bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Feasibility Study on the Pressure Monitoring Above the Injection Zone for CO2 Geological Storage in the Uinta Basin, USA
Authors: Bakelli Omar , Xiao Ting , McPherson Brian , Vega-Ortiz Carlos , Moodie Nathan , Chellal Hichem A. K. , Mellal Ilyas 
Published: August 2024

ABSTRACT:
Geological Carbon Storage (GCS) offers a promising solution to mitigate climate change, but ensuring safe and permanent CO2 confinement demands reliable monitoring techniques. This study investigates the feasibility of using pressure changes above the CO2 injection zone (AIZ) for leak detection and storage assessment in the Uinta Basin, Utah. Focusing on the Cretaceous Dakota Formation as a potential storage reservoir, we employed a coupled fluid-flow and poroelasticity model to simulate various leakage scenarios. These scenarios included both the injection well and a nearby legacy well, each experiencing varying leakage rates, pressure changes was analyzed at two monitoring points (AIZ-1 and AIZ-2) situated above the injector and legacy wells, respectively. The simulations revealed minor to significant pore pressure changes (ranging from 0.1 kPa to 2790 kPa) above the injection zone, directly influenced by the leakage rate. Notably, pressure changes were found to be more sensitive to leaks compared to gas saturation changes, enabling early detection, especially at higher leakage rates. While the AIZ-1 sensor exhibited larger and earlier pressure changes due to its proximity to the injection point, the wider monitoring coverage offered by the AIZ-2 sensor necessitates further consideration for optimal monitoring strategies. These findings demonstrate the promising potential of AIZ pressure monitoring as a valuable tool for CO2 leak detection and storage assessment in the Uinta Basin. However, successful implementation requires high-precision pressure measurements for accurate data acquisition and analysis. This study contributes significantly to a more comprehensive understanding of CO2 plume behavior and leakage potential, ultimately paving the way for developing safer and more reliable GCS practices.

1. INTRODUCTION
In the task to mitigate climate change and achieve the Paris Agreement's net-zero emissions goal by 2050, Geological Carbon Storage (GCS) has emerged as a potentially significant tool (IPCC, 2005). This technology captures carbon dioxide (CO2) from industrial processes (point-source emissions) or directly from the air (direct air capture) and safely stores it in deep underground porous rock formations sealed by impermeable layers (Boot-Handford et al., 2014).
Monitoring underground CO2 migration and containment is crucial for the safe and responsible implementation of GCS projects (Xiao et al., 2024). A diverse toolkit of techniques exists, each offering unique insights (Hannis, 2012). For instance, seismic surveys map the plume's physical extent and potential leakage pathways through changes in acoustic properties (Ma et al., 2016).
Back to Basics: Experimental Measurement of Liquid and Solid-Liquid Properties to Predict Hydraulic Fluid Behavior in Fractures
Authors: AlDajani O. A. , Germaine J. T. , Einstein H. H. 
Published: August 2024

ABSTRACT:
The primary mechanisms to initiate hydraulic fractures in rock include overcoming the tensile resistance of the rock, overcoming its shear resistance, or a combination of both. The focus of this study is the solid-liquid interaction in hydraulic fractures using basic measurements and models to aid in investigating these mechanisms. The materials of study were Opalinus Shale and hydraulic oil. The basic measurements included liquid density, viscosity, surface tension, and contact angle with the rock. These measurements were used to determine the characteristic capillary length, capillary number, spreading, and imbibition parameters. Two fracture scenarios were considered for a range of apertures:
A- liquid inside a pre-existing fracture was modelled as parallel plates to determine the Laplace pressure and adhesion force.
B- liquid penetrating a newly created fracture was modelled as a capillary to determine the dynamic and equilibrated rise.
This study provides a theoretical framework to assess solid-liquid interaction effects in fractures and introduces the capillary draw amplification coefficient. The results of this study provide insight into the lag or lack thereof between the liquid front and the fracture tip during hydraulic fracturing and how the liquid interacts with the fracture after it has been created. These, in turn, have implications on the mechanism of fracturing and potential operational considerations.

1. INTRODUCTION
Several mechanisms play a role in the hydraulic fracturing process. There are two main ways to initiate hydraulic fractures in rock:
1. increasing the liquid pressure beyond the tensile resistance of the rock will result in tensile fractures.
2. decreasing the effective stress (by increasing the pore pressure) to have the Mohr circle tangent to the shear failure envelope will result in shear fractures.
After initiation, the propagation of hydraulic fractures depends on many factors. One of these factors that affect hydraulic fracture behavior is the solid-liquid interaction. A higher viscosity liquid pressurizing rock may result in different behavior than a lower viscosity liquid.
The motivation of this study was to investigate the solid-liquid behavior that occurs in the hydraulic fracturing, specifically in the experiments conducted by AlDajani (2022). These hydraulic fracture experiments are beyond the scope of this paper, but the materials used in the study are the same. The liquid used as a fracturing fluid was hydraulic oil and the rock being hydraulically fractured was Opalinus Shale.
Continuous in Situ Characterization by AFM of Surface Mechanical and Electrical Features of Shale Organic Matter Under Different Atmospheres
Authors: Kang Ying , Ning Zhengfu , Lyu Fangtao , Jia Zejiang 
Published: August 2024

ABSTRACT:
Unconventional reservoirs, which are the mainstay of CO2 enhancement and carbon sequestration, are not well characterized in terms of micro-surface electrical properties. In this study, the micro-surface morphology and potential of organic matter (OM) under three atmospheres: dry, water-wet, and ScCO2 were characterized in detail using atomic force microscopy (Tapping mode, KPFM). The results showed that the micro-surface morphology of the OM fluctuated in the range of less than ten nanometers, and the micro-surface roughness under dry and ScCO2 conditions was higher than that under water-wet conditions, which indicated that the ScCO2 extraction and induced swelling were effective. In addition, the contact potential difference of the organic surface under water-wet and ScCO2 conditions was positive, and there was no correlation with the change of surface morphology. Combined with the reduction of Young's modulus, the difference of organic surface potential and the reduction of Young's modulus provide a good physical basis for the emergence of micro-cracks and other defects under the external forces, and provide a new idea for revealing the adsorption characteristics of unconventional reservoirs and realizing the long-term and stable carbon geologic sequestration.

1. INTRODUCTION
Due to the decrease of conventional oil and gas resource production rates and the impact of the greenhouse effect in recent years, unconventional oil and gas reservoirs, such as shale, have become an important option for enhancing resource production rates and realizing carbon geologic sequestration (Farokhpoor et al., 2013; J. Zhang et al., 2023). A large number of studies have been carried out on rock damage, fracture generation and other related phenomena, but most of these studies have focused on the macro-scale level and lacked detailed analysis of related changes at the micro- and nano-scale (J. He et al., 2020; Yin et al., 2023; Gu et al., 2023). For unconventional reservoirs such as shale, which is both a key target for the implementation of CO2 enhanced recovery measures and an ideal place to realize efficient and stable carbon geological storage. Direct surface characterization of them can provide a better understanding of the CO2 action mechanism.
Simulation of Coupled THMC Processes in Fractured Rocks Using a Dual-Media Approach
Authors: Mosley K. , Hartley L. , Turnbull R. , Cottrell M. , Bym T. , Mas Ivars D. 
Published: August 2024

ABSTRACT:
Simulation of coupled thermo-hydro-mechanical-chemical processes in fractured rocks is relevant to many areas of applied geoscience. Groundwater flow and reactive transport (HC processes) in hard rocks are primarily controlled by the network of rock fractures, and therefore best modelled in a discrete fracture network. By contrast, heat and stress (TM processes) are mediated via the rock mass, and thus best represented as a continuum. Here, we present an approach using dual, coincident meshes, each simulating the relevant processes in their ‘natural’ media. A sequential coupling between TM and HC processes is achieved by computing the effective stress on fractures and updating their hydraulic properties.
The simulated processes are modelled in PFLOTRAN, using a linear elastic constitutive model for rock deformation. Several updates to the PFLOTRAN code were required to enable this, as verified against analytical cases and other numerical codes. We present an example application to a model of a nuclear waste repository in Finland, which simulates the evolution of thermal stress due to radiogenic heating from spent fuel canisters. The results illustrate how continuum-based TM processes influence near-field flows around the repository that can only be accurately captured in a DFN, thus demonstrating the advantages of a dual-media approach.

1. INTRODUCTION
Simulation of coupled thermo-hydro-mechanical-chemical (THMC) processes in fractured rocks is relevant to many areas of applied geoscience and geo-engineering, including in nuclear waste disposal, enhanced geothermal systems, CO2 sequestration and mining applications. The ability to accurately predict the influence of coupled processes in the context of fractured media has potentially far-reaching economic and environmental consequences. In this study, we introduce a novel workflow for simulation of such processes, which employs a ‘dual-media’ representation of the modelled rock volume.
In any numerical THMC model, a range of different couplings to geomechanical processes can feasibly be implemented. These include thermo-mechanical, hydro-mechanical and chemo-mechanical coupled processes. For the purposes of this study, the focus was primarily on the thermo-mechanical coupling between the rock's temperature and its stress state. The fundamental mechanism by which this is governed is the thermal expansion/contraction of the rock (and other modelled materials), as determined by the thermal expansion coefficient. Such expansion induces deformations, or ‘strains’, in the rock mass, which in turn bring about alterations in the stress field. A coupling to hydraulic processes (i.e. groundwater flow) can also be incorporated by computing the impact of thermal and mechanical strains on the rock's hydraulic properties – whether that be on the porosity field in the case of porous materials, or indeed on fracture apertures and transmissivities in the case of fractured rocks.
Computational-Rock Mechanics in Pedagogy and Practice
Authors: Kayen R. , Russo B. M. 
Published: August 2024

ABSTRACT:
Point cloud modeling of rock slopes using LIDAR and Structure-from-Motion digital stereophotogrammetry provides, at a minimum, thousands of facets and facet normals that can be used to identify the densities of orientations of rock mass discontinuities, the geometries of potentially removable blocks, and the character of the excavation face. As part of the Engineering Geology graduate curriculum at the Civil and Environmental Engineering program at the University of California, Berkeley we teach graduate students an integrated methodology for [a] gathering point cloud information be laser or camera; [b] computing facets and facet normals form point clouds for stereonet presentation and geometric analysis of block dimension; [c] extract rock mass discontinuities from stereonet data to analyze key blocks, assess discontinuous deformation analysis (DDA) behavior, and model rock slope stability. These new methods require a suite of different software tools discussed in the paper to move through the workflow process. Computational rock mechanics provides data sets that are orders of magnitude richer in detail and result in better understanding of rock slope and tunnel key block behavior. Full application of computational rock mechanics methods should reduce the cost of bolting by identifying critical support orientations and design loads.

1. INTRODUCTION
This paper is intended to serve as an instruction manual for teachers who include digital methods in rock mechanics. Innovations in digital methods for computing surface models have advanced such that models can be used for quantitative rock mechanics analyses. An array of new remote sensing tools utilizes laser and photogrammetric means to build digital twins of a surface at millimeter-to-centimeter accuracy by processing a point cloud of the target. The oldest of these technologies, Terrestrial Laser Scanning (TLS), has transformed the ability of engineers to document geotechnical sites.
Though TLS remains an expensive technique for capturing point clouds of data needed to model surfaces, the cost has dropped in the last decade, and is now widely available on common cell phones. A remarkable new computer vision-based method, Structure-from-Motion (SfM), allows engineers to build complex pointcloud visualizations with digital cameras (airborne or handheld) at a fraction of the cost. In the sections below, we outline a procedure for gathering data and moving through the analysis process to extract meaningful rock mechanics information from point cloud data. The procedural steps are outlined in Figure 1.
Stress Distribution in Accreting Sediments: A Geomechanical Study of Upper-Plate Faults
Authors: Lopez-Campos G. , Nikolinakou M. A. , Flemings P. B. , Saffer D. M. 
Published: August 2024

ABSTRACT:
We study the influence of an upper-plate fault on the stress state of accreting sediments under large-scale deformation. We develop drained evolutionary geomechanical models using the Finite Element program Elfen. We simulate sediments as porous-elastoplastic material, and we model the fault as a pre-existing contact surface with a varying frictional strength that is lower than the intact sediment. The weaker fault results in a decrease in sediment differential stress near and especially seaward of the fault. A significant section of the wedge is affected by this stress variation. In contrast, the stress ratio is that of Coulomb failure further away from the fault. We also show that the maximum principal stress the sediments can support decreases with decreasing fault strength. This study offers a significant improvement over previous models of continuum wedge sediments that predict Coulomb failure throughout the wedge. Our results improve our understanding of near-fault stress state, hence improving our understanding of seismic hazards in subduction zones and providing practical insights for reservoir quality and the design of safe and economic well trajectories.

1 INTRODUCTION
Accretionary wedges are geological structures that develop at convergent plate boundaries, particularly at subduction zones. They form as a result of offscraping sediments from the subducting oceanic plate, which then accumulates on the leading edge of the overriding plate (e.g., Moore et al., 2011; Buiter et al., 2016; Gao et al., 2018).
Understanding the state of stress in accretionary wedges is crucial for the study of earthquake mechanics in subduction zones (e.g., Brodsky et al., 2017; Huffman and Saffer, 2016; Suppe, 2007). It provides insights for earthquake occurrence, large or slow-slip events (e.g., Kodaira et al., 2012; Tobin et al., 2022; Liu and Rice, 2007) and tsunami potential (e.g., Dean et al., 2010; Riedel et al., 2016). In addition, estimates of mean and differential stress, as well as porosity evolution can help improve the assessment of reservoir quality and the design of safe and economic well trajectories (e.g., Morley et al., 2011).
The accumulation of sediments in an accretionary wedge resembles a bulldozer gathering snow as it moves. Hence, wedge sediments are often assumed to be at compressional failure (e.g., Davis et al., 1983; Dahlen et al., 1984; Flemings and Saffer, 2018). Several field observations of faulting, folding and lateral compression as seen in seismic images and drilling measurements (e.g., Flemings and Saffer, 2018; Henry et al., 2003; Moore et al., 1990; Westbrook et al., 1988) provide evidence that the accretionary wedge is at a state of failure in compression.
Optimal Camera Angle for Measuring Joint Roughness Using UAV-Based 3D Photogrammetry
Authors: Leem J. , Choi J. , Kang I. S. , Song J.-J. 
Published: August 2024

ABSTRACT:
Joint roughness strongly affects rock mass engineering properties, including shear strength and hydraulic behavior. Integrating 3D photogrammetry with unmanned aerial vehicle (UAV) technology rapidly generates 3D roughness profiles from 2D images. However, inaccuracies in roughness measurements can occur due to survey errors, and the directional nature of roughness complicates the analysis of how these errors affect the inaccuracies. This study simulates joint roughness coefficient (JRC) measurement distortion due to UAV-based 3D photogrammetry errors, considering image distortion, joint plane orientation, and JRC direction. We measured JRC values through 3D photogrammetry on joint planes of a rock mass at Mt. Gwanak, Seoul, and compared them with JRC values distorted through the simulation. The comparison result shows that the simulation has a high performance in predicting JRC errors with an RMSE of 1.23. Based on the simulation, we propose guidelines for camera angle and UAV movement direction to minimize JRC measurement errors. The study recommends that flying the UAV along the strike of a joint plane with a camera angle orthogonal to the plane can minimize JRC measurement errors when the roughness of interest corresponds to the dip vector of the joint plane.

1. INTRODUCTION
Joint roughness has a significant impact on both the mechanical and hydraulic behavior of rock masses (Paixão et al., 2022), and it should be a critical factor in designing rock structures. The Joint Roughness Coefficient (JRC), one of the most commonly used roughness parameters in practice (Barton, 2023), can be physically assessed through tilt tests (Barton and Choubey, 1977) or estimated visually from roughness profiles. Since measuring JRC values from visual inspection can be subjective, research has also been conducted using statistical parameters such as fractal dimension (Tse and Cruden, 1979), maximum amplitude of the profile (Barton and Bandis, 2017), and the standard deviation of profile gradients Z2 (Myers, 1962).
The methods of obtaining roughness profiles can be categorized into two methods: contact and non-contact methods (Ge et al., 2014). Contact methods such as linear profiling and stylus profilometry are advantageous over non-contact methods in terms of cost-effectiveness, but they are time-consuming and unsuitable for surveying large areas (Paixão et al., 2022). When investigating large rock surfaces, non-contact methods like 3D photogrammetry or LiDAR (Light Detection and Ranging) technology are preferred for acquiring 3D roughness profiles due to their efficiency compared to the time-consuming contact methods.
New Insights for Stress Conditions of Laboratory Shear Tests
Authors: Chai Shupeng , Zhao Qi 
Published: August 2024

ABSTRACT:
Numerous laboratory tests have been performed to investigate the shear behavior of rock discontinuities using various experimental setups. Stress heterogeneity on rock discontinuities can significantly influence the shear behavior, however, it has seldom been specified clearly. Instead, the macroscopic or average stress on the joints other than the local stress distribution was usually analyzed in most laboratory shear tests. In this study, numerical simulations considering a simple linear velocity weakening law are conducted on smooth rock joints in various laboratory setups to analyze the stress distribution before and during slip. The results show nonuniform normal and shear stress distribution in almost all the laboratory tests and significant local stress concentration near the edges of the shear surface. The estimated sample-average friction coefficient is slightly higher than the dynamic friction coefficient but lower than the static friction coefficient. Furthermore, a sudden release of the shear stress, especially near the stress-concentrated edges, can be observed in the slip phase during a stick-slip cycle. This study provides a critical review of laboratory shear tests on rock joints and contributes to our understanding of stress distribution and variation during stick-slip shear.

1. INTRODUCTION
Rock discontinuities including joints, fractures, faults, and bedding planes commonly exist in rock masses (Elsworth et al. 2016; Marone 1998). Shear failure on rock discontinuities can occur in various engineering cases, such as underground excavations including tunneling, carven and mining (Chai et al. 2023; Wu et al. 2023), slopes and dams (Chai 2023), fluid-injection projects including oil and gas extraction (Elsworth et al. 2016), enhanced geothermal systems (Zhao et al. 2020), and CO2 or waste storage (Elsworth et al. 2016), etc. The shearing of rock discontinuities has also been reported to affect earthquake nucleation (Kaproth & Marone 2013).
Various laboratory shear setups have been developed to investigate the shear behavior of rock discontinuities. They include direct shear (DS) tests (Petit 1988), true triaxial direct shear tests (Zhao et al. 2023), single direct shear tests (Rubinstein et al. 2004), double direct shear tests (Marone 1998), triaxial direct shear tests (Frash et al. 2016), triaxial shear (TS) tests (Thompson et al. 2005), biaxial shear tests (Buijze et al. 2020), axial shear tests (Rubino et al. 2022), oblique shear tests (Ghazvinian et al. 2013), and rotary shear (RS) tests (Zhao et al. 2018). Among these test setups, the DS, TS, and RS tests are commonly used by the rock mechanics community.