 <span class="html-italic">D</span>) and (<b>f</b>) Axial velocity (<span class="html-italic">Z</span> = 47 <span class="html-italic">D</span>).</p> Full article ">Figure 4 Cont.
<p>Influence of the height of twist tape on different sections on tangential and axial velocities: (<b>a</b>) Tangential velocity (<span class="html-italic">Z</span> = 8 <span class="html-italic">D</span>), (<b>b</b>) Axial velocity (<span class="html-italic">Z</span> = 8 <span class="html-italic">D</span>), (<b>c</b>) Tangential velocity (Z = 30 D), (<b>d</b>) Axial velocity (<span class="html-italic">Z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) Tangential velocity (<span class="html-italic">Z</span> = 47 <span class="html-italic">D</span>) and (<b>f</b>) Axial velocity (<span class="html-italic">Z</span> = 47 <span class="html-italic">D</span>).</p> Full article ">Figure 5
<p>Influence of the height of the twist tape at different cross-sections on the turbulent dissipation and turbulent flow energy: (<b>a</b>) Turbulent dissipation (<span class="html-italic">Z</span> = 8 <span class="html-italic">D</span>), (<b>b</b>) Turbulent kinetic energy (<span class="html-italic">Z</span> = 8 <span class="html-italic">D</span>), (<b>c</b>) Turbulent dissipation (Z = 30 D), (<b>d</b>) Turbulent kinetic energy (<span class="html-italic">Z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) Turbulent dissipation (<span class="html-italic">Z</span> = 47 <span class="html-italic">D</span>) and (<b>f</b>) Turbulent kinetic energy (<span class="html-italic">Z</span> = 47 <span class="html-italic">D</span>).</p> Full article ">Figure 6
<p>Influence of the number of the twist tape on tangential velocity and axial velocity: (<b>a</b>) tangential velocity (<span class="html-italic">n</span> = 3), (<b>b</b>) axial velocity (<span class="html-italic">n</span> = 3), (<b>c</b>) tangential velocity (<span class="html-italic">n</span> = 4), (<b>d</b>) axial velocity (<span class="html-italic">n</span> = 4), (<b>e</b>) tangential velocity (<span class="html-italic">n</span> = 6) and (<b>f</b>) axial velocity (<span class="html-italic">n</span> = 6).</p> Full article ">Figure 7
<p>Influence of the number of the twist tape at different cross-sections on the turbulent dissipation and turbulent flow energy: (<b>a</b>) turbulent dissipation (<span class="html-italic">z</span> = 10 <span class="html-italic">D</span>), (<b>b</b>) turbulent kinetic energy (<span class="html-italic">z</span> = 10 <span class="html-italic">D</span>), (<b>c</b>) turbulent dissipation (z = 30 D), (<b>d</b>) turbulent kinetic energy (<span class="html-italic">z</span> = 30 <span class="html-italic">D</span>), (<b>e</b>) turbulent dissipation (<span class="html-italic">z</span> = 50 <span class="html-italic">D</span>) and (<b>f</b>) turbulent kinetic energy (<span class="html-italic">z</span> = 50 <span class="html-italic">D</span>).</p> Full article ">Figure 8
<p>Pressure distribution of twist tape pipes with placement angle of 10° at different cross-section positions.</p> Full article ">Figure 9
<p>Pressure distribution of twist tape pipes with placement angle of 15° at different cross-section positions.</p> Full article ">Figure 10
<p>Pressure distribution of twist tape pipes with placement angle of 20° at different cross-section positions.</p> Full article ">Figure 11
<p>Pressure distribution of twist tape pipes with placement angle of 25° at different cross-section positions.</p> Full article ">Figure 12
<p>The effect of the placement angle of twist tape on pressure drop.</p> Full article ">Figure 13
<p>Pressure distribution of twist tape pipes with height of D/5 at different cross-section positions.</p> Full article ">Figure 14
<p>Pressure distribution of twist tape pipes with height of D/6 at different cross-section positions.</p> Full article ">Figure 15
<p>Pressure distribution of twist tape pipes with height of D/8 at different cross-section positions.</p> Full article ">Figure 16
<p>Pressure distribution of twist tape pipes with height h of D/10 at different cross-section positions.</p> Full article ">Figure 17
<p>The effect of the height of the twist tape on the pressure drop.</p> Full article ">Figure 18
<p>Pressure distribution of twist tape pipes with number of three at different cross-section positions.</p> Full article ">Figure 19
<p>Pressure distribution of twist tape pipes with number of four at different cross-section positions.</p> Full article ">Figure 20
<p>Pressure distribution of twist tape pipes with number of six at different cross-section positions.</p> Full article ">Figure 21
<p>The effect of the numberof the twist tape on the pressure drop.</p> Full article ">
19 pages, 2769 KiB  
Article
Two-Phase Swirling Flow and Gas Hydrate Particle Deposition Behavior in Bending Pipelines
by Yongchao Rao, Long Zheng, Shuli Wang, Wenjing Wu, Zijia Gong, Shidong Zhou and Chuang Wen
Processes 2025, 13(3), 725; https://doi.org/10.3390/pr13030725 - 3 Mar 2025
Viewed by 238
Abstract
The present study employs numerical simulation to analyze the behavior of gas hydrate particles in bending pipelines, focusing on the influence of swirl flow on particle deposition under varying bending angles, pipe-to-diameter ratios, Reynolds numbers, and twist rates. Results indicate that larger bending [...] Read more.
The present study employs numerical simulation to analyze the behavior of gas hydrate particles in bending pipelines, focusing on the influence of swirl flow on particle deposition under varying bending angles, pipe-to-diameter ratios, Reynolds numbers, and twist rates. Results indicate that larger bending angles, smaller twist rates, and higher Reynolds numbers produce stronger swirl flows at pipe entry and sustain higher swirl numbers along the pipeline. Conversely, larger pipe-to-diameter ratios result in greater swirl number variations, slower attenuation, and weaker outflow. Moreover, the phenomenon of hydrate particle deposition is more serious in the straight pipe section. Particle retention at the pipe outlet is 1.5 times higher than in the bending section. The bent pipe is more conducive to the flow of particles. For instance, with a bend rate increasing from 1 to 4, the swirl number decreases by 57.49%. Additionally, the deposition rate of particles is reduced at higher Reynolds numbers, with rates falling below 1% at a Reynolds number of 20,000. These findings highlight the need to optimize swirl flow parameters to reduce hydrate deposition, preventing blockages and improving pipeline safety in industrial applications. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
►▼ Show Figures

Figure 1

Figure 1
<p>Flowchart for the present study.</p> Full article ">Figure 2
<p>Pipeline system for the numerical simulation of gas hydrate flows (Reprinted from Rao et al. [<a href="#B23-processes-13-00725" class="html-bibr">23</a>], an open-access article from Springer Nature).</p> Full article ">Figure 3
<p>Variation of swirl number under different bending pipe angles.</p> Full article ">Figure 4
<p>Variation of swirl number under different twisted rates.</p> Full article ">Figure 5
<p>Variation of swirl number under different Re.</p> Full article ">Figure 6
<p>Residual time distribution of hydrate particles.</p> Full article ">Figure 7
<p>Distribution of particle position and mass concentration in each section of the elbow at different times.</p> Full article ">Figure 8
<p>Distribution of particle mass concentration at the exit of the pipe.</p> Full article ">Figure 9
<p>Profiles of particle mass concentration fractions at different positions of the elbow under different twisted rates.</p> Full article ">Figure 10
<p>Variation curves of particle deposition rate in elbow under different influencing factors.</p> Full article ">
20 pages, 10429 KiB  
Article
A Numerical Simulation Investigation on the Distribution Characteristics of Coal Seam In Situ Stress Under the Influence of Normal Fault
by Zhihua Rao, Qingjie Du, Chunsheng Xiang, Zhongying Han and Yanbo Liang
Processes 2025, 13(2), 538; https://doi.org/10.3390/pr13020538 - 14 Feb 2025
Viewed by 334
Abstract
This study focuses on the complex stress distribution in coal seams influenced by normal fault using the fault development zone of the LF-M1 oilfield in southern China as a case study. Based on 3D seismic and drilling data, a key research area was [...] Read more.
This study focuses on the complex stress distribution in coal seams influenced by normal fault using the fault development zone of the LF-M1 oilfield in southern China as a case study. Based on 3D seismic and drilling data, a key research area was delineated, and strata were reclassified considering rock parameter similarity. An FLAC3D model encompassing hanging wall, normal fault, and footwall strata was developed to systematically analyze geostress near the fault under various conditions. The results indicate that the normal fault induces non-uniform and discontinuous stress patterns in the coal seam’s transverse plane. Stress weakening occurs near the fault, with a pronounced concentration on its flanks, approaching in situ stress levels in the far field. Coal’s Poisson’s ratio, elastic modulus, and fault dip negatively correlate with horizontal in situ stress, whereas other parameters show positive correlations. The maximum horizontal stress is more sensitive to parameter variations than the minimum. Stress weakening is most influenced by coal’s Poisson’s ratio, followed by coal’s elastic modulus, fault elastic modulus, fault Poisson’s ratio, fault dip, and fault thickness and the coal seam thickness. Notably, a 20% decrease in coal’s Poisson’s ratio leads to a 23.32% stress reduction at measuring point 1. Conversely, the coal seam thickness has a minimal impact on stress across the fault. When the coal seam thickness increases by 20%, the maximum horizontal stress at measuring point 2 only decreases by 0.06%. In summary, fault geometry, rock mechanics parameters, and external loads collectively complicate stress distributions near faults, posing risks of drilling accidents such as wellbore instability, leakage, and reservoir damage, necessitating careful consideration. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
►▼ Show Figures

Figure 1

Figure 1
<p>Plane distributive maps of T2 fault in LF M1 oilfield.</p> Full article ">Figure 2
<p>Three-dimensional seismic interpretation profile and study area selection of LF M1 oilfield.</p> Full article ">Figure 3
<p>Three-dimensional numerical model diagram.</p> Full article ">Figure 4
<p>Model boundary conditions and rock layer distribution.</p> Full article ">Figure 5
<p>The layout of stress measurement lines and points in the middle of the coal seam.</p> Full article ">Figure 6
<p>Cloud maps of in situ stress distribution in the plane where the coal seam is located on the hanging wall and the in situ stress curves at measurement line 1.</p> Full article ">Figure 7
<p>Cloud maps of in situ stress distribution on the plane where the footwall coal seam is located and stress curves at measurement line 2.</p> Full article ">Figure 8
<p>The stress variation curves at the measuring line under different coal elastic modulus values: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 9
<p>Stress variation curves at measurement lines under different Poisson’s ratios for coal rock: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 10
<p>Stress variation curves at measurement lines under different coal seam thickness conditions: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 11
<p>Stress variation curves at measurement lines under different elastic modulus conditions of fault rocks: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 12
<p>Stress variation curves at measurement lines under different Poisson’s ratios for fault rocks: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 13
<p>Stress variation curves at measurement lines under different fault thickness conditions: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 14
<p>Stress variation curves at measurement lines under different fault dip angles: (<b>a</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 1; (<b>b</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 1; (<b>c</b>) <span class="html-italic">σ</span><sub>h</sub> at measuring line 2; (<b>d</b>) <span class="html-italic">σ</span><sub>H</sub> at measuring line 2.</p> Full article ">Figure 15
<p>Bar chart of maximum horizontal in situ stress change rate at different measuring points.</p> Full article ">
16 pages, 6464 KiB  
Article
Prospects on Mixed Tutton Salt (K0.86Na0.14)2Ni(SO4)2(H2O)6 as a Thermochemical Heat Storage Material
by Jacivan V. Marques, João G. de Oliveira Neto, Otávio C. da Silva Neto, Adenilson O. dos Santos and Rossano Lang
Processes 2025, 13(1), 1; https://doi.org/10.3390/pr13010001 - 24 Dec 2024
Viewed by 620
Abstract
In this paper, a novel mixed Tutton salt (K0.86Na0.14)2Ni(SO4)2(H2O)6 was successfully synthesized as a single crystal and evaluated as a thermochemical heat storage material. Its thermal and thermochemical properties were [...] Read more.
In this paper, a novel mixed Tutton salt (K0.86Na0.14)2Ni(SO4)2(H2O)6 was successfully synthesized as a single crystal and evaluated as a thermochemical heat storage material. Its thermal and thermochemical properties were correlated with the structure, which was determined by powder X-ray diffraction using the Le Bail and Rietveld methods. The elemental ratio between the K+ and Na+ monovalent cations was established by energy-dispersive X-ray spectroscopy. Similar compounds such as Na2Ni(SO4)2(H2O)4 and K2Ni(SO4)2(H2O)6 were also synthesized and used for structural comparisons. The (K0.86Na0.14)2Ni(SO4)2(H2O)6 salt crystallizes in monoclinic symmetry with the P21/c-space group, typical of hexahydrate crystals from the Tutton salt family. The lattice parameters closely resemble those of K2Ni(SO4)2(H2O)6. A comprehensive analysis of the intermolecular contacts, based on Hirshfeld surfaces and 2D fingerprint mappings, revealed that the primary interactions are hydrogen bonds (H···O/O···H) and ion-dipole interactions (K/Na···O/O···Na/K). The unit cell exhibits minimal void space, accounting for only 0.2%, indicative of strong atomic packing. The intermolecular molecular and atomic packing are important factors influencing crystal lattice stabilization and thermal energy supplied to release crystallographic H2O. The thermal stability of mixed Tutton salt ranges from 300 K to 365 K. Under the dehydration of its six H2O molecules, the dehydration reaction enthalpy reaches 349.8 kJ/mol, yielding a thermochemical energy storage density of 1.79 GJ/m3. With an H2O desorption temperature ≤393 K and a high energy storage density ≥1.3 GJ/m3 (criteria established for applications at the domestic level), the (K0.86Na0.14)2Ni(SO4)2(H2O)6 shows potential as a thermochemical material for small-sized heat batteries. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
►▼ Show Figures

Figure 1

Figure 1
<p>Photograph of an as-grown (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> single crystal.</p> Full article ">Figure 2
<p>PXRD patterns of Na<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>, (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> and K<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> powder crystals. The inset shows in detail the 2θ angular region between 20 and 25°.</p> Full article ">Figure 3
<p>(<b>a</b>) PXRD pattern of the (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> crystal at 300 K; (<b>b</b>) molecular structure; (<b>c</b>) molecular packing.</p> Full article ">Figure 4
<p>Refined PXRD patterns of the Na<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub> and K<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> salts.</p> Full article ">Figure 5
<p>EDX elemental analysis spectrum of a (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> crystal.</p> Full article ">Figure 6
<p>(<b>a</b>) Asymmetric units of the (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> crystal. (<b>b</b>) Hirshfeld surface mapping according to <span class="html-italic">d</span><sub>norm</sub>. (<b>c</b>) Two-dimensional fingerprint plots decomposed into stratified histograms.</p> Full article ">Figure 7
<p>Hirshfeld surface mapping according to (<b>a</b>) <span class="html-italic">d</span><sub>i</sub>, (<b>b</b>) <span class="html-italic">d</span><sub>e</sub>, (<b>c</b>) shape index, and (<b>d</b>) curvedness.</p> Full article ">Figure 8
<p>Crystal voids along the <span class="html-italic">a</span>-<span class="html-italic">c</span> crystallographic axes of the (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> unit cell.</p> Full article ">Figure 9
<p>(<b>a</b>) Coupled TG-DTA thermogram and (<b>b</b>) DSC curve of the (K<sub>0.86</sub>Na<sub>0.14</sub>)<sub>2</sub>Ni(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub> crystal.</p> Full article ">
18 pages, 8443 KiB  
Article
Effects of Modified Cross-Linkers on the Rheology of Water-Based Fracturing Fluids and Reservoir Water Environment
by Hua Song and Junyi Liu
Processes 2024, 12(12), 2896; https://doi.org/10.3390/pr12122896 - 18 Dec 2024
Viewed by 725
Abstract
Improving the chemical structure of the cross-linker is a potential method for reducing reservoir pollution and enhancing the fracturing efficiency of shale reservoirs. In this investigation, a three-dimensional (3-D) spherical cross-linker comprising branched chains was synthesized, and the 3-D structure of the cross-linker [...] Read more.
Improving the chemical structure of the cross-linker is a potential method for reducing reservoir pollution and enhancing the fracturing efficiency of shale reservoirs. In this investigation, a three-dimensional (3-D) spherical cross-linker comprising branched chains was synthesized, and the 3-D structure of the cross-linker was analyzed through scanning electron microscopy (SEM). Furthermore, we constructed a multifunctional coupled collaborative evaluation device that can be used to evaluate numerous properties associated with water-based fracturing fluids, including fluid viscosity, adsorption capacity, and water pollution. Meanwhile, the influence of varying reservoir conditions and cross-linker content on the fluid viscosity of water-based fracturing fluids and the potential for reservoir contamination has been evaluated and elucidated. The results indicated that the synthesized cross-linker exhibited a superior environmental protection of the shale reservoir and an enhanced capacity for thickening fracturing fluids in comparison to commercial cross-linkers. Moreover, cross-linker content, reservoir temperature, reservoir pressure, and fracture width can affect fluid viscosity and reservoir residual in different trends. The addition of 0.3% nano-cross-linker (Synthetic products) to a water-based fracturing fluid resulted in an apparent viscosity of 160 mPa·s at 200 °C, and the adsorption capacity and water content of the shale reservoir were only 0.22 µg/m3 and 0.05 µg/L, respectively. Additionally, an elevation in reservoir temperature resulted in a reduction in the adsorption capacity. However, the cross-linker content in groundwater underwent a notable increase, and the cross-linker residue in water increased by 0.009 µg/L. The impact of reservoir pressure on fluid viscosity and groundwater pollution potential exhibited an inverse correlation compared to that of reservoir temperature, and the above two parameters changed by +18 mPa·s and −0.012 µg/L, respectively. This investigation provides basic data support for the efficient fracturing and reservoir protection of shale reservoirs. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
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<p>Multifunctional coupling evaluation device for water-based fracturing fluid.</p> Full article ">Figure 2
<p>Adsorption and content evaluation of cross-linkers in shale reservoir cracks. (<b>a</b>) Adsorption process of cross−linker in shale reservoir. (<b>b</b>) Assessment of cross−linker content in groundwater.</p> Full article ">Figure 3
<p>Synthesis process (<b>a</b>) and chemical characterization methods (<b>b</b>,<b>c</b>) of nano-cross-linkers.</p> Full article ">Figure 4
<p>The effect of different cross-linker contents on the rheology and water pollution of water-based fracturing fluids (<b>a</b>,<b>b</b>).</p> Full article ">Figure 5
<p>Comparison of the interaction of cross-linkers with reservoir rocks and groundwater solubility.</p> Full article ">Figure 6
<p>The effect of different reservoir temperatures on the rheology (<b>a</b>), water pollution (<b>b</b>), and rock adsorption (<b>c</b>) of water-based fracturing fluids.</p> Full article ">Figure 7
<p>Microscopic mechanism of reservoir temperature on molecular activity and interaction.</p> Full article ">Figure 8
<p>Effect trend of different reservoir pressures on the viscosity of the water-based fracturing fluid (<b>a</b>,<b>b</b>).</p> Full article ">Figure 9
<p>Effects of different reservoir pressures on the interactions between cross-linkers and molecules and changes in microstructure.</p> Full article ">Figure 10
<p>Fluid viscosity under the interaction of different reservoir temperatures and reservoir pressures.</p> Full article ">Figure 11
<p>Effect of reservoir fracture width on the performance of water-based fracturing fluid (<b>a</b>) and microscopic mechanism analysis (<b>b</b>,<b>c</b>).</p> Full article ">
28 pages, 7321 KiB  
Article
Experimental Study on the Stress Sensitivity Characteristics of Wave Velocities and Anisotropy in Coal-Bearing Reservoir Rocks
by Zehua Zhang, Xiaokai Xu, Kuo Jian, Liangwei Xu, Jian Li, Dongyuan Zhao, Zhengzheng Xue and Yue Xin
Processes 2024, 12(12), 2819; https://doi.org/10.3390/pr12122819 - 9 Dec 2024
Viewed by 665
Abstract
As the effective stress in coal-bearing reservoirs changes, the elastic wave velocities, stress sensitivity, and anisotropic characteristics of coal rocks exhibit certain variations. Therefore, this study selected samples from the same area (sandstone, mudstone, and anthracite) and conducted experiments on their transverse wave [...] Read more.
As the effective stress in coal-bearing reservoirs changes, the elastic wave velocities, stress sensitivity, and anisotropic characteristics of coal rocks exhibit certain variations. Therefore, this study selected samples from the same area (sandstone, mudstone, and anthracite) and conducted experiments on their transverse wave velocities (Vs) and longitudinal wave velocities (Vp) and wave velocity ratios in three directions (one perpendicular and two parallel to the layering), using the RTR-2000 testing system under loading pressure conditions. The results indicate that the longitudinal and transverse wave velocities of the coal rock samples show a phase-wise increase with rising pressure. The wave velocities and wave velocity ratios of sandstone, mudstone, and anthracite demonstrate certain anisotropic characteristics, with an overall trend of decreasing anisotropy strength that stabilizes over time. The anisotropic characteristics of the longitudinal wave velocities in sandstone and mudstone are stronger than those of the transverse wave velocities, whereas in anthracite, the anisotropic characteristics of the transverse wave velocities are stronger than those of the longitudinal wave velocities. Thus, it can be concluded that Vp is a sensitive parameter for detecting the anisotropic characteristics of sandstone and mudstone, while Vs serves as a sensitive parameter for detecting the anisotropic characteristics of anthracite. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
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<p>Experimental sample diagram: (<b>a</b>) Sandstone; (<b>b</b>) Mud shale; (<b>c</b>) Anthracite.</p> Full article ">Figure 2
<p>Experimental equipment and system schematic diagram: (<b>a</b>) GCTS triaxial testing system; (<b>b</b>) Schematic diagram of ULT-200 ultrasonic testing system; (<b>c</b>) High-temperature resistant pressure head integrated with longitudinal and transverse wave dual probes.</p> Full article ">Figure 3
<p>Flow chart of the experimental thought process.</p> Full article ">Figure 4
<p>Stress–strain curve diagram of sandstone.</p> Full article ">Figure 5
<p>Stress–strain curve diagram of mud shale. (<b>a</b>) 36 MPa; (<b>b</b>) 30 MPa.</p> Full article ">Figure 6
<p>Stress–strain curve diagram of anthracite: (<b>a</b>) 12 MPa; (<b>b</b>) 10 MPa.</p> Full article ">Figure 7
<p>Graph of longitudinal and shear wave velocities of sandstone under uniaxial loading: (<b>a</b>) Longitudinal wave velocity of sandstone under loading; (<b>b</b>) Transverse wave velocity of sandstone under loading.</p> Full article ">Figure 8
<p>Longitudinal and transverse wave velocity diagrams of mud shale uniaxial loading: (<b>a</b>) Longitudinal wave velocity of mud shale with pressure; (<b>b</b>) Transverse wave velocity of mud shale with pressure.</p> Full article ">Figure 9
<p>Graph of longitudinal and transverse wave velocities of anthracite under uniaxial loading: (<b>a</b>) Longitudinal wave velocity of anthracite under loading; (<b>b</b>)Transverse wave velocity of anthracite under loading.</p> Full article ">Figure 10
<p>Graph of the mean characteristics of coal rock sample density and wave velocity.</p> Full article ">Figure 11
<p>Characteristics of P-wave and S-wave velocities of coal rock samples.</p> Full article ">Figure 12
<p>Sandstone wave velocity ratio under uniaxial loading conditions.</p> Full article ">Figure 13
<p>Wave velocity ratio of mud shale under uniaxial loading conditions.</p> Full article ">Figure 14
<p>Wave velocity ratio of anthracite under uniaxial loading conditions.</p> Full article ">Figure 15
<p>Characteristic diagrams of dynamic elastic mechanical parameters of sandstone: (<b>a</b>) Young’s modulus; (<b>b</b>) Shear modulus; (<b>c</b>) Bulk modulus.</p> Full article ">Figure 15 Cont.
<p>Characteristic diagrams of dynamic elastic mechanical parameters of sandstone: (<b>a</b>) Young’s modulus; (<b>b</b>) Shear modulus; (<b>c</b>) Bulk modulus.</p> Full article ">Figure 16
<p>Characteristic diagrams of dynamic elastic mechanical parameters of mud shale: (<b>a</b>) Young’s modulus; (<b>b</b>) Shear modulus; (<b>c</b>) Bulk modulus.</p> Full article ">Figure 16 Cont.
<p>Characteristic diagrams of dynamic elastic mechanical parameters of mud shale: (<b>a</b>) Young’s modulus; (<b>b</b>) Shear modulus; (<b>c</b>) Bulk modulus.</p> Full article ">Figure 17
<p>Characteristic diagrams of dynamic elastic mechanical parameters of anthracite: (<b>a</b>) Young’s modulus; (<b>b</b>) Shear modulus; (<b>c</b>) Bulk modulus.</p> Full article ">Figure 17 Cont.
<p>Characteristic diagrams of dynamic elastic mechanical parameters of anthracite: (<b>a</b>) Young’s modulus; (<b>b</b>) Shear modulus; (<b>c</b>) Bulk modulus.</p> Full article ">Figure 18
<p>Anisotropic characteristic diagram of sandstone under uniaxial loading conditions: (<b>a</b>) Characteristic diagram of anisotropic factors of sandstone S1; (<b>b</b>) Characteristic diagram of anisotropic factors of sandstone S2.</p> Full article ">Figure 19
<p>Anisotropic characteristic diagram of mud shale under uniaxial loading conditions: (<b>a</b>) Characteristic diagram of anisotropic factors of mud shale Y1; (<b>b</b>) Characteristic diagram of anisotropic factors of mud shale Y2.</p> Full article ">Figure 19 Cont.
<p>Anisotropic characteristic diagram of mud shale under uniaxial loading conditions: (<b>a</b>) Characteristic diagram of anisotropic factors of mud shale Y1; (<b>b</b>) Characteristic diagram of anisotropic factors of mud shale Y2.</p> Full article ">Figure 20
<p>Anisotropic characteristic diagram of mud shale under uniaxial loading conditions:(<b>a</b>) Characteristic diagram of anisotropic factors of anthracite M1; (<b>b</b>) Characteristic diagram of anisotropic factors of anthracite M2.</p> Full article ">Figure 20 Cont.
<p>Anisotropic characteristic diagram of mud shale under uniaxial loading conditions:(<b>a</b>) Characteristic diagram of anisotropic factors of anthracite M1; (<b>b</b>) Characteristic diagram of anisotropic factors of anthracite M2.</p> Full article ">
17 pages, 3088 KiB  
Article
The Carrying Behavior of Water-Based Fracturing Fluid in Shale Reservoir Fractures and Molecular Dynamics of Sand-Carrying Mechanism
by Qiang Li, Qingchao Li, Fuling Wang, Jingjuan Wu and Yanling Wang
Processes 2024, 12(9), 2051; https://doi.org/10.3390/pr12092051 - 23 Sep 2024
Cited by 69 | Viewed by 1513
Abstract
Water-based fracturing fluid has recently garnered increasing attention as an alternative oilfield working fluid for propagating reservoir fractures and transporting sand. However, the low temperature resistance and stability of water-based fracturing fluid is a significant limitation, restricting the fracture propagation and gravel transport. [...] Read more.
Water-based fracturing fluid has recently garnered increasing attention as an alternative oilfield working fluid for propagating reservoir fractures and transporting sand. However, the low temperature resistance and stability of water-based fracturing fluid is a significant limitation, restricting the fracture propagation and gravel transport. To effectively ameliorate the temperature resistance and sand-carrying capacity, a modified cross-linker with properties adaptable to varying reservoir conditions and functional groups was synthesized and chemically characterized. Meanwhile, a multifunctional collaborative progressive evaluation device was developed to investigate the rheology and sand-carrying capacity of fracturing fluid. Utilizing molecular dynamics simulations, the thickening mechanism of the modified cross-linker and the sand-carrying mechanism of the fracturing fluid were elucidated. Results indicate that the designed cross-linker provided a high viscosity stability of 130 mPa·s and an excellent sand-carrying capacity of 15 cm2 at 0.3 wt% cross-linker content. Additionally, increasing reservoir pressure exhibited enhanced thickening and sand-carrying capacities. However, a significant inverse relationship was observed between reservoir temperature and sand-carrying capacity, attributed to changes in the drag coefficient and thickener adsorption. These results verified the effectiveness of the cross-linker in enhancing fluid viscosity and sand-carrying capacity as a modified cross-linker for water-based fracturing fluid. Full article
(This article belongs to the Special Issue Environmentally Friendly Production of Energy from Natural Gas Hydrates)
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<p>Collaborative evaluation device of water-based fracturing fluid performance.</p> Full article ">Figure 2
<p>Synthesis process (<b>a</b>) and chemical characterization (<b>b</b>) of nano-titanium cross-linker.</p> Full article ">Figure 3
<p>Sand-carrying experimental device and schematic diagram of water-based fracturing fluid.</p> Full article ">Figure 4
<p>Effect of cross-linker content on fracturing fluid viscosity and sand-carrying capacity (453 K, 170 s<sup>−1</sup> and 20 MPa). (<b>a</b>): fracturing fluid viscosity. (<b>b</b>): sand-carrying capacity.</p> Full article ">Figure 5
<p>Micro mechanism of sand carrying in fracturing fluid by the cross-linker type and cross-linker content.</p> Full article ">Figure 6
<p>Effect of reservoir temperature on fracturing fluid viscosity and sand-carrying capacity (0.3% cross-linker content, 170 s<sup>−1</sup> and 20 MPa). (<b>a</b>): fracturing fluid viscosity. (<b>b</b>): sand-carrying capacity.</p> Full article ">Figure 7
<p>Microscopic model differences of fracturing fluid at different reservoir temperatures. (<b>a</b>): Microscopic grid variation. (<b>b</b>): sand-carrying capacity of synthetic crosslinker.</p> Full article ">Figure 8
<p>Effect of reservoir pressure on fracturing fluid viscosity and sand-carrying capacity (0.3% cross-linker content, 170 s<sup>−1</sup> and 453 K). (<b>a</b>): fracturing fluid viscosity. (<b>b</b>): sand-carrying capacity.</p> Full article ">Figure 9
<p>Effect of reservoir pressure on fracturing fluid viscosity and sand -carrying capacity (0.3% cross-linker content, 20 MPa and 453 K). (<b>a</b>): Synthetic. (<b>b</b>): Commercial.</p> Full article ">
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