bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study of Proppant Crushing and Conductivity Reduction Within Rough Fracture in Shale Gas Formations
Authors: Liu L. , Ma X. F. , Zou Y. S. , Zhang S. C. , Zhang X. H. , Wang W. C. , Liu S. K. 
Published: August 2024

ABSTRACT:
To investigate the impact of surface roughness on proppant crushing and its effect on fracture conductivity in Shale Gas Formations, laboratory conductivity experiments were performed on standard core columns drilled along hydraulic fractures. The morphology of proppants within the fractures was observed using computed tomography (CT) and scanning electron microscopy (SEM). The results indicate that the roughness of the fracture surface has a greater impact on ceramic proppants than on quartz sand in terms of crushing rate. For high roughness surfaces, quartz sand is suitable for shallow reservoirs, while ceramic proppant is more suitable for deep reservoirs. The rougher the surface of the fracture, the greater the decrease in its conductivity. When the compressive stresses vary from 20 MPa to 50 MPa, the quartz sand crushing rate increases from 10% to 33%, while the ceramic proppant crushing rate grows from 8% to 22%. The CT scan results indicate that the proppant is prone to breakage at the raised area of the fracture surface. The scanning electron microscopy (SEM) results show that the proppant is more prone to crushing and damage at the raised areas of the surface of the fracture. This article innovatively analyzes the crushing of proppants under various rough fracture surfaces, offering guidance for optimizing proppants in different reservoir conditions.

1. INTRODUCTION
On a global scale, oil and gas resources remain irreplaceable and non-renewable energy sources. With the decreasing recoverable reserves of conventional oil and gas resources year by year, shale oil, as a new type of unconventional oil and gas resource with great potential, has become an important component of global oil and gas resources (Shah et al., 2010; Davies et al., 2012; Zeng and Wei, 2017). Reservoir fracturing transformation is the core technology for enhancing the utilization of oil and gas reservoirs (Cui A et al., 2014; Saldungaray PM et al., 2015). However, the effective establishment of an artificial fracture network in reservoir fracturing transformation is crucial for creating high-conductivity oil and gas flow channels. The efficient migration and placement of proppants in artificial fractures are fundamental for enhancing the support provided by fractures. (Asabi et al., 2018; Wei et al., 2019; Ghanizadeh et al., 2016; Han, J. A. et al., 2016).
A Study of the Key Factors Associated with a Massive Pillar Failure in an Underground Limestone Mine Using Numerical Models
Authors: Rashed G. , Yuting X. , Evanek N. 
Published: August 2024

ABSTRACT:
Several massive ground collapses occurred in the past decade in US underground stone mines where surface subsidence occurred in most of them. The occurrence of a massive ground collapse in stone mines places the mine workers at great risk. The National Institute for Occupational Safety and Health (NIOSH) initiated a project to better understand the causes of these massive collapses and reduce/eliminate their future occurrence. Previously the authors investigated one of these massive collapses and it was found that pillar failure was the most likely cause for the collapse. In this study, the authors further investigated the impact of pillar benching, karst cavities, and geological discontinuities on the potential for pillar failure. 3D LiDAR scans were utilized to determine the extent, location, and dimensions of the karst cavities. Stress and deformation analysis were conducted using 3DEC models to gain more insight about the impact of floor benching and poor rock mass quality on stone pillar stability. Poor rock mass quality can be attributed to the existence of karst cavities, small joint spacing, and poor joint conditions at the study mine. Based on the numerical modeling results, floor benching in association with linear karst cavity and geological discontinuities in pillars can create a large uncontrolled displacement, sliding along pre-existing joints, and induce tensile stresses near the center of the pillar that may result in a brittle pillar failure.

INTRODUCTION
Between 2015 and 2021, five massive ground collapses occurred in underground room-and-pillar stone mines in the United States (Evanek et al., 2022 and Rumbaugh et al., 2022). The depth of cover at these collapses was less than 600 ft (∼183 m). These events pose a significant risk of ground failure and air blast that may result in injuries, fatalities, destruction of ventilation controls, and a potential surface subsidence (Evanek et al., 2022). In general, massive collapses can be attributed to roof or pillar failure. An example of massive roof failure is the collapse that occurred at the Lake Lynn Experimental Mine (Iannacchione et al. 2007), while the collapse that occurred at Whitney mine was an example of pillar failure (Esterhuizen et al., 2018).
Assessing CO2 Leakage Risks and Fault Stability: A Coupled Flow and Geomechanics Simulation with Uncertainty Analysis of Fault Properties
Authors: Yoon Sangcheol , Prioul Romain , Bailey William J. , Birchwood Richard , Rodriguez-Herrera Adrian , Stefani Joe 
Published: August 2024

ABSTRACT:
This study investigates coupled flow and geomechanics simulations of carbon dioxide (CO2) injection within a hypothetical saline aquifer. We intentionally set a scenario to enable fluid migration and fault reactivation in the synthetic model of the SEG Advanced Modeling Corporation (SEAM) CO2 project. The numerical model consists of a main turbidite aquifer, along with several geological layers including a capping shale layer, middle, as well as upper aquifers. In addition, two faults, western and eastern, cut across the section striking North-South. We assume the western fault is a sealing fault while the eastern side has either no fault or is an open fault with a high-permeability damage zone. Our modeling approach employs fine grids near the faults to explicitly represent the fault's 6-m thin damaged zone. We also use a Mohr-Coulomb failure envelope for nonlinear plastic analysis into a two-way coupling scheme. We undertook a stochastic analysis to quantify the impact of fault properties on their post-failure behavior. Using the stress path along the fault plane over time, we show that the characteristics of faults can significantly affect areas of reactivation. Assuming uniform fault properties, an increase in pore pressure can cause shear failure at the upper or lower parts of the fault where it intersects with the target aquifer, because of a significant increase in shear stress. Sensitivity analysis of various parameters, suggests a time evolution of the fault response, with an early emphasis on parameters like cohesion and friction angle affecting reactivation timing. Over time, the permeability of the damage zone gains prominence, influencing the extent of fault reactivation due to its effect on the pressure propagation of the damage zone. Coupled flow and geomechanics simulation can provide useful insights into establishing robust measurement and monitoring plans to mitigate fault reactivation and fluid migration through faults. While the choice of the Mohr-Coulomb model was consistent with our scenario-based approach to "magnify" the effects of fluid migration for this study, we note that in real field situations, other fit-for-purpose plasticity models with different fault permeability evolution may be more appropriate.
Geomechanical Properties of Hydrate-Bearing Sediments from the Gulf of Mexico - Viscoplastic Behavior
Authors: Cardona Alejandro , Bhandari Athma R. , Flemings Peter B. 
Published: August 2024

ABSTRACT:
The geomechanical behavior of hydrate-bearing sandy silts controls in-situ stresses and compression upon hydrate dissociation. Here, we measure the uniaxial strain compression of natural hydrate-bearing (pressure cores) and hydrate-free reconstituted samples from Green Canyon 955 - deepwater Gulf of Mexico. We document these hydrate-bearing sandy silts behave viscoplastically. Under constant strain rate compression under uniaxial strain conditions, sandy-silts with hydrate are stiffer but have a larger uniaxial lateral stress ratio (K0) than equivalent non-hydrate-bearing sediments. When we pause the compression, the stress ratio increases towards K0 = 1.0 in the hydrate sample, whereas the K0 remains constant for the hydrate-free sample. We develop a model to link these experimental observations quantitatively. Our model assumes that the hydrate phase and the sediment skeleton share any applied external load. Model results show the hydrate phase bears a more significant fraction of the applied load because the hydrate is less compressible than the sediment skeleton. The viscoplastic behavior of hydrate-bearing sediments will impact gas production and in situ stresses. For example, viscous deformation away from the production zone affects water flow, affecting gas and water flow rates closer to the well. Furthermore, the time dependency of the stress ratio may affect hydraulic fracturing strategies in these reservoirs as the rate of pressurization may impact stress evolution on the wellbore.

1. INTRODUCTION
Gas hydrates are crystalline solids with guest molecules trapped within water lattices (Sloan and Koh 2007). In natural environments, methane is the most common guest molecule. These compounds are stable at high pressure and low temperature, which delimits their geological distribution to permafrost and submarine settings (Boswell and Collett 2011). Methane hydrates are envisioned as a new energy resource and an active component in the carbon cycle.
Silt- and sand-rich marine environments commonly host high concentrations of hydrates. Coarse-grained deposits in Green Canyon 955 (GC 955) - Gulf of Mexico (Flemings et al. 2020; Meazell et al. 2020), Krishna-Godavari Basin offshore India (Collett et al. 2019), and in the eastern Nankai Trough in offshore Japan (Komatsu et al. 2015) contain hydrate saturations exceeding 80%.
Elastic Wave Behaviors Across Rocks Subjected to Cyclic Tensile Loads
Authors: Yang Hui , Han Dongya , Wu Shan , Zhao Qi 
Published: August 2024

ABSTRACT:
Understanding wave behaviors across rocks exposed to cyclic loads is of great significance to the communities of geomechanics and geophysics. This study aims to investigate the elastic wave properties of rocks (including wave speed, amplitude, and dominant frequency) under the cyclic tensile loading condition. For this purpose, we performed ultrasonic measurements on quartz diorite rock sample during the progressive cyclic direct tensile loading (PCDTL) experiments via a custom-built test system. Our results indicate that wave responses of the quartz diorite rock under the PCDTL condition are highly affected by the applied cyclic tension. Specifically, increasing tensile load causes reductions in wave velocity, amplitude, and dominant frequency during the uploading process of each cycle, and the recovery of these wave properties is observed during the corresponding unloading process. The recovery of wave signatures gets lower with the increasing cyclic number, indicating that the cumulative tension cycles cause accumulated drops in wave attributes. Besides, wave amplitudes exhibit more significant changes compared to wave velocity and dominant frequency during the PCDTL procedure. The findings of this research provide insights into the cyclic tension-induced evolution of wave properties in rock masses and may serve as guidance for the interpretation of field-scale geophysical data.

1. INTRODUCTION
Rock masses are frequently subjected to cyclic loads stemming from geological processes (like tectonic movements), rock engineering applications (e.g., drilling and blasting), seismic activities (such as earthquake rupturing and volcanic eruption), etc. (Bagde et al., 2005; Haimson, 1978; Xiao et al., 2010). Therefore, characterizing the properties of rocks under cyclic loading conditions is of great significance to underground tunneling and excavation, the extraction of hydrocarbon resources and geothermal energy, the evaluation and maintenance of rock structures, and so on (Cerfontaine and Collin, 2018). Since elastic waves are an effective and efficient tool for monitoring and characterizing subsurface rocks, understanding elastic wave behaviors in rocks under various stress states has been one of the hotspots in geophysics and geotechnics (Barton, 2006; Winkler et al., 1979).
Is there a Universal Rock Mass Classification System?
Authors: Ambah E. , Elmo D. 
Published: August 2024

ABSTRACT:
This paper examines the consequences of subjectivity on universal design methodologies, and emphasizes the need for a cohesive and globally accepted rock mass classification (RMC) framework to foster innovation and efficiency in rock engineering projects. Challenges posed by varied rock mass classification systems and core logging practices complicate the task of data collection and preparation for emerging technologies. Integrating new technologies into rock engineering relies heavily on quality, standardized data. Inconsistencies in terminology, measurement standards, and emphasis on specific rock characteristics can introduce biases which will hinder the development of robust designs. This paper examines the importance of overcoming data preparation hurdles in order to utilize the full potential of new technologies in rock engineering. By unravelling the intricacies of this multidimensional problem, this study provides a foundation for discussions on standardization, collaboration, and innovation within the field, ultimately paving the way for more reliable and efficient rock engineering practices on a global scale. This research aims to provide insights that will contribute to the overarching goal of developing universal design methods for rock engineering while addressing the current challenges of data preparation in rock engineering.

1. INTRODUCTION
In the past few years, the field of Artificial Intelligence has flourished. Numerous, unrelated industries have adopted machine learning to improve workflow, worker safety and productivity (Patel et al., 2021). Interest in artificial intelligence models for applications in the Rock Engineering field has increased significantly in recent years.
Artificial Intelligence (A.I.) was defined by John McCarthy (2004) as "the science and engineering of making intelligent machines, especially intelligent computer programs. It is related to the similar task of using computers to understand human intelligence, but AI does not have to confine itself to methods that are biologically observable". To this end, various models have been developed and deployed for Rock Engineering applications such as using Convoluted Neural Networks (C.N.N.) for optical rock fracture mapping (Azhari et al, 2021).
Longwall-Induced Shale Gas Well Casing Deformations and Stresses-Critical Effects of Geologic and Geometric Parameters
Authors: Su W. H. , Zhang P. 
Published: August 2024

ABSTRACT:
This paper summarizes geo-mechanical findings from the ongoing Gas Well Stability research at the National Institute for Occupational Safety and Health (NIOSH)-in particular, the critical effects of geologic and geometric parameters on longwall-induced gas well casing deformations and stresses. Overburden geology is one of the most important factors affecting the longwall-induced casing deformations and stresses. The large contrast of bending stiffness at the soft-to-hard rock interfaces has been found to induce large casing deformations and stresses. Overburden depth to the mining seam is also an influential factor. Shallow overburden depth induces large horizontal displacement and resulting casing deformation and stress, due to smaller longwall-induced vertical pressure. Deep overburden depth induces large longwall-induced vertical pressure, which tends to limit longwall-induced horizontal movement. Strata dip would magnify longwall-induced deformations by 20% for each degree of strata dip with down dip longwall excavation. The gas well setback distance is a critical geometric parameter. The effect of longwall-induced deformation decreases exponentially as the setback distance increases. Longwall-induced casing deformation and stress will be mitigated or totally uncoupled if the production casing is uncemented. Longwall-induced fracture zone height is linearly propositional to the panel width.

1.I NTRODUCTION
Over 2,000 unconventional shale gas wells have been drilled through active and future Pittsburgh Seam coal reserves in Pennsylvania, West Virginia, and Ohio. These unconventional gas wells, whether tapped into the Marcellus or Utica formations, contain very high gas pressure and volume. Strata deformations associated with underground longwall coal mining could induce stresses and deformations in the shale gas well casings, which in certain situations could compromise the mechanical integrity of the production casing. Damaged production casing could potentially introduce high-pressure, high-volume explosive gas into underground mine workings to jeopardize underground miners' safety and health.
To provide critical scientific data to the stakeholders, which includes the Mine Safety and Health Administration, Pennsylvania Department of Environmental Protection, West Virginia Department of Mine Safety and Training, Ohio Department of Natural Resources, coal operators, and gas operators, NIOSH initiated a gas well stability research program in 2016 to evaluate the effects of longwall-induced deformations on shale gas well casing integrity under deep, medium, and shallow covers. This paper summaries important findings from the ongoing NIOSH Gas Well Stability research; in particular, the important geo-mechanical research findings on overburden geology, overburden depth, strata dip, gas well setback distance, gas well casing cementing alternative, and longwall-induced fracture zone.
Assessment of Subsurface Ice-Based Thermal Energy Storage: THM Coupled Geomechanical Study
Authors: Tounsi H. , Zhang Y. , Rutqvist J. , Birkhozler J. 
Published: August 2024

ABSTRACT:
Ice-based thermal energy storage systems, utilizing both sensible and latent heat capacities of water, have achieved successful commercialization and are currently operational in numerous installations worldwide. However, conventional chilled water and ice-based energy storage systems often necessitate substantial space to store significant quantities of cooling energy. To address this limitation, the subsurface emerges as a promising solution. Nevertheless, the freezing of the ground introduces potential alterations in its behavior, leading to changes in pore pressure and ground movement.
In this study, the TOUGH multiphase flow code was enhanced by incorporating water/ice phase change capabilities and subsequently validated against analytical and experimental data. Our investigation focused on the subsurface as a potential storage site for ice, taking into account the impact of ground permeability, spacing between freezing pipes, freeze/thaw damage, and refrigerant temperature. Numerical simulations using a Thermo-Hydro-Mechanical approach were conducted over a 10-year period, representing 10 cycles of seasonal freeze/thaw, to comprehensively assess the performance and long-term stability of a generic subsurface ice storage system.

1 INTRODUCTION
Amid the global push for sustainable energy solutions, the reliability of renewable sources like solar and wind power is undeniable. However, their intermittent nature highlights the urgent need for efficient energy storage to balance clean energy supply and demand. This paper focuses on addressing the demand for cooling in hot regions, driven by rising temperatures due to climate change. Among various energy storage technologies, ice thermal storage has shown promise for building cooling at a district scale (Chan et al., 2006; Gang et al., 2016). This method typically involves chilling a glycol solution, circulating it through coils immersed in a water tank to freeze the water during off-peak hours, and then thawing the ice for cooling during peak hours.
Despite the proven effectiveness of ice thermal storage, challenges arise when integrating renewable energy sources into the freezing process, particularly in urban areas due to space constraints (Yan et al., 2016). To address these challenges, this study explores the concept of subsurface ice-based thermal energy storage. This innovative approach involves installing underground freeze pipes through which a glycol solution circulates, allowing the ground to freeze in winter and extracting the stored cold energy for air conditioning in summer.
Effect of Thermal Cycling on Cemented Sandstone in Relation to CCS
Authors: Smith H. , Soldal M. , Grande L. , Griffiths L. 
Published: August 2024

ABSTRACT:
As widespread Carbon Capture and Sequestration becomes more relevant, challenges related to thermal cooling upon injection and the potential for significant stress perturbation needs to be accounted for in geomechanical modelling. The current work shows an example of how temperature fluctuations related to CO2 injection can affect the stress changes within a reservoir using a stiff cemented sandstone analogue for deep reservoirs, and further demonstrates how a laboratory test program can be efficiently used to better define thermal aspects of typical geomechanical parameters such as Young's moduli and Poisson's ratio. The current program has shown how elastic moduli can be affected by changes in temperature, and how these changes can affect the estimation of stress changes within a reservoir. This comprehensive triaxial test also displayed a non-linear behavior at lower effective radial stresses during temperature reduction, which can be related to plastic deformation achieved during cooling.

1. INTRODUCTION
As carbon capture and Sequestration (CCS) has gained the public's attention, the necessity to demonstrate that CCS can be deployed safely is key to make CCS an accepted solution as a contribution for reducing global emissions. To predict the reservoir response and ensure safe operations, geomechanical models are used to determine the influence of pressure and temperature change due to injection on the in situ stress conditions.
To provide accurate predictions, one of the first steps will be the production of relevant laboratory data to both populate numerical models with the relevant parameters, and to validate these models through laboratory experiments simulating pressure and temperature changes expected due to injection.
These models will need to accommodate reservoir responses to typical challenges related to CCS. Thermal effects play a significant role in the geomechanical behavior of reservoirs during CCS operations, where cool CO2 is injected into a warmer reservoir. The resulting changes in temperature lead to contraction of the rock matrix and modification of the stress state (Fjær, 2008; Søreide et al., 2014; Thompson et al., 2021). In sandstone reservoirs, cooling is expected to lead to reduction of effective horizontal stress due to thermal contraction of the rock (Søreide et al., 2014). This reduction in horizontal stress can potentially lead to a more critical stress-state. To understand and predict the influence of temperature on stress in the reservoir, it is critical to determine the relative parameters that may be used to model the influence of cooling.