bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Determination of Elastic Properties of Laminar Shale Based on Adaptive Threshold Algorithm of Image Segmentation Technology
Authors: Sun Zhengxin , Jin Yan , Guo Xuyang , Luo Jiaqi 
Published: August 2024

ABSTRACT:
The characterization of elastic properties of laminar shale is crucial for geomechanical modeling. It plays a vital role in shale gas exploration and development, such as reservoir evaluation, drilling, and hydraulic fracturing. The well-log interpretation has been widely adopted in mineral identification. However, the scale of the log data is more than eight cm per point, and more than the accuracy of the logging data is needed for fine formation analysis. Therefore, this paper proposes an adaptive image segmentation method for predicting elastic parameters based on large thin sections. This method uses an adaptive threshold algorithm to eliminate the noise and improve efficiency in processing relevant boundary information using the finite element method, validated by a numerical uniaxial compression simulation. The results show that the mineral layer's proportion, distribution, and physical properties significantly impact the accuracy of elastic modulus calculations. The deviation between the elastic properties obtained in this study and those obtained through the finite element method is 0.14. This difference can be attributed to the mechanisms determining static and dynamic elastic properties.

1. INTRODUCTION
The physical properties of rocks are mainly determined by mineral composition and distribution. Thin-section identification technology plays a crucial role in evaluating and developing oil and gas resources. It can accurately identify the characteristics of reservoir rocks, the type of diagenesis, and the structural characteristics of reservoir space and pore space (Liu et al., 2021). This technology enables geologists and engineers to understand the physical properties and depositional environments of reservoirs more accurately and thus obtain key parameters of oil and gas reservoirs (Krutko et al., 2019). This is indispensable for formulating oil and gas development strategies and reserve calculations.
The significant advantages of rock thin-section identification are its intuition, speed, simplicity, accuracy and practicality. Through thin-section observation, researchers can directly see rocks' microstructure and mineral composition and thus make accurate judgements on their properties. However, the traditional method of rock thin section identification has certain limitations. It mainly relies on visual observation by experts under an optical microscope, which leads to a huge workload and strain on human resources when faced with a large number of rock samples, may affect the accuracy and quantification of the identification results due to the subjective nature of naked-eye observation. In addition, traditional identification methods require the delivery of physical samples and visual observation, and prolonged preservation may lead to deterioration in the quality of thin sections, thus affecting the accuracy of the identification results.
Research on the Evolution of Fracture Network Considering Anti-Frac Hits of Oilfield
Authors: He Xinru , Zhu Haiyan , Zhao Peng , Chen Shijie , He Xiao , She Chaoyi , Zheng Majia , Wang Dajiang , Li Yuanzhao , Song Junbei 
Published: August 2024

ABSTRACT:
Currently, the issue of Frac hits in shale gas wells is prominent, significantly disrupting the production of neighboring wells. In response to the Frac hits in shale hydraulic fracturing, we based on the three-dimensional discontinuous boundary element method, establishes a numerical model of competitive expansion of multiple fractures under different natural fracture parameters. It systematically analyzes the evolution characteristics of fracture networks under stress shadow effects, optimizes fracturing construction parameters, and develops a fracturing network design method to avoid Frac hits. The research results indicate: (1) When the number of perforation clusters in the fracturing section is small, leading to a higher likelihood of Frac hits. When the number of perforation clusters is large, the middle fractures are difficult to extend, and reservoir transformation is ineffective. (2) The possibility of interwell interference increases with a higher density or length of natural fractures. Increasing the injection volume of fracturing fluid restricts the expansion of the hydraulic main fractures, resulting in reduced fracture length, width, and height. (3) To avoid Frac hits while ensuring reservoir transformation effectiveness, a set of fracturing network design method charts is established. This research have significant guiding implications for mitigating Frac hits in deep shale gas reservoirs.

1. INTRODUCTION
This depression belongs to the Cenozoic faulted lake basin of the eastern basin, rich in shale oil and formed in a semi deep-water to deep-water sedimentary environment. These shale layers exhibit typical deep basin lacustrine characteristics and are typical representatives of lacustrine shale oil, with enormous exploration and development potential (Ma et al, 2023). At present, the volume fracturing technology of shale oil and gas horizontal wells has developed rapidly, and basically formed the fracturing technology of "close cutting + sand imposition + temporary plugging and turning". Although the technological progress is very rapid and the stimulation effect is good, the phenomenon of inter-well Frac hits and even casing variation occurs frequently (Zhang et al, 2022).
Shear Band Development and Permeability Anisotropy Evolution in Fault Gouge
Authors: Li Q. , Chen J. Y. , Zhang C. Y. , Zhang F. S. , Gan Q. , Elsworth D. 
Published: August 2024

ABSTRACT:
The fault zone generally undergoes grain breakage during shear slip events, resulting in the change of shear mode and pore structure in fault gouge. We establish a discrete elemental model of shear tests of granular fault gouge under different normal stresses at the constant velocity, to investigate the effects of grain breakage on fault friction strength evolution and shear band development as well as permeability. With the increase of normal stress, the fault friction strength increases by about 20% due to grain contact area evolution, accompanied by many small slip events triggered by grain breakage. Additionally, the fault gouge has a high tendency to dilation under low normal stress, causing an increase in permeability; while the fault gouge compacts rapidly due to grain breakage under high normal stress, leading to the decrease in permeability. Consequently, a constitutive model about porosity evolution is developed through relating to volumetric strain. Further analyses show that the heterogeneous grain breakage leads to the local reduction in porosity, promoting shear band development and changing the microstructural characteristics: P shears dominate microstructure of shear bands at low normal stress. With the increase of normal stress, more R1 shears with larger angle develop.

1. INTRODUCTION
A large amount of fine-grained gouge materials usually exists in the fault cores, which are mainly evolved from the abrasion and fragmentation of the rock mass on both sides of the fault during the fault sliding process (Billi et al., 2003). The presence of fault gouge affects the friction strength magnitude and stability of the fault. In mature fault zones, most of the deformation from sliding locates at the fault gouge, with undergoing a long-term process of grain breakage (Scuderi et al., 2017). This continuous evolution of grain size distribution and morphology during the shearing process profoundly alters the friction mechanical properties and permeability of the fault (Zhang et al., 2020). This also impacts the microstructure of the faults and induces the development of shear bands within the fault gouge (Balsamo and Storti, 2010). These macro-micro features resulting from grain breakage are often correlated with the deformation and strength of the fault and can be used to further understand the slip behavior of the fault (Kuo et al., 2014).
Mechanical Performance of One Latex Cement System for Thermal Storage Wells
Authors: Meng M. , Pytiana T. , Frash L. , Bijay K. , Madenova Y. , Uwaila I. , Li W. , Zhang W. 
Published: August 2024

ABSTRACT:
To minimize heat losses in the high temperature thermal storage wells, Brookhaven National Lab introduced one type of hydrophobic lightweight thermally insulating cement with a thermal conductivity three times lower than that of regular cement. However, the repeated thermal shock conditions that are the major concern for well integrity can be especially difficult for lightweight cements. This study provides an in-depth evaluation of the latex cement's mechanical performance under in situ conditions, including pressures up to 10 MPa and temperature as high as 200 °C. Before being subjected to thermal shock, the cement showed an elastic modulus ranging from 0.3 to 1.9 GPa, a Poisson ratio between 0.05 to 0.19, and a strength between 4.7 and 27.5 MPa. However, after thermal shock, there is a noticeable increase in its mechanical properties: the elastic modulus spans from 1.6 to 3.7 GPa, the Poisson ratio becomes 0.12 to 0.36, and the strength increases to 6.3 to 27.2 MPa. Although these observations indicate excellent cement performance after thermal cycling, its resistance to cyclic loading decreased after thermal shock tests. Additionally, this formulation shows strong plasticity, and our well integrity simulation shows potentially pose risk to the bond between the cement and the casing.

1. INTRODUCTION
High Temperature Reservoir Thermal Energy Storage (HT-RTES) is a promising solution for large-scale energy storage that can stabilize the electric grid, increase its flexibility, and provide energy on demand. HT-RTES systems are designed to store large amounts of energy over the long term and contribute to the overall affordability and sustainability of the current energy system (Dobson et al., 2023; Jin et al., 2023). To ensure its high efficiency and low cost, we need effective strategies to prevent heat losses in the system. The wellbore, serving as the conduit connecting subsurface reservoirs to surface heat sources, plays a crucial role in the heat exchange process via heat transfer fluids. Without proper design, significant heat loss could occur across the wellbore, diminishing system efficiency and potentially damaging the cement behind casing, leading to well leakage and total loss of the well (Meng et al., 2023).
Geomechanical and Petrophysical Effects of Long-Term Hydrogen Exposure on Berea Sandstone – An Experimental Study
Authors: Thiyagarajan S. R. , Emadi H. , Hussain A. , Maury Fernandez D. , Ispas I. , Henderson S. K. , Watson M. 
Published: August 2024

ABSTRACT:
Hydrogen is gaining traction on a global scale as a future low-carbon energy carrier. Underground Hydrogen Storage (UHS) is critical to successfully implementing the hydrogen economy. UHS requires many lab-scale and large-scale studies to understand the behavior of hydrogen in the subsurface before they can be incorporated into the energy system. So far, most of the experimental investigations conducted on UHS focus on the microbial, hydrogeological, and geochemical effects of hydrogen storage in the subsurface. However, studies focused on the geomechanical effects are scarce. In this work, eight Berea sandstone cores were exposed to brine, pure hydrogen, and hydrogen in the presence of brine for 90 days at reservoir conditions of 10 MPa and 60°C to study the geomechanical effects of hydrogen on the samples. Tests for the Berea sandstone's properties for petrophysical (permeability and porosity) and geomechanical (strength, Young's modulus, and Poisson's ratio) properties. The results demonstrate that long-term interactions with hydrogen cause changes in all the properties of the cores. The results also demonstrate changes in the geomechanical properties of the reservoir after three months of hydrogen exposure, which has not been extensively studied, and the results can be used in simulation, site selection, and risk assessment studies.

1. INTRODUCTION
Renewable energy production is viewed as an alternative to environmentally detrimental fossil fuel energies (coal, oil, and natural gas), contributing to global net-zero carbon emissions by 2050(Perera, 2023; Ugarte et al., 2023). According to a study by the International Renewable Energy Agency (IRENA), renewable energy will become the primary energy source, increasing worldwide share from 16% in 2020 to 77% by 2050 (IRENA, 2023). While there is a rising global interest in renewable energy, wind and solar energy have limitations: they depend on unpredictable factors such as weather. Renewable energy's intermittent generation creates a supply-demand imbalance, making renewable energies unreliable since they cannot maintain a continuous supply (Abdellatif et al., 2023; Heinemann et al., 2021; Kanaani & Sedaee, 2022; Muhammed et al., 2022; P. & P.G., 2023). To balance supply and demand, surplus energy from wind and solar energies can be converted to hydrogen through electrolysis, stored in the energy storage system, and subsequently utilized when demand arises (Okoroafor et al., 2022; Zamehrian & Sedaee, 2022).
Predicting Scour in Unlined Rock Spillways: A Coupled Analytical-Numerical Modeling Approach
Authors: Weidner L. , George M. F. , Clohan D. 
Published: August 2024

ABSTRACT:
Hydraulic plucking of rock blocks bounded by discontinuities is one of the primary modes of scour in unlined spillways. The methods used in the current state-of-practice either model a single block in considerable detail or introduce many simplifications to reduce model runtime and complexity. We present a method for simulating block scour at the spillway scale using an open-source discrete fracture network and block slicing program coupled with FLOW-3D. We built a custom implementation of limit equilibrium block theory for this task which enables eroded blocks to have any convex polyhedral shape. Preliminary results from this method highlight that block shapes introduce significant anisotropy to erosion behavior, which is not captured in other methods.

1. INTRODUCTION
Hydraulic plucking of rock blocks bounded by discontinuities is known to be one of the primary modes of scour in rock masses, resulting in channelization and head cutting. As such, understanding this process has immense implications for the design and maintenance of engineering structures such as spillways and dam foundations interacting with water. Modeling block scour can be accomplished using empirical relationships (Annandale, 1995), physics-based analytical stability solutions (Bollaert & Schleiss, 2002; George & Sitar, 2016; Goodman & Shi, 1985), or numerical simulations using coupled fluid-solid numerical methods (e.g., Gardner, 2023). Empirical methods are fast to apply at a spillway scale but are based on simplified inputs. Analytical methods apply directly to individual blocks but require many inputs of the forces acting on each block face - which can be time consuming to estimate.
Three-dimensional numerical methods currently in development can model scour and plucking of individual blocks directly by modelling fluid-solid interactions, but they are typically impractical at the spillway scale due to prohibitively large computational requirements (Gardner, 2023; Gardner & Sitar, 2019; Teng et al., 2023). Existing numerical models used in practice generally simplify the geometry to two-dimensional cross sections (Bollaert & Schleiss, 2005). Current methods are unable to both explicitly model hydraulic plucking mechanisms at the spillway scale and do this in three dimensions with arbitrary block shapes. Using the actual 3D block geometry is required to represent the block kinematics which is widely known to be a predominant factor in stability of rock blocks. Simplifications using rectangular blocks are unable to account for anisotropy caused by oblique joint orientations, and the stability of more irregular polyhedrons may vary significantly from a regular cube (George & Sitar, 2016).
Deformation Characteristics and Damage Evolution Mechanisms of Dry and Saturated Argillaceous Siltstone Under Cyclic Loading
Authors: Wu P , Chen J , Fu X. D , Huang J. H 
Published: August 2024

ABSTRACT:
Argillaceous siltstone is a common hydrophilic rock in geotechnical engineering, and its mechanical properties undergo significant changes under the combined influence of water and cyclic loading. Therefore, systematically investigating the mechanical behavior of argillaceous siltstone under cyclic loading in different moisture conditions is of great significance for guiding engineering design and improving the accuracy of disaster prediction. In this study, triaxial cyclic loading tests were conducted on dry and saturated specimens of argillaceous siltstone from Shiyan, Hubei Province, under different frequencies and confining pressures. A comparative analysis was performed on the strength and deformation characteristics of dry and saturated specimens, as well as the influence of frequency and confining pressure on their mechanical properties. The evolution of damage in argillaceous siltstone under cyclic loading was elucidated. The results indicate that: (1) Compared to dry specimens, the strength of saturated specimens significantly decreases, and the movement of the hysteresis loop towards larger strains is more pronounced; (2) Deformation of dry specimens shows minimal variation with increasing frequency, while an increase in frequency significantly accelerates the degradation of saturated specimens; (3) Lower confining pressures can restrain crack development in saturated specimens, but excessively high confining pressures can accelerate their failure; (4) After saturation, damage variables are noticeably influenced by frequency, showing a trend of initially decreasing and then increasing with changes in confining pressure.

1. INTRODUCTION
In China, red-colored soft rock formations, commonly referred to as the "red layer" in engineering contexts, are widely distributed. Among these formations, argillaceous siltstone stands out as a crucial component. Characterized by minerals such as montmorillonite and kaolinite, argillaceous siltstone exhibits hydrophilic properties, resulting in significant mechanical changes upon immersion in water. This type of rock is particularly prevalent in the southern regions of China, notably in the southwest and south-central areas, where heavy precipitation is common, rendering water presence inevitable in various construction projects.
A Training Experiment on the Cost and Benefit of Training U-Net for Laboratory Signal Processing
Authors: Kong A , Wang C. , Lin Q. , Qiquan X. , Opperman N. , Wu C. , Knippel E. P. , Hampton J. C. 
Published: August 2024

ABSTRACT:
U-Net is used by seismologists for picking phases of seismic waveforms. Applying U-net to process laboratory acoustic emission (AE) signals is useful for lab-scale experiments. In this paper, we document experiments on training two different U-Nets with a dataset containing 6532 manual pickings. This is to prepare for optimizing (or challenging) the maximum phase picking accuracy in the next step. Two label options (i.e., manual picking versus AIC auto-picking), two mask options, and two loss function options are considered in the training experiments. We observe the accuracy of the U-Nets, the shape of the output probability string, and the training and validation loss curves. The training time for U-Net-Two is shorter than that of U-Net-One. The binary-cross-entropy loss function is, as expected, proper for the initial stage of training. Applying the alternative option of the loss function may be useful for fine-tuning the model. We find that the length of the non-zero probability points in the label should be adjusted according to the frequency of the waveform. Shifting the signals and labels simultaneously will not affect the training. In the future this "shifting treatment" will be used for data augmentation.

1. INTRODUCTION
While originally developed for biomedical imaging segmentation [1], U-Net is useful for many other tasks that require classification at the data-point-scale. In recent years, the application of U-Net for picking different phases of seismic waveforms has received broad attention [2]. Such a technique for processing seismic waveforms has immediate application to laboratory AE signal processing. However, training a U-Net for processing laboratory AE signals faces many challenges. First, environmental noise in laboratory AE signals can be catalog based, so the usefulness of conducting transfer learning using a well-trained U-Net is limited. Second, the training of a U-Net demands a large amount of manually labeled P-wave arrivals. Previously successful training of a U-Net for seismic waveform processing utilized an extensive data pool consisting of over 700,000 manually labelled P and S arrival times picked from over 30 years of earthquake recordings provided by the Northern California Earthquake Data Center [2].
An Experimental Study on the Influence of Cyclic Loading and Eccentric Casing Geometry on Cement Sheath Integrity
Authors: Zheng Danzhu , Ozbayoglu Evren , Miska Stefan , Baldino Silvio 
Published: August 2024

ABSTRACT:
Zonal isolation is essential for the longevity and productivity of any oil or gas well. Losing zonal isolation can lead to environmental problems such as contamination of freshwater tables, sustained annular pressure buildup (SAP), and extensive and expensive remedial work. In this study, we studied the fatigue failure of cement through cyclic loading experiments on thick-wall-cylinder samples. To simulate the actual wellbore conditions, we designed a two-layered sample, incorporating casing and cement. A dedicated tri-axial facility was modified to introduce cyclic internal casing pressure. Low and high-impact cyclic loading tests were conducted for both concentric and eccentric thick-wall-cylinder samples. The fatigue behavior of Class H cement and CNTs-reinforced Class H cement was studied. Besides the study of fatigue behavior, the influence of casing eccentricity was studied by analyzing the first-cycle failure. The Mohr-Coulomb failure criterion was employed to analyze the experimental data, supporting the validity of the analytical eccentric casing model established in prior research.
The experimental results demonstrate the fatigue properties of the cement sheath and validate the impact of an eccentric casing geometry. This outcome is significant for enhancing cement system design and optimizing wellbore operational strategies, including applications like hydraulic fracturing and enhanced oil recovery processes.

1. INTRODUCTION
The main goal of cementing is to provide reliable zonal isolation throughout the life of a well. The integral of cement protects the casing and prevents the formation fluid from migration. Cement quality is influential to wellbore integrity and zonal isolation. Zonal isolation is essential for the longevity and productivity of any oil or gas well. Nowadays, most wells around the world are extending deeper and deeper. Downhole conditions become increasingly complicated. Changes in downhole conditions, in terms of temperature and pressure, expose cement sheath to deductive stress that impacts the integrity (Goodwin & Crook, 1990). There are many reports about cement sheath failure in deep wells where high pressure and temperature exist. Cement failure is manifested by interzonal annular fluid movement and abnormally high annular pressure at some point behind the casing up to and at the surface (Nelson, 2006). Subsurface geo-mechanical changes can also cause severe defects in oil and gas wells' cement barriers. Damages in cement sheath, such as voids, cracks, and channels or debonding between cement and casing, caused by either a poor cementing operation or due to the thermal/pressure fluctuations in a well, can threaten the integrity of cemented sheath and compromise zonal isolation.