bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Upscaling in Highly Heterogeneous Rock Masses: Impact on Anisotropy and Subsurface Stress Prediction in the Bone Spring and Wolfcamp Formations of the Delaware Basin, USA
Authors: Cheng L. , Crawford B. R. , Chen H. , Macquaker J. H. , McLendon D. 
Published: August 2024

ABSTRACT:
The unconventional Bone Spring and Wolfcamp Formations are the development focus in the Delaware Basin. However, the high heterogeneity of the reservoir rocks challenges the selection of landing zones and increases the uncertainty of well performance. Estimating faithful elastic properties and predicting stress profiles along the wellbores are key to improve production and stimulation design. We acquire over 3,000 feet of continuous cores from five wells in New Mexico, Delaware Basin. We combine a variety of high-resolution, whole core-based characterization techniques that include hyperspectral and dual energy computed tomography imaging, ultrasonic velocities, and scratch index profiling, to quantify intrinsic, fine-scale variability in vertical transversely isotropic elastic properties indicating Young's modulus and Poisson's ratio perpendicular and parallel to bedding. Geomechanical averaging of this thinly bedded medium is then upscaled to a petro-mechanical facies scale for geological modeling and stress prediction. Elastic anisotropy as an emergent property of the upscaling process is contrasted with the anisotropy determined from the traditional core-plug based approach. Implications for stress profile prediction are discussed.

1. INTRODUCTION
The Permian Basin of west Texas and southeast New Mexico constitutes the largest oil reserve and the highest producing oil field in the United States. The component Delaware Basin to the west incorporates significant development in the Bone Spring and Wolfcamp Formations. The Bone Spring Formation represents a mixed siliciclastic-carbonate succession deposited as sediment gravity flows under cyclical sea level fluctuations (Montgomery, 1997; Blake, 2020). Due to the cyclic sedimentation associated with changing sea level, the Bone Spring Formation can be subdivided into 1st, 2nd, and 3rd Bone Spring carbonates followed by sand units. The underlying Wolfcamp Formation records deepwater deposition of organic-rich mudstones interbedded with calcareous mudstones, calcareous siltstones, carbonates, and argillaceous mudstones that were deposited within mixed carbonate-siliciclastic fan systems (Yeap, 2021). In general, the Wolfcamp Formation can further be separated into A, B, C, and D units (Gaswirth, 2017). Both formations consist of mixed sediment gravity flow and suspension sedimentation deposits which often exhibit thin beds and facies resulting in high heterogeneity (Bievenour and Sonnenberg, 2019). Thin bed analysis is critical for reservoir property characterization but can be challenging when heterogeneity regularly exists at length scales below wireline log resolution (2 – 3 feet). Therefore, acquiring high-resolution measurements can significantly assist in identifying and quantifying thin-bed heterogeneity and properties assignment.
Optimizing Overall Slope Angle and Net Present Value (NPV) Through the Utilization of Ground-Based Pit Wall Monitoring Data
Authors: Quansah E. A. , Anani A. , Adewuyi S. 
Published: August 2024

ABSTRACT:
In open pit mining operations, the decision to select the ultimate pit slope angle is critical due to its significant impact on safety and economic outcomes like net present value, mine life, operational costs, and safety risks. Recognizing the variability in rock properties and the discrepancies between planned and actual conditions, this paper introduces a robust framework that aligns the monitoring of pit wall conditions with optimizing pit slope angles. We proposed the use of data from the geotechnical model to conduct stability analysis with Rocscience software, combining real-time radar and prism system data. This adaptive approach aims to enhance the stability and safety of mines while optimizing economic returns. Additionally, it utilizes the Whittle software for determining the optimal pit slope angle, balancing safety requirements with operational cost efficiencies. This comprehensive framework promises substantial benefits, including reduced risk of slope failure, extended mine life, and decreased mining costs. Ultimately, by incorporating this methodology into the mining operation decision making process, significant improvement will be seen in safety and economic profitability, marking a significant advancement in open-pit mining management. This paper highlights the importance of adaptive, data-informed decisions in enhancing both the economic viability and safety of mining operations.

1. INTRODUCTION
Rock slope failure is one of the main hazards in open-pit mines. This causes about 14% of injuries and deaths of workers at various mines around the world (Aleotti & Chowdhury, 1999). This highlights the critical need for continuous innovative research and solutions aimed at mitigating such risks. It also suggests the need to keep safety a top priority for safe ore production and profitability. While working under safe conditions, it is also germane to consider improved ore recovery for profit maximization. In either way, optimizing pit angle may improve slope stability and increase profit by reducing stripping (Read & Stacey, 2010). However, this task necessitates a comprehensive understanding of the geotechnical parameters and the dynamics of slope movement.
Sub-Level Caving Blast Modelling to Determine the Impact of Blast Design Parameters and Rock Mass Characteristics on Fragmentation
Authors: Khodayari A. R. , Xu C. , Dowd P. , Dare-Bryan P. C. , Metcalfe A. 
Published: August 2024

ABSTRACT:
Sub-level caving (SLC) is a mass mining method that relies on the gravitational flow of blasted ore and the collapse of waste rock. The fine end and the coarse end of blasted particles impact material flow through sublevel interval. Improving blast induced fragmentation has the potential to improve ore recovery, reduce dilution and improve productivity by reducing the remediation of ground support and providing more efficient draw point extraction, while also improving the efficiency of downstream hauling, crushing, and grinding processes. Numerical simulations were conducted using a hybrid finite/discrete element compute engine coupled with a non-ideal detonation model. The model geometries take into consideration the uneven distribution of explosives within each blast due to the fan-shaped rings of blast holes, and the complex environment of blasting into broken ground. The modelling used existing field data from the Ernest Henry Mine to define the blast design, characterize the rock mass, and compare field and modelled fragmentation across a range of explosive densities and burden sizes. Further modelling investigated the influence of discontinuity density in the rock mass on fragmentation.

1. INTRODUCTION
The initial step in the comminution process in metalliferous mining involves the fragmentation of the rock mass containing ore. Typically, this is achieved through methods such as drilling and blasting. The fragmentation size distribution after blasting can have a significant impact on the efficiency of downstream processes such as the hauling of the ore, crushing and grinding (Grant et al., 1995), (Campbell & Thurley, 2017), (Jimeno et al., 1995), (Hamdi et al., 2001), (Aler et al., 1996). Within a sub-level caving operation (Figure 1) finer ore is more mobile and flows faster to the draw point, but it can produce sticky mud or slurry in damp circumstances. While larger fragments or boulders can block the flow of material and produce hang-ups, which are a safety hazard and lead to poor ore recovery (Campbell & Thurley, 2017). Determining the optimal fragment size presents a challenge due to the complex interplay of multiple factors associated with blasting parameters, rock characteristics, and operational conditions.
MultiFracSimPPM: A Data-Driven Probabilistic Predictive Model for Hydraulic Fracture Growth from Uniformly and Non-Uniformly-Spaced Perforation Clusters
Authors: Michael Andreas , Kalu Chukwuemeka , Bouabdallah Nassim 
Published: August 2024

ABSTRACT:
The thrust of this study is the assessment of using non-uniform-spaced perforation-clusters (as opposed to uniformly-spaced perforation clusters) in order to promote improved multi-frac growth geometries, by reducing stress-induced interference during simultaneous-HF growth. A probabilistic predictive model (PPM) that integrates empirical data obtained from laboratory-scale experiments is overviewed. MultifracSimPPM employs published results from multi-frac growth experiments on transparent gelatin blocks with single-phased perforations and various perforations-spacing arrays. A realistic and dependable expectation for multi-frac geometry was generated through the implementation of a Monte-Carlo simulation scheme, assessing such "limited-entry" technique. Statistical bias is introduced into random probabilistic distributions using this empirical dataset by MultifracSimPPM, resulting in geometric profiles that correspond to experimental findings that disprove the initial hypothesis (non-uniformly-spaced perforation clusters did not perform better than uniformly-spaced perforation clusters). Integrating economic principles could further enhance HF-treatment design, leading to higher post-stimulation hydrocarbon production and improved economics.

1. INTRODUCTION
Multistage hydraulic fracturing (HF) operations in horizontal wells enables hydrocarbon production from unconventional, low-permeability shale formations. The key element of HF modelling remains the prediction of the generated HF growth. When it comes to reservoir stimulation using multistage HF treatments, where many HFs are being "pumped" simultaneously within each frac stage, the problem's complexity increases exponentially. Standard treatment design software do not incorporate "real-world" phenomena, such as dominant HF creation and inactive perforation clusters (Michael, 2022). This work presents a probabilistic predictive model (PPM) that incorporates empirical inputs from laboratory-scale experiments. HF geometry is arguably the most critical element of HF-treatment design, with a number of considerations made for influencing multi-frac growth to optimize production and economics.
Employing random sampling, the algorithm, which is executed in MATLAB, populates output arrays that contain vectors of the expected HF heights and lengths. The statistical probability of occurrence of the corresponding HF-growth dimensions (length and height) in our laboratory experiments is utilized to populate these input arrays. The width of each HF is determined using the "Perkins-Kern-Nordgren" (PKN) geometry model.
Subsequently, the calculated HF length, height, and width are applied to the formation of semi-ellipsoid-shaped HF-growth profiles that illustrate the anticipated final multiple-HF-growth geometry. The homogeneity of multiple-HF growth is likewise quantified by using our novel fracture-geometric-homogeneity index (FGHI), as a metric.
Case Study: Investigation, Analysis and Mitigation of Rock Instability for a Potential Slope Failure in Highly Weathered Granite at Pinto Valley Mine in Arizona
Authors: Ureel S. D. 
Published: August 2024

ABSTRACT:
In the mining and civil engineering industries, slope stability issues have become essential problems to avoid ensuring site safety, maximum ore extraction and limited interruptions in production. Slope failures in mining operations are a cause for concern when dealing with potential safety hazards, accidents and injuries for mining personnel and damage to equipment. Predicting, monitoring and investigating slope failures are pertinent for safe working conditions and should be inspected continuously. A high wall composed of a small top layer of alluvium underlined by highly weathered granite at the Pinto Valley Mine in Arizona expressed warning signs such as rockfall, talus/debris retained on lower benches, tension cracks and displacements on the slope stability radar (SSR) during production adjacent to the slope. Detailed inspections, monitoring and mitigation were immediately initiated following these signs of instability.
If the area of interest is not critical to production, the easiest plan of action would be to leave the material in place and let the slope fail naturally as long it will not cause any safety hazards; however, this is not the case for failure researched in this paper. Mine blasting and production need to continue below the failure due to high grade ore in the vicinity. This can only happen if the failure mechanism is well understood and the rate of displacement is low. This study was performed to understand the mechanisms that triggered the failure, the rock conditions before and after the failure and to show how to proceed with controlled mining procedures in organized manner. This study will show observations before, during and after the slope instability as well as successful mitigation efforts and analyses. The results acquired illustrated that slope instability can be predicted from SSR, the SRR exhibited real time monitoring and provided initiation for mining safety protocols and procedures.

1. INTRODUCTION
Slope stability plays an important role in rock engineering. During the design, construction and post design phases of rock slope stability, engineers and geologists need to pay close attention to the rock conditions within the rock slope to prevent slope failures, protect employees and maintain economic profit. Slope geometry, material properties, and insitu stress conditions need to be investigated in order to understand the potential for rock slides, wedge failures, and other instabilities.
Investigation of the Frost-Induced Shallow Alpine Rockfall Process Using 3D FDEM
Authors: Sun Lei , Grasselli Giovanni 
Published: August 2024

ABSTRACT:
Increasing rockfall activities in alpine areas have been observed under the global climate change circumstance. One widely accepted explanation of the alpine rockfall is that the warming and thawing of ice-rich bedrock permafrost decreases effective shear strength and destabilizes rock substrates in unusual hot summers. However, small but frequent shallow collapses are also widely observed in mountainous areas when the temperature decreases in late autumn or cold winter. The research work presented herein proposes a numerical framework for simulating the frost heaving/cracking process and revealing the related shallow alpine rockfall mechanism, based on the three-dimensional (3D) combined finite discrete element method (FDEM), where complex coupled thermal-mechanical processes at low-temperature are considered, e.g., the heat transfer, water-ice transition, ice-rock interaction, and cracking. Results suggest that shallow collapses are observed when the temperature decreases in late autumn or cold winter. Cracks initiate and propagate in the rock mass, driven by the ice-rock interaction in cold seasons, deteriorate the structure stability and induce shallow rockfall. Knowledge of long-term thermal/water evolution of a rock slope therefore provides valuable insight into progressive rock deformation and related alpine rockfall hazards.

1. BACKGROUND
Increasing rockfall activities in alpine areas have been observed under the global climate change circumstance (Harris et al. 2009; Ravanel and Deline 2011), and are linked to the frost heaving/cracking behavior (Hallet 2006; Draebing and Krautblatter 2019). One wildly accepted explanation of the alpine rockfall is that the warming and thawing of ice-rich bedrock permafrost decreases effective shear strength and destabilize rock substrates in unusual hot summers (Gruber et al. 2004; Hasler et al. 2012). However, small but frequent shallow collapses are also widely observed in mountainous areas when the temperature decreases in late autumn or cold winter (Gruber and Haeberli 2007; Wu et al. 2021). Frost cracking is hypothesized to play an important role in the destabilization of steep permafrost (Matsuoka and Murton 2008), which can be inferred from the evidence that ice is common in fractures of bedrock and the fresh detachment scars of rockfall. Therefore, understanding the frost heaving/cracking mechanism is critical to shallow rockfall disasters in cold regions. To address this knowledge gap, a 3D numerical framework is developed to study the frost heaving and cracking process in fractured rock masses and further investigate the shallow rockfall mechanism based on the 3D FDEM (Munjiza 2004), which takes the advantage of simulating both continuum and discontinuum behavior.
An Investigation of Fault Geometric Effects on Fault Activation Mechanisms in CO2 Storage
Authors: Mortazavi A. , Maratov T. 
Published: August 2024

ABSTRACT:
In response to the escalating greenhouse gas emissions and climate change problem, promising solutions have emerged in the form of Carbon Capture and Storage (CCS) projects, offering potential avenues for mitigating environmental impact. This study explores the behavior of CO2 storage reservoirs and associated fault reactivation mechanisms using three-dimensional (3D) numerical modeling using Distinct Element Code (3DEC). The critical role of the reservoir-caprock interface is highlighted by the vertical displacement measurements from numerical simulation. Proximity to the reservoir-seal contact point correlates with maximum deformation magnitudes of 0.052 m, while the surface level (Z = 0 m) is subject to less significant deformation (0.01 m), indicating favorable reservoir stability. Aligning closely with previous 2D analyses, further parametric studies with real-world data and prolonged observations would be beneficial for validating modeling assumptions.

1. BACKGROUND
For the past couple of decades, CO2 Capture and Storage (CCS) has been consistently recommended and employed in response to the intensified greenhouse gases emission problem. In practice, in a CO2 reservoir, increasing pressure resulting from injection can lead to crack propagation and damage to borehole and seal rock through various mechanisms (Rutqvist, 2012; Zoback & Gorelick, 2012). As pressure builds within the reservoir due to CO2 injection, it can induce stresses in the surrounding rock mass, potentially exceeding the rock's strength. This can lead to the initiation and propagation of fractures, particularly in zones of pre-existing weaknesses such as faults or joints. Large amounts of pressure can cause deformation and compaction of the reservoir rock, leading to subsidence or heave around the borehole. This can result in borehole instability, including casing failure, collapse, or even blowouts. Furthermore, if the seal rock (caprock) above the reservoir is not sufficiently impermeable or strong, increased pressure from CO2 injection can cause it to fracture or deform, compromising its ability to contain the injected CO2. This can lead to CO2 leakage pathways, allowing the gas to migrate towards the surface or into underground rock layers, posing environmental and safety risks. Hence, such a promising solution in the form of CCS requires a safe and efficient storage site design to avoid above-described injection- or sequestration-induced damage that may ultimately lead to the gas leakage.
A Unified Computational Framework for Modelling Rock Failure Evolution: From Progressive Degradation to Catastrophic Rupture and Avalanche
Authors: Wang Liang , Lei Qinghua 
Published: August 2024

ABSTRACT:
In this study, we develop a novel unified computational framework for modelling the evolutionary behaviour of fractured rocks from progressive damage to catastrophic rupture and runout. In this framework, physical laws are coupled with failure criteria to describe the combined effects of time-dependent degradation and strain-driven processes; heterogeneities are considered by the representation of pre-existing fractures and statistical distribution of elasticity in rocks; an implicit time integration scheme is adopted to capture the deformational behaviour across multiple time scales; the particle finite element technique is applied to track the large deformation of rock masses. We demonstrate this computational framework for investigating rock failure evolution in both natural settings and engineering configurations, i.e. weathering-induced rock slope failures and tunnelling-induced rockbursts. We show that the model can realistically capture the complex responses of fractured rocks prior to failure, diverse rupture patterns during the failure, and various mass movement dynamics after the failure. Numerical simulations also indicate the strong control of geological heterogeneities on rock failure evolution. This unified computational framework can serve as a robust and powerful tool to unravel the origin of catastrophic rock failures, assess the risks related to potential extreme geohazards, and develop physics-based early warning systems in practice.

1. INTRODUCTION
The entire history of rock mass failure involves long-term destabilisation processes (Amitrano & Helmstetter, 2006), the formation of ‘system-sized’ fractures (Main, 2000), and the avalanche of failed materials, which are strongly coupled over the space and time domains. More specifically, destabilisation processes could lead to various failure patterns and dynamics, which may further affect the post-failure runout characteristics (L. Wang & Lei, 2023). Therefore, understanding the evolutionary behaviour of geomaterials across multiple time and length scales is of central importance for predicting the timing and magnitude of failure events (Ö. Aydan et al., 1996; Eberhardt, 2008). However, the involved material and geometric nonlinearities have posed a great challenge to developing numerical models for rock mass failures.