Journal of Natural Gas Science and Engineering最新文献

{"title":"Influence of desulfurization strategies for methane gaseous direct injection engine on carbon dioxide emissions","authors":"Marcus Fischer , Marco Günther , Stefan Pischinger , Ulrich Kramer , Christian Nederlof , Tobias van Almsick","doi":"10.1016/j.jngse.2022.104822","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104822","url":null,"abstract":"<div><p><span>The use of fuels produced with renewable electricity from wind and solar energy and with CO</span><span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span><span><span> from unavoidable sources or directly captured form the air (so called e-Fuels) is of great interest as a proposition for further limiting the climate impact of road transportation. One of the most efficiently producible e-fuels is e-methane. Feeding methane from renewable sources into the gas grid is one of the most promising pathways to achieve carbon neutral road transportation on a well-to-wheel (WTW) basis. Currently, the use of odorants is mandatory in the gas grid. It is common that sulfur compounds<span> are used as odorants, which can lead to sulfur poisoning of the catalytic converters<span> if an internal combustion engine is operated with it. Consequently, </span></span></span>desulfurization will be necessary to maintain high catalyst efficiency over lifetime, which will increase the tank-to-wheel (TTW) CO</span><span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span><span><span> emissions through increased fuel consumption. For desulfurization, it is necessary to increase the catalyst brick temperature to levels above 800 °C. This paper investigates how such high temperatures can be realized and derive implications on engine operation and gas grid regulation. To this end, experimental studies were conducted with a 1-liter 3-cylinder prototype engine from Ford-Werke GmbH featuring variable intake valve<span> timing, a compression ratio of 14 and a turbocharger with variable turbine geometry (VTG). The engine was operated with gas </span></span>direct injection<span> at up to 16 bar pressure. The ECU software allowed to apply deliberate oscillations of the lambda signal (“wobbling” of the air/fuel ratio) and cylinder individual air/fuel ratios to achieve a sufficient exhaust aftertreatment. The three-way-catalyst for the investigations were particularly suitable for methane operation due to a high palladium loading and increased oxygen storage capacity of the washcoat. Different load points were used for the investigations, ranging from near idle to medium engine speed and load. The catalyst brick temperature was increased considerably by splitting the mean air/fuel ratio between lean and rich operation on different cylinders (so called “lambda spli”), which is limited by the ignition limits of air/methane charges. Furthermore, too extreme lambda split leads to unstable engine operation. Sufficient hydrocarbon reduction can be achieved at a catalyst brick temperature above 500 °C, which cannot be achieved for near idle load points without additional measures (e.g. electrically heated catalyst). Desulfurization of the catalyst requires brick temperatures above 800 °C and is accordingly not achievable with stable engine operation in a significantly large area of the low load operation conditions. In this case additional he","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"108 ","pages":"Article 104822"},"PeriodicalIF":4.965,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1826676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation research on solid fluidization exploitation of deepwater superficial layer natural gas hydrate reservoirs based on double-layer continuous pipe","authors":"Geng Zhang ,&nbsp;Jun Li ,&nbsp;Hongwei Yang ,&nbsp;Gonghui Liu ,&nbsp;Qin Pang ,&nbsp;Tong Wu ,&nbsp;Honglin Huang","doi":"10.1016/j.jngse.2022.104828","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104828","url":null,"abstract":"<div><p>In this paper, a new method for exploiting shallow marine natural hydrate reservoirs is proposed using a double-layer continuous pipe. In order to research the multiphase flow<span><span> behavior and hydrate decomposition characteristics during the hydrate mining process, a non-isothermal transient gas-liquid-solid multiphase flow model is established considering the coupling effect of multiphase flow, heat transfer and hydrate phase transition. The model's accuracy is verified by comparisons with laboratory and field data. Numerical simulation results show that the hydrate decomposition is slow in the first 2 h of mining, thus the volume fraction of each phase in the pipe changes little; with the increase of time, the volume fraction of each phase in the pipe changes significantly until it reaches a stable state after about 5 h of mining. When the mining rate exceeds 15 kg/s, the hydrate particles will not be fully and effectively transported, and a short time aggregation phenomenon will occur. Increasing the temperature of the injected seawater is beneficial to promote the hydrate decomposition, which in turn increases gas production. While, increasing the </span>wellhead<span> backpressure<span> and seawater displacement facilitates in reducing gas production. The research findings will be of reference value for gaining insight into studying complex multiphase flow behaviors involving hydrate phase transition and provide a new approach to exploiting subsea shallow natural gas hydrate reservoirs.</span></span></span></p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"108 ","pages":"Article 104828"},"PeriodicalIF":4.965,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1830304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development status of crosslinking agent in high-temperature and pressure fracturing fluid: A review","authors":"Li Nianyin ,&nbsp;Jiajie Yu ,&nbsp;Wang Daocheng ,&nbsp;Wang Chao ,&nbsp;Kang Jia ,&nbsp;Liu Pingli ,&nbsp;Huang Chengzhi ,&nbsp;Xiong Ying","doi":"10.1016/j.jngse.2021.104369","DOIUrl":"https://doi.org/10.1016/j.jngse.2021.104369","url":null,"abstract":"<div><p>With the continuous development of unconventional oil and gas in recent years, researchers have set higher requirements on crosslinker<span> performance. Therefore, research on the crosslinking agent that is suitable for the high-temperature/high-pressure (HT/HP) fracturing fluid system is particularly important. This work reviews the development status of a crosslinker for the HT/HP fracturing fluid system. Our results show that the cost of a boron crosslinking agent is low; however, it is not suitable under very high temperatures. Metal crosslinking agents are suitable for a wide range of pH but have poor shear resistance. Meanwhile, the nano crosslinking agent has a high applicable temperature and a strong comprehensive performance but is relatively expensive. How to further improve the adaptability of crosslinking agents to high temperature and pressure and reduce the additive dosage are the focus of future research.</span></p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104369"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1813510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-field coupling theory and research progress of methane extraction in deep coal seams: A review","authors":"Youping Xu ,&nbsp;Ting Liu ,&nbsp;Baiquan Lin","doi":"10.1016/j.jngse.2022.104796","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104796","url":null,"abstract":"<div><p><span>Methane extraction in deep coal seams<span> is a multi-field coupling process affected by multiple factors, and a systematic multi-field coupling theory is of guiding significance for ensuring the safety and efficiency of such extraction. In this study, the theoretical framework was constructed for the multi-field coupling theory of methane extraction in coal mines. First, the key scientific issues were identified. Subsequently, based on the stress distribution and structure of the coal seam, the longwall panel was divided into three zones, i.e., the virgin zone, the excavation disturbed zone and the goaf. Furthermore, the research progress of multi-field coupling during methane extraction were analyzed for the three zones, respectively. Finally, the deficiencies of current researches on multi-field coupling theory for methane extraction were revealed, and the future research directions were pointed out. The following research findings were obtained: Deep coal mining is accompanied by a notable multi-field coupling phenomenon, and the occurrence of compound disasters promote the difficulty in disaster control. However, we can adopt appropriate measures to decouple compound disasters after fully grasping the triggering mechanism and development process of the fields. In this way, the disasters can be controlled separately. In addition, from the perspective of the whole longwall panel, the main development directions are to reveal the </span></span>gas flow in cross-scale structures and to develop a unified model for gas migration in the multi-scale structure.</p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104796"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3270824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An improved solution to flow assurance in natural gas pipeline enabled by a novel self-regulated bypass pig prototype: An experimental and numerical study","authors":"Jianheng Chen ,&nbsp;Xiaoming Luo ,&nbsp;Limin He ,&nbsp;Haixiao Liu ,&nbsp;Lin Lu ,&nbsp;Yuling Lü ,&nbsp;Donghai Yang","doi":"10.1016/j.jngse.2022.104776","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104776","url":null,"abstract":"<div><p>Bypass pigging is an emerging strategy in effectively overcoming inherent issues of high pig speed and overflow of pigging-induced slug volume concomitantly caused by traditional pigging for natural gas pipelines, which is attracting wide attention for flow assurance in oil and gas industry. In view of most bypass pigs with simple bypass structures, the risk of pig stalling or pipeline blockage accidents can be encountered when suffering from increased resistance forces. Accordingly, a novel bypass pig prototype with a self-regulated module is proposed in this study as an improved solution to strengthening pigging safety, efficiency and flow assurance. A self-regulated, easily assembled bypass pig prototype was fabricated for experimental studies in a horizontal transparent gas pipeline system. The pressure mitigation and pig velocity characteristics were fully evaluated under varying bypass fractions. Specifically, when the bypass fraction increases from 0% to 3%, the average pig velocity can be reduced by 64.3–81.5% and pressure fluctuations are more stable. Besides, as an important structural parameter in affecting pig velocity and accuracy of dynamic pigging simulation, the pressure drop coefficient of gas through the bypass pig structure with an internal regulating valve was numerically studied. Compared to the common bypass pig with only a simple bypass port, the addition of the bypass regulating valve will notably increase the pressure drop coefficient. In particular, when the bypass fraction is increased to 7%, pressure drop coefficients for the bypass pig without or with an internal valve are 1.03 and 1.97, respectively, with the deviation of 90.9%. Finally, an optimal design scheme for bypass pigging operations was newly proposed to optimize bypass fractions in accordance with practical scenarios. This study can provide an effective pathway towards the implementation of self-regulated bypass pigging technology in substantially improving flow assurance of natural gas pipeline systems.</p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104776"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3453546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shale gas load recovery modeling and analysis after hydraulic fracturing based on genetic expression programming: A case study of southern Sichuan Basin shale","authors":"Lan Ren ,&nbsp;Zhenhua Wang ,&nbsp;Jinzhou Zhao ,&nbsp;Jianjun Wu ,&nbsp;Ran Lin ,&nbsp;Jianfa Wu ,&nbsp;Yongqiang Fu ,&nbsp;Dengji Tang","doi":"10.1016/j.jngse.2022.104778","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104778","url":null,"abstract":"<div><p><span>For shale gas<span><span> reservoir, fracture network fracturing in horizontal well is the key </span>technology to guarantee its commercial exploitation, and the load recovery is a critical parameter which determines the post-fracturing performance. It has been reported that there is a huge difference in load recovery but the control factors are not well understood. It seriously affects the stimulation effect of fracture network fracturing in shale gas wells. Therefore, it is important to analyze the main control factors affecting the load recovery to optimize the design of fracture network fracturing. Further, the load recovery is affected by many factors such as geological, engineering, and production. However, traditional methods are blind to the accurate analysis of the impact on the load recovery. Notably, machine learning (ML) technology has achieved remarkable success in solving the problems of multi-factor nonlinear fitting and black box prediction. Therefore, the genetic expression programming (GEP) is adopted to express the nonlinear relationship in a clear and precise manner in this paper. The data of 189 wells were collected in southern Sichuan, including geological and engineering factors. A feature comprehensive index calculation method was established, and the relative importance of these features analyzed, and then screened out 18 reconstructed features based on geological and engineering factors that affect flow back. The mutual influence between the features was eliminated through principal component analysis of the reconstructed features. Thus the load recovery calculation model was developed and the influence of main control features (variables) on the flow back was analyzed by using partial dependence plot. Statistical parameters showed that satisfactory performance can be obtained through GEP model (training set </span></span><em>R</em> = 0.835, test set <em>R</em> = 0.815). The research results show that the GEP calculation model can quickly and accurately calculate the load recovery, obtain the influence law of main controlling factors of geological engineering on shale gas flow back and improve the control of load recovery. Therefore, the method based on GEP can effectively study the main control factors affecting the flow back of shale gas, and hence it can be used as a fast reliable tool to effectively evaluate the load recovery.</p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104778"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3453547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of clathrate hydrates dissociation conditions in the presence of gas dehydration, sweetening, and other nitrogenated additives using a predictive thermodynamic approach","authors":"Ali Rasoolzadeh ,&nbsp;Ali Bakhtyari ,&nbsp;Khayyam Mehrabi ,&nbsp;Jafar Javanmardi ,&nbsp;Khashayar Nasrifar ,&nbsp;Amir H. Mohammadi","doi":"10.1016/j.jngse.2022.104773","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104773","url":null,"abstract":"<div><p><span>–Despite numerous experimental data on gas hydrate<span><span> equilibrium conditions in the presence of glycols, alkanolamines, and nitrogenated additives that are frequently utilized in the gas refinery, the apparent lack of a precise predictive thermodynamic model is still perceived. This study presents an unprecedented </span>thermodynamic framework benefitting from the modified van der Waals-Platteeuw (vdW-P) model for the hydrate phase, the Peng-Robinson </span></span>equation of state<span> (PR EoS) for the vapor/gas phase, and combinations of free-volume Flory Huggins (FVFH) and Pitzer-Debye-Hückel (PDH) equations for the water activity in the aqueous phase<span>, in which the FVFH activity model is utilized for the additives with molecular interactions solely, while the PDH model is employed when the ionic interactions also exist. When the model assessed a databank of 1075 data points, 0.29% (0.80 K) and 9.67% (0.49 MPa) deviations were observed in the temperature and pressure calculations, respectively. In particular, for 877 data points (glycols, urea, acetamide, and formamide), employing FVFH solely resulted in 0.32% (0.88 K) and 10.54% (0.50 MPa) temperature and pressure deviations, respectively, whereas the combination of FVFH + PDH yielded 0.17% (0.48 K) and 5.81% (0.47 MPa) errors in temperature and pressure estimations, respectively in 198 data points of the systems comprised of amines, hydrazine, and piperazine. The maximum deviation of temperature prediction did not exceed 6.80 K (2.39%). The results reveal the effective performance of the proposed calculation approach.</span></span></p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104773"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2631321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Control of directional long borehole on gas drainage and optimal design: Case study","authors":"Qiming Zhang ,&nbsp;Enyuan Wang ,&nbsp;Zhonghui Li ,&nbsp;Hao Wang ,&nbsp;Zhaozhao Xue","doi":"10.1016/j.jngse.2022.104766","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104766","url":null,"abstract":"<div><p>The Directional Long Borehole (DLB) technique, which has the benefits of low construction costs and high drainage efficiency, will be extensively used in future mining operations for gas drainage and utilization. Choosing the right borehole parameter is critical for improving the drilling stability and drainage efficiency of DLB. This paper begins with research on the gas migration and enrichment law in the mining-induced fissure, and proposes a gas migration channel zoning model. Furthermore, the dynamic process of gas migration in fissure fields is analyzed, as well as the key borehole parameters are identified. The optimal DLB parameters are eventually addressed and presented for the 2205 working face via combined UDEC and COMSOL. Research indicates that: (1) The mining-induced fissure serves as a channel for gas flow, and presents different pore morphology in space, forming a gas migration channel zoning model. The model's permeability increases initially and then decreases from the gob upward, increasing in an O-ring outward diffusion from the gob's center, it can be represented as a rectangular ladder platform with 15 zones. (2) Gas goes through a dynamic process of state change during drainage that involves adsorption/desorption, diffusion, and seepage. The main factors that affect this process are negative pressure, borehole length, borehole diameter, and the location of the borehole in the fissure zone. (3) The optimal parameters of DLB in the 2205 working face, are 2 drill sites, each with 5 sets of 500 m long boreholes, with a diameter of 133 mm, and a pumping negative pressure of 13 kPa, and placed in a layer height of 22 m. DLB provides benefits over the high-level suction highway in terms of construction cost, drainage effectiveness, and timeliness. The findings can be used to guide the design of DLB, enhance gas energy utilization, and prevent gas disasters.</p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104766"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1830309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Process simulation and optimisation for acid gas removal system in natural gas processing","authors":"Yick Eu Chew ,&nbsp;Zulfan Adi Putra ,&nbsp;Dominic C.Y. Foo","doi":"10.1016/j.jngse.2022.104764","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104764","url":null,"abstract":"<div><p><span>Acid gases such as hydrogen sulphide (H</span>₂S) and carbon dioxide (CO₂<span><span>) are abundant in natural gas, which affect the economics of plant operations and the environment. Chemical absorption<span><span> is one of the most established technologies for </span>acid gas removal<span>. However, it suffers with a major drawback, i.e. high energy consumption. In this work, an integrated simulation-optimisation approach was employed to minimise energy consumption and hence operating cost in an acid gas removal (AGR) system for natural gas processing. The integrated approach made use of commercial simulation software Aspen HYSYS and optimisation software LINGO to establish a </span></span></span>surrogate model<span> that has the best operating conditions while satisfying sales gas requirements. Operational parameters such as alkanolamine flowrates<span>, absorber pressure, and alkanolamine temperature were taken into account. Moreover, Pareto analysis is carried out for multi-objective optimisation in maximising profit and minimising CO</span></span></span>₂<span> content. The integrated approach was demonstrated on a case study involving an AGR system in a natural gas processing plant. Results showed that with the optimal operating conditions, profit of the plant is predicted to increase by 9.15% for the same CO</span>₂ basis (i.e. 0.77 mol%); the profit is expected to increase by 23.3% at higher CO₂ content (i.e. 1 mol%). It was observed that the maximum profit and minimum CO₂ content is achieved at amine recirculation rate of 1914.49 m³/h, pressure of 54 kg/cm², and temperature of 49.54 °C. Furthermore, sensitivity analysis illustrated that profit is proportional to the sweet gas price whereas electricity cost is the most vital parameter in reducing the overall profitability.</p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104764"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2554426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of pore-fracture structure and permeability of coal by microwave irradiation under uniaxial compression","authors":"Nan Yang ,&nbsp;Guozhong Hu ,&nbsp;Jian Zhu ,&nbsp;Haoran Duan ,&nbsp;Tonghui Wang ,&nbsp;Yifan Li","doi":"10.1016/j.jngse.2022.104759","DOIUrl":"https://doi.org/10.1016/j.jngse.2022.104759","url":null,"abstract":"<div><p><span><span>In a natural coal reservoir environment, the </span>coal seam<span> is constrained by in-situ stress and gas pressure. Damage on the coal microstructure due to microwave irradiation (MI) differs significantly different from that under no-load conditions. In this study, the effect of MI on the pore-fracture structure and seepage characteristics of load-constrained coal is investigated using a custom-developed microwave fracturing experimental device, nuclear magnetic resonance test device, and permeability test device. Based on the relationship between microwave and pore-fracture structure parameters and the permeability of loaded coal, the pore-fracture structure evolution and permeability growth law of loaded coal under MI are determined. The results show that the number of micropores in coal decreases and the T</span></span>₂ curve of micropores is shifted to the right under the combined effect of MI and external stress load. The numbers of mesopores, macro-pores, and micro-fractures increase, and the T₂ curve exhibits a broader peak span. The pore-fracture structure evolution effect of loaded coal increases with the microwave power and MI time. Under high-power MI, the pore-fracture structure evolution of the loaded coal shows a “decrease - increase – decrease” trend as the stress load increases, whereas a “decrease – increase” trend is shown under low-power MI. Under the same microwave parameters, the permeability of unloaded and loaded coal increases by a maximum of 15.7 and 364.7 times, respectively. In particular, the permeability increases by 3.1–11.4 and 17.8–49.7 times under external stress loads of 4 and 2 MPa, respectively. The combination of high MI power and short MI duration under the same microwave energy facilitates the development of the pore-fracture structure and increases the permeability of loaded coal. Microwaves have a differential thermal effect on mineral in coal, which reduce the physical properties of the coal. Pore-fracture structure and permeability are further enhanced by the stress load.</p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"107 ","pages":"Article 104759"},"PeriodicalIF":4.965,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3270826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}