Articoli di riviste: "Cryogenic fracturing"

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Cha, Minsu, Naif B. Alqahtani, Bowen Yao, Xiaolong Yin, Timothy J. Kneafsey, Lei Wang, Yu-Shu Wu e Jennifer L. Miskimins. "Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation". SPE Journal 23, n. 04 (6 febbraio 2018): 1271–89. http://dx.doi.org/10.2118/180071-pa.

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Summary A laboratory study of cryogenic fracturing was performed to test its ability to improve oil/gas recovery from low-permeability reservoirs. Our objective is to develop well-stimulation technologies using cryogenic fluids [e.g., liquid nitrogen (LN)] to increase permeability in a large reservoir volume surrounding wells. The new technology has the potential to reduce formation damage caused by current stimulation methods and minimize or eliminate water usage. The concept of cryogenic fracturing is that a sharp thermal gradient (thermal shock) created at the surfaces of formation rocks by applying cryogenic fluid can cause strong local tensile stress and start fractures. We developed a laboratory system for cryogenic fracturing under true-triaxial loading, with LN-delivery/control and -measurement systems. The loading system simulates confining stresses by independently loading each axis up to approximately 5,000 psi on 8×8×8-in. cubes. Temperature in boreholes and at block surfaces and fluid pressure in boreholes were continuously monitored. Acoustic and pressure-decay measurements were obtained before and at various stages of stimulations. Cubic blocks (8 × 8×8-in.) of Niobrara shale, concrete, and sandstones were tested, and stress levels and anisotropies varied. Three schemes were considered: gas fracturing without cryo-stimulation, gas fracturing after low-pressure cryogen flow-through, and gas fracturing after high-pressure cryogen flow-through. Results from pressure-decay tests show that LN stimulation clearly increases permeability, and repeated stimulations further increase the permeability. Acoustic velocities and amplitudes decreased significantly after cryo-stimulation, indicating fracture creation. In the gas fracturing without the stimulation, breakdown (complete fracturing) occurs suddenly without any initial leaking, and major fracture planes form along the plane containing principal-stress and intermediate-stress directions, as expected theoretically. However, in the gas fracturing after cryogenic stimulations, breakdown occurred gradually and with massive leaking because of thermal fractures created during stimulation. In addition, the major fracture direction does not necessarily follow the plane containing the principal-stress direction, especially at low confining-stress levels. In tests, we observed that cryogenic stimulation seems to disrupt the internal stress field. The increase in borehole temperature after stimulation affects the permeability of the specimen. When a stimulated specimen is still cold, it maintains high permeability because fractures remain open and local thermal tension is maintained near the borehole. When the rock warms back, fractures close and permeability decreases. In these tests, we have not used proppants. Overall, fractures are clearly generated by low- and high-pressure thermal shocks. The added pressure of the high-pressure thermal shocks helps to further propagate cryogenic fractures generated by thermal shock. Breakdown pressure is significantly lowered by LN stimulation, with observed breakdown-pressure reductions up to approximately 40%.

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Alameedy, Usama, e Ali Al-Behadili. "An Overview of How the Petrophysical Properties of Rock Influenced After Being Exposed to Cryogenic Fluid". Journal of Engineering 29, n. 11 (2 novembre 2023): 1–16. http://dx.doi.org/10.31026/j.eng.2023.11.01.

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Exposure to cryogenic liquids can significantly impact the petrophysical properties of rock, affecting its density, porosity, permeability, and elastic properties. These effects can have important implications for various applications, including oil and gas production and carbon sequestration. Cryogenic liquid fracturing is a promising alternative to traditional hydraulic fracturing for exploiting unconventional oil and gas resources and geothermal energy. This technology offers several advantages over traditional hydraulic fracturing, including reduced water consumption, reduced formation damage, and a reduced risk of flow-back fluid contamination. In this study, an updated review of recent studies demonstrates how the thermal shock caused by the cryogenic liquid during the fracturing process substantially affects the rock's physical properties. Additionally, changes in permeability, porosity, and pore structure brought about by cryogenic treatments are highlighted. This work aims to draw attention to the studies that deal with the effect of thermal shock on rock petrophysical properties and establish the ideal conditions for employing cryogenic liquids in these contexts. Simulation studies, laboratory trials, and field application cases have been undertaken to assess the efficacy of cryogenic liquid fracturing technology. These investigations have provided important insights into the physical and mechanical impacts of thermal shock on rock and the performance of cryogenic liquid fracturing in real-world situations.

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Ahmed, Amna, Teresa Zhu e Amna Majeed. "Taking the hydro out of hydrofracturing: Application of ultra-light weight proppants to cryogenic liquid nitrogen as a fracturing fluid". University of Ottawa Science Undergraduate Research Journal 1 (23 agosto 2018): 57. http://dx.doi.org/10.18192/osurj.v1i1.3711.

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In the last decade, hydraulic fracturing has rapidly gained popularity worldwide, emerging as the leading method of natural gas extraction in the United States. However, the practice remains controversial due to its contribution to greenhouse gas emissions and the contamination of freshwater used in fracturing fluids. Although waterless fracturing fluids have been developed, including those using N2, CO2, oil, and alcohol, their application has been limited largely due to reduced fracturing power. Recent research has demonstrated that cryogenic nitrogen may prove a viable alternative, if this issue is properly addressed. Addition of durable, lightweight proppants is one way to increase fracturing power. This study aims to investigate the effect of proppant addition on the fracturing capabilities of cryogenic nitrogen. Three ultra-lightweight proppants will be combined with liquid nitrogen and fracturing power will be measured using triaxial stress tests. This novel approach has not yet been explored and will open more avenues of research into sustainable and efficient fracturing using cryogenic nitrogen.

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Zhang, Yan, Yu Wu, Savenok Olga Vadimovna, Jiadi Yin, Haozhe Geng e Decheng Li. "Experimental Investigation on Cracking Characteristics of Dry and Saturated Shales in Nitrogen Fracturing after Liquid Nitrogen (LN2) Injection". Geofluids 2023 (13 aprile 2023): 1–19. http://dx.doi.org/10.1155/2023/8861524.

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Cryogenic LN2 fracturing is one of the environmentally friendly waterless fracturing technologies that promote the fracture complexity of shale gas reservoir. The water-ice phase transition under freezing condition causes frost heave in saturated shale. The effect of moisture in shale should be taken into account during cryogenic damage process. Therefore, the differences of cracking characteristics between dry and saturated shales were studied in this paper. A laboratory triaxial and high temperature fracturing system was developed for nitrogen fracturing dry and saturated shale after LN2 injection. The influence of moisture on breakdown pressure was studied under different confining pressures (3 MPa, 6 MPa, 9 MPa, and 12 MPa) and bedding directions (parallel bedding and vertical bedding). The experimental results demonstrated that when the confining pressure increased from 3 MPa to 12 MPa, the breakdown pressure of dry parallel bedding after LN2 preconditioning decreased 7.12 MPa, 6.06 MPa, 4.58 MPa, and 3.11 MPa, respectively. Therefore, LN2 preconditioning could damage shale resulting in a lower breakdown pressure, but the effect of cryogenic damage decreased with the confining pressure increasing. The moisture in shale had little impact on nitrogen fracturing without LN2 injection because the breakdown pressure difference between dry and saturated shales was small. However, the breakdown pressure of saturated shale after LN2 preconditioning was always lower than that of dry shale. The breakdown pressure of saturated parallel bedding shale after LN2 injection decreased 8.62 MPa, 7.67 MPa, 6.08 MPa, and 4.63 MPa, respectively, with the confining pressure increasing from 3 MPa to 12 MPa. The breakdown pressure difference between dry and saturated shales was impacted by the migration of unfrozen water and frost heave. In addition, the extent of cryogenic damage varied substantially between different bedding directions. When the confining pressure was 3 MPa, the breakdown pressure of saturated parallel bedding shale reduced by 69.18% after LN2 preconditioning, but that of saturated vertical bedding shale only decreased by 22.49%. The tensile strength of shale had a greater influence on the breakdown pressure. According to the Brazilian disc test results, the tensile strength of matrix was much higher than that of bedding planes. As a result, it is useful to wet the shale in order to reduce the breakdown pressure. The fracturing direction of horizontal drilling should be consistent with the bedding direction for better cryogenic fracturing effect.

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Longinos, Sotirios Nik, Lei Wang e Randy Hazlett. "Advances in Cryogenic Fracturing of Coalbed Methane Reservoirs with LN2". Energies 15, n. 24 (14 dicembre 2022): 9464. http://dx.doi.org/10.3390/en15249464.

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Coalbed methane (CBM) is a significant unconventional natural gas resource existing in matrix pores and fractures of coal seams and is a cleaner energy resource compared to coal and crude oil. To produce CBM, stimulation operations are required, given that the coal permeability is generally too low. Hydraulic fracturing is the most widely used technology for reservoir stimulation; however, there are a few challenging issues associated with it, e.g., huge water consumption. In the past decade, the use of liquid nitrogen (LN2) as a fracturing fluid has been intensively studied for stimulating CBM reservoirs, achieving considerable progress in understanding fracturing mechanisms and optimizing fracturing techniques. This paper presents a thorough review of experimental design and observations, modeling procedures and results, field applications, and published patents. Existing studies are divided into five different groups for discussion and comparison, including immersion tests, injection tests, jet drilling tests, numerical modeling, and field applications. Based on the comprehensive evaluation of the outcomes, it is obvious that cryogenic fracturing using LN2 is a promising eco-friendly fracturing technique that can effectively enhance coal rock permeability to increase the production of CBM.

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Tarom, N., Muhammad Zain Rasheed, Shehan Khan, M. M. Hossain e Mohammad Sarmadivaleh. "Thermal Hydraulic Fracturing Applying Cryogenic Freezing Technique". IOP Conference Series: Materials Science and Engineering 495 (7 giugno 2019): 012076. http://dx.doi.org/10.1088/1757-899x/495/1/012076.

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Cha, Minsu, Xiaolong Yin, Timothy Kneafsey, Brent Johanson, Naif Alqahtani, Jennifer Miskimins, Taylor Patterson e Yu-Shu Wu. "Cryogenic fracturing for reservoir stimulation – Laboratory studies". Journal of Petroleum Science and Engineering 124 (dicembre 2014): 436–50. http://dx.doi.org/10.1016/j.petrol.2014.09.003.

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Elwegaa, Khalid, e Hossein Emadi. "The Effect of Thermal Shocking with Nitrogen Gas on the Porosities, Permeabilities, and Rock Mechanical Properties of Unconventional Reservoirs". Energies 11, n. 8 (15 agosto 2018): 2131. http://dx.doi.org/10.3390/en11082131.

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Cryogenic fracturing is a type of thermal shocking in which a cold liquid or gas is injected into a hot formation to create fractures. Research has shown that like traditional hydraulic fracturing, cryogenic fracturing could improve oil/gas recovery from unconventional reservoirs. Research has also shown, though, that, unlike traditional hydraulic fracturing, which uses water-based fluids, cryogenic fracturing limits and can even heal damage that is near the wellbore. Previous studies on thermal shocking, however, have generally examined only a few parameters at a time. To provide a more complete overview of the process, this study examines the effects of thermal shocking with low-temperature nitrogen gas on the porosities, permeabilities, and rock mechanical properties of unconventional reservoirs. Three cycles of thermal shocking were applied to a core sample and an outcrop sample from an unconventional reservoir. Each sample was heated at 82 °C for 1 h, and then nitrogen at −18 °C was injected at 6.89 MPa for 5 min. The porosities and permeabilities of the cores and the velocities at which ultrasonic waves travelled through them were measured both before and after each thermal shock. The results strongly suggest that the thermal shocking produced cracks. The porosity increased by between 1.34% and 14.3%, the permeability increased by between 17.4% and 920%, and the average P-wave velocity decreased by up to 100 m/s. From the reduction in P-wave velocity, it was determined that the brittleness ratio increased by between 2 and 4 and the fracability index increased by between 0.2 and 0.8.

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Cha, Minsu, Naif B. Alqahtani e Lei Wang. "Cryogenic Fracture Proliferation from Boreholes under Stresses". Processes 11, n. 7 (6 luglio 2023): 2028. http://dx.doi.org/10.3390/pr11072028.

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Cryogenic fracturing has been explored in recent years as a waterless fracturing method for well stimulation to avoid issues encountered in water-based hydraulic fracturing. Cryogenic stimulation using liquid nitrogen applies large thermal gradients on reservoir rocks to induce fractures. This study investigates the initiation and proliferation of cryogenic fractures from boreholes under external stress on specimens. We flowed liquid nitrogen through boreholes drilled through the center of transparent PMMA cylinders under uniaxial stress and monitored fracture proliferation, temperatures, and borehole pressures. Our results show that the effect of stress resembles that of hydraulic fractures such that fractures propagate more in the direction of the stress. Under loading perpendicular to the borehole axis, a cloud of annular and longitudinal fractures extends more in the direction of loading. Under loading parallel to the borehole axis, longitudinal fractures dominate, and annular fractures become more suppressed and more sparsely distributed than those of unconfined specimens. Even if fractures are driven to initiate against the influence of stress, such as those from a boundary edge of a high stress concentration, they gradually deflect in the direction of stress, similar to hydraulic fractures from perforation holes that curve toward a direction perpendicular to the minimum stress direction.

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Yang, Zheqi, Baosheng Zhang e Jianfei Bi. "Laboratory Investigation of Cryogenic Fracturing of HDR Wellbores Under Triaxial-Confining stresses". Journal of Physics: Conference Series 2520, n. 1 (1 giugno 2023): 012016. http://dx.doi.org/10.1088/1742-6596/2520/1/012016.

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Abstract Hot dry rock (HDR) contains abundant thermal energy, which can be extracted through fracturing and used for electricity generation. Due to its deep depth, high temperature and high-pressure conditions, it is difficult to initiate fractures for conventional hydraulic fracturing technology. This paper studies the advantage of cryogenic fracturing on the HDR. We have carried out a series of laboratory experiments on granite samples with different lengths of the open hole under triaxial-confining stresses (10 MPa). The nitrogen fracturing wellbores of high temperature (100−300 °C) granites are processed by LN2 (liquid nitrogen) and NoLN2 (no liquid nitrogen) and retained with 20 mm and 30 mm open hole to form four control groups. The fracturing results showed that LN2 cryogenic stimulation is more effective in reducing the HDR initiation pressure. With a 20 mm open hole, the breakdown pressure of samples with LN2 decreases by 13.9%-18.7% compared with untreated samples. When the open hole changes from 20 mm to 30 mm, the breakdown pressure of samples with NoLN2 is reduced by 6.7%-15%. The longer the open hole of the samples is, the more complex the fracture patterns after the nitrogen fracturing are. This can be attributed to the length of the open hole. The longer it is, the more complex the micro-fractures on the surface are, and the force of the direction parallel to the cross-section is significantly increased. The results of our research afford Enhanced Geothermal Systems (EGS) basics and help the early realization of thermal power generation from HDR.

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An, Qi, Chunyang Hong e Haitao Wen. "Fracture Patterns of Rocks Observed under Cryogenic Conditions Using Cryo-Scanning Electron Microscopy". Processes 11, n. 7 (7 luglio 2023): 2038. http://dx.doi.org/10.3390/pr11072038.

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Cryogenic fracturing, which uses liquid nitrogen (LN2) as a fracturing fluid, is a waterless fracturing method. However, previous attempts to investigate the fracture morphology of rocks after LN2 quenching have been mainly based on standard scanning electron microscopy (SEM) analysis at room temperature. This can be problematic since thermally-induced fractures created by temperature difference tend to close as a sample warms and thermal stress relaxes. To address this issue, we established a novel approach employing Cryo-scanning electron microscopy (Cryo-SEM) to investigate the fracture patterns induced by liquid nitrogen quenching under cryogenic conditions. This method can achieve in-situ visualization of fractures and pores with a nano-scale resolution at −190 °C. X-ray computed tomography (CT) is also employed to illustrate the fracture distribution inside samples. Cryo-SEM and standard SEM are compared, and statistical assessments are conducted to quantify fracture aperture size and closure scale. The results demonstrate that Cryo-SEM can more accurately preserve native fracture morphology and provide a more accurate means of evaluating fracture scales generated during LN2 quenching, particularly at higher temperature differences between rock and liquid nitrogen. Distinct fracture patterns and fracture width are observed for various rock types (i.e., coal, sandstone, shale, granite) by using these methods. More prominently, the maximum fracture width of coal, sandstone, shale and granite were 89.17 µm, 1.29 µm, 0.028 µm and 2.12 µm when the temperature difference between LN2 and rock samples were 296 °C. LN2 is shown to exhibit superior fracturing efficiency on coal and granite, characterized by complex fracture networks with branched fractures. This research contributes to our understanding of liquid nitrogen fracturing mechanisms and may offer effective approaches for unconventional reservoirs stimulation.

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Carpenter, Chris. "Cryogenic-Fracturing Treatment of Synthetic-Rock With Liquid Nitrogen". Journal of Petroleum Technology 69, n. 06 (1 giugno 2017): 70–71. http://dx.doi.org/10.2118/0617-0070-jpt.

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Zhang, Kuangsheng, Zhenfeng Zhao, Meirong Tang, Wenbin Chen, Chengwang Wang, Xinyu Mao e Nianyin Li. "A new type of experimentally proposed in situ heat/gas clean foam fracturing fluid system". Journal of Petroleum Exploration and Production Technology 10, n. 8 (18 agosto 2020): 3419–36. http://dx.doi.org/10.1007/s13202-020-00983-5.

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Abstract When cold fluid is injected into low-temperature, low-pressure, low-permeability reservoirs containing wax-bearing heavy oil, cryogenic paraffin deposition and heavy oil condensation will occur, thus damaging the formation. Moreover, the formation pressure coefficient is low and the working fluid flowback efficiency is low, which affects the fracturing stimulation effect. Therefore, an in situ heat/gas clean foam fracturing fluid system is proposed. This system can ensure that conventional fracturing fluid can create fractures and carry proppant in the reservoir, generate heat in situ to avoid cold damage, reduce the viscosity, and improve the fluidity of crude oil. The in situ heat fracturing fluid generates a large amount of inert gas while generating heat, thus forming foam-like fracturing fluid, reducing fluid loss, improving proppant-carrying performance, improving gel-breaking performance, effectively improving crack conductivity, and is clean and environmentally friendly. Based on the improved existing fracturing fluid system, in this paper, a new type of in situ heat fracturing fluid system is proposed, and a system optimization evaluation is conducted through laboratory experiments according to the performance evaluation standard of water-based fracturing fluid. Compared with the traditional in situ heat fracturing fluid system, the fracturing fluid system proposed in this study generates a large amount of inert gas and form foam-like fracturing fluid, reduces fluid loss, enhances the proppant-carrying capacity and gel-breaking performance, improves crack conductivity, the gel without residue and that the gel-breaking liquid is clean and harmless.

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JPT staff, _. "Field Applications of Cryogenic Nitrogen as a Hydraulic-Fracturing Fluid". Journal of Petroleum Technology 50, n. 03 (1 marzo 1998): 38–39. http://dx.doi.org/10.2118/0398-0038-jpt.

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Cha, Minsu, Naif B. Alqahtani, Xiaolong Yin, Timothy J. Kneafsey, Bowen Yao e Yu-Shu Wu. "Laboratory system for studying cryogenic thermal rock fracturing for well stimulation". Journal of Petroleum Science and Engineering 156 (luglio 2017): 780–89. http://dx.doi.org/10.1016/j.petrol.2017.06.062.

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Liew, M. S., Kamaluddeen Usman Danyaro e Noor Amila Wan Abdullah Zawawi. "A Comprehensive Guide to Different Fracturing Technologies: A Review". Energies 13, n. 13 (30 giugno 2020): 3326. http://dx.doi.org/10.3390/en13133326.

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Hydraulic fracturing has made the production of gas more economical. Shale gas possesses the potential to arise as a main natural gas source worldwide. It has been assessed that the top 42 countries, including the U.S., are predicted to own 7299 trillion cubic feet (tcf) of technically recoverable shale gas resources. The main goal of this paper is to serve as a guide of different shale gas extraction methods. The significance of these methods and possible pros and cons are determined. Each technique was explained with the support of literature review. Specifically, this paper revealed that some fracking methods such as pulsed arc electrohydraulic discharges (PAED), plasma stimulation and fracturing technology (PSF), thermal (cryogenic) fracturing, enhanced bacterial methanogenesis, and heating of rock mass are at the concept stage for conventional and other unconventional resources. Thus, these found to be significant for stimulating natural gas wells, which provides very good production results. This paper also discovered that fracking remains the recommended technique used by the oil and gas industries.

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Cha, Minsu, Naif B. Alqahtani, Xiaolong Yin, Lei Wang, Bowen Yao, Timothy J. Kneafsey, Jennifer L. Miskimins e Yu-Shu Wu. "Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes". Energies 14, n. 17 (1 settembre 2021): 5433. http://dx.doi.org/10.3390/en14175433.

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In cryogenic fracturing, a rock surface exposed to cryogenic fluids undergoes a large thermal gradient, and the resultant local tensile stress overcomes rock strength and initiates fractures. This study investigates the development of cracks generated from the cryogenic treatment of a borehole under no external confining stress on specimens. The experiments were performed on transparent PMMA specimens to observe fracture proliferation around boreholes. Liquid nitrogen was flowed through the boreholes to cool the borehole surface. The results show that initial fracture growth is characterized by abrupt starts and stops, and as the fracture propagates outward, the growth appears more continuous. In an early stage, horizontal/radial fractures and vertical fractures are the defining patterns. Horizontal fractures tend to be separated by a specific exclusion distance (i.e., spacing between cracks). While distinct horizontal/vertical fractures and exclusion distance manifest themselves at an early stage, fractures resulting from fracture interactions and curvatures can develop into complex shapes at later stages. Cryogenic thermal loading induces distinctively curved fractures. The tendency of curvature may prevent greater penetration. An increase in the borehole pressure during liquid nitrogen flow, however, can lessen fracture tortuosity and facilitate radial propagation. A high flow pressure and rate are also advantageous in that they accelerate cooling and fracture propagation.

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Wang, Guilin, Fan Sun, Runqiu Wang e Tianci Cao. "Simulation of cryogenic fracturing of rock-like materials using material point method". Journal of Natural Gas Science and Engineering 96 (dicembre 2021): 104300. http://dx.doi.org/10.1016/j.jngse.2021.104300.

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Yao, Bowen, Lei Wang, Xiaolong Yin e Yu-Shu Wu. "Numerical modeling of cryogenic fracturing process on laboratory-scale Niobrara shale samples". Journal of Natural Gas Science and Engineering 48 (dicembre 2017): 169–77. http://dx.doi.org/10.1016/j.jngse.2016.10.041.

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Zhang, Hongyuan, Zhongwei Huang, Shikun Zhang, Zheqi Yang e John D. Mclennan. "Improving heat extraction performance of an enhanced geothermal system utilizing cryogenic fracturing". Geothermics 85 (maggio 2020): 101816. http://dx.doi.org/10.1016/j.geothermics.2020.101816.

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Mohd Ridzuan, Nur Fadhilah Aimuni, Tahrin Othman, Afifah Zakiyyah Juri, Jaharah A. Ghani e Che Hassan Che Haron. "Cryogenic Machining Performance of M303 at High Cutting Speeds". Jurnal Kejuruteraan 36, n. 3 (30 maggio 2024): 1167–73. http://dx.doi.org/10.17576/jkukm-2024-36(3)-25.

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The material M303 is commonly used in the fabrication of machinery, automotive components, locomotive axle housings, and injection moulds. It is a stainless martensitic chromium steel known for its high strength, wear resistance, and corrosion resistance. The primary purpose of this study is to investigate the machinability of M303 under cryogenic conditions, specifically focusing on high cutting speeds. By exploring the effects of cryogenic machining on M303, the study aims to provide insights into the performance and characteristics of this material under extreme cutting conditions. This study investigates the influence of cutting parameters on the machinability of M303 in a cryogenic environment using liquid nitrogen (LN2) and coated carbide cutting tools in a high-speed turning process. The study focuses on high cutting speeds and examines essential machinability factors, including cutting forces, surface finish, and tool life. The experimental design utilises a Taguchi L4 orthogonal array to systematically study feed rates (0.1-0.2 mm/rev), depth of cut (0.2-0.6 mm), and high cutting speeds (260-340 m/min). Notably, at a low cutting speed of 260 m/min, coupled with low feed rates and depth of cut, the study reveals the longest tool life of 48.57 mintues was achieved. This condition is characterized by a good surface finish and low cutting forces with Ra of 0.9 µm and cutting force of 100 N respectively. The predominant wear occurs on the flank face, primarily due to fracturing and chipping, especially under high combinations of cutting parameters. Conversely, gradual wear is observed under low combinations of cutting parameters, resulting in an extended tool life. In conclusion, the application of LN2 proves effective under conditions of low cutting parameters. The study suggests that the risk of fracturing the cutting tool increases at higher feed rates and depths of cut, especially when combined with elevated cutting speeds. This research provides valuable insights into optimizing the machining of M303 for enhanced efficiency and tool longevity.

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Ren, Keda, e Chengzheng Cai. "Numerical Investigation into the Distributions of Temperature and Stress around Wellbore during the Injection of Cryogenic Liquid Nitrogen into Hot Dry Rock Reservoir". Mathematical Problems in Engineering 2021 (19 giugno 2021): 1–13. http://dx.doi.org/10.1155/2021/9913321.

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Cryogenic liquid nitrogen fracturing is expected to provide an effective stimulation method for hot dry rock reservoirs to increase heat production. This paper establishes a three-dimensional model to calculate the distributions of temperature and stress of the reservoir rock when liquid nitrogen is injected into the wellbore. The sensitivity of different parameters and water fracturing to the stress state is studied. The results indicate that when liquid nitrogen is injected into the bottom of well, a huge heat exchange occurs on the rock surface, which generates great thermal stress on the fluid-solid interface, and the value of thermal stress exceeds the tensile strength of rock. For the effect of parameters, the primitive temperature of the rock has a significant impact on the value of maximum principal stress. The pressure drop and ambient pressure affect the thermal stress slightly. At the same time, a series of experiments are conducted to validate the effect of thermal stress induced by liquid nitrogen injection on the rock fracture. As the temperature rises, the shale samples are broken more severely at the action of thermal stress. Thus, the study of liquid nitrogen fracturing provides a scientific and effective method for geothermal exploitation.

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Zhao, Xinrui, Lei Wang, Bowen Yao, Minsu Cha e Yu-Shu Wu. "Cryogenic fracturing of synthetic coal specimens under true-triaxial loadings-An experimental study". Fuel 324 (settembre 2022): 124530. http://dx.doi.org/10.1016/j.fuel.2022.124530.

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Yang, Ruiyue, Zhongwei Huang, Yu Shi, Zheqi Yang e Pengpeng Huang. "Laboratory investigation on cryogenic fracturing of hot dry rock under triaxial-confining stresses". Geothermics 79 (maggio 2019): 46–60. http://dx.doi.org/10.1016/j.geothermics.2019.01.008.

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Longinos, Sotirios Nik, Mirlan Tuleugaliyev e Randy Hazlett. "Influence of subsurface temperature on cryogenic fracturing efficacy of granite rocks from Kazakhstan". Geothermics 118 (marzo 2024): 102919. http://dx.doi.org/10.1016/j.geothermics.2024.102919.

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Huang, Chengyu, Wenhua Wang e Weizhong Li. "A Novel 2D Model for Freezing Phase Change Simulation during Cryogenic Fracturing Considering Nucleation Characteristics". Applied Sciences 10, n. 9 (9 maggio 2020): 3308. http://dx.doi.org/10.3390/app10093308.

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A 2D computational fluid dynamics (CFD) model in consideration of nucleation characteristics (homogeneous/heterogeneous nucleation) using the volume of fluid (VOF) method and Lee model was proposed. The model was used to predict the process of a multiphase flow accompanied by freezing phase change during cryogenic fracturing. In this model, nucleation characteristic (homogeneous and heterogeneous nucleation) during the freezing process and the influence of the formed ice phase on the flowing behavior was considered. Validation of the model was done by comparing its simulation results to Neumann solutions for classical Stefan problem. The comparison results show that the numerical results are well consistent with the theoretical solution. The maximum relative differences are less than 7%. The process of multiphase flow accompanied by the freezing of water was then simulated with the proposed model. Furthermore, the transient formation and growth of ice as well as the evolution of temperature distribution in the computational domain was studied. Results show that the proposed method can better consider the difference between homogeneous nucleation in the fluid domain and heterogeneous nucleation on the wall boundary. Finally, the main influence factors such as the flow velocity and initial distribution of ice phase on the fracturing process were discussed. It indicates that the method enable to simulate the growth of ice on the wall and its effect on the flow of multiphase fluid.

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Tang, Shibin, Jiaxu Wang e Peizhao Chen. "Theoretical and numerical studies of cryogenic fracturing induced by thermal shock for reservoir stimulation". International Journal of Rock Mechanics and Mining Sciences 125 (gennaio 2020): 104160. http://dx.doi.org/10.1016/j.ijrmms.2019.104160.

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Mair, David, Alessandro Lechmann, Romain Delunel, Serdar Yeşilyurt, Dmitry Tikhomirov, Christof Vockenhuber, Marcus Christl, Naki Akçar e Fritz Schlunegger. "The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland)". Earth Surface Dynamics 8, n. 3 (17 luglio 2020): 637–59. http://dx.doi.org/10.5194/esurf-8-637-2020.

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Abstract. Denudation of steep rockwalls is driven by rock fall processes of various sizes and magnitudes. Rockwalls are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, which can precondition the occurrence of rock fall. However, it is still unclear how the fracturing of rock together with cryogenic processes impacts the denudation processes operating on steep rockwalls. In this study, we link data on long-term rockwall denudation rates at the Eiger (Central Swiss Alps) with the local bedrock fabric and the reconstructed temperature conditions at these sites, which depend on the insolation pattern. We then estimate the probability of bedrock for failure through the employment of a theoretical frost cracking model. The results show that the denudation rates are low in the upper part of the NW rockwall, but they are high both in the lower part of the NW rockwall and on the SE face, despite similar bedrock fabric conditions. The frost cracking model predicts a large difference in cracking intensity from ice segregation where the inferred efficiency is low in the upper part of the NW rockwall but relatively large on the lower section of the NW wall and on the SE rock face of the Eiger. We explain this pattern by the differences in insolation and temperature conditions at these sites. Throughout the last millennium, temperatures in bedrock have been very similar to the present. These data thus suggest the occurrence of large contrasts in microclimate between the NW and SE walls of the Eiger, conditioned by differences in insolation. We use these contrasts to explain the relatively low denudation rates in the upper part of the NW rockwall and the rapid denudation in the SW face and in the lower part of the NW rock face where frost cracking is more efficient.

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Cai, Chengzheng, Feng Gao e Yugui Yang. "The effect of liquid nitrogen cooling on coal cracking and mechanical properties". Energy Exploration & Exploitation 36, n. 6 (22 marzo 2018): 1609–28. http://dx.doi.org/10.1177/0144598718766630.

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Liquid nitrogen is a type of super-cryogenic fluid, which can cause the reservoir temperature to decrease significantly and thereby induce formation rock damage and cracking when it is injected into the wellbore as fracturing fluid. An experimental set-up was designed to monitor the acoustic emission signals of coal during its contact with cryogenic liquid nitrogen. Ultrasonic and tensile strength tests were then performed to investigate the effect of liquid nitrogen cooling on coal cracking and the changes in mechanical properties thereof. The results showed that acoustic emission phenomena occurred immediately as the coal sample came into contact with liquid nitrogen. This indicated that evident damage and cracking were induced by liquid nitrogen cooling. During liquid nitrogen injection, the ring-down count rate was high, and the cumulative ring-down counts also increased rapidly. Both the ring-down count rate and the cumulative ring-down counts during liquid nitrogen injection were much greater than those in the post-injection period. Liquid nitrogen cooling caused the micro-fissures inside the coal to expand, leading to a decrease in wave velocity and the deterioration in mechanical strength. The wave velocity, which was measured as soon as the sample was removed from the liquid nitrogen (i.e. the wave velocity was recorded in the cooling state), decreased by 14.46% on average. As the cryogenic samples recovered to room temperature, this value increased to 18.69%. In tensile strength tests, the tensile strengths of samples in cooling and cool-treated states were (on average) 17.39 and 31.43% less than those in initial state. These indicated that both during the cooling and heating processes, damage and cracking were generated within these coal samples, resulting in the acoustic emission phenomenon as well as the decrease in wave velocity and tensile strength.

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Lundberg, Joyce, e Donald McFarlane. "Cryogenic fracturing of calcite flowstone in caves: theoretical considerations and field observations in Kents Cavern, Devon, UK". International Journal of Speleology 41, n. 2 (luglio 2012): 307–16. http://dx.doi.org/10.5038/1827-806x.41.2.16.

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31

Ahmed, Amna, Amna Majeed e Teresa Zhu. "The Application of Ultra-Lightweight Proppants to Cryogenic Liquid Nitrogen as a Fracturing Fluid: A Research Protocol". Undergraduate Research in Natural and Clinical Science and Technology (URNCST) Journal 2, n. 8 (22 agosto 2018): 1–5. http://dx.doi.org/10.26685/urncst.64.

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32

Xu, Jizhao, Cheng Zhai, Shimin Liu, Lei Qin e Yong Sun. "Feasibility investigation of cryogenic effect from liquid carbon dioxide multi cycle fracturing technology in coalbed methane recovery". Fuel 206 (ottobre 2017): 371–80. http://dx.doi.org/10.1016/j.fuel.2017.05.096.

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33

Song, Weiqiang, Xian Shi, Chunguang Wang, Jianchun Xu, Shaojie Chen e Zhongwei Chen. "Predicting the radial heat transfer in the wellbore of cryogenic nitrogen fracturing: Insights into stimulating underground reservoir". Energy Science & Engineering 8, n. 3 (22 gennaio 2020): 582–91. http://dx.doi.org/10.1002/ese3.479.

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34

Zhang, Jicheng, Leilei Si, Junguo Chen, Mehmet Kizil, Chunguang Wang e Zhongwei Chen. "Stimulation Techniques of Coalbed Methane Reservoirs". Geofluids 2020 (10 luglio 2020): 1–23. http://dx.doi.org/10.1155/2020/5152646.

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Coalbed methane (CBM) plays an important role in securing world energy supply and transiting electricity generation from fossil fuel to renewables. CBM reservoirs are generally very tight and require effective stimulation to achieve economic extraction. In recent years, an increasing number of coal seam stimulation techniques were developed, but selecting the most suitable stimulation technique for a particular CBM reservoir condition is becoming increasingly challenging. Therefore, it is deemed very important to compare the effectiveness of different stimulation techniques in a meaningful way to guide future research directions in this area. In this paper, the stimulation techniques were firstly classified into different categories according to the stimulation mechanisms. Then, the associated principles, the history of advances, and challenges of different stimulation techniques were comprehensively reviewed. Two indexes were proposed to compare the stimulation effectiveness at the laboratory and field scales, respectively. Finally, the comparison and evaluation of each stimulation technique in respect to the stimulation effectiveness, influence range, duration, and environment were conducted in detail; the cryogenic liquid nitrogen stimulation technique receives the highest total score among the discussed laboratory-scale stimulation techniques. Hydraulic fracturing and gas injection stimulation techniques gain the highest total score among key field-scale stimulation techniques. Considering the time required for each stimulation method to take effect, high-voltage electric fracturing may have a greater potential in the future. This work is expected to help better select the optimal stimulation technique for reservoir specific conditions.

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35

Yin, Guangzhi, Delei Shang, Minghui Li, Jie Huang, Tiancheng Gong, Zhenlong Song, Bozhi Deng, Chao Liu e Zhicheng Xie. "Permeability evolution and mesoscopic cracking behaviors of liquid nitrogen cryogenic freeze fracturing in low permeable and heterogeneous coal". Powder Technology 325 (febbraio 2018): 234–46. http://dx.doi.org/10.1016/j.powtec.2017.10.058.

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36

Longinos, Sotirios Nik, Azza Hashim Abbas, Arman Bolatov, Piotr Skrzypacz e Randy Hazlett. "Application of Image Processing in Evaluation of Hydraulic Fracturing with Liquid Nitrogen: A Case Study of Coal Samples from Karaganda Basin". Applied Sciences 13, n. 13 (4 luglio 2023): 7861. http://dx.doi.org/10.3390/app13137861.

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Research of microstructure and permeability evolution of coal following LN2 treatment elucidate the process of cryogenic fracturing due to environmentally friendly behavior in comparison with conventional hydraulic fracturing. The evolution of the 2D microstructure of bituminous coal before and after LN2 treatment was examined using a high-resolution camera. The image processing was implemented using functions from the OpenCV Python library that are sequentially applied to digital images of original coal samples. The images were converted into binary pixel matrices to identify cracks and to evaluate the number of cracks, crack density, total crack area, and average crack length. Results were visualized using Seaborn and Matplotlib Python libraries. There were calculations of total crack area (TCA), total number of cracks (TNC), crack density (CD), the average length of cracks (Q2), first (Q1) and third (Q3) quartiles in fracture length statistics. Our findings demonstrate a progressive increase in the Total Crack Area (δTCA) with longer freezing times and an increased number of freezing–thawing cycles. In contrast, the change in crack density (δCD) was generally unaffected by freezing time alone but exhibited a significant increase after several freezing–thawing cycles. Among the freezing times investigated, the highest crack density (CD) value of 300 m−1 was achieved in FT60, while the lowest CD value of 31.25 m−1 was observed in FT90 after liquid nitrogen (LN2) treatment. Additionally, the FTC4 process resulted in a 50% augmentation in the number of cracks, whereas the FTC5 process tripled the number of small cracks.

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37

Wang, Xiuying, Yu Wang, Jiujun Xu, Juncai Sun, Yuqian Wang e Guangming Xie. "Effects of Cooling Media on Microstructure and Mechanical Properties in Friction Stir Welded SA516 Gr.70 Cryogenic Steel Joints". Materials 17, n. 18 (23 settembre 2024): 4661. http://dx.doi.org/10.3390/ma17184661.

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SA516 Gr.70 steels were welded by friction stir welding (FSW) under various media of air, water, and water + CO2 cooling, and the effect of the cooling media on the microstructure and mechanical properties of joints was systematically analyzed. The nugget zone (NZ) under the air-cooling condition contained coarse bainite + martensite. Martensite was obtained by decreasing the cooling media temperature. Furthermore, tensile fracturing of the joints occurred in the basal metal (BM), and the ultimate tensile strength of the joints under various cooling media was similar to that of the BM. However, with decreasing cooling media temperature, the total elongation of the joints noticeably increased. Good strength (545 MPa) and elongation (16.8%) were obtained in the joints under the water + CO2 cooling condition since the fine martensite microstructure enhanced the plastic deformation capacity of the joints. In addition, in the NZ under water + CO2 cooling condition, good toughness of 110 J/cm2 was obtained due to a high fraction of high-angle boundaries and fine martensite.

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38

Yang, Ruiyue, Chunyang Hong, Wei Liu, Xiaoguang Wu, Tianyu Wang e Zhongwei Huang. "Non-contaminating cryogenic fluid access to high-temperature resources: Liquid nitrogen fracturing in a lab-scale Enhanced Geothermal System". Renewable Energy 165 (marzo 2021): 125–38. http://dx.doi.org/10.1016/j.renene.2020.11.006.

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39

Patel, Sanket, Isaac Wilson, Hari Sreenivasan e Shanker Krishna. "Numerical simulations of proppant transportation in cryogenic fluids: Implications on liquid helium and liquid nitrogen fracturing for subsurface hydrogen storage". International Journal of Hydrogen Energy 56 (febbraio 2024): 924–36. http://dx.doi.org/10.1016/j.ijhydene.2023.12.268.

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40

Köhler, Andreas, Valerie Maupin, Christopher Nuth e Ward van Pelt. "Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard". Annals of Glaciology 60, n. 79 (7 maggio 2019): 23–36. http://dx.doi.org/10.1017/aog.2019.15.

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ABSTRACTGlacial seismicity provides important insights into glacier dynamic processes. We study the temporal distribution of cryogenic seismic signals (icequakes) at Holtedahlfonna, Svalbard, between April and August 2016 using a single three-component sensor. We investigate sources of observed icequakes using polarization analysis and waveform modeling. Processes responsible for five icequake categories are suggested, incorporating observations of previous studies into our interpretation. We infer that the most dominant icequake type is generated by surface crevasse opening through hydrofracturing. Secondly, bursts of high-frequency signals are presumably caused by repeated near-surface crevassing due to high strain rates during glacier fast-flow episodes. Furthermore, signals related to resonance in water-filled cracks, fracturing or settling events in dry firn or snow before the melt season, and processes at the glacier bed are observed. Amplitude of seismic background noise is clearly related to glacier runoff. We process ambient seismic noise to invert horizontal-to-vertical spectral ratios for a sub-surface seismic velocity model used to model icequake signals. Our study shows that a single seismic sensor provides useful information about seasonal ice dynamics in case deployment of a network is not feasible.

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41

Xu, Jizhao, Cheng Zhai, Lei Qin, Shangjian Wu, Yong Sun e Ruowei Dong. "Characteristics of Pores under the Influence of Cyclic Cryogenic Liquid Carbon Dioxide Using Low-Field Nuclear Magnetic Resonance". Geofluids 2018 (2 luglio 2018): 1–14. http://dx.doi.org/10.1155/2018/1682125.

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The enhancement of coalbed methane extraction by repeatedly injecting CO2 has been investigated for many decades, mostly focusing on the fracturing and flooding effect in numerous lab experiments, simulations, and field applications, whereas the effect of the accompanying heat transfer during cyclic liquid CO2 (LCO2) injection has rarely been studied. In this paper, the influence of the cyclic injection of cryogenic LCO2 with different cycle numbers and time on the coal pore variation was explored using low-field nuclear magnetic resonance to extract the T2 spectral information. The results have shown that as the cycle number increased, the adsorbed water (AW) decreased while the capillary water (CW) and bulk water (BW) values increased, and the pore volumes were magnified greatly based on the tendencies of fitted polynomial curves of Isa1 values and fitted exponential curve of Isa2 values. With increasing cycle time, the increase ratios of AW, CW, and BW were not independent but mutually influenced, and the Isa1 values approximately displayed a “rapid increase-slow increase” tendency, while Isa2 roughly showed fluctuating or “increase-decrease” tendencies. The changes in the IWS and FWS showed that the increased pore connectivity could allow more water to infiltrate into the pores at the saturation state and accelerate the removal of fluid water during the centrifugation state. The φe and φr variations indicated that longer cycle time coupled with a larger cycle number could cause damage generation and enhance the pore connectivity.

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42

Huang, Chengyu, Wenhua Wang, Yunze Xu e Weizhong Li. "Experimental Study on Displacement of Water by Sub-Zero N-Hexanol in a Straight Channel". Energies 13, n. 20 (16 ottobre 2020): 5409. http://dx.doi.org/10.3390/en13205409.

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Series of displacement tests of water by cold n-hexanol (below 0 °C) in a straight tube were conducted to investigate the freezing-accompanied displacement process, which occurs during the cryogenic fracturing process. The interrelationship between water freezing and displacement flow was studied. It was found that the displacement flow could significantly affect the water distribution in the flow channel. Along with the displacement proceeding, the n-hexanol overtook the water in the flow direction gradually, and the water in the center of the channel was driven to the edge area. Moreover, the initially integrated water phase split into several parts during the displacement process. Once the water freezing occurred, two typical ice blockage patterns, i.e., complete ice blockage and incomplete ice blockage, were observed. In incomplete ice blockage pattern, the channel cross-section was partly occupied by the ice phase, which mainly affected the rate of subsequent fluid flow. In complete ice blockage pattern, the channel cross-section was fully occupied by the ice phase, which cut off the fluid flow in the original direction. Based on the test results, the influences of the initial water temperature, initial water column length and flow rate of n-hexanol on the formation of different ice blockage patterns are discussed. The decrease of the initial water temperature and the increase of the initial water column length are preferred to induce the occurrence of complete ice blockage. However, changing n-hexanol flow rate could lead to the occurrence of both incomplete ice blockage and complete ice blockage, which depends on the actual situations.

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43

Weber, Samuel, Jan Beutel, Jérome Faillettaz, Andreas Hasler, Michael Krautblatter e Andreas Vieli. "Quantifying irreversible movement in steep, fractured bedrock permafrost on Matterhorn (CH)". Cryosphere 11, n. 1 (16 febbraio 2017): 567–83. http://dx.doi.org/10.5194/tc-11-567-2017.

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Abstract. Understanding rock slope kinematics in steep, fractured bedrock permafrost is a challenging task. Recent laboratory studies have provided enhanced understanding of rock fatigue and fracturing in cold environments but were not successfully confirmed by field studies. This study presents a unique time series of fracture kinematics, rock temperatures and environmental conditions at 3500 m a. s. l. on the steep, strongly fractured Hörnligrat of the Matterhorn (Swiss Alps). Thanks to 8 years of continuous data, the longer-term evolution of fracture kinematics in permafrost can be analyzed with an unprecedented level of detail. Evidence for common trends in spatiotemporal pattern of fracture kinematics could be found: a partly reversible seasonal movement can be observed at all locations, with variable amplitudes. In the wider context of rock slope stability assessment, we propose separating reversible (elastic) components of fracture kinematics, caused by thermoelastic strains, from the irreversible (plastic) component due to other processes. A regression analysis between temperature and fracture displacement shows that all instrumented fractures exhibit reversible displacements that dominate fracture kinematics in winter. Furthermore, removing this reversible component from the observed displacement enables us to quantify the irreversible component. From this, a new metric – termed index of irreversibility – is proposed to quantify relative irreversibility of fracture kinematics. This new index can identify periods when fracture displacements are dominated by irreversible processes. For many sensors, irreversible enhanced fracture displacement is observed in summer and its initiation coincides with the onset of positive rock temperatures. This likely indicates thawing-related processes, such as meltwater percolation into fractures, as a forcing mechanism for irreversible displacements. For a few instrumented fractures, irreversible displacements were found at the onset of the freezing period, suggesting that cryogenic processes act as a driving factor through increasing ice pressure. The proposed analysis provides a tool for investigating and better understanding processes related to irreversible kinematics.

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Rybalkin, L. A., e I. M. Serdyuk. "Development of a methodology to research the influence of liquid nitrogen exposure on carbon material". Interexpo GEO-Siberia 2, n. 3 (18 maggio 2022): 300–306. http://dx.doi.org/10.33764/2618-981x-2022-2-3-300-306.

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Recently, studies, which are dedicated to the effect of cryogenic substances on the structure of coal, are gaining popularity. The impact of liquid nitrogen on coal leads to micro- and macrostructural disturbances in the continuity of coal due to drastic cooling of the moisture in the microcracks and pore space of the coal, while the volume of ice microcrystals increases. This approach provides the opportunity to treat the massif without additional injection of liquid agents into seams to create pressure to disintegrate it, unlike traditional methods of increasing the filtration surface in coal. Research work, which are presented in this field, are aimed at studying the multiplicity of increase in porosity and fracturing of coal in the process of single or multiple exposure to portions of liquid nitrogen. A distinctive feature of the ongoing research is the evaluation of the results of cryotreatment of samples by non-destructive methods of measuring the pore space. Thus, the conclusion about the change in permeability is made without direct measurements of the gas filtration rates in the samples. Changes shown by CT scans show an increase in the total number of open pores and channels, however they do not illustrate the increase in gas permeability in general. As a part of this work, we carried out a number of studies on axial gas filtration in dense coal samples, which were under controlled all-round loading. Preparatory work was carried out to dry the samples and further saturate them with moisture to identical values in the entire batch. A scheme for conducting experiments to study the effect of cryotreatment on the internal structure of coal using the methods of stationary axial gas filtration and NMR relaxometry is proposed. The development of this technique contributes to obtaining reliable data on the increase in the gas permeability of coal samples. The data can be useful in designing methods and approaches to increase the degree of degassing by treating degassing wells at coal mining enterprises.

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45

Wen, Haitao, Ruiyue Yang, Zhongwei Huang, Chunyang Hong, Jianxiang Chen, Richao Cong e Xiaozhou Qin. "Experimental Comparisons of Different Cryogenic Fracturing Methods on Coals". SSRN Electronic Journal, 2022. http://dx.doi.org/10.2139/ssrn.4236234.

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46

Wen, Haitao, Ruiyue Yang, Zhongwei Huang, Chunyang Hong, Jianxiang Chen, Richao Cong e Xiaozhou Qin. "Experimental comparisons of different cryogenic fracturing methods on coals". Journal of Petroleum Science and Engineering, novembre 2022, 111250. http://dx.doi.org/10.1016/j.petrol.2022.111250.

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47

Longinos, Sotirios Nik, e Randy Hazlett. "Cryogenic fracturing using liquid nitrogen on granite at elevated temperatures: a case study for enhanced geothermal systems in Kazakhstan". Scientific Reports 14, n. 1 (2 gennaio 2024). http://dx.doi.org/10.1038/s41598-023-50223-z.

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AbstractCryogenic fracturing using liquid nitrogen (LN2) is a novel stimulation technology that enhances porosity, permeability, and rock-fluid contact area in subsurface formations targetted for geothermal energy extraction. In our experimental study, granite cores collected from the Zhylgyz region in South Kazakhstan were equilibrated at various elevated temperatures before treatments involving LN2 exposure time. Compression, Brazilian, and fracture toughness tests were performed on granite with starting temperatures ranging from 100 to 500 °C to quantify the impact of initial temperature on cryogenic fracturing and to compare with baseline geomechanical tests at 50 °C without LN2 exposure. The results show that LN2 cooling of hot granite induces mechanical rock failure and permeability enhancement. Moreover, the degree of thermo-fracturing augments with initial granite temperature, total freezing time, and number of freezing–thawing cycles. The peak load before failure of granite specimens, both in compression and Brazilian tests, reduces with the increased sample temperature difference and length of LN2 treatment. The fracture toughness of our semi-circular bend (SCB) LN2-treated specimens diminished with increasing temperature difference between granite and boiling point. In both experimental LN2 treatment processes, the specimens with an initial temperature of 500 °C before LN2 treatment formed many new fissures and extensions of pre-existing ones, showing that the plastic behavior is augmented. While cryo-fracturing experimental confirmation is recommended with site-specific samples in planning geothermal operations, these results in our work indicate a threshold downhole temperature, e.g., > 300 °C, for enhanced stimulation outcomes.

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48

Zhao, Xinrui, Lei Wang, Bowen Yao e Yu-Shu Wu. "Cryogenic Fracturing of Synthetic Coal Specimens Under True-Triaxial Loadings-An Experimental Study". SSRN Electronic Journal, 2022. http://dx.doi.org/10.2139/ssrn.4057962.

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49

Wen, Haitao, Ruiyue Yang, Meiquan Lu, Zhongwei Huang, Chunyang Hong, Richao Cong e Xiaozhou Qin. "Corrigendum to “Experimental comparisons of different cryogenic fracturing methods on coals” [220 Part A (January 2023) 111250]". Geoenergy Science and Engineering, dicembre 2022, 211318. http://dx.doi.org/10.1016/j.geoen.2022.211318.

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Zhang, Yuliang, Yiming Gu e Guowei Ma. "Mode-I Fracture Toughness and Fracturing Damage Model for Sandstone Subjected to Cryogenic Treatment to − 160 °C". Rock Mechanics and Rock Engineering, 22 maggio 2024. http://dx.doi.org/10.1007/s00603-024-03915-5.

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