bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory Study on the Strength Deterioration Characteristics of Solid Potash Ore Samples in Moist Environment
Authors: Zhang J. W. , Wang S. , Yang S. L. , Chen X. , Wei W. J. , Li L. H. 
Published: August 2024

ABSTRACT:
Potassium salt rock is a typical discontinuous heterogeneous material formed naturally, which is mainly composed of carnallite, sylvite, halite and so on. Potassium salt is widely used in various industry fields (such as agriculture, chemical industry, medicine, metallurgy, electroplating, printing and dyeing, glass, etc.) and has a large demand. One of the important sources is the mining of solid potassium salt mines. Through the laboratory test of solid potassium salt ore samples obtained from an underground potassium salt mine in a mine in Laos, various mechanical parameter data of potassium salt ore deformation and failure can be obtained intuitively and effectively, so as to provide theoretical and data basis for the design of specific engineering parameters such as pillar strength calculation and size optimization. In this paper, the large potassium salt ore obtained from the underground mining site of a potassium salt mine in Laos was cut and cored, and the cylinder and disc standard specimens of the potassium salt rock were obtained. By simulating the underground moist environment under different humidity conditions, potassium salt cylinder specimens with different water contents were prepared in the laboratory. Then, the uniaxial compressive strength test and other indoor tests were carried out on these potassium salt specimens, and the test results were obtained and analyzed in depth. The results show that the potassium salt ore sample exhibits typical plastic rheological properties under the condition of unconfined uniaxial compression, and its uniaxial compressive strength in the natural state is roughly between 6.7MPa -9.3MPa; and within a certain range of water content, the uniaxial compressive strength of potash ore samples gradually decreases with the increase of water content. Through the analysis of strength deterioration characteristics of solid potash ore, it can provide scientific guidance for the optimization of pillar size in underground mining of solid potassium salt ore with different moist environments, and then lay a theoretical foundation for improving the underground mining recovery rate of potassium salt ore and reducing the waste of resources.

1. INTRODUCTION
Potassium salt is a non-metallic mineral with potassium chloride and sulfate minerals as the main components (Bai et al., 2014). The main potassium salt minerals are sylvite, carnallite, potassium magnesium alum, anhydrous potassium magnesium alum, polyhalite, potassium magnesium alum, soft potassium magnesium alum and so on. In its raw state, potassium salt is an important industrial and agricultural mineral, which has important economic value, (Cheng, 2007). It is mainly used as potassium fertilizer, which is an important agricultural fertilizer resource and one of the three essential fertilizers for crops. Therefore, it is of great significance to study the mining of underground solid potash ore.
Mechanism Transition for Fracture Energy Dissipation of Shale Under Crack-Parallel Compression
Authors: Zhang Min , Zhang Guangqing , Ling Yansen , Yang Feng , Zhong Anhai , Zheng Xuelin 
Published: August 2024

ABSTRACT:
The microcracking processes in front of the rock fracture tip could determine the macro-fracture propagation. Understanding the effect of crack-parallel stress on the microcracking processes could facilitate characterization of fracture propagation in shales and guide hydraulic fracturing. The gap test is improved by replacing elastoplastic pads with a micro servo pump for applying precise crack-parallel stresses. The fracture propagation with crack-parallel stress is captured, where microcracking processes are identified unifying digital image correlation (DIC) and acoustic emission (AE) method. Based on the crack cohesive model, the influence of crack-parallel stress on fracture energy is characterized. Experiments show that the parallel stress of 10MPa increases the fracture energy of shale by about 25%, due to more shear type microcracks forming macro-fracture. The microcracks are spread over a wider damage zone rather than concentrated in fracture processes zone (FPZ) because of the crack-parallel compression. Hence the whole damage zone instead of FPZ dominates fracture extension. This work provides fundamental understandings in propagation of hydraulic fracture in shale under reservoir conditions.

1. INTRODUCTION
Hydraulic fracturing is a key technology increasing reservoir permeability by injecting high-pressure fluids to form fractures(Xing, Zhang, Luo, et al., 2019). Essentially, hydraulic fracture extends in the reservoir under the crack parallel compression. There are various standard specimens to characterize fracture resistance of rock, such as three-point-bend and compact tension, but all the standard tests almost ignore the effect of crack parallel stress.
The crack parallel stress is part of triaxial stresses from confining pressure, which is parallel to the fracture propagation. Some fracture tests under confining pressure have checked the effect of triaxial stresses. The straight notched round bar was proposed to obtain mode I fracture toughness of shale influenced by confining pressure(Antinao Fuentealba et al., 2024), using linear fracture mechanics. Experiments present that fracture toughness is double when confining pressure is increased to 70 MPa. The Brazil splitting tests with confining pressure indicate that the tensile strength of shale increases by up to 58.5%(Guo et al., 2022), as well as the sandstone and limestone samples. It indirectly shows obvious effect of confining pressure on rock fracture toughness because fracture toughness is proportionate to tensile strength(Dutler et al., 2018).
Experimental Study on the Size Effect of Fracture Process Zone of Mixed Mode I-II Crack in Sandstone
Authors: Sun Bin , Zhang Guangqing , Luo Senlin , Cai Dingshan , Lin Yansen , Zhou Dawei 
Published: August 2024

ABSTRACT:
Rock cracks tend to grow in the form of tensile and shear failure, i.e., mixed mode I-II crack. Size effect of fracture process zone (FPZ) should be highlighted due to it may alter the fracture growth. To study the size effects of FPZ on the development characteristics of mixed mode cracks, three-point bending experiments with off-center initial crack were carried out on sandstone with ratio of length and height of 3. Combined with digital image correlation (DIC) method, the variation of deflection angle and displacement field around the crack tip were analyzed. The results show that the FPZ length increases with the specimen size while the normalized length of the FPZ decreases. The FPZ begins to develop at 60-70% pre-peak and is fully developed at 90% post-peak. The cracks of different sizes begin to deflect when the FPZ is fully developed, and the deflection is completed at 60% post-peak. The deflection angle of FPZ decreases with the sample size. To ensure that the local tensile stress is the maximum, the cracks will deflect and cause the local shear stress to decrease and disappear, which is more obvious in small-size specimens. This study further revealed the fracture mechanism of mixed mode I-II crack under different sizes.

1. INTRODUCTION
Cracks are common internal structure in rock materials, due to different external forces, there will be different forms of expansion, generally can be divided into three modes: mode I (open) cracks, mode II (slip) cracks and mode III (tear) cracks (Surberg and Tschegg, 2001).
In view of different shapes of prefabricated cracks, Lin and Labuz, (2013) et al. studied mode I fractures of sandstone. The results show that the critical crack opening displacement does not change with the prefabricated crack shape. The FPZ length is about 10 times the maximum particle size of the sample. The critical crack opening displacement and FPZ length in mode II cracks are larger than those in mode I cracks (Lin et al., 2014; Moazzami et al., 2020).
Because cracks in actual rock structure often do not exist in a single fracture mode, such cracks are called mixed mode cracks. In practical engineering, mixed mode I-II cracks (hereinafter referred to as mixed mode cracks) are the most common (Aliha and Ayatollahi, 2013). In the mode I fracture, the fracture receives only tensile stress (Meirong. et al., 2024). Compared with mode I cracks, mixed mode cracks are not only subjected to tensile stress, but also to shear stress (de Moura et al., 2016). Since the shear resistance of rock materials is stronger than the tensile resistance, cracks generally start and expand in the direction perpendicular to the maximum tensile stress, that is, tensile failure is still the main type of mixed mode cracks (Song et al., 2018). Due to the existence of shear stress, there is a deflection Angle in the initiation of mixed mode cracks compared with mode I cracks.
Investigation on the Damage Mechanisms of Unconsolidated Sand, Tight Sand and Shale Induced by Cryogenic Temperature
Authors: Zheng Xuelin , Lu Mingjing , Wang Dongying , Qian Qin , Zhong Anhai , Zhang Liaoyuan , Yang Feng , Li Yuan , Zhang Yuzhe , Su Quansheng , Zhou Dawei , Zhang Min , Zhang Guangqing 
Published: August 2024

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).
Experimental Study on Shale Mechanical Properties Interacted with Supercritical Carbon Dioxide and Brine
Authors: Feng Jie , Ma Tianshou , Liu Yang 
Published: August 2024

ABSTRACT:
Supercritical carbon dioxide (SC-CO2) can be utilized to displace methane in shale gas reservoirs due to its low viscosity, high diffusivity, and high density. However, injection of SC-CO2 can cause a series of physical and chemical interactions with the pore brine and shale rock, leading to irreversible changes in the mechanical properties of the shale. To investigate changes in the mechanical properties of the shale that interacted with SC-CO2 and brine, Longmaxi shale samples were soaked in pure SC-CO2 and SC-CO2 + brine for seven days at 50 ° C and 15MPa. Uniaxial and triaxial compression tests were performed on the soaked samples, and acoustic emission was monitored during the loading process. The results indicated that the Longmaxi shale exhibited a more pronounced reduction in strength under the SC-CO2+brine condition compared to the pure SC-CO2 condition. In the loading process, the acoustic emission signals exhibit a distinct staged characteristic, and the signals are generated primarily during the unstable crack expansion stage. The observed increase in the fractal dimension of the signals at the same circumferential pressure indicates that the shale damage is multifaceted, resulting in a reduction in the stability of the shale. This study may help to elucidate the alterations in the mechanical properties of shale as a consequence of its interaction with SC-CO2. Furthermore, the findings may provide a foundation for the recovery of shale gas using CO2 displacement.

1. INTRODUCTION
With the rapid growth of the global economy and the increasing level of industrialization, the supply of traditional fossil energy has gradually failed to meet the energy needs of today's society (Zou et al., 2016). Shale gas, as one of the most important unconventional oil and gas resources, has attracted a lot of attention because of its abundant reserves, cleanliness, low cost, and long supply cycle (Zhou and Zhang, 2020). Shale reservoirs are typically characterized by low porosity, low permeability, and high clay content (Jin et al., 2012), so hydraulic fracturing is commonly used to enhance shale gas production (Daneshy, 2010). However, it can result in significant water loss, damage to the physical properties of the reservoir, and contamination of surface water with back-draining fluids (Estrada and Bhamidimarri, 2016; Yang et al., 2019; DiStefano et al., 2019). Supercritical carbon dioxide (SC-CO2) is often used to enhance shale gas recovery due to its low viscosity, low surface tension, and high extraction capacity in its supercritical state (Adwani, 2007; Wang et al., 2011; Yang et al., 2008). This method has several advantages, including no damage to the reservoir, high efficiency of jet breakthrough, and the ability to lower the viscosity of crude oil and displace shale gas (Lu et al., 2021; Zhao et al., 2021).
A Comparative Study of Preparation Methods, Weighting Agents, and Temperature on Quality of E-M Compatible Borehole Imaging Fluid
Authors: Abbasian L. , Akindele O. M. , Abugharara A. N. A. , Butt S. D. 
Published: August 2024

ABSTRACT:
Imaging fluids plays a crucial role in mitigating the impact of borehole groundwater on borehole E-M imaging results. Such fluid must possess specific characteristics such as low conductivity to minimize electromagnetic wave attenuation, appropriate dielectric permittivity to prevent signal ringing at the fluid-wellbore boundary, higher density than water for settlement at the bottom hole, and long-term stability throughout the imaging process. This study meticulously examines the influence of agitation and temperature on the quality of oil-based imaging fluids, comparing two major preparation methods with distinct grain sizes of the weighting agent. One is the conventional method involving a critical heating step of the emulsifier in 20% of the imaging fluid liquid base, while the second involves dissolving the emulsifier in the liquid base by agitation. Evaluation of the produced fluids encompasses considerations of their stability over time, settlement in various water temperatures, and rheological properties. The results of these experiments reveal the pros and cons of the agitation process compared to the conventional method, weighting agent grain size, and temperature on the overall quality of the produced imaging fluid.

1. INTRODUCTION
High frequency electromagnetic waves are used as the source of Ground Penetrating Radar (GPR) to image and map subsurface geological formations and structures (Jol, 2008). Borehole GPR utilizes high frequency electromagnetic waves for mapping out the downhole subsurface geology. This GPR data quality can be influenced by the presence of borehole water or the media between the antenna and the wellbore Li (2023). Hence, the selection of a proper borehole fluid will help overcome the impact of ground water on imaging data quality. Borehole water should be replaced by an imaging fluid at the bottom hole and cover the E-M antennas while imaging.
The ideal borehole fluid (imaging fluid) should have specific properties such as low conductivity (low EM wave attenuation), appropriate dielectric permittivity close to that of the host rock to avoid signal ringing between the fluid-wellbore boundary, higher density than water to enable it settle at the bottom hole, and stability such that it does not discompose while imaging. Following the above characteristics, the imaging fluid is made up of a liquid base with low dielectric permittivity and conductivity, a weighting agent to increase its density than water to about Specific Gravity (SG) of 1.2 and an emulsifier to ensure its stability by preventing the separation and settlement of suspended solids.
Thermal Measurements and Geothermal Gradient from Deep Boreholes in the Revell Batholith, Northwest Ontario
Authors: Kasani H. A. , DesRoches A. , Sykes E. , Parmenter A. , Khorshidi M. 
Published: August 2024

ABSTRACT:
The Revell Site, in northwestern Ontario, within the Canadian Shield, is presently being studied as one of the sites for hosting a deep geological repository (DGR) in Canada. Preliminary site investigation included the drilling and coring of six 1-km long boreholes. The thermal characterization involved obtaining temperature logs from multiple sources in boreholes and laboratory thermal properties testing of different rock types. After drilling, coring, and flushing of the borehole, downhole temperature data were collected in this order: (1) continuous logs from geophysical dynamic fluid temperature probe, (2) discrete temperature data measured during hydraulic packer testing, and (3) discrete temperature data collected post installation of a Westbay monitoring system. The hydraulic testing and Westbay data provided the most reliable estimates of in-situ temperature profile with an average geothermal gradient of 9.9°C/km. This gradient is within the lower range of the data from other study sites in the Canadian Shield. The low gradient is consistent with low concentrations of natural uranium, thorium, and potassium in the tested core samples, which results in a low radiogenic heat generation rate. This paper presents a summary of the thermal data collection in the first three boreholes and development of a thermal model for the site, which provides boundary conditions for thermal simulations of the DGR. This initial thermal property dataset and site model also provides a prediction against which data from the latter three boreholes can be expected.

1. INTRODUCTION
Deep geological disposal is an internationally accepted method for the safe and long-term management of used nuclear fuel. Safe long-term performance of a Deep Geological Repository (DGR) spans over the construction, operation, and post-closure phases which includes geological processes such as earthquakes and glacial advance and retreat.
The Nuclear Waste Management Organization (NWMO) is implementing Adaptive Phased Management (APM), the approach approved by the Government of Canada in 2007 for the long-term management of used nuclear fuel. The NWMO site selection process is described in NWMO (2010). As part of APM, the NWMO is conducting preliminary site assessment activities in potential siting areas in: i) crystalline rocks in the northern portion of the Revell batholith within the Canadian Shield, near the Township of Ignace in the traditional territory of Wabigoon Lake Ojibway Nation (WLON) in northwest Ontario (referred to as the Revell Site), and ii) in sedimentary rocks in the Municipality of South Bruce in the traditional territory of Saugeen Ojibway Nation (SON) in southern Ontario (referred to as the South Bruce Site).
Monitoring the Propagating Process of Hydraulic Fracture with Fiber Optic Strain and Strain Rate Technology
Authors: Hao Yalong , Chen Mian , Wang Su , Zhao Changjun , Mao Yu 
Published: August 2024

ABSTRACT:
A true tri-axial experiment was conducted to simulated hydraulic fracture propagating process with a 30 cm cubic block cement sample. At the same time, optic fiber in the cement sample recorded strain signals. In this paper, a fiber strain/strain rate calculation method based on wavelet noise reduction algorithm is proposed. The experimental results show that different spatial relationships between the optic fiber and the fracture surface correspond to different optic fiber signal responses. When the fracture surface is perpendicular to the optical fiber, obvious red stretching strips will be formed due to the fracture hitting the optical fiber. However, when the fracture surface is parallel to the optical fiber, the optical fiber will produce a large-scale micro-stretching zone. At the same time, the coupling effect between the fiber and the formation can also affect the signal responses. These results are profitable to understanding Distributed Acoustic Sensing (DAS) signals in the field.

1. INTRODUCTION
Horizontal well fracturing technology in low permeability reservoirs greatly improves the efficiency of unconventional oil and gas development (Warpinski et al., 1991). Distribution and morphology of hydraulic fractures are extremely important for oil and gas production. But it has never been fully understood what the expansion pattern of underground hydraulic fractures actually looks like. Oil companies and service companies have developed technologies such as microseismic, tiltmeters, tracers, etc. for this purpose (Fisher et al., 2005, Maxwell et al., 2009, Magdalene et al., 2022). Due to the complexity of the subsurface, all monitoring techniques can only indirectly reflect some of the characteristics of the hydraulic fracture.
Low-frequency DAS(LF-DAS) signals (&lt;0.05 Hz) are emerging as a new tool for monitoring fracture morphology, providing a completely new approach to hydraulic fracture monitoring (Jin et al., 2017). (Liu et al., 2020 and 2021) used the displacement discontinuity method to simulate the response of a fracture hitting a fiber under single and multiple clusters, and used the fiber data to invert the fracture hitting point location and fracture width information. (Chen et al., 2022) analyzed and summarized the evolution of the strain rate waterfall diagram before and after the fracture hit the fiber. (Smith Leggett et al., 2022) proposed a "zero-strain" localization method for assessing the dynamic location of fracture leading edges by indoor fiber-optic monitoring of fracturing. (Chen et al., 2021) applied machine learning algorithms to fiber optic data processing in an attempt to assist in determining information such as the location of fracture hits.