Bibliografie tematiche / Cryogenic fracturing

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Letteratura scientifica selezionata sul tema "Cryogenic fracturing"

Autore: Grafiati

Pubblicato: 8 ottobre 2024

Ultima modifica: 7 luglio 2025

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Articoli di riviste sul tema "Cryogenic fracturing"

Cha, Minsu, Naif B. Alqahtani, Bowen Yao, et al. "Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation." SPE Journal 23, no. 04 (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, and Ali Al-Behadili. "An Overview of How the Petrophysical Properties of Rock Influenced After Being Exposed to Cryogenic Fluid." Journal of Engineering 29, no. 11 (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, and 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 (August 23, 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, and Decheng Li. "Experimental Investigation on Cracking Characteristics of Dry and Saturated Shales in Nitrogen Fracturing after Liquid Nitrogen (LN2) Injection." Geofluids 2023 (April 13, 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, and Randy Hazlett. "Advances in Cryogenic Fracturing of Coalbed Methane Reservoirs with LN2." Energies 15, no. 24 (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, and Mohammad Sarmadivaleh. "Thermal Hydraulic Fracturing Applying Cryogenic Freezing Technique." IOP Conference Series: Materials Science and Engineering 495 (June 7, 2019): 012076. http://dx.doi.org/10.1088/1757-899x/495/1/012076.

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Cha, Minsu, Xiaolong Yin, Timothy Kneafsey, et al. "Cryogenic fracturing for reservoir stimulation – Laboratory studies." Journal of Petroleum Science and Engineering 124 (December 2014): 436–50. http://dx.doi.org/10.1016/j.petrol.2014.09.003.

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Elwegaa, Khalid, and Hossein Emadi. "The Effect of Thermal Shocking with Nitrogen Gas on the Porosities, Permeabilities, and Rock Mechanical Properties of Unconventional Reservoirs." Energies 11, no. 8 (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, and Lei Wang. "Cryogenic Fracture Proliferation from Boreholes under Stresses." Processes 11, no. 7 (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, and Jianfei Bi. "Laboratory Investigation of Cryogenic Fracturing of HDR Wellbores Under Triaxial-Confining stresses." Journal of Physics: Conference Series 2520, no. 1 (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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Più fonti

Capitoli di libri sul tema "Cryogenic fracturing"

Yu, Donghe, Yuanzhao Jia, Xi Yu, et al. "Research on Fracture Propagation by Cryogenic Volume Fracturing Based on Dem." In Springer Series in Geomechanics and Geoengineering. Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-7560-5_152.

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Huang, Peng-peng, Mu Li, Wei-wei Hao, Hao Wang, Ya-fei Li, and Yi Zou. "Laboratory Investigation of Cryogenic Fracturing Effect of Hot Dry Rock Wellbores Under Triaxial-Confining Stresses." In Springer Series in Geomechanics and Geoengineering. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-0268-8_17.

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Yao, Bowen, and Lei Wang. "Modeling of Cryogenic Fracturing Processes." In Hydraulic Fracture Modeling. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-12-812998-2.00012-6.

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Cha, M., N. Alqahtani, B. Yao, et al. "Studying cryogenic fracturing process using transparent specimens." In Energy Geotechnics. CRC Press, 2016. http://dx.doi.org/10.1201/b21938-35.

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Cha, M., N. Alqahtani, B. Yao, X. Yin, Y. Wu, and T. Kneafsey. "Development of laboratory system for cryogenic fracturing study." In Energy Geotechnics. CRC Press, 2016. http://dx.doi.org/10.1201/b21938-61.

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Atti di convegni sul tema "Cryogenic fracturing"

Winterfeld, Philip H., Bowen Yao, and Yu-Shu Wu. "Experimental and Simulation Studies of Cryogenic Effects in the Near-Wellbore Region." In SPE Reservoir Simulation Conference. SPE, 2023. http://dx.doi.org/10.2118/212233-ms.

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Abstract We modified our parallel thermo-hydraulic-mechanical simulator of fully coupled multiphase fluid and heat flow and geomechanics in porous and fractured media to simulate cryogenic fracturing with liquid nitrogen. This included developing a physical property module for nitrogen-water systems and formulating fracture initiation and extension criteria. We simulated cryogenic fracturing experiments on small concrete blocks to verify the simulator modifications. Then, we simulated two field cases, one with an injector-producer pair with cryogenic fracturing that enhanced the permeability in a vertical plane around the wellbore and extending in the direction of the producer. The second case was cryogenic fracturing and cooling of the near-wellbore region in a shallow, heated reservoir. The induced fractures were horizontal but their lengths were non-uniform due to the pressure and temperature gradients.

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McDaniel, B. W., Steven R. Grundmann, William D. Kendrick, Dennis R. Wilson, and Scott W. Jordan. "Field Applications of Cryogenic Nitrogen as a Hydraulic Fracturing Fluid." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 1997. http://dx.doi.org/10.2118/38623-ms.

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Grundmann, Steve R., Gary D. Rodvelt, Greg A. Dials, and Robert E. Allen. "Cryogenic Nitrogen as a Hydraulic Fracturing Fluid in the Devonian Shale." In SPE Eastern Regional Meeting. Society of Petroleum Engineers, 1998. http://dx.doi.org/10.2118/51067-ms.

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Longinos, Sotirios, Mirlan Tuleugaliyev, Alina Serik, Lei Wang, and Randy Hazlett. "Laboratory Investigation on Cryogenic Fracturing of Coal Rocks: An Experimental Study in Kazakhstan." In SPE Annual Caspian Technical Conference. SPE, 2022. http://dx.doi.org/10.2118/212127-ms.

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Abstract Cryogenic fracturing with liquid nitrogen (LN2) has been identified as a feasible and promising waterless fracturing method for coalbed methane extraction for its environmental safety and effectiveness. Though it performed well in certain field tests in the late twentieth century, the use of LN2 as the fracturing fluid is still largely unexplored. This research work examines the thermo-mechanical properties of coal specimens from the Karaganda basin in Kazakhstan. Coal specimens were subjected to LN2 treatment under varied lab-controlled conditions, such as the freezing time (FT) length and number of freezing-thawing cycles (FTC), both in dried and water-saturated conditions. SEM investigation for FTC and FT experiments for dried coal samples indicated that the LN2 freezing-thawing process can enhance the cryogenic fracture extent and the fracture interconnectivity. Moreover, uniaxial compressive tests indicated that compressive strength decreases beneficially with an increase in both the number of freezing-thawing cycles, while water-saturated experiments indicated substantial change after liquid nitrogen treatment compared to dried ones.

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Zheng, Xuelin, Mingjing Lu, Dongying Wang, et al. "Investigation on the Damage Mechanisms of Unconsolidated Sand, Tight Sand and Shale Induced by Cryogenic Temperature." In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0350.

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ABSTRACT: Liquid nitrogen (LN) fracturing is a new approach that utilizes the LN cryogenic temperature to induce complex fracture networks in tight reservoirs. Under the cryogenic treatment of LN, the damage and fracture characteristics of different lithologies such as shale, tight sand, and unconsolidated sand are different, and there are currently few scholars conducting relevant research. This article innovatively designed a visualization experimental method for the continuous propagation of fractures induced by cryogenic LN. Based on digital image correlation (DIC) methods, it explored the differences in the damage mechanisms of unconsolidated sand, tight sand and shale induced by LN cryogenic temperature. The results showed that there were no macro fractures in tight sand and unconsolidated sand, only discrete local deformation occurred, while macro induced fractures appeared in shale. Based on damage mechanics, the numerical simulation method and model of damage induced by LN cryogenic temperature for different lithologies were established by COMSOL to simulate the thermal stress-induced damage characteristics of different lithologies. The results show that the cementation mode of rock skeleton is the main reason for the difference of damage mechanism of different lithologies induced by LN cryogenic temperature. The conclusion is that cryogenic LN can effectively induce macro fractures in shale, while inducing micro damage in unconsolidated sand and tight sand. The research results provide a theoretical basis for the design and feasibility of LN fracturing. 1. INTRODUCTION In recent years, with the continuous progress of horizontal wells and segmented fracturing technology, there has been a wave of exploration and development of shale oil and gas resources, especially the shale oil and gas revolution in the United States, which has greatly increased the production of oil and gas resources in the United States, making it a major exporter of oil. The rise of shale oil and gas is profoundly affecting the global petroleum energy landscape. Shale oil and gas reservoirs have extremely low permeability and generally have no natural production capacity. It is well known that stimulated reservoir volume (SRV) has become the key to shale oil and gas extraction in fracturing and transformation. Therefore, how to form more artificial fractures and increase SRV in shale oil and gas reservoir fracturing and transformation is a key and difficult problem (Zoback and Kohli, 2019).

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Han, Songcai, Xinchuang Yan, Lile Li, et al. "Numerical Modeling of Cracking Behaviors of Coal Reservoirs Subjected to Cryogenic Shock." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0466.

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ABSTRACT Thermally-induced cracking has attracted extensive attention in improving reservoir permeability. In this paper, a thermo-elastic coupling model incorporating the strain-based elastic-brittle damage theory is used to analyze the cracking behaviors of the coal reservoir subjected to cryogenic liquid nitrogen shock. The evolution of temperature and thermally-induced stress with damage is analyzed. The effect of different factors including in-situ stress difference, elastic modulus, thermal expansion coefficient, thermal conductivity and quenching temperature on the induced crack morphology is investigated. It is found that the failure mechanism of the coal rock during cryogenic shock is mainly dominated by elastic brittle tensile damage. The induced fracture morphology is more sensitive to elastic modulus and thermal expansion coefficient relative to in-situ stress difference and thermal conductivity. The increases in elastic modulus and thermal expansion coefficient will bring about more fractures with greater complexity. The higher in-situ stress difference or lower thermal conductivity can generate more short thermal fractures. The critical quenching temperature for inducing thermal cracks around the wellbore is between −110 °C and −105 °C. The results of this study can provide some guidelines for cryogenic fracturing in coal reservoirs. INTRODUCTION Coalbed methane (CBM) reservoirs have the characteristics of low permeability and low porosity. At present, hydraulic fracturing is still the most widely used stimulation technology to improve the overall permeability of unconventional oil and gas reservoirs, including CBM, shale gas and tight gas (Montgomery et al., 2010; Kumari et al., 2018; Ma et al., 2021). However, hydraulic fracturing will bring about a series of thorny problems, such as high fracture initiation pressure in hard formation, pore plugging and water locking effect in water sensitive formation, serious waste of water resources, treatment of flowback fluid and environmental pollution. Compared with hydraulic fracturing, cryogenic liquid nitrogen (LN2) waterless fracturing can overcome these negative problems (Gregory et al., 2011; Rozell et al., 2012, Hung et al., 2020). The representative advantage of LN2 fracturing is that the low temperature LN2 with a boiling point of −195.8 °C produces a huge temperature difference in the rock (Jacobsen et al., 1986), resulting in tens of MPa of thermal stress. In addition, hundreds of times of the gas-liquid ratio of nitrogen also plays an important role in rock cracking. However, because of its high risk of vaporization, it is necessary to control the pressure in the wellbore through the safety valve, thus weakening the effect of nitrogen expansion-induced fracturing (Cha et al., 2018).

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Zhang, Hongyuan, and Zhongwei Huang. "Experimental and Numerical Study on Transient Heat and Mass Transfer of Cryogenic Fluid in Wellbore During Cryogenic Fracturing." In Offshore Technology Conference Asia. Offshore Technology Conference, 2020. http://dx.doi.org/10.4043/30376-ms.

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Alqatahni, Naif B., Minsu Cha, Bowen Yao, et al. "Experimental Investigation of Cryogenic Fracturing of Rock Specimens Under True Triaxial Confining Stresses." In SPE Europec featured at 78th EAGE Conference and Exhibition. Society of Petroleum Engineers, 2016. http://dx.doi.org/10.2118/180071-ms.

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Longinos, Sotirios, Lei Wang, Anna Loskutova, Dichuan Zhang, and Randy Hazlett. "Cyclic LN2 Treatment of Coal Samples from Coal Basin in Kazakhstan." In SPE EuropEC - Europe Energy Conference featured at the 83rd EAGE Annual Conference & Exhibition. SPE, 2022. http://dx.doi.org/10.2118/209697-ms.

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Abstract In recent years liquid nitrogen (LN2) fracturing technology has been investigated as a promising stimulating technique in coalbed methane (CBM) development. Using the immersion method, this study experimentally examines and illustrates the efficacy of LN2 cryogenic fracturing for a CBM reservoir in the Karaganda Basin of East Kazakhstan. Coal core plugs were frozen with LN2 under different lab-controlled conditions like the length freezing time (FT) and the number of freezing thawing cycles (FTC). Then these treated core plugs were subjected to uniaxial compressive strength test and SEM analysis for comparisons. The results from SEM analysis showed that the LN2 freezing-thawing process can augment the cryogenic fracture and the fracture interconnectivity. Moreover, uniaxial compressive test indicated that compressive strength is kept decreasing with successively increasing the number of freezing-thawing cycles and the same decreasing trend was observed with freezing time experiments compared with the coal sample without liquid nitrogen case.

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Qu, Hai, Zhelun Li, Ying Liu, Zhijun Zeng, and Xu Liu. "Study on the Fracturing Pattern and Damage Characteristics of Deep Shale by Liquid Nitrogen Fracturing." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0375.

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ABSTRACT Liquid nitrogen (LN) can undermine the structure of the rock and its mechanical properties. It is also effective in engineering applications of deep resource exploitation. There are few lab experiments that use LN as a fracturing fluid directly. In this work, we have studied LN fracturing performances in deep shales under actual triaxial-confining stresses by a high-pressure LN fracturing device. Microcracks and matrix structures have been analyzed by scanning electron microscopy. The breakdown pressure and fracture morphologies have been compared with hydraulic fracturing. The result demonstrates that LN fracturing can obviously lower fracture initiation pressure and increase fracture complexity. The increase of differential stress ratio does not reduce fracture complexity. Microcracks and pore clusters can be induced on LN fracture surfaces, improving matrix permeability. Curved cracks, branched cracks, and horizontal bedding planes can be thermally induced around the borehole. Low fluid viscosity of LN can facilitate the fracture propagation and network generation during the fracturing process. The longer the bare-hole, the more thermally induced microcracks around the borehole, and the more complex macro fractures. Moreover, LN pretreatment can lower fracture initiation pressure actually. The productive findings obtained in this work are expected to provide an alternative for the sustainable development of deep shales resources. INTRODUCTION Deep shale gas resources below 3400 m are widely distributed and have the potential for sustainable natural gas development(Altammar et al., 2019).The deep shale formations have characteristics of low porosity and permeability and characterized by significant in-situ stresses, horizontal stress differences, and high temperature(Carpenter, 2017). Hydraulic fracturing is a traditional measure to stimulate these formations. However, the burden of hydraulic fracturing operations has been a topic of great importance to the energy industry and public alike(Han et al., 2018). Traditional hydraulic fracturing is challenging to generate complex fractures, and the production is usually less than expected (Cong et al., 2021). Cryogenic liquid nitrogen (LN, −196 °C at atmospheric pressure) fracturing is one possible method of solving these water-related issues(Yang et al., 2019). When LN is injected into the reservoir formation, the sudden heat transfer could cause shrinkage of the rock and exert a sharp thermal gradient that can induce numerous fractures at the surface of the formation rocks (Elwegaa et al., 2019). The significant thermal stress between LN and rock will lower fracture initiation pressure and create complex fractures(Wan et al., 2018). Therefore, LN fracturing will be an effective engineering method to develop high-temperature or deep formation resources(Wan et al., 2019).

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