bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Resolution Fluid Flow Simulation in X-Crossing Rough Fractures
Authors: Ifrene Ghoulem E. H. , Egenhoff Sven , Pothana Prasad , Nagel Neal , Li Bo 
Published: September 2023

ABSTRACT
Modeling of fluid flow in rock fractures is a key issue in answering numerous geoengineering problems in the fields of geophysics, reservoir engineering, rock mechanics, to geothermal processes. Although fluid flow in single fractures has been extensively studied in the last 7 decades, fractures commonly seen in fractured reservoir systems intersect each other forming complex geometric structures. Such fracture networks likely affect fluid flow behavior and solute transport. To investigate the impact of geometric characteristics of connected rough-walled fractures with an X junction shape on linear and nonlinear fluid flow behaviors, a sensitivity analysis was carried out by conducting a series of numerical fluid flow simulations on X shape fractures, generated by scanning real rock fractures with distinct roughness (low, medium, and high), intersecting angles, and apertures. The fluid flow through these fractures at different flow rates was simulated by solving Naiver-Stokes equations. The results show that tortures paths and the formation of eddies are more accentuated on the rough fracture than the smoother ones, and the tortuosity of the streamlines is related to the roughness and the geometric characteristics of the intersection. Simulation results of the different models were compared, which show that the intersection significantly impacts the relationship between the hydraulic gradient and the flow. Therefore, the pressure gradient increases with the decrease of the intersection angle especially for low aperture and rough cases.

INTRODUCTION
Understanding fluid flow through a fractured rock mass has great importance to numerous underground industrial activities, such as geothermal extraction (Zhao, 2016), CO2 storage (Catherine Noiriel et al., 2013), oil and gas exploration (Bo Li et al., 2016), underground oil storage (Qiao et al., 2017; Wang et al., 2015), and hydraulic fracturing (Blanton TL,1982).
It is important to measure the impact of roughness to improve the performance of large-scale models since most existing large-scale models still rely heavily on simplified smooth parallel-plate models and related models for natural rock fractures with rough walls (Zimmerman et al., 1992; Zimmerman and Bodvarsson, 1996; Ge 1997; Bodin et al., 2007; Zhao et al., 2013; Wang et al., 2015).
Assessment of Empirical Methods-Based Pillar Strength Estimation Through Numerical Modelling
Authors: Cammarata G. , Elmo D. , Brasile S. 
Published: September 2023

ABSTRACT
Over the past decades, many pillar strength relationships have been formulated from empirical observation of stable and failed case histories. These empirically derived equations are still widely adopted as a general technique for estimating pillar strength and simplified methods for evaluating the pillar stress (i.e., tributary area method). These generally accepted assessment methods might result in non-fully optimized solutions in terms of safe and, at the same time, economical designs. Numerical methods provide a better alternative to evaluate the mechanical behaviour of pillars in the context of progressive failure and, in turn, for a proper definition of the safety margins. In this paper, we propose using numerical modelling to determine the pillar strength through 3D analyses. An advanced constitutive model (Hoek-Brown with softening) is adopted to predict brittle mechanisms in rock masses. The results are compared with those obtained through empirical methods, providing insights about the implications of adopting empirical pillar design methods.

INTRODUCTION
In mining excavations, rock pillars are commonly adopted in most underground mining methods to support adjacent underground openings and thus guarantee the stability of the rooms for extracting the ore in a safe working environment. A system of pillars is designed to provide a suitable factor of safety that relates the pillar strength, defined as the maximum resistance to the axial compression, to the pillar stress.
Over the past decades, stone mine pillars have been the subject of many studies that have led to the formulation of empirical strength equations (e.g., Hedley and Grant 1972; Von Kimmelmann et al. 1984; Krauland and Soder 1987; Potvin et al. 1989; Sjoberg 1992; Lunder and Pakalnis 1997; Walton and Sinha 2021), which generally refer to square pillars. However, several equations have been developed to predict the increase in strength from a square to a rectangular pillar (e.g., Mark and Chase 1997; Esterhuizen et al. 2011), which also include the effect of pillar length. Although all these empirically derived equations should only apply to design conditions consistent with the database supporting their development, they are still widely adopted as a general technique. Due to the complexity of the engineering problem, which is usually associated with rock fracturing and spalling failure process as the mine depth increases, it is difficult to consider which empirical method is the most appropriate. For such a reason, the significant limitations of the empirical methods have received the attention of several authors (e.g., Sinha and Walton 2019; Wang and Cai 2021; Wessels and Malan 2023) and should be carefully considered when pillar design is carried out.
Workflow for Discontinuity Set Characterization in Rock Masses Using 3D Digital Outcrop Models Derived from UAV Survey in an Iron Ore Mine Slope
Authors: Ribas G. P. , Gontijo A. A. , Matos A. R. , Gomes L. , Silva J. , Barros M. , Cacciari P. P. 
Published: September 2023

ABSTRACT
The rapid development of unmanned aerial vehicle (UAV) technology has enabled numerous open pit and underground mining companies to leverage this tool for slope stability assessment and the construction of geotechnical models. The use of aerophotogrammetry techniques with UAVs enables geotechnical and geological engineers to work in a safe and agile manner, maintaining a safe distance from hazardous areas. These techniques can identify the orientation of discontinuities in the rock mass, which is vital in evaluating slope stability. Moreover, new semi-automatic extraction techniques for discontinuities in rock masses allow aerophotogrammetric models to be utilized in geomechanical characterization in a more accessible and efficient way. With the use of 3D point cloud analysis software, the primary sets of discontinuities in a rock mass outcrop can be identified, measured, and utilized in various applications. This study presents a methodology for constructing three-dimensional models of a mine slope and utilizing them to determine the primary orientations of discontinuity sets using images captured through UAV survey. The method comprises four primary steps: (i) UAV flight and image capture, (ii) 3D point cloud construction using SfM technique, (iii) detection and measurement of discontinuities, and (iv) statistical data analysis.

INTRODUCTION AND OBJECTIVES
The collection of structural data is a critical task in characterizing rock masses and evaluating slope stability in mining. Traditionally, this task is carried out manually using a geologist's compass, exposing the technical team to various risks. Additionally, many areas are inaccessible to the team, resulting in data gaps.
With the advancement of aerial surveys using unmanned aerial vehicles (UAV) and the structure from motion (SfM) image processing technique, 3D point clouds (3DPC) can be generated from RGB images taken by UAVs, as described by Francioni et al. (2019). This 3DPC can be used in various applications, such as terrain analysis, slope stability, and hazard monitoring, which can reduce risk exposure and provide crucial information to the technical team, as discussed by Papathanassiou et al. (2020).
Effects of Fractures on Seismic Wave Propagation Path: Laboratory Studies
Authors: Madenova Y. , Suorineni F. T. , Mukhamedyarova Z. 
Published: September 2023

ABSTRACT
In this study, discrete physical models using different blocks and hole sizes, and backfill characteristics are used to simulate changing underground mine conditions due to mining activities. In addition to voids and various backfills, this study includes fractures to investigate their effect on seismic wave propagation. The fracture systems in concrete blocks with sizes of 150 mm, 225 mm, 300 mm, 375 mm, and 450 mm were created by filling holes of various diameters in the concrete cubes with a static cracking agent (SCA). This process mimicked blast and stress-induced fracturing in the underground mine environment. AE measurements indicate that AE signal attenuation from fractures is more severe than due to backfill and in presence of fractures, backfill did not create a favorable environment for AE wave propagation toward receivers. AE signal arrival time to receivers mainly depends on the direction of AE wave propagation rather than the geometrical arrangement of the sensors in the presence of the voids, backfills, and fractures. AE signal arrivals to receivers are governed by the subsurface variability, Snell's law, and AE wave propagation direction. These factors should be considered to enhance the current source location approaches in microseismic monitoring systems.

INTRODUCTION
A major concern in deep underground mines is seismicity and rockburst of which frequency increases with mining depth. These phenomena significantly influence mine safety, productivity, and operating costs. Considering the undesirable impacts and consequences of seismic activities and rockbursts, their forecasting and control play a critical role in deep underground mines. Seismically active mines rely on microseismic monitoring systems to predict microseismic events and to minimize the exposure of personnel and equipment to seismic hazards. The microseismic monitoring system is able to identify, locate and quantify the mine seismicity enabling a better understanding of the rockburst mechanism.
Brittle-Ductile Transition and Correction to Brittleness Index of Deep Shale Gas Formation
Authors: Kong L. , Jiang S. , Li Y. , Song G. 
Published: September 2023

ABSTRACT
The brittle to ductile transition phenomenon in deep shale gas formations is a challenge for hydraulic fracturing and is of interest from both a geological and an engineering perspective. A series of uniaxial and triaxial compressive experiments at increasing confining pressures was conducted on Longmaxi shale core plug samples from a deep gas reservoir (&gt;3500m). The stress-strain curves at confining pressure &lt;45MPa show the shale samples experience linear elastic response and brittle failure. The peak strength increases greatly as confining pressure increases. At 100MPa confining pressure, approximately the in-situ horizontal stress of the shale samples, the test demonstrates the existence of an elastic-plastic response and high residual strength after peak failure, indicating ductile property. The brittleness index was calculated from elastic properties and strength properties, respectively, and the correlation model was established with respect to the confining pressure. The correlation model is used to modify the log-based brittleness index from elastic response. This model reflects the ductile property of a deep shale gas formation subjected to brittle-ductile transition. This method can be applied to the nearby wells that have no drilling cores and improve the accuracy of the brittleness index evaluation.

INTRODUCTION
Deep shale reservoirs will be a source of oil and gas resources in the upcoming decades as shallow reservoirs are steadily depleted (Ma et al., 2021). On the other hand, developing and utilizing natural gas is an important step towards the carbon-neutral goal as the world is transferring from conventional oil to clean energy (Wang et al., 2022). Fuling Area is the one of the most commercialized shale gas fields in China and the Longmaxi shale formation has been studied extensively in the past decade (Nie et al., 2020). Yet, studying geological features in deep formation (deeper than 3500 meters depths) bring up more challenges in tectonics, sedimentology, and diagenesis. Particularly, stimulation by hydraulic fracturing didn't provide detail to the level of expectation which impacted gas production (Zhao et al., 2022). The critical problem lies in the geomechanical properties and brittleness evaluation.
Investigation to Integrated Geomechanics of Casing Deformation and a New Technique: A Case in Deep Gas Shale of Sichuan Basin, China
Authors: Zhu Haiyan , He Xinru , Li Yang , Tang Xuanhe , Huang Chuhao , Zeng Bo , Song Yi 
Published: September 2023

ABSTRACT
To investigate the mechanism of casing deformation and failure during volumetric fracturing of deep gas shale in Sichuan Basin, we put forward targeted comprehensive prevention and control measures. Based on the idea of geological-engineering integration, a three-dimensional geo-mechanical model is established, which coupled the formation - cementing sheath - casing during hydraulic fracturing of deep shale reservoir. Taking TB01 well as an example, the correlation between induced stress, cementing quality, fault or natural fracture dislocation and other factors in the process of hydraulic fracturing was analyzed. The main cause of fault or natural fracture dislocation under the influence of multiple factors is determined firstly. Then, the effectiveness of fracturing scale controlling, casing and cementing quality improvement and other process measures are investigated. Finally, based on the above study, a novel process and supporting tools for fault pre-slip are proposed in this paper. The feasibility of the process is demonstrated, and the structural parameters of the supporting tools are optimized. Taking Luzhou as an example, it provides theoretical and technical support of deep shale gas in safety and high efficiency.

INTRODUCTION
China has abundant reserves of shale gas with great development potential. Speeding up the development of shale gas is of great significance for relieving the pressure on natural gas supplies and adjusting energy structure. Shale gas is developed according to the causes of casing deformation, many of those who learn to conduct the research, puts forward the effect of thermal stress[1-3], asymmetric fracturing[4-9], the cementing quality [10-15] and fault slip[16-30], etc.
At present, most scholars have recognized that fault activation in the process of hydraulic fracturing may be the main controlling factor leading to casing deformation[17-29], which has been verified by more and more field data. These research understandings provide theoretical guidance for the field, however, casing deformation still occurs from time to time, and there is still a lack of specific measures to solve the problem, which needs further research.
Study on the Collapse Behaviors of a Single Cavitation Bubble Near a Concave Wall
Authors: Wu Xiaoya , Zhang Yiqun , Hui Chengyu , Huang Haochen , Tan Yawen , Li Gensheng 
Published: September 2023

ABSTRACT
The enormous power emitted from cavitation bubbles has been positively utilized in drilling rate improvement and increasingly comes into prominence in oceanic hydrate recovery. Previous studies mentioned that the collapse process of a cavitation bubble near a wall is seriously affected by the wall shape. In present study, the dynamics of a single cavitation bubble near a concave wall with hydrate properties are numerically investigated. The evolutions of the bubble profile varying with the defined parameter θ have been computed. Then, the effect of θ on the bubble volume and collapse time was discussed. Moreover, the cavitation damage towards the concave wall was preliminarily revealed. The simulated results show that the shrinkage process of a cavitation bubble near a concave wall mainly includes a jet penetration stage and a collapse stage. Increasing θ leads to the reduction of bubble shrinkage rate and the extension of collapse time. With the θ varying from 0° to 180°, the pressure at wall center emitted by shock wave increases gradually, while the impinging pressure induced by micro-jet reaches its maximum when θ = 90°. The thermal effect is greatest when θ = 90° due to its higher generated temperature and micro-jet velocity.

INTRODUCTION
Cavitation demonstrates that the vapor bubbles occur in liquid as the local pressure decreases below the saturated pressure value (Brennen, 2014; Franc & Michel, 2006; Zhang et al., 2017). The source of severe erosion on warship propellers, hydraulic pumps and turbines originates from the collapse of cavitation bubble clouds, in which process the instantaneous high pressure and high temperature are generated (Choi & Chahine, 2016; Franc et al., 2011). Generally, when the bubbles collapse in the vicinity of a wall, they will release shock waves and micro-jets with high velocity. Once its aggressiveness exceeds the threshold determined by the material properties, it will cause deformation, pits and craters on the surface of the material (Choi et al., 2014; Hsiao et al., 2014; Pöhl et al., 2015). Although the cavitation phenomenon is undesirable in many hydraulic engineering situations, the extreme energy generated by cavitation bubbles has been positively used in some technologies. For example, the cavitation jet producing cavitation bubble in flows, has been adopted for pipes cleaning (Bukharin et al., 2020; Peng et al., 2018), drilling rate improvement (Li et al., 2002; Li et al., 2005; Li et al., 2007), and metal peening (Soyama, 2020; Soyama et al., 2011; Soyama et al., 2020).
Peak Particle Velocity for Blasting Rock Modeling
Authors: Yang R. , Green S. 
Published: September 2023

ABSTRACT
Blasting mechanisms are a complex coupling of the rock mass properties and the explosive detonation performance as well as the blast design parameters. Both rock mass and explosive properties have parameters that are inherently not well defined. Thus, blast modeling is greatly challenging to predict rock fragmentation, blast vibration, and the broken-rock mass movement. For blast modeling, previous work has shown that near-field signature-hole blast vibration monitoring is an effective method to obtain critical blast model input. In a blast field, multiple charges create nonlinear additive strains at a given point in the rock and time, which further complicates blast modeling. This paper shows how the measured peak particle velocity ("PPV") from the signature-hole blast vibration serves as a key controlling parameter for modelling. Using PPV as the controlling parameter, pressures and strains can be approximated at a point of interest. Rock breakage is then related by simplified approximations to the pressures and strains. The modelling method described in the paper relates all blast design parameters to the PPV induced by multiple charges at a point in the rock. Therefore, using PPV as a key parameter allows blasting models to simulate all blast design parameters and significantly simplifies blast modeling.

INTRODUCTION
Predicting the results of rock blasting has been a long-standing challenge since its inception. However, the complex and dynamic mechanisms of rock blasting remain unclear (Fourney, 2015). The variables affecting the blast results are numerous, including rock mass properties, explosive properties, and blast design parameters. These variables interact in a nonlinear manner, making rock blast modeling more difficult than static or quasi-static rock mechanics modeling.
If a blasting model is built purely based on the first principles of physics, it must involve many parameters related to rock properties and explosives. However, these parameters are often difficult to impossible to measure, which makes it challenging to obtain relevant blast modelling input. Moreover, most of these blast models cannot simulate full blasts and design parameters. Even a single modeling prediction requires a large amount of computing time and can only simulate a small number of blastholes. This forms a major impediment to the engineering applications of blast modelling.
Geothermal Energy Storage: A Conceptual Assessment of Geologic Thermal Storage Systems in North Dakota
Authors: Gyimah E. , Metwally M. , Tomomewo O. S. , Hurtado J. P. , Alamooti M. , Gosnold W. 
Published: September 2023

ABSTRACT
Geothermal energy and Aquifer thermal energy storage can provide beneficial ways of storing energy in excess and providing energy when needed. North Dakota's renewable energy system is impacted by its harsh winters. Geologic aquifer thermal aquifer storage system is a large scale geothermal system that can act as energy storage media. Aquifer thermal storage systems are dependent on heat conductivity of rocks, storage capacity of aquifer, fluid flow, geochemistry and geo-mechanics. The goals of the project are to 1) evaluate the amount of energy that can be stored in deep aquifers; 2) access the amount of energy that is thermally recoverable; 3) monitor changes in geo-mechanical parameters. CMG STARS, a three-phase multi-component thermal and steam additive simulator, was used for the thermal numerical simulation which takes into account the geo-mechanics (thermal dilation and re-compaction). A conventional reservoir with representative porosity and permeability is modelled in CMG and Semi Analytical Model (SAM) was used to calculate the wellbore dynamics involved with geothermal operations. This is used to calculate heat transfer to the surrounding formation and determine our heat loss. Our preliminary results show us the reservoir pore volume dilation re-compaction model changes from cold water injection. The grid block void porosity dilation re-compaction model changes are greatly influenced by grid block pressure.

INTRODUCTION

Geothermal Energy and Aquifer Thermal Energy Storage (ATES)
Geothermal energy refers to the earth's thermal energy that can be converted into electrical energy. Emissions from the geothermal energy industry are substantially low, which is an excellent asset to reaching a low-carbon economy. Hot dry rocks and hydrothermal resources are the primary geothermal energy sources. Water from surface seeps through faults and cracks of earth and is warmed by hot rocks or water is trapped by impermeable layers to create geothermal reservoirs. Sedimentary basins have great geologic and reservoir properties for low-cost energy generation for geothermal energy. Hot water moves from deep sources to shallow reservoirs for hot water geothermal reservoirs. Hydrothermal systems use steam or water for electricity generation. Enhanced geothermal systems extract thermal energy from geothermal resources with lower permeability and fluid saturation. (Grant & Bixley, 2011)(Barbier, 2002)