bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Consistent Approach for Stress Field Orientation Determination from Multiple Measurements: Calipers, Images and Sonic
Authors: Gaede O. , Karpfinger F. , Donald A. 
Published: January 2025

ABSTRACT:
A method is presented to qualify the maximum horizontal stress direction on basis of dipole shear sonic anisotropy in near-vertical wellbores. The proposed scheme follows a similar qualification standard to that used for stress observations on the basis of image logs and caliper logs in the World Stress Map Project. Image log analysis and shear wave anisotropy analysis will often complement one another and add confidence when both are observed. The combination of geological setting and rock properties, together with drilling practices, does not always result in clear borehole failure, limiting the ability to quantify stress direction from images alone. Shear sonic anisotropy is often able to identify horizontal stress imbalance where borehole failure has yet not occurred. Herein, we review the methodology to determine stress direction on the basis of dipole borehole sonic data, including examination of the effect of hole ovality. The use of slowness frequency dispersion curves is particularly important, as dispersion curve analysis is essential for distinguishing shear sonic anisotropy due to horizontal differential stresses from that caused by lithological fabric and natural fractures. A new machine-learning-based analysis of the dispersion data is used to uniquely identify the crossover characteristics of stress-sensitive zones.

1 INTRODUCTION
Stress field characterization is an important input for all subsurface geomechanics applications. Improved understanding of the stress direction and the stress regime will help to reduce the risk of drilling operations and enhance the success of hydraulic fracturing (Fjaer et al., 1992; Zoback, 2010).
Over the last 30 years four-arm caliper (Plumb and Hickman, 1985) and borehole image data (Zoback et al., 1985) have been established as the industry standard measurements to interpret the in-situ horizontal stress direction.
The interpretation of the stress direction is closely linked to the near-wellbore stresses that are a function of the far-field stresses and the borehole pressure. Breakouts (BO) can be observed when compressive stresses on the bore-hole wall exceed compressive shear strength of the formation (usually the case when borehole pressure is too low).
Role of Negative Pore Pressure in Injection-Induced Post-Slip of Rock Fractures
Authors: Fang Z. , Wu W. 
Published: January 2025

ABSTRACT:
Negative pore pressure induced during unconventional energy production may provide new insights into assessing and mitigating injection-induced post-slip of rock fractures. Using triaxial experimental setup in the laboratory, we sheared sawcut, filled, and natural fractures in granite under zero, positive, and negative pore pressures and measured the evolution of fracture permeability. The results suggest that negative pore pressure increases the peak strength in the sawcut and filled fractures, while reducing their permeability and post-peak stressing rate. The reduction in post-peak destressing rate is most closely related to negative pore pressure in the sawcut fracture with the lowest fracture permeability, whereas in the natural fracture, the reduction in post-peak destressing rate is associated with increased hydraulic aperture following consecutive shear tests. Moreover, in the sawcut fracture, the decay in post-peak stressing rate is more rapid under negative pore pressure, corresponding to a rapid reduction in post-slip frequency during injection-induced seismicity. This rapid decay inhibits post-slip events after the shut-in of fluid injection.

1. INTRODUCTION
Injection-induced post-slip is commonly observed during unconventional energy production and is driven by pore pressure diffusion, shear stress redistribution, and slip-stress transfer (Cebry and McLaskey, 2020; Kim and Avouac, 2023; Guglielmi et al., 2015). Post-slip events are characterized by a declining frequency over time since the peak strength, resulting from an exponential reduction in post-peak stressing rate after the mainshock perturbation (Dieterich, 1994). A rapid decay represents swift re-sealing of fractures after the peak strength (Miller, 2020).
According to available data of post-slip frequency versus time since peak strength (Table 1), the decay rate exponent from natural earthquakes varies more widely and is generally lower than that from induced seismicity of lower seismic magnitudes. The normalized post-peak stressing rate, calculated as the normalized post-slip frequency (Dieterich, 1994), drops more rapidly to nearly zero for induced earthquakes. Field observations indicate that the decay rate exponent increases with deeper post-slip events (Shebalin and Clément, 2017), contrasting with the higher exponents of the shallower induced seismicity. Fluid extraction during energy production has been demonstrated to result in fracture compression and inhibit post-slip events (Segall, 1985), which potentially increases the decay rate exponent. Thus, understanding the post-peak stressing rate during unconventional energy production may uncover the rapid decay of injection-induced post-slip events.
A Novel Experimental Protocol for Fault Generation and Reactivation Studies
Authors: Kiewiet M. Duque Nogueira , Monmusson L. , Kiewiet L. , Penny I. , Maney B. , Kager S. , Giwelli A. , Banks S. , Barroso E. V. 
Published: January 2025

ABSTRACT:
In this paper, we present an innovative workflow that allows the performance of coupled direct shear tests in a large direct shear rig utilising whole core samples extracted from wellbores to enable the investigation of fault generation and reactivation processes using rock materials that more closely relate to a given underground study area, whilst minimising the need for large outcrop or synthetic rock samples in experimental campaigns. The methodology involves the preparation and shearing of a composite sample made from the intact (i.e., not fractured) core sample and cement paste and then sub-coring of the sheared composite sample to obtain a 38 mm diameter plug containing the fault zone for further investigation in axisymmetric triaxial setups. The examination of the sheared plug obtained in the first trial confirmed the generation of the fault zone at the predicated angle and location, evidencing the technique's success. It represents a significant advance in our capabilities to characterise sheared materials from diverse depth ranges and geological contexts, complementing field observations and helping to address several aspects relevant to industry and academia.

1. INTRODUCTION
Tectonic and anthropogenic stress changes within and near an underground reservoir can significantly impact the integrity of faults and fractures, potentially leading to fault reactivation, with a follow-on impact on the reservoir's containment (vide, e.g., Wriput and Zoback, 2000). Therefore, it is crucial to assess the mechanical integrity of these discontinuities and understand the alterations in fluid flow along or across them in response to changes in the surrounding stress state. This knowledge is essential for the safe and effective storage or production of natural gas, CO2, and hydrogen accumulations.
In this context, experiments that replicate fracture or fault generation and their reactivation while monitoring changes in their hydraulic conductivity and microseismic response can provide insightful information for the understanding of faults’ static and dynamic behaviour and better predict how geological events or injection or production strategies could affect the reservoir's overall stability and sealing potential.
Stability Analysis of Gas Hydrate Wellbore During Drilling Based on Thermal-Hydro-Mechanical-Chemical Coupling
Authors: Li Xiongrong , Dong Baohong , Huang Sha , Li Bin , Li Jing , Wei Yaoran , Yang Heng 
Published: January 2025

ABSTRACT:
During the drilling of hydrate-bearing formation, temperature and pressure differences between the reservoir and the wellbore cause the decomposition of hydrates around the wellbore. It reduces the mechanical properties of the reservoir and leads to wellbore instability. Most of the research primarily focuses on the stress disturbances around the well due to temperature and pressure changes, with relatively few studies addressing the stability of hydrate-bearing wellbores during the invasion of drilling fluids. This study investigates the mechanical response characteristics of hydrate-bearing formation during the drilling process, based on a dual-coupling platform for hydrate decomposition phase transition and geomechanics. The platform integrates the thermal–hydro– chemical module and the mechanical analysis module using TOUGH+HYDRATE and FLAC3D software, respectively. An interpolation algorithm is employed to transfer and call seepage field parameters and mechanical field parameters between the two software programs. This study considers changes in hydrate saturation, formation temperature, and pressure caused by drilling fluid invasion into the reservoir. Sensitivity analysis are conducted on the hydrate reservoir's response to drilling fluid density, temperature and formation permeability. Additionally, the wellbore collapse period for hydrate formations is predicted. The results show that invasion of drilling fluid into the hydrate formation causes a rapid rise in pore pressure around the wellbore. The decomposition of hydrate leads to a decrease in the mechanical properties of the formation, increasing the risk of wellbore collapse. With the increase of drilling fluid density and reservoir permeability, the decomposition of hydrate around the well accelerates. The period of wellbore collapse for the hydrate formation is 10.2 days under the basic case.

1. INTRODUCTION
Natural gas hydrates can be considered as the future hydrocarbon energy (Kvenvolden, 1993; Wood and Jung, 2008; Sloan and Koh, 2007). China's sea areas hold about 80 billion tons of oil equivalent in natural gas hydrate resources, with 74.4 billion tons in the South China Sea. This makes it a key source of clean and efficient oil and gas replacement for the country. Currently, several countries are engaged in natural gas hydrate extraction, using methods such as depressurization, thermal stimulation, and chemical inhibition(Xu and Li, 2015; Moridis et al, 2011). However, safe and reliable drilling technology is essential for the successful exploration and development of these resources.
A THM Model for CH4-CO2 Transport in Fractured Coal
Authors: Tian Jianwei , Gao Yanan 
Published: January 2025

ABSTRACT:
In the context of the global energy transition and the drive towards achieving net-zero carbon emissions, unconventional gas extraction methods have gained significant attention. This paper presents an advanced fully coupled thermo-hydro-mechanical (THM) model for enhancing methane (CH4) production and simultaneously storing carbon dioxide (CO2) in fractured coal seams. Our innovative approach integrates the complex interactions between thermal, hydraulic, and mechanical processes within the fracture network, addressing the dynamic evolution of matrix and fracture permeability ratios. By injecting CO2 into coal seams, methane is desorbed and produced more efficiently, while CO2 is securely stored within the fractures and pores of the coal matrix. The proposed model investigates the dual benefits of enhanced CH4 production and CO2 storage, offering a sustainable solution for energy production and greenhouse gas mitigation. Comprehensive simulations demonstrate the model's effectiveness in improving gas recovery rates and provide insights into the long-term stability of CO2 storage in geological formations. This study highlights the critical role of THM coupling in fracture networks and the dynamic permeability changes, ensuring a robust and efficient process for both gas extraction and CO2 sequestration, thereby contributing to the goals of the energy transition and net-zero carbon targets.

1. INTRODUCTION
The burgeoning energy demands of rapidly developing nations such as China and India have propelled coal seam gas (CSG), primarily methane (CH4), to the forefront as a significant energy resource. Simultaneously, escalating concerns over climate change have underscored the urgency for effective carbon dioxide (CO2) sequestration methods. Injecting CO2 into coal seams emerges as a promising strategy that not only facilitates long-term CO2 storage but also enhances CH4 recovery, offering a dual benefit of energy production and greenhouse gas mitigation (Gunter et al., 1998; Luo et al., 2013).
Despite the potential, the application of CO2 enhanced CH4 recovery and the simultaneous decarbonization faces substantial obstacles. Key among these are the complex multiphysics phenomena inherent in the process, including gas adsorption/desorption, diffusion, and the mechanical deformation of coal matrices (Bustin et al., 2016). The multiscale heterogeneity of coal seams—characterized by variations in porosity, permeability, and the presence of natural fractures—further complicates predictive modelling and optimization efforts. These challenges necessitate sophisticated modelling approaches to accurately simulate and manage the gas transport and storage mechanisms within coal seams.
2D Lineaments Extraction, Drainage Pattern Evaluation Using Digital Elevation Modelling and Tectonic Stress Magnitudes Analysis of Southern and Northern Potwar Deformed Zones (SPDZ & NPDZ), Pakistan
Authors: Fayyaz. Najwa 
Published: January 2025

ABSTRACT:
This research investigates the tectonic architecture and geomorphic evolution of the Southern and Northern Potwar Deformed Zones (SPDZ & NPDZ), leveraging cutting-edge geospatial and geophysical techniques. High-resolution Digital Elevation Models (DEMs) facilitated the extraction of 2D lineaments and drainage patterns, elucidating tectonic controls on fluvial morphology. The hydrological network was analyzed using the D8 method, while lineament extraction employed Hough transformation algorithms to enhance precision. Stream profile analyses quantified geomorphic indices, revealing marked contrasts in erosion and uplift rates between SPDZ and NPDZ. Advanced structural analyses utilized Rose and Mohr Diagrams to delineate fault orientations and compute tectonic stress magnitudes. Temporal structure maps, derived from seismic interpretations and two-way travel time (TWT) data, unveiled subsurface geometries, prominently featuring folded and thrust fault systems. A comprehensive correlation between drainage networks and tectonic lineaments highlighted their synergistic impact on regional landscape dynamics. This study confirms a compressive tectonic regime with localized strike-slip deformation and provides critical insights into the interplay of tectonic processes and geomorphic responses within the Potwar Plateau. These integrative methodologies present significant implications for structural analysis and hydrocarbon exploration in geologically intricate terrains.

1. INTRODUCTION
The Potwar Plateau is part of the Northwestern Himalayan Fold and Thrust Belt, located on the western border of the India-Eurasia collision zone. The Potwar Plateau's tectonic settings are impacted by the northward sinking of the Indian plate beneath the Eurasian plate. We utilized SRTM's Digital Elevation Models (90 m resolution version 3.0) The vectorization of flow directions enabled us to determine stream pathways. The retrieved drainage network included 112 streams that provided elevation and upstream area information based on their geographical positions (Ahmed, 2019).
The stream profile analysis assisted us in calculating the geomorphic indices and uplift rates for each stream under particular assumptions. The streams in NPDZ have higher steepness and concavity indices than the streams in SPPZ. The direction of lineaments and drainage patterns contributed to the mathematical deformation calculation. Seismic methods were utilized to investigate the Eocene successions, which are two conspicuous and significant reflectors (Najwa, et al., 2023). The seismic line's two-way travel time (TWT) was utilized to generate temporal structure maps. The Tectonic and geological map of Northern and Southern Potwar Deformed Zones is shown in Figure 1.
Research on Cross-Layer Propagation of Fractures in Coal Measures Strata
Authors: Wang Jia , Zhou Fujian , Wang Zhiwei , Li Shenjian , Sheng Mao 
Published: January 2025

ABSTRACT:
Hydraulic fracturing in coal measures strata encounters difficulties in the longitudinal penetration of fractures. To figure out which engineering parameters can hydraulic fractures penetrate through coal measure strata, a series of mechanical tests, in-situ stress measurement and true triaxial fracturing experiments were carried out. We found that the mechanical strength of mudstone is significantly higher than that of coal: in terms of the average values, the elastic modulus, uniaxial compressive strength, tensile strength, and fracture toughness of mudstone are 2.65 times, 1.47 times, 2.27 times, and 2.78 times those of coal, respectively. The higher of the fracturing fluid viscosity and injection rate, the easier for hydraulic fracture to penetrate. According to fracture penetration chart, a critical line was fitted. When injection rate &gt; 6 m3/min & viscosity &gt; 50 mPa·s or injection rate &gt; 4 m3/min & viscosity &gt; 150 mPa·s, hydraulic fracture can penetrate through coal measures strata.

1. INTRODUCTION
As an unconventional nature gas resource, coalbed methane (CBM) has the characteristics of clean, efficient, and large resource reserves. It is one of the important energy reserves. According to the prediction of CBM, the resource volume of CBM in the land area with a burial depth of 300-2000 m in China can reach 3.146×1012 m3(Chenglin et al., 2009). The exploration and development of CBM has great significance.
However, in western China, there exists a thin interbed reservoir with alternating mudstone and coal (Fig. 1). The production of CBM after fracturing is lower than expected due to inadequate communication in the vertical fracture direction. Previous fracturing experiments focus on hydraulic fractures propagate in coal, pay little attention to the research of hydraulic fracture penetration in coal measures strata.
Consequently, in this study, cores of coal and mudstone were employed to carry out macroscopic mechanical tests. The mechanical parameters of mudstone and coal were compared. The in-situ stress was restored through the Kaiser stress test. On this basis, True triaxial fracturing experiments were designed and conducted to explore the effects of injection rate and fracturing fluid viscosity on the fracture's cross-layer penetration capability. Eventually, a chart of fracture cross-layer penetration conditions was developed to provide a basis for on-site fracturing design.
Renewable Management Strategies for Geothermal Energy Reservoirs
Authors: Hamid Osman , Abdalrahman Eslam M. 
Published: January 2025

ABSTRACT:
The primary goal of this research is to develop and implement a robust management protocol for geothermal reservoirs that enhances energy extraction efficiency, prolongs operational life, and minimizes environmental impact.
The study employs a multifaceted approach starting with geoscientific exploration to pinpoint potential geothermal sites. Detailed feasibility studies follow, examining technical, economic, and environmental aspects to evaluate the viability of energy extraction. Drilling and well-testing are then carried out to acquire precise data on reservoir properties. This data feeds into advanced reservoir modeling using FEM (Finite Element Method), which simulates reservoir behavior to inform infrastructure development and operational strategies.
The application of this comprehensive strategy yielded significant improvements in reservoir output and longevity. The findings underscore the efficacy of FEM simulations in optimizing resource management and in mitigating environmental risks.
The innovative integration of geoscientific exploration, feasibility analysis, and FEM modeling represents a leap forward in geothermal reservoir management. The study's methodology sets a precedent for the application of sophisticated computational techniques in natural resource management.
Effective management of geothermal reservoirs can be achieved through an iterative process of exploration, data acquisition, and simulation-based planning. This approach not only secures the sustainable harnessing of geothermal energy but also ensures that extraction processes are economically viable and environmentally responsible. The customizable nature of the management protocol allows it to be adapted to a variety of geothermal contexts, promising wider applicability across different geologic settings.

Introduction
Geothermal energy represents a highly sustainable and renewable source of energy, generated from the Earth's internal heat. It is widely recognized for its capability to provide reliable, baseload power while producing minimal greenhouse gas emissions. The effective management of geothermal reservoirs is critical for ensuring their long-term productivity, maximizing the energy output, and mitigating potential environmental impacts.
Managing geothermal reservoirs involves several interconnected steps, beginning with exploration and site selection. Extensive geological, geochemical, and geophysical surveys are conducted to identify subsurface formations that exhibit high thermal potential. This initial phase is followed by detailed feasibility studies that assess both the economic and technical viability of the geothermal project. Environmental considerations are central to this analysis, as geothermal systems interact closely with local ecosystems and geological structures.