bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards an Efficient iPad-Based LiDAR Structural Mapping Methodology for Underground Mines
Authors: Grenon M. , Caron A. , Karampinos E. , Dorion J. F. 
Published: September 2023

ABSTRACT
Structurally controlled instability is a major failure mechanism in underground hard rock mines. From a design perspective, it is important to effectively define the structural regime to assess the potential rockmass failure mechanisms. In a mining context, detailed structural mapping can be challenging due to the large extent of the underground excavations and limited access to the rock face. Structural mapping can be performed using manual mapping approaches or remote sensing techniques. Fixed photogrammetry and terrestrial laser scanning have been used in the past for rockmass characterization. However, these approaches are often time consuming and consequently not widely used in practice for structural mapping in underground mines. Mobile LiDAR systems have been increasingly used for 3D mapping applications. However, it has not been demonstrated that they can be effectively used as mapping tool in the context of a mine in production. This paper presents the results from an underground mapping campaign using a mobile LiDAR scanner approach, an iPad Pro 5th generation, in an arctic mine in northern Canada. A comparison between the results from the developed methodology and manual structural mapping demonstrated significant advantages and remaining challenges in the use of the mobile LiDAR approach for rockmass characterization.

INTRODUCTION
In underground hard rock mines, rock mass instability poses a serious hazard to the safety of personnel and equipment. The structural regime largely controls the mechanical behaviour of jointed rock masses around the underground excavations. Under low-stress conditions, gravity failure of large blocks formed by the presence of rock discontinuities can be a significant hazard. Figure 1 shows a rehabilitated section in the ramp of an operating hard rock mine after a structurally controlled fall of ground in the back. Under these conditions, it is essential to consider the complex structural regime in the design and support of underground excavations. It is, therefore, necessary to adequately characterize the structures in the rock mass using a combination of qualitative observations and quantitative measurements.
Energy Budgeting of Laboratory Hydraulic Fracturing in Granite with Different Viscosity Injection Fluids
Authors: Butt Awais , Hedayat Ahmadreza , Moradian Omid 
Published: September 2023

ABSTRACT
In this study, Barre granite cubes were hydraulically fractured in laboratory, using different viscosity injection fluids. Hydraulic Fracturing (HF) experiments were monitored with real-time acoustic emission (AE) setup which consisted of 16 calibrated Nano-30 sensors. The spectral parameters (corner frequency and low-frequency spectral plateau) were determined for each AE event by fitting the Brune Omega-squared model to the detected AE signals. Seismic parameters such as seismic moment, source radius stress drop, and seismic energy were determined after incorporating the focal mechanisms information determined through moment-tensor inversion. Higher breakdown pressures and fracture propagation times were observed for experiment conducted with higher-viscosity fluid. An inverse relationship was observed between corner frequency and seismic moment, similar to those observed for natural and induced seismicity emitted during large-scale events. The stress drop was found to be fairly constant across a wide range of seismic moment. The seismic moment, stress drop, and seismic energy were significantly higher for the higher viscosity injection fluid. However, the corner frequency and source radius were slightly larger for the lower-viscosity fluid. The seismic efficiency was &lt;&lt;1% (10−6-10−4 %) for both experiments but it was much lower for the experiment conducted with lower-viscosity injection fluid, implying a more aseismic response.

INTRODUCTION
Hydraulic fracturing (HF) is a technique used over the past decades, mainly to increase the reservoir rock permeability for geothermal resource extraction from kms deep crystalline granitic rock. However, HF is a complex phenomenon where it is often difficult to predict the HF growth and the underlying fracture mechanisms. In addition, the HF behavior can be significantly influenced by some key factors including hydro-mechanical properties of the host rock, in-situ stress, and injection parameters (injection fluid rate and viscosity) (Haimson and Fairhurst, 1967). Different viscosity injection fluids have been utilized for the stimulation process mainly to control the HF growth (Ishida et al. 2004). Many previous studies have shown that the attributes of produced fracture network can be drastically different depending on the viscosity of the injection fluid (Tanaka et al. 2020). For example, lower-viscosity injection fluids have been shown to produce more tortuous cracks with many secondary branches (Ishida et al. 2016). Increased stimulated reservoir volume has been shown to achieve with relatively lower-viscosity injection fluids (Warpinski et al. 2005). Understanding the characteristics of the generated HF for different viscosity injection fluids can be crucial to derive appropriate estimations for an efficient HF design.
A New Laboratory Testing Platform to Study Saturation, Swelling/contraction, Desiccation Cracking, and Permeability of Gas/liquid of Engineered Barrier Materials at High Pressure-Temperature Conditions
Authors: Noh D.-H. , Kim S. , Eun J. , Kim Y.-R. 
Published: September 2023

ABSTRACT
This study introduces a new testing platform, which allows an application of high pressure (up to 5 MPa), high temperature (up to 200°C), and simultaneous measurements of vertical deformation, stress, and the permeability of gas/liquid. The test cell is designed for the radial fluid flow to minimize the risk of a preferential leak along the gap between the test specimen and the internal wall of the test cell, which can be prominent during the thermally-induced contraction of bentonite. The testing platform is calibrated by examining the swelling pressure during the saturation process and water permeability of the fully saturated bentonite specimen. After that, a temperature rise, up to 80°C, is imposed on the test cell to monitor the change in the vertical stress. With the partially saturated bentonite specimen, the temperature is raised up to ∼150°C, beyond the boiling point, to induce further desiccation cracks. After that, change in the vertical stress is continuously monitored during the temperature increase and ensuing nitrogen injection to measure the gas permeability. Once the heating period is completed, the test specimen is taken out of the cell and investigated further using the micro-CT machine to capture the distribution of internal desiccation cracks. This study also examines the effect of bentonite reinforcement using inorganic microfibers on the development of desiccation cracks.

INTRODUCTION
Bentonite has been widely used for many engineering applications, such as for the barrier of pollutant transfer, for the stability of engineered construction, etc., due to its characteristics of high swelling pressure, low hydraulic permeability, and adsorption capacity (Smith et al. 1980; Yong et al., 1986; Cho et al. 2000). These characteristics improve even further as the dry density of bentonite increases. Bentonite has also been considered the best candidate as an engineered barrier material for a geological repository of high-level nuclear wastes, including spent nuclear fuels (SNF). Most of the past geological repository concepts suggested the temperature at the canister of SNF should not exceed 100°C to better control the sealing performance of bentonite (Martin et al. 2014; Abootalebi and Siemens 2018). On the other hand, however, several current research efforts are examining the impact of higher temperatures, up to 200°C, on the safety functions of buffer materials, which in turn, can help to achieve shorter cooling times on the ground, more efficient packaging, reduced need for disposal containers and transportation, and smaller facility footprints (Pusch 1980; Gens and Garcia-Fontanet 1997; Gens et al. 2022; Chang et al. 2022).
Analysis of Rotary Steerable Systems Versus Conventional Mud Motors for Vertical and Horizontal Wells in the Caney Formation, Southwest Oklahoma
Authors: Hayes J. , Mayibeki D. , Al Dushaishi M. , Hareland G. 
Published: September 2023

ABSTRACT
Rotary steerable systems (RSS) have transformed directional drilling over the years and are becoming widely accepted throughout the world. RSS technology has been proven to provide the required strength and agility in challenging and abrasive environments as well as provide a higher rate of penetration (ROP) by allowing more weight transfer to the bit. Due to the higher price of RSS, some companies have stayed loyal to the conventional bent housing (CBH) with a performance drilling motor, regardless of the RSS benefits. This paper examines the performance and cost benefits of standalone RSS (SA-RSS), motor driven RSS (MD-RSS), and CBH systems. Three wells drilled in the Caney formation in Southwestern Oklahoma were selected for the analysis. Results showed that using RSS in the 12.25" intermediate vertical section and the 8.75"/8.5" lateral section was more cost-effective than a CBH system. The cost per foot for the CBH was 1.6 to 2.3 times higher than RSS in the vertical section and 1.7 times higher in the lateral section. The RSS ROP was 2.3 to 4.8 times faster than CBH in the vertical section and 1.6 times faster in the lateral section.

INTRODUCTION
In the USA and worldwide unconventional oil and gas wells are pushing the technical limits of existing drilling tools and technology to drill longer horizontal and extended reach wells (ERW), with ERW becoming the mainstream technology. For example, horizontal wells in the United States averaged about 10,000 feet of lateral length in the early 2000s but averaged 18,000 feet in 2019 (USA Energy Administration, 2020). One of the longest ERW wells drilled in the world (offshore Orlan, Russia) was in 2017 and reached a total depth (TD) of 49,000 feet (Slav, 2019). In Oklahoma, the test area for this paper, 1,379 horizontal wells were completed between 2020 and 2022, with an average well length of 18,624 feet and an average perforated length of 8,000 feet (Oklahoma Corporation Commission, 2023).
Mechanical Unit Control of Hydraulic Fracture Geometry
Authors: Gross M. , Dershowitz W. 
Published: September 2023

ABSTRACT
This paper presents a quantitative evaluation of the effect of mechanical stratigraphy on induced hydraulic fracture shape and extent. A detailed geomechanical and hydrodynamic model was built for Hydraulic Fracture Test Site 1 (HFTS-1) in the Permian Basin, considering available geomechanical, geological and geophysical characterization data. This model was then implemented using a discrete fracture network (DFN) approach, to facilitate simulation of induced (tensile) hydraulic fractures, and reactivation of pre-existing natural fractures.

INTRODUCTION
The geometry of natural and induced tension cracks is important to civil, mining, geothermal, and energy applications. According to Griffith Crack theory for failure of brittle materials (Griffith, 1921), natural and induced tension cracks in an infinite, homogeneous, isotropic medium are circular or elliptical. Over 100 years of laboratory studies have provided empirical support for this theory. However, extensive evidence from microseismic monitoring and offset well intersections indicates that the shape of in situ hydraulic fractures vary considerably from the elliptical ideal.

GEOMECHANICAL STRATIGRAPHY
Mechanical stratigraphy refers to the subdivision of a layered rock mass into distinct units (mechanical units) that reflect internally consistent rock properties and styles of deformation (Laubach et al., 2009). In response to tectonic deformation, elements of mechanical layering often control fracture dimensions, terminations and failure mode (Gross et al., 1995, 1997; Ferrill et al., 2014). This mechanical behavior occurs across many scales, and for an unconventional oil and gas field is manifested by hydraulic fracture lengths considerably greater than their heights (Fu et al., 2022), an indication that anisotropic layering limits the vertical growth of hydraulic fractures (i.e., serve as frac barriers).
Observations of natural fractures in outcrops provide insight into the growth and geometry of induced hydraulic fractures in the subsurface (Lacazette and Engelder, 1992; Engelder, 2004; Engelder et al., 2009). Surface morphology preserved on opening-mode fractures ("joints") are manifestations of fracture initiation, propagation and arrest, as demonstrated in Figure 1. In this siltstone bed from the Appalachian Plateau in upstate New York, lineations on the fracture surface converge backwards to the initiation point (yellow dot), about one-third of the way above the bottom of the bed. The lineation pattern shows the joint grew radially in all directions, until it reached the bottom and top of the bed.
Comparison of Constitutive Models for Numerical Modeling of Strainburst Assessment
Authors: Bravo L. , Delonca A. , Robbiano F. , Orellana L. F. 
Published: September 2023

ABSTRACT
Rockburst is one of the most important hazards in underground world, and therefore there is a need to adequately assess their occurrence. While different works allows the mechanism and the hazard to be better understood, there is still work to do to accurately model the phenomenon. In this paper, Mohr Coulomb and IMASS constitutive models are considered into a numerical simulation using FLAC 3D to simulate the occurrence of strainburst. Three rock types are considered, with different strength and fracturing, under different stresses and stress ratio K. In each simulation environment, the strainburst are assessed considering the zone where plasticity is observed (failed zone). The depth of failure measured is compared with well-known published empirical graphs. For K of 1, the results show that the IMASS model presents closest depth of failure estimated by the empirical graphs in high stress environment. For a K different from 1, both models are close to the empirical value, but the IMASS model presents closest values. Moreover, when considering a fractured rock mass, IMASS does not assess properly the depth of failure, but present a better assessment that the Mohr-Coulomb model for higher GSI.

INTRODUCTION
Due to the global increase in ore demand and the exhaustion of superficial resources, the underground mines are going deeper (Wang et al. 2021). As the depth of mining increases, stress induced rock fracturing is inevitable and when stored energy is suddenly released, rocks fail violently, leading to seismic events and rockbursts (Kaiser & Cai, 2012). The large quantity of rockburst events and the severity of those incidents are undeniable evidence that rockburst is a universal and serious problem in the underground world and therefore it is necessary to adequately assess its occurrence (Wang et al., 2021).
A rockburst occurs when a volume of rock is strained beyond its elastic limit (Sepehri et al., 2020). A definition of this phenomenon is proposed by Blake & Hedley (2003), based on the 1984 Mine Safety and Health Administration definition: rockburst is a sudden and violent failure of a large volume of overstressed rock, resulting in the instantaneous release of large amounts of accumulated energy.
Influencing Factors in Rock Cutting Using High Pressure Water Jets Under Submerged Downhole Conditions
Authors: Velmurugan N. , Gerbaud L. , Chambres C. , Naderi S. , Xiang J. , Latham J.-P. 
Published: September 2023

ABSTRACT
Utilizing deep geothermal energy is an important factor in successful transition to a clean, affordable and non-intermittent source of energy. However, high costs due to low drilling performance is a showstopper in scaling geothermal energy. It has been noted that there is a significant drop in the rate of penetration (ROP) in hard crystalline granite rocks averaging between 1-2m/h. These hard rocks are found at depths greater than 4 km and increasing the ROP by a factor of 4 could reduce the drilling costs by 65%. In the framework of ORCHYD (Novel Drilling Technology Combining Hydro-Jet and Percussion for ROP Improvement in Deep Geothermal Drilling) project, we investigate ways to reduce the confining stresses of the underground rock so as the energy required to break the rock will be significantly lower and thus, increasing the ROP. A high-pressure water jet (HPWJ) of up to 250 MPa is generated in the bottomhole conditions to create peripheral groove of a few millimeters to release the rock layer from the surrounding stress regimes – reducing the energy required to break the rock using percussion drilling. Nevertheless, generating the required energy for rock slotting depends on several factors such as nozzle type, output pressure and confining pressure. In this paper, we investigate experimentally the influencing factors of HPWJ for rock slotting in bottomhole drilling conditions.

INTRODUCTION
Scaling geothermal energy is a potential solution in serving our transition needs to a clean, sustainable, non-intermittent and renewable energy source. However, to effectively utilize this energy source, it is required to drill deeper wellbores than previously done in the oil and gas industry. On an average, it is required to drill to depths greater than 4 km to achieve a temperature of above 150 °C in the reservoir rocks to be useful for electricity generation. With nearly 50% contribution to the geothermal exploration, very high drilling costs is a showstopper in making geothermal truly scalable. A majority of the drilling performance, measured as rate of penetration (ROP) in hard crystalline rocks found at such depths is 1 − 2 m/h, e.g., Soultz-sous-Forêts in France (Baujard et al., 2017), and our study shows that increasing ROP by a factor of 4 can reduce the total drilling costs by up to 65%.
Brittle Creep and Associated Acoustic Emissions in Granite Under Unconfined Compression
Authors: Zafar Sana , Hedayat Ahmadreza , Li Bing Q. , Moradian Omid 
Published: September 2023

ABSTRACT
Time-dependent processes in rock govern its long-term behavior hence understanding of these processes is of great importance especially for long-lasting surface and underground structures. Results from conventional creep experiments have shown that three stages of creep (trimodal creep curve) exist for brittle materials. The first stage is the primary stage where the strain rate is inversely proportional to time. In the secondary stage, partially reversible strain occurs in which the strain rate is small and constant. The final stage is the tertiary stage where accelerated strain rate occurs, causing the failure of the rock. It is hypothesized that Acoustic emission (AE) can be used as a proxy to identify the transitions from one stage to another in creep; however, the different focal mechanisms of the fractures produced in the three stages of creep in brittle rocks have not been discussed in detail. The study presented in this paper aims at investigating how AE signatures can monitor the brittle deformations during the three stages of creep and its correlation with the mechanical observations, so that these AE signatures can be used to gain important information in the field. Creep experiments were conducted on double-flawed prismatic Barre granite specimen in the laboratory under uniaxial compression to investigate the temporal and spatial evolution of the AE events during the primary, secondary and tertiary stages of creep. Results illustrated that brittle creep in granite follows the Omori's law and inverse Omori's law in the primary and tertiary creep regimes, respectively. Non-double-couple (NDC) sources were the dominant failure mechanisms in all stages of creep. These results can be of great importance as continuous and non-destructive monitoring of structures in rock can serve as precursory indications of instability of the rock engineering structures as well as in the analysis of earthquake aftershocks and recurrences.

INTRODUCTION
Fracturing in rocks can happen over time; hence, it is important to understand the microcracking mechanisms of time-dependent deformation in rocks. The analysis of time-dependent effects is significant in multiple areas, including the study of seismic hazards like earthquake recurrence and aftershocks (Scholz in 1968). It is also crucial in evaluating the long-term stability of rock engineering structures, such as tunnels, mining rooms and pillars, rock slopes, and nuclear waste repositories (Diederichs and Kaiser 1999, Nara et al. 2010, Paraskevopoulou et al. 2018, Zhang et al. 2020, and Zhao et al. 2022). Moreover, time-dependent effects also have a significant impact on the exploration and utilization of resources such as oil and gas reservoirs and enhanced geothermal systems (EGS) (Demarest 1976; Cornet 2007).
Enhancing Drilling Performance of Mud Hammers by Combining High Pressure Water Jets Slotting
Authors: Gerbaud L. , Jahangir E. , Velmurugan N. , Sellami H. , Cazenave F. 
Published: September 2023

ABSTRACT
Geothermal energy is a leading candidate in fulfilling our transition efforts to a clean, sustainable, non-intermittent and renewable energy source. However, high drilling costs act as a showstopper in geothermal exploration. One of the main factors contributing to this high price is the drop in drilling performance when drilling through hard crystalline granite rocks that are usually found at depths greater than 4 km. Studies show that increasing the drilling performance by a factor of 4 with respect to the current drilling rates of 1-2 m/h can reduce the drilling costs up to 65%.
Percussion drilling using down the hole (DTH) hammer has proven to be efficient in drilling through hard rocks. In ORCHYD project, we combine high-pressure water jet (HPWJ) with a DTH hammer to increase the rate of penetration (ROP) by a factor of 3 to 4. The HPWJ creates a peripheral groove in the rock surface facing the drill bit. This peripherical groove of few millimeters is expected to release the rock surface from the surrounding confining stress regimes – requiring lower energy to break the rock using percussion drilling. It is also expected that the free surface created by the groove aids in reflecting the waves created during percussion. A DTH mud hammer is modified to allow the flow of HPWJ through the hammer body and redirect it to the periphery of the drill bit. The prototype developed in this work was tested on a laboratory scale drilling test rig under realistic downhole drilling conditions. At the current stage of the project, it is demonstrated that slotting peripheral grooves using the HPWJ improves the ROP of the hammer drilling system by a factor of 2 to 2.5.

INTRODUCTION
Deep geothermal energy is a promising and increasingly important source of energy production worldwide. Geothermal electricity production is particularly attractive for both rich and poor economies due to its ability to generate both heat and electricity, which are in high demand. Enhanced Geothermal Systems (EGS) are becoming more popular as they allow for combined electricity and heat production at geothermal power plants (Angelone (2014)). However, drilling operations are a major component of the total project cost, representing up to 40% of the total cost (Angelone (2014)). For a 3 km well, the cost can reach up to 15 M€ (Angelone (2014)), which makes it challenging to extract geothermal energy in an economically viable manner.