bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on the Mechanism of Wellbore Stability and Drilling Fluid Technology Countermeasures in Ultra-Deep Composite Salt Formations in the Tarim Basin
Authors: Zhang Zhen , Fang Zheng , Li Jiaxin , Sheng Yong , Zhou Bo , Zhao Li , Lu Yunhu 
Published: August 2024

ABSTRACT:
In the Tarim Oilfield, drilling encountered the Cambrian strata's composite salt layer, resulting in significant wellbore narrowing and collapse. The lithology of the composite salt layer primarily consists of salt and gypsum interbed, exhibiting complex and variable features. Given the recurring drilling incidents, it is imperative to investigate wellbore instability mechanisms within these composite salt layers and adjust related drilling fluid techniques. This paper analyzed the engineering properties of composite salt rock, carried out experiments on physical and chemical properties and rock mechanical strength, and elucidated the control mechanism of wellbore stability of composite salt rock; experiments were carried out on the dissolution rate and creep characteristics of salt rock, and a model for characterizing the density and chlorine content of drilling fluids for maintaining the wellbore stability was set up. Model analyses and on-site verifications were carried out. The study results show that the composite salt layer belongs to the wellbore stability mechanism controlled by the combination of dissolution and creep in water; the appropriate drilling fluid density and chloride ion concentration can prevent the dissolution and creep of the composite salt layer. By utilizing the appropriate density of undersaturated brine drilling fluid and fine-tuning the chloride ion concentration, the salt rock's dissolution rate and creep rate in the wellbore can be effectively balanced, and the wellbore stability can be improved.

1. INTRODUCTION
Wellbore instability poses a significant global technical challenge in drilling engineering [1]. Salt and gypsum layers are common in both onshore and offshore deepwater oil and gas drilling [2-3]. During drilling operations, especially in the case of composite salt layers, the variable lithology and complex mechanical, physical, and chemical properties exacerbate the issue of wellbore instability, leading to incidents such as narrowing, enlargement, collapse, and sticking [4-5]. Consequently, both domestic and international scholars have conducted extensive research on collapse prevention drilling fluids for salt and gypsum layers, leading to the development of relatively mature saturated and undersaturated brine drilling fluid systems [6]. These advancements have contributed to alleviating the complexities encountered in downhole operations. However, due to limitations in research approaches and the focus on specific regions, as well as the inherent complexity and variability in lithology and structure of salt and gypsum layers across different areas [7], the issue of wellbore instability in composite salt layers remains unresolved.
Preliminary Blast Fragmentation Modeling in an Underground Aggregate Operation
Authors: Shields L. , Calnan J. , Silva J. , Maldonado E. , Agioutantis Z. 
Published: August 2024

ABSTRACT:
The availability of fragmentation models for underground mine-to-mill optimization is fundamental, given that fragmentation models establish which blasting parameters can be manipulated to produce a desired particle size distribution. Given the ever-changing conditions in which mining takes place (geology, stress conditions, mining procedures, etc.), any applicable model must be flexible, adaptable, and dynamic to provide a range of predictions with acceptable accuracy. This paper discusses the results and model validation of using multivariate regression analysis to analyze blast fragmentation data from an underground aggregate operation. These are the initial results with respect to the development of a probabilistic model for underground bench blasts that predicts the resultant particle size distribution.

1. INTRODUCTION
In underground mining, optimizing blasting practices to achieve the desired particle size distribution (PSD) is crucial for enhancing downstream processing efficiency, energy consumption reduction, and overall ore recovery (Fuerstenau & Han, 2003). Traditional approaches to blast design and fragmentation modeling in surface mining operations have been well-established (Cunnigham, 1987; Kuznetsov, 1973, Lilly, 1986; Ouchterlony, 2003). However, the unique challenges posed by underground environments, including confinement conditions, excavation stability, and limited visibility, demand innovative solutions (Siddiqui et al., 2009; Demenagas, 2008).
The efficiency of aggregate quarry operations heavily relies on optimizing blasting processes, which directly impact subsequent stages of the mine-to-mill workflow. One critical aspect of this optimization lies in predicting the particle size distribution resulting from blasting activities (McKee, 2013). A thorough understanding of particle size distribution facilitates better control over downstream processes such as crushing, grinding, and sorting, ultimately enhancing overall operational efficiency and profitability.
Traditionally, the prediction of particle size distribution following blasting has been approached using empirical models or simplistic statistical techniques. However, the inherent complexity and variability of geological formations, coupled with the diverse characteristics of explosive materials, demand a more sophisticated and data-driven approach (Nadolski et al., 2015). In this context, Multivariate Regression Analysis (MRA) or Multivariate Multiple Regression emerges as a powerful tool for accurately predicting particle size distribution by incorporating multiple variables that influence blasting outcomes.
Proactive Identification of Adverse Geological Structure in a Deep Mine Environment
Authors: Hall A. , Marshfield S. , Simser B. , Howell L. , Lindsay J. , Cai M. 
Published: August 2024

ABSTRACT:
This paper details proactive measures taken to identify adverse geological structures present in the rock mass before mining occurred in the area. During the sinking of Glencore's Onaping Depth winze and subsequent excavation of the shaft stations, a major fault had to be crossed. This structure exhibited erratic behavior ranging from local wedge formation in tunnels to major rock bursting when it had been encountered historically at shallower depths. Through the use of scout holes, diamond drill holes drilled ahead of the mining face, the ground conditions around the fault ahead of the shaft and drift development were characterized. The holes provided a wealth of data for ground condition assessment, from physical examination of the core to in-situ evaluation of the rock mass using acoustic and optical televiewer surveys. Examination of the scout holes identified up to a 50 m zone of anomalous ground conditions below the fault. Based on the proactive identification of the anomalous zone, the ground support was enhanced, and the strategy for mining through the area was modified. Whenever feasible, permanent excavations were relocated further away from the fault zone. For the drives that had to go through the fault, conservative ground control measures were employed. This resulted in a significant risk reduction and improved operator safety associated with the construction of the critical excavations. Seismic data were collected while mining through this area, and the data confirmed the presence of anomalous ground conditions.

1. INTRODUCTION
The presence of large geological structures can be a significant factor leading to increased frequency of rockbursts and large seismic events in deep underground mines. Predicting the rock mass behavior associated with geological structures is challenging because the structures are not always easily identified until after an excavation has been made. Many geological structures are benign and cause few ground control problems. On rare occasions, a structure may have locked-in stress, which could potentially cause severe rock mass failures. Seismic monitoring is extensively used to provide real-time feedback on the local rock mass response to mining. To some extent, the data can be used to evaluate geotechnical risks. However, it is important to note that this dataset shows a response to mining activity and is not available until the excavation process begins. Reactionary mitigation efforts are employed after a rockburst or a significant seismic event has occurred, in contrast to proactive efforts aimed at preventing the event or reducing its potential damage severity.
Production Enhancement by Microproppants: Concept Proof Using Laboratory Experiment and Numerical Modeling
Authors: Han Yanhui , Liang Feng , Liu Hui-Hai 
Published: August 2024

ABSTRACT:
In our previous work, an improved fracturing treatment, which combines a mixture of solid delayed acid generating material (SDAGM) with microproppants in the pad/pre-pad fluids during the engineering process, was demonstrated to be an effective technology by a series of laboratory tests and further investigated with mesoscopic fluid dynamics – microscopic solid mechanics coupling simulations. In this work, two field-scale porous media fluid flow models, consisting of rock matrix, randomly distributed microfractures and a major hydraulic fracture, are developed to evaluate the production enhancement of using microproppants for a producing well in an unconventional reservoir. The rock matrix is constructed as porous media with hydraulic properties of tight carbonate formation. The fluid flow in the rock matrix and fractures are mutually communicated. The permeability of zones representing hydraulic fracture and microfractures are determined by upscaling the hydraulic conductivities of fracture and microfractures containing supporting proppants and microproppants. The simulation can predict the well productivity with and without microproppants in the hydraulic fracturing treatment. This developed model can be applied to optimize the concentration of microproppants in the field operation to maximize the well productivity.

1. INTRODUCTION
Horizontal drilling and multistage hydraulic fracturing are two critical technologies that make it economically feasible to produce hydrocarbon from unconventional reservoir formations. Horizontal drilling increases the wellbore length exposed to reservoir mass. Hydraulic fracturing enhances production by creating fractures and sustaining their opening using solid particles (called proppants) such that the contact area between producing rock mass and fluid pathways (fractures and well) are significantly increased.
Most unconventional formations, such as shales and tight carbonates, contain extensive natural microfractures. Before hydraulic fracturing treatment, these microfractures may be sealed and thus inactive. Hydraulic fracturing will change the stress state around the newly created main fractures, which may reactivate existing natural fractures impacted by the stress change (see Fig. 1). In addition, new microfractures may also be created. Similar to main hydraulic fractures, these microscopic fractures, pre-existing or newly created, will close after the hydraulic fracturing pressure is released. If they can be kept open (e.g., during production), the well productivity can be further enhanced significantly. However, the proppants designed for supporting the main hydraulic fractures cannot enter these microfractures because of their large size relative to the microfracture aperture.
Experimental and Numerical Investigations into Fracturing Process of Brittle Rocks
Authors: Khadivi Babak , Masoumi Hossein 
Published: August 2024

ABSTRACT:
Tensile strength plays a vital role in the efficient design of underground openings and support system in rock engineering practice. Among various approaches developed for estimating this property, Brazilian testing has received considerable attention in analytical, numerical, and experimental studies. The test has been deployed for various materials such as rock and concrete; however, its fracturing process at micro and macro scales has not yet been thoroughly characterized. In this study, a coupled experimental-numerical technique was used to characterize the failure process of granite to better understand the fracturing process of brittle rocks under indirect tensile loading. In the experimental part, two independent monitoring techniques, Acoustic Emission (AE) and high-speed imaging, were deployed to investigate micro and macro cracking processes. The sample's behaviour was then simulated using a Distinct Element Method (DEM) code through Trigon logic to further compare the brittle failure characteristics with the experimental results. The collective results revealed that the tensile microcracks are the first to initiate during the failure with higher intensity compared to shear microcracks, resulting in a dominant tensile failure at macro scale. Also, it was noted that the sample's failure started from the center, which keeps the Brazilian results valid for brittle rocks while some overestimations may be added due to following shearing and the lack of enough stiffness in the testing machine.

1. INTRODUCTION
The initiation of fractures in brittle rocks can occur through tensile events, highlighting the significant role of tensile strength in the design of rock engineering projects (Griffith, 1921, Tapponnier and Brace, 1976, Stacey, 1981, Diederichs and Kaiser, 1999, Perras and Diederichs, 2014, Khadivi et al., 2023). Therefore, accurate assessment of tensile strength and cracking mechanism is essential for better understanding the mechanical behavior of brittle rocks. The convenience of sample preparation and straightforward testing operation have made the Brazilian test the most popular approach to estimate the tensile strength across a wide range of materials (Hobbs, 1964, Barla and Innaurato, 1973, Jonsén et al., 2007, Bahaaddini et al., 2019). Valid testing results are obtained by inducing a tensile fracture at the center, splitting the sample along the compressive diameter into two halves (Colback, 1966, Carmona and Aguado, 2012).
Enhanced Method for Measuring Joint Roughness Using Sub-Millimeter Resolution 3D Laser Scanning
Authors: Shintassova M. , Sepúlveda S. A. , Fatolahzadeh S. 
Published: August 2024

ABSTRACT:
Accurate estimation of joint roughness is critical for characterizing the mechanical and hydraulic properties of rock joints, thereby contributing to informed assessments of the rock mass classification, shear strength, and permeability estimates. The most prevalent way to quantify joint roughness is the Joint Roughness Coefficient (JRC). However, this conventional approach has shown subjectivity and bias, which can significantly affect engineering design strategies. To accurately assess JRC, this study proposes to use 3D laser scanning technology. In this work, a high-resolution scanner was used in the field for the first time on borehole cores. Scanned 3D roughness surfaces were used to obtain statistical roughness parameters, followed by the determination of JRC using empirical equations. This paper examines the use of a sub-millimeter resolution scanner on the example of joint surfaces of core samples and discusses the importance of scanning resolution and noise reduction in the measurement of roughness of discontinuities. It was found that this approach is also applicable to several-meter-long joints in outcrop formations, provided that a scaling relationship for JRC is applied. The results indicated a similarity in JRC values derived from laser scanning and visual profiling tools.

1. INTRODUCTION
Joint roughness is a measure of surface irregularities of a rock fracture and is described by surface topography. This rock property is important to quantify the mechanical and hydraulic properties of rock joints. There is a range of contact and non-contact methods to measure it. Contact techniques include linear profiling and local surface orientation methods (Barton & Choubey, 1977; Fecker & Rengers, 1971). Non-contact tools are triangulation (structured light projection, photogrammetry) and distance measurement methods (laser scanning and laser profilometry) (Fardin, Feng, & Stephansson, 2004; Huang, Oelfke, & Speck, 1992; Jessell et al., 1995; Tatone & Grasselli, 2009).
The most common roughness parameter used in geotechnical practice is the Joint Roughness Coefficient (JRC) introduced by Barton and Choubey (1977). JRC is estimated based on a comparison of profiles of a joint surface obtained from a profile comb (Fig.1) to the standardized set of 10 roughness profiles of JRC values ranging from 0 to 20 (Fig.2).
A Comprehensive Comparison Between Discrete Fracture Network and Generalized Anisotropic Material Behavior for Modeling Jointed Rock Mass
Authors: Ko B. H. , Moallemi S. , Dang H. K. , Yacoub T. 
Published: August 2024

ABSTRACT:
Rock masses are blocky assemblages formed by networks of natural discontinuities (fractures), such as joints, foliations, shear zones or faults, formed by geological activities. To accurately predict the mechanical behavior of rock mass, it is essential to consider these fractures. The complex interaction between intact rock and those fractures coupled with man-made excavation imposes critical limitations to predict rock mass behavior solely via kinematic or analytical methods. In this context, numerical modeling approach fills the need for a powerful tool that can provide geotechnical engineers with sophisticated solutions to complex rock mechanics problems. This paper demonstrates different approaches to model joint sets in 3D Finite Element Method (FEM) to model discontinuities in jointed open pit mine. They include the explicit representation of discontinuities using Discrete Fracture Network (DFN) and incorporation of a special constitutive model that considers anisotropic material behavior to the solid elements that implicitly account for the presence of joint sets. The investigation presents findings from simulations involving models with single and multiple joint sets. Notably, the focus is given to validating the use of DFN and the benefits for slope stability assessment. The obtained results showed high levels of agreement between the two modeling approaches, underscoring the efficacy of DFN in replicating the complex behavior of geological structures. These insights contribute to the enhancement of the rock slope designs with significant implications for the safety and profitability of mining operations.

1. INTRODUCTION
In open pit mining, the primary objective is to maintain the structural integrity of the slope surface and prevent/mitigate any potential failures. Achieving a cost-effective yet stable design for open-pit mines requires a comprehensive grasp of lithology, rock mass characteristics, and structural geology. Thus, conducting a robust slope stability assessment for open pit excavations is of utmost importance to ensure the safety of mining operations.
The presence of geological structures (also termed as natural discontinuities) such as joints, foliations, and faults within rock mass introduces complexities in stress distribution and stability, which are unique to the geological history of different regions. Therefore, a thorough consideration of natural discontinuities is imperative in geomechanical analyses and design exercises to gain accurate prediction of rock mass behavior. They play a pivotal role in controlling the driving failure mechanism to slope instability. With respect to the distribution, surface condition, and orientations of discontinuities, the mechanical response of rock mass should vary extensively.
Research on the Cuttings Transport in Large-Sized Hole Based on CFD-DEM Method
Authors: Zhao Jun , Huang Wenjun , Gao Deli 
Published: August 2024

ABSTRACT:
During drilling large-sized hole, due to the low return velocity of the drilling fluid and weak cuttings transport effect, it is difficult to clean the borehole, resulting in serious backpressure even pipe sticking, high equivalent circulating density (ECD), low rate of penetration (ROP), etc., which will bring significant time costs and economic losses. In this paper, a CFD-DEM coupling model is built to accurately simulate the dynamic transport process of cuttings. For the liquid phase, the Euler method is used to describe its motion characteristics through the flow field. For the solid phase, the Lagrange method is used to solve the variation of physical quantities of cuttings over time. And the coupling of fluid and solid phase is achieved through mutual forces. The reliability of this CFD-DEM coupling model is validated through experiments. Based on a large number of numerical simulations and the nonlinear regression method, a data-driven mathematical model for predicting the cuttings bed height is developed, which is useful in hole-cleaning design and drilling parameters optimization. The Pearson correlation coefficient R2 is 0.893451, indicating high accuracy of this mathematical model.

1. INTRODUCTION
Hole cleaning is one of the major challenges during drilling large-sized hole section, especially in the horizontal sections. Under the effect of gravity, cuttings will accumulate at the bottom of the annulus and be transported upwards in the form of cuttings bed. However, if the cuttings bed is too high, the cuttings in the lower part of the cuttings bed will be stuck and unable to move, resulting in the stationary bed that is difficult to remove and poor hole cleaning. This may cause downhole complications and accidents, such as serious backpressure even pipe sticking, high ECD, low ROP, etc., which bring significant time costs and economic losses. Therefore, conducting research on cutting transport is of great significance for on-site operations.
In the past, many researchers have conducted a large number of studies on cuttings transport, including experiments, numerical simulation and theoretical modeling. Experimental studies on cuttings transport began in the 1940s (Zhu 2022), analyzing the influence laws of various parameters through measured results and observation of phenomena. Sorgun (2013) summarized an empirical formula for the height of cuttings bed under water and four non-Newtonian fluids. Kim et al. (2014) studied the transport characteristics of cuttings in inclined annulus with the inclination of 30-75°. Song et al. (2017) proposed a mathematical model for cuttings concentration in a Microhole-Horizontal-Well based on 136 sets of experiments. Through massive experiments, Huque et al. (2022) believed that fluid velocity and cuttings size were the two most key parameters for cuttings transport efficiency in an inclined well.