bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unloading Response of Tunnels in Deep Brittle Rock Mass Considering Ubiquitous Minor Joints
Authors: Peng S. Y. , Li X. B. , Chen G. Q. , Mitani Y. 
Published: September 2023

ABSTRACT
Minor joints exist ubiquitously in deep-buried brittle rock masses subjected to high in-situ stress. These joints affect the strength and deformation properties and lead to the concentration and dissipation of stress wave propagation. Through modeling and verification, the rock mass model in the study with closable minor joints can perform the plasto-elastic behavior under static compression, and the increase of wave velocity with confining stress under dynamic load. The unloading response of tunnels is analyzed in two influencing factors: unloading rate and lateral stress coefficient. According to the results, the increase of unloading rate will intensify stress oscillation and increase additional dynamic stress disturbance of the joint rock mass near the tunnel boundary. As the vibration dissipates kinetic energy, the additional dynamic stress disturbance farther away from the tunnel boundary is decreased. Additionally, the minor joints can open or close in particular directions depending on the complex in-situ stress and the stress distribution of the surrounding rock mass. At the location along the direction of open joints and close to the stress release source, the joint rock mass may have a higher additional stress concentration than in the elastic model.

INTRODUCTION
The scarcity of shallow mineral resources and construction space has substantially escalated the depth of tunnel excavation (Li et al., 2017; Xie et al., 2015). Deep rock mass subjected to gravitational and tectonic stress reserves enormous strain energy and exhibits evident fracture development. Deep tunnel excavation is typically a dynamic unloading process (Cai, 2008; Lu et al., 2012). In particular, the strain energy will be immediately released within several milliseconds and induce a pulse load when the tunnel is excavated utilizing drilling and blasting (Yang et al., 2013). This process may lead to various observed hazard phenomena, such as spalling (Jiang et al., 2013), rock burst (Ortlepp & Stacey, 1994), large deformation (He et al., 2005), and zonal disintegration (Jia & Zhu, 2015). Meanwhile, the intensity and frequency of disasters escalate as excavation depth increases, threatening construction and operation safety (Cai, 2016). Therefore, the mechanism of unloading failure of deep tunnels in rock mass has always attracted the attention of many researchers.
Uncertainty Quantification of Young's Modulus on Core Scale: A Bayesian Analysis on a Comprehensive Geomechanical Model
Authors: Wu Zhidi , Edelman Eric , Smith Phil , Smith Sean , Irons Trevor , McPherson Brian 
Published: September 2023

ABSTRACT
The ability to accurately measure the static Young's modulus is crucial for understanding subsurface storage reservoirs. However, obtaining this data can be difficult and costly. Much previous research focused on the impact of one or two factors on geomechanical properties at a single scale, but a more comprehensive understanding is needed. This study examines the impact of six rock properties - porosity, clay content, permeability, sample size, and the framework grain content to cement content (FGC/CC) ratio on Young's modulus in samples from five rock facies. The goal is to systematically quantify the effects of these secondary rock properties on a primary geomechanical property in a range of sandstones at the core scale. This study suggests that the pore abundance and the relative amount of framework grains and cements play competing roles in rock's elastic behavior. In addition, the surrogate model yields the minimum uncertainty and reflects nonlinear trends between Young's modulus and secondary rock properties. Overall, we represented a data-driven approach to quantify the uncertainty of Young's modulus of rocks using cost-effective experimental measurements.

INTRODUCTION
Understanding and minimizing uncertainties in geomechanical properties can lead to successful geological investigations and complex engineering projects and prevent accidents such as reservoir leakage and wellbore collapse. Elastic modulus is a primary property (among mechanical properties), but data are often unavailable and can be costly to measure. Alternative to direct measurements, estimating elastic modulus is more effective if the roles of secondary properties, such as geological, hydrological, and petrophysical properties, can be quantified. Previous studies often evaluate the correlation between primary and secondary properties to predict primary geomechanical properties (Han et al., 1986; Chang et al., 2006). However, the correlations between primary and secondary properties are not comprehensive, and the uncertainty associated with predictive primary geomechanical properties is generally unknown. Therefore, a framework for the Bayesian assessment of a comprehensive geomechanical model with constrained uncertainty has been developed to address this challenge. The comprehensive geomechanical model is capable of predicting elastic modulus based on main secondary properties.
Study on Matrix Acidizing of Low-Permeability Hybrid Sediment Rocks Using Microemulsion Retarded Acid
Authors: Liu Shiduo , Liu Yong , Xiong Tingsong , Zhang Yang , Shang Litao , Xie Guiqi , Zhang Haining , Sun Xun , Sui Guojie , Zhao Endong , Wang Qing , Zhou Fujian 
Published: September 2023

ABSTRACT
The high reaction rate of hydrochloric acid, the low dissolution rate of organic acids, and the difficulty of injection of highly viscous gelled acids are all unsuitable for the acidification of low-permeability hybrid sediment reservoirs. The lithology of hybrid sediment rock reservoir is complex, and the dissolution rate of single acid is low. In this paper, an oil-in-water (O/W) microemulsion retarded acid is developed, and acidizing performance is studied. The microemulsion can be diluted in the acid system, and the structure of the microemulsion is not destroyed. The average particle size is less than 10 nm. The microemulsion acid can effectively reduce the oil-water interfacial tension, reducing the resistance to enter low-permeability cores. By adding microemulsion to the multi-hydrogen acid system, the dissolution rate is greater than 45 %. The retarded mechanism is that the polyhydric acid gradually releases hydrogen ions, then the microemulsion adsorbs on the rock surface. At the same time, the corrosion rate of microemulsion retarded acid and N80 steel is only 1.07 g/m2 h. Microemulsion retarders can adjust the surfactant composition according to the rock mineral composition to achieve the effect of high acid dissolution and substantial retardation and provide guidance for the stimulation of hybrid sediments rock reservoirs in the field.

INTRODUCTION
The global exploration and development of oil and gas resources have been continuously increasing, leading to significant progress in exploiting clastic and carbonate reservoirs. However, more research must be conducted on another widely distributed sedimentary rock type, hybrid sediment rocks (Feng et al., 2011). Hybrid sediment rock reservoirs share similarities and differences with conventional sandstone or carbonate reservoirs. The most significant difference lies in the mineral composition, lithology complexity, complex pore structure, low permeability, and strong heterogeneity of hybrid sediment rocks (Chen et al., 2015). In western China's northwestern region of the Qaidam Basin, a mixed sedimentary environment consisting of carbonate, mudstone, and fine sandstone has formed (Li et al., 2022). This region has significant oil and gas reserves, but the reservoir's low permeability and complex lithology require stimulation to reduce oil and gas flow resistance and improve production.
Study on the Fracturing Pattern and Damage Characteristics of Deep Shale by Liquid Nitrogen Fracturing
Authors: Qu Hai , Li Zhelun , Liu Ying , Zeng Zhijun , Liu Xu 
Published: September 2023

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).
Experimental Investigation on Corrosion and Emulsification During CO2 Injection in Heavy Oil Reservoirs
Authors: Luo Chen , Liu Huiqing , Wang Zuochen , Lyu Xiaocong , Huang Yaowei , Peng Chao 
Published: September 2023

ABSTRACT
Carbon dioxide (CO2) injection possesses an immense potential for production improvement in heavy oil reservoirs. The primary interest of this work is to investigate the corrosion effect of carbonated water formed by CO2 and formation water on reservoir rock, and the emulsification of crude oil. This study used the scanning electron microscope and interfacial tension (IFT) setup to research the core micro-structure and oil-water IFT. The results showed that the corrosion ability of carbonated water gradually increased as pressure increased within a certain range of pressure. When the pressure increased from 8MPa to 16MPa, the average corrosion rate increased from 0.45% to 0.66%. Moreover, the injection of CO2 caused the appearance of corrosion pits and cracks, surface particles peeled off and dissolved, and cracks extending as pressure increased. The dynamic IFT between the decyl trimethyl ammonium bromide solution and crude oil changed less and stabilized in less quickly without CO2 injection. The dynamic IFT decreased faster with pressure increase after CO2 injection, which was favorable for crude oil emulsification and emulsion stabilization. There is a positive correlation between Equilibrium IFT and temperature at the condition of low temperature.

INTRODUCTION
The global heavy oil resources are abundant. The proven recoverable heavy oil resources are 126.74 billion tons, 71% of which are distributed in the Americas and the Middle East (Liu et al., 2019; Shah et al., 2010). The key to exploiting heavy oil is to reduce viscosity and improve fluidity(Al-Samhan et al., 2022; Wang et al., 2023). Thermal recovery is the most commonly used method for heavy oil extraction at home and abroad (Bueno & Mejía, 2022). However, in heavy oil thermal recovery, the large reservoir depth, strong formation heterogeneity, and high crude viscosity, will lead to low thermal energy utilization, high development cost, and low extraction efficiency (Khelkhal et al., 2022). CO2 is a commonly used replacement medium, with various special mechanisms such as replenishing formation energy, reducing crude oil viscosity, extracting light components and blending (Kumar et al., 2022). Meanwhile, CO2 as a greenhouse gas seriously impacts on global climate, and CO2 utilization and storage can effectively reduce carbon emissions, so CO2 is of great significance for thick oil development (Lan et al., 2019).
Numerical Simulation of Sandstone Degradation Under Freeze-Thaw Cycles with Grain-Based Model
Authors: Huang C. , Zhu C. , Ma Y. 
Published: September 2023

ABSTRACT
In this study, the grain-based model (GBM) is used to evaluate the influence of freeze-thaw cycles (FTCs) action on the mechanical properties of sandstone. Five mineral components of sandstone are built in the numerical model based on GBM. To explore the influence of FTCs, water particles are distributed on the boundaries of different mineral components. Inter-particle heat conduction module captures the heat transfer process, resulting in temperature redistributions and the development of thermal strains. A modified elastoplastic model is used to capture the accumulation of residual strain that occurred during the ice-water phase change. The micro-cracks in sandstone samples after FTCs reflect the damage caused by FTCs. The uniaxial compressive test is carried out to evaluate the deterioration of FTCs on uniaxial compressive strength (UCS) and Young's modulus of sandstone specimens. Furthermore, it is found that the brittleness of sandstone is decreased with the increasing freeze-thaw cycles. These numerical results prove that the GBM developed in this study can be used to capture the deteriorative effects of FTCs on sandstone. This study provides a better understanding of the influence of FTCs on the mechanical properties of sandstone, which might be helpful for the design and assessment of climate-resilient infrastructure.

INTRODUCTION
Global warming has exposed more and more areas undergoing freeze-thaw cycles. The freeze-thaw cycles deteriorate the mechanical properties of rock which raises the risk of geotechnical infrastructures failure in these regions. At temperatures below 0 °C, the water contained within pores solidifies into ice, resulting in a volume increase of approximately 9 % (Hou et al. 2021). This volume expansion caused by the phase change of water increases the frost-heaving pressure on the surrounding rock, which produces microcracks or enlarges the pre-existing joints of rock masses (Wang and Zhou 2018). The increasing discontinuities in rock mass allow more water to fill into rock and cause damage to the physical and mechanical properties of rock under freeze-thaw cycles. Therefore, it is significant to understand the damage mechanism of rock under freeze-thaw cycles for the safe design of civil infrastructures in cold regions.
Amphibolites Study from Various Borehole Depth
Authors: Lokajícek T. , Aminzadeh A. , Svitek T. , Petružálek M. , Prikryl R. 
Published: September 2023

ABSTRACT
In this study the elastic properties of crystalline rocks – amphibolites from different boreholes were studied. We studied the depth effect on the elastic properties of mineralogically quite homogenous rocks – amphibolites. The samples were taken from three different crustal levels – shallow (tens of meters) Stařechov (Czech Republic), medium deep (first thousands of meters) KTB (Germany), and deep crustal depths (up to 12 km) KSDB3 (Russia). The elastic properties were first determined experimentally using high-pressure apparatus and 3D ultrasonic testing. The effect of main rock fabric components were evaluated using the method of inverse calculation from experimental data. There was found an increase of P-wave velocity, P-wave stiffness elastic constants with the depth for 19 samples, collected from different depth, and all loaded to 400 MPa of hydrostatic pressure. This fact can be explained by the stress memory effect. Stiffness constants and Young modulus were determined for primary material orientation

INTRODUCTION
Elastic anisotropy is a crucial physical property of crustal rocks namely when reflecting deformational history of the rock. Knowledge of the anisotropy of deep crustal rocks (e.g., Kern et al. 1991) is of special interest for studies focused on the evolution of the crust. The relationship between amphibolite elastic properties and mineral composition and/or rock fabric has been extensively studied in the past (Siegesmund et al. 1989). The influence of microcracks on the elastic wave velocity and its anisotropy has been noted in many previous studies (Crampin 1977, Babuška and Pros 1984 among others). Numerous studies are focused on the systematic study of elastic properties of rocks extracted from boreholes e.g., KTB (Berckhemer et al. 1997) or KSDB3 (Nikitin et al., 2001, Saikia et al. 2021). In all of these studies, there is missing comparative research concentrated on the relationship between the actual depth of rock occurrence and its elastic properties.
Nuclear Magnetic Resonance Experimental Study on Pore Structure Effect of Deep Shale Under Liquid Nitrogen Freezing
Authors: Qu Hai , Chen Xiangjun , Liu Ying , Liu Xu , Zeng Zhijun 
Published: September 2023

ABSTRACT
The freezing of liquid nitrogen (LN2) can affect the rock's structure, which can be used in the extraction of natural gas from deep shale formations. However, its effect on the pore structure of the shale remains unclear. To address this issue, this study subjected three different types of deep shale: Carbonaceous (C) shale, siliceous (Si) shale and calcareous (Ca) shale. The mineral composition was determined by X-ray diffraction (XRD). And the physical properties of deep shale were analyzed by nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The evolution of porosity of shale samples under LN2 cooling by different lithology, rock temperature and cyclic cooling were compared to explore the effect of LN2 freezing on the pore structure. The results of this study indicated that LN2 fluid would be a promising source of longitudinal and bedding fractures in carbonaceous shales. And the resulting fractures would increase the permeability of the shale. In addition, repeated freezing also lead to the formation of conductive fractures in the shale. In conclusion, since LN2 has low-temperature properties, has a freeze-damaging effect on reservoir rocks and promotes microfracture development, it is important to inject LN2 as fracturing fluid during the reservoir process to improve the effect of fracturing transformation.

INTRODUCTION
As an important component of unconventional oil and gas resources, shale gas has played an important role in recent years in meeting the growing global demand for fossil energy (Alfi et al., 2019; Qu, Hu, et al., 2022; Wu et al., 2017). As shale gas reservoirs are characterized by low pore permeability and large burial depth, corresponding production enhancement measures need to be implemented to achieve effective extraction of shale gas. In response to the problems of water scarcity and environmental pollution caused by hydraulic fracturing, the liquid nitrogen (LN2) waterless fracturing proposed in recent years can be one of the key technologies for effective development of deep shale gas and alleviating water scarcity (Qu, Tang, et al., 2022). The cold impact effect of LN2 on the rock is used to reduce the difficulty of rock fracturing, thus improving the fracturing effect of the reservoir (Qu et al., 2023). Therefore, it is important to clarify the study of the fracturing mechanism of low-temperature LN2 on deep shale rocks and explore the feasibility of LN2 fracturing in deep shale rocks for the guidance of shale gas development (Qu, Liu, et al., 2022; Wu et al., 2019; Yang et al., 2021).
The Effect of Quantity and Spacings of Notches on Hydraulic Fracturing at Different Stress Regimes
Authors: Powlay B. , Karakus M. , Amrouch K. , Chester C. 
Published: September 2023

ABSTRACT
Due to the increased understanding of mining techniques previously uneconomical larger orebodies are becoming viable and block caves are increasingly common. One such technological advance is the use of Hydraulic Fracturing.
With the majority of research for hydraulic fracturing being focused on reservoir development, a need to better understand how this translates into mining is required. Exploring how fractures initiate, grow, and the influence of notch spacings and density, more knowledge is gained around prescribing fractures to the mining industry and environments needs.
By using multiple perforations, due to coalescing of fractures, more complex fracturing could be through the change in localized stresses. To understand the influence of fracture density, lab work was undertaken looking at how density of notches and notch spacing influence the fracture growth, breakdown pressure, and propagation pressures in Adelaide Black Granite under two different stress regimes.
The results show that location of notches has minimal impact on pressures but create changes in the fracture direction. This work confirms that with multiple notches this technique can be used to change fracture propagation. providing solid foundation for designing campaigns with multiple simultaneous injections, and fractures density within the mining industry.

INTRODUCTION
Block caving is gaining traction as a viable method of mining within hard rock mining environments. As easy shallow depth orebodies are becoming rare and scarcer, then methods to extract deeper orebodies safely has become a need of the industry.
Block caving has an initially high outlay of costs and slow turn around in producing tons relative to Sub Level Caving methods, but in the long term requires less active development and low running costs alongside the ability to design footprints to meet the needs of the stresses, structures and environments, it equates to an economically sound, customizable, and relatively simple mining method.
The challenges faced with the block cave mining method, and future caves that are established at depths are mostly related to the higher stress environment and cave propagation and stalling. A way to mitigate these risks is through the use of hydraulic fracturing. By inducing fractures in a favorable manner into the environment stress can be redistributed, highly stressed zones can be activated, and competent rocks weakened for the promotion of cave growth