bluuebunny/crossref_metadata_2025_split huggingface dataset:
Digital Representation of Microstructures of Cretaceous Formation Rock Cuttings in the Tarim Basin
Authors: Liang H. , Luo J. Q. , Wen T. , Yan H. , Feng W. X. , Jin Y. , Xia Y. 
Published: August 2024

ABSTRACT:
The Cretaceous Baxigai formation and Shushanhe formation in the Tarim Basin are characterized by the development of high-maturity hydrocarbon source rocks, and the extensive development of tectonic and lithologic traps, which have good prospects for oil and gas exploration. However, it is in the deep-ultra-deep zone, where complicated accidents occur frequently in drilling, logging is difficult to carry out, and the lack of complete cores is not conducive to rock mechanics-related research. In this paper, we use AMICS to form a pseudo-color map of mineral distribution, complete the denoising step based on the image segmentation of RGB images, then use the "8-neighborhood method" to obtain the edge coordinates of the mineral particles, and finally fit the edges by the "least-squares method", and then digitally reconstruct the microcosm of the rock chips. Finally, the edges are fitted by the "least squares" method to digitally reconstruct the microstructure of the rock chips. The algorithm established in this paper solves the problem of missing cores in the Cretaceous strata of the Tarim Basin, realizes the digital characterization of rock microstructures, and provides a digital geometric model for the subsequent numerical simulation work, based on which the related research can be carried out.

1. INTRODUTION
With the development of oil and gas industry, it has become the main trend of conventional oil and gas exploration and development to advance to the deep and ultra-deep neighborhood. The Tarim Basin is rich in oil and gas resources, and in recent years, there have been continuous breakthroughs in exploration and development. The natural gas of the Tarim Basin is mainly enriched in the depression at the periphery of the basin and in the Paleozoic carbonate rocks, among which the tertiary reserves of natural gas in the Kuche depression exceed one trillion cubic meters, and it is the main source of gas for China's "West-to-East Natural Gas Pipeline" project (Ke et al., 2014).
Influence of Specimen Shape on New Simple Shear Test Using Rock Prism Specimen
Authors: Sato I. , Togashi Y. , Kotabe H. , Hatakeyama K. , Osada M. 
Published: August 2024

ABSTRACT:
Rock masses are subjected to simple shear mode deformation during earthquake. Currently, there is no standardized simple shear test method for rocks in Japan. The authors propose a new test method, the simple shear test of a prismatic rock specimen using torsional shearing. In this test, prism specimens are radially installed on the pedestal, the cap is placed on the specimen tops, and then specimens are torsionally sheared by a torque with fixed axial displacement of the cap. In this study, to investigate the influence of radial shear load distribution by the applied torque on stress-strain relationships, proposed tests were conducted by varying the length/width ratio of the prismatic Berea sandstone specimens from 1 - 2.5. The results demonstrated that the more smooth stress-strain relationship, the shorter specimen length. On the other hand, the longer specimens showed more complex failure modes, and the strain decreased with increasing torque and did not increase monotonically.

1. INTRODUCTION
Rock masses are subjected to simple shear mode deformation during earthquake. Currently, there is no standardized simple shear test method for rocks in Japan (Japanese Geotechnical Society, 2015). Since heterogeneity and anisotropy predominate in rock masses (Togashi et al. 2018; 2021a; 2021b), the deformation mode applied in loading tests has a significant influence on the mechanical behavior of rock masses. Therefore, it is necessary to test the appropriate loading mode for each event, and simple shear mode tests are necessary for rock deformation during earthquake.
Torsion tests on rock have been conducted in a small number of cases (Talesnick and Ringel, 1999; Paterson and Olgaard, 2000). In these tests, the end face of the specimen and the cap were rigidly bonded with adhesive and subjected to high cell pressures of 10 - 50 MPa to transfer shear load. However, using an adhesive strong enough to withstand the shear load of the rock may damage or deteriorate the cap and pedestal. It may not be reusable. It is not suitable for studies where multiple tests are essential, such as estimating failure criteria.
The authors propose a new test method, the simple shear test of a prismatic rock specimen using torsional shearing as shown in Fig. 1 (Togashi et al. 2023). In this test, prism specimens are radially installed on the pedestal, the cap is placed on the specimen tops, normal load is applied to the specimen, and then specimens are torsionally sheared by a torque with fixed axial displacement of the cap. This method enables the reproduction of the simple shear mode deformation experienced by rock masses during earthquakes. Additionally, it is possible to replicate arbitrary rock mass conditions by varying the normal stress.
Numerical Simulation of Wellhole Stability in Cretaceous Fractured Water-Sensitive Formation in Tarim Basin
Authors: Zhou Bao , Zeng Ping , Chi Jun , Xu Kaifeng , Lu Hui , Xia Yang , Jin Yan 
Published: August 2024

ABSTRACT:
The Cretaceous Baxigai Formation and the Shushanhe Formation in the Tarim Basin are fractured water-sensitive formation. Wellbore instability is frequent during the drilling process. It's urgent to clarify the mechanism of the fractured water-sensitive formation, and to guide drilling operations. The formation occurrence is determined based on the formation micro-scanner imaging (FMI). And the digital wellbore model is established. Numerical simulation of the fluid-solid coupling process in the digital wellbore model is carried out by 3DEC to analyze the effects of drilling fluid density, fracture permeability, number of fractures and drilling fluid immersion time on the wellbore stability. The results show that: (1) increasing density is beneficial to improve the wellbore stability at the early stage; (2) with the increase of the fracture permeability, the wellbore state becomes more serious; (3) with the increase of the number of fractures and the increase of the immersion time of drilling fluid, the risk of the wellbore instability increases. The model in this paper can be used to study the dynamic process of wellbore instability in fractured water-sensitive formations, reveals the mechanism of wellbore instability in the Cretaceous mudstone of the Tarim Basin, and it can provide opinions and guidance for drilling.

1. INTRODUCTION
With the increasing demand of energy and the exploration of conventional energy, deep well and ultra-deep well drillings are now more widely performed exploratory (Zhang S et al., 2015). However, several problems such as collapse, jamming and leakage are encountered during the drilling process owing to high temperature, high pressure and complex geological conditions, and these wellbore instability increases costs of ultra-deep drilling (Gholami R et al., 2014). In fractured formation, drilling fluids penetrate into formation leads to the reduction of rock strength, decrease in friction angle, especially in water-sensitive formation (Chen X et al., 2002).
A large amount of oil and gas is founded in the Ordovician carbonate formation of the Tarim Basin with buried depth of more than 7200m. Some reservoirs are distributed near the faults and it substantially makes formation fractured (Lai et al., 2021). The upper formation named Cretaceous Baxigai formation and Shushanhe formation is mudstone with a thickness of 150m-300m. Wellbore instability occurs frequently in the progress of drilling mudstone formations. Clarify the mechanism of wellbore instability to ensure safe drilling and reduce drilling costs is prompted recent exploration.
Numerical Stress Computation Around Cavity Using Boundary Element Method for Elastic Material
Authors: Habibi A. 
Published: August 2024

ABSTRACT:
Precise estimation of field variable values around a cavity is vital for excavation operation safety. The singular nature of stress around the cavity makes the computations challenging for Finite Element Method (FEM) software. Although the Boundary Element Method (BEM) offers a semi-analytical formulation, it gives rise to a set of new challenges in boundary condition enforcement, allocating the traction variables at corners, integration, solving, and post-processing. In this study, the problem of a small cavity inside a three-dimensional elastic domain has been explored using continuous and semi-discontinuous elements. The results of the BEM code were compared with an analytical solution and industrial software (Abaqus). The comparison of stress values indicates that with much fewer elements, BEM is still capable of providing proper results with a few percent of errors. For remote coordinates, error values are less than one percent; for locations too close to the cavity, with a finer mesh, error values are reduced to one percent with the same simple integration scheme. Additionally, for such simulation, semi-discontinuous elements result in higher error values even at remote locations and low deviation ratios.

1. INTRODUCTION
Stress concentration near a cavity and its higher values compared to the remote stress values at the boundary is a well-established subject. This stress intensity could impact the stability of rock during an excavation operation. A precise estimation of stress values using analytical solutions or numerical software can reduce the chance of rock failure. Yet analytical solutions are a proper basis for code and software error evaluation, they just address a set of specific problems and geometries.
Boundary Element Method (BEM) is a numerical tool for engineers to approximate stress and displacement values by scattering elements over boundary surfaces. In this study, direct BEM formulation has been used which includes singular integrands and discontinuous boundary-imposing challenges (Aliabadi, 2002; Crouch et al., 1983; Gao & Davies, 2002; Hall, 1994; Leng, 2007). Among many methods for dealing with discontinuous Boundary Conditions (BC), non-conforming elements have been extensively utilized. Semi-Discontinuous Element (SDE) is one of the methods that simplify the BC imposing by introducing new nodes to differentiate degrees of freedom (Aliabadi, 2002; Dyka & Millwater, 1989; Mi & Aliabadi, 1992; Mitra & Ingber, 1993; Parreira, 1988; Yan & Lin, 1994). A simpler method, referred to as Unique Traction (UT) in this work, neglects all challenges. Both UT and SDE have been utilized in this study.
Characterization of Water-Rock Interaction in Water-Sensitive Tight Oil Reservoirs and its Mitigation Method with Pilot Tests
Authors: Xie Bobo , Wang Bin , Wang Mingxing , Teng Jinchi , He Bingxian , Liang Tianbo 
Published: August 2024

ABSTRACT:
The injection of fracturing fluid into water-sensitive reservoirs can cause a rapid pressure decline during production, and the estimated ultimate recovery (EUR) of the well is only 1/4 to 1/3 of that in neighboring plays without water sensitivity. Laboratory experiments are conducted to analyze the impact of water-sensitive minerals on the rock matrix, and quantify the in-situ damage during the shut-in and production. Furthermore, water-sensitive inhibitors are developed, whose effectiveness is then examined in field pilot tests. The composition change of reservoir cores is analyzed using XRD, and their microstructure change is analyzed using SEM before and after interacting with the fracturing fluid in the mimicked reservoir condition. After water-sensitive inhibitors are developed, their effectiveness on mitigating the rock damage is characterized using the in-situ CT scans. The oil production rate and types of stabilizers of 34 oil wells in P3w1 pay zone and 29 oil wells in P3w2 pay zone are summarized. Finally the effect of stabilizer on oil production rate is investigated. The smectite ratio is over 70% in clay minerals. When the rock sample is submerged in the stabilizer solution, no clay swelling is observed. The in-situ CT scans show that the porosity decreased by 0.99% after interacting with the fracturing fluid. While when stabilizers are used in the fracturing fluid with concentration of 2%, the damage of rock permeability is reduced by 49.35%, and porosity increases by 0.66%. No obvious difference in well production is noticed when the KCl solution is used in the field. On the contrary, well production increases 40% because of the use of stabilizer. An in-situ characterization method is proposed based on a coreflood in a micro-CT, which can show the real-time change of pore structure and permeability of a rock sample. An effective water-sensitive stabilizer formula is developed, which can be a promising tool to develop water-sensitive tight oil reservoirs based on current fracturing techniques.
Experimental Study on Permeability and Desorption of Tectonic Coal Under Mechanical Vibration
Authors: Li K. C. , Hou B. , Zhai Z. W. 
Published: August 2024

ABSTRACT:
Coalbed methane (CBM) is one of the unconventional oil and gas resources. The potential of CBM resources in the north of Qinshui Basin is good, but it has not reached the scale of industrial exploitation. CBM mining not only can obtain energy, but also has important significance in reducing coal mine safety accidents and reducing greenhouse effect. In this paper, according to the characteristics of low porosity, low permeability and soft structure of coal reservoirs in the study area, the permeability and desorption of tectonic coal samples collected from different mining areas are measured and analyzed under mechanical vibration. The experimental results show that the low frequency mechanical vibration has obvious effect on the permeability of tectonic coal samples. Increasing the mechanical vibration frequency can promote the large amount of methane desorption in coal reservoirs with more primary fractures and increase the production of CBM. This study can provide a technical reference for the mining of tectonic CBM.

1. INTRODUCTION
Qinshui Basin is located in the central and southern part of Shanxi Province, China, which is rich in coal reserves and also contains a large amount of coal-bed methane (Zhou, 2013). The northern part of the basin is mainly coal-bearing strata of Upper Carboniferous Taiyuan Formation and Lower Permian Shanxi Formation (Wang et al., 2006). CBM mainly exists in the form of adsorption in the coal body, and its production is a complex process of adsorption/desorption, diffusion/seepage (Yi, 2007). At present, the main methods used to increase production are hydraulic fracturing (Jiang et al., 2016; Johnson et al., 2002; Hou et al., 2022), heat injection (Wang et al., 2015; Wang et al., 2023; Goraya et al., 2019), gas injection (Jessen, et al., 2008; Mazzotti, et al., 2009), vibration (Tanuwijaya, C., & Ariadji, T. 2009; Cui et al., 2024) and other mining methods. In order to explore a technology suitable for the combined extraction of CBM from surface and underground of shallow mid-level tectonic coal in northern Qinshui Basin, the permeability and desorption of tectonic coal samples collected from different mining areas were measured before and after mechanical vibration. The influence of vibration frequency on permeability and desorption of tectonic coal is studied, which provides a technical reference for vibration mining of tectonic coal bed methane.
The Influence of Stress Heterogeneity on Hectometer Scale Hydraulic Stimulation Experiments
Authors: Bröker K. , Valley B. , Gholizadeh Doonechaly N. , Rosskopf M. , Hertrich M. , Giardini D. , BedrettoLab team _ , Rinaldi A. P. , Clasen Repollés V. , Obermann A. , Ma X. 
Published: August 2024

ABSTRACT:
From 2022 to 2023, a series of hydraulic stimulation experiments were conducted at the Bedretto Underground Laboratory in Switzerland (BedrettoLab) to study the creation of an engineered geothermal reservoir in crystalline rock. A 400 m long stimulation borehole was divided into 14 intervals using a multi-packer system. During the volume characterization, an azimuthal rotation of borehole breakouts was observed, indicating a stress perturbation caused by a major fault zone intersecting the experimental volume. In this study, we present the seismo-hydromechanical observations from seven hydraulic stimulations in four selected intervals. This is the first systematic comparison of repeated stimulations in different intervals at the BedrettoLab. Two of these intervals are neighboring the fault zone, while the other two are located further away. We utilize data from a dense multiparameter monitoring network to show that the stress perturbation affects the reactivation of similarly oriented pre-existing fractures. In our example, the stress perturbation caused by the fault zone prevents the reactivation of structures in the nearby interval, while similar structures are clearly reactivated in the three other intervals. Reactivation pressures from pressure-flow rate plots agree with the pressures encountered at the onset of seismicity. Given that the prevailing fractures are well oriented for shear reactivation within the far field stress field, hydraulic shearing is considered the probable reactivation mechanism.

1 INTRODUCTION
Interest in engineered geothermal systems (EGS) as a low emission, renewable energy source (Lu, 2018; Aghahosseini and Breyer, 2020) has grown since the late 2000s. In Central Europe, EGS reservoirs with sufficiently high temperatures are located at depths of several kilometers, where the permeability of the crystalline basement rocks is insufficient for geothermal energy extraction. Permeability enhancement is achieved through hydraulic stimulation, which can involve hydraulic shearing of natural fractures or shear zones, hydraulic fracturing of intact rock, or a combination of both (McClure and Horne, 2014). This permeability enhancement goes hand in hand with induced seismicity, which can reach damaging levels if large fault zones are reactivated (e.g. Deichmann and Giardini, 2009; Evans et al., 2012; Ellsworth et al., 2019). To address this challenge, several scaled-down in situ hydraulic stimulation experiments have been conducted at decameter scale in underground research laboratories in representative crystalline rock types (e.g. Amann et al., 2018; Zimmermann et al., 2019; Schoenball et al., 2020; Fu et al., 2021).
A Comparison of Tensile Testing Techniques and Predictive Correlations Using Simulated Rock
Authors: Lindenbach E. J. , Foran J. R. , Bearce R. G. 
Published: August 2024

ABSTRACT:
The mechanical properties of rock are important parameters in the structural analysis of dams as they help inform an understanding of how a structure is likely to behave under loading. One commonly utilized but difficult-to-obtain engineering parameter is the tensile strength of rock. Direct tensile strength (DTS) testing of rock is rarely performed due to cost considerations and the complexity associated with the testing. The majority of testing is performed using indirect tensile methods, such as the Brazilian Tensile Test (BTS), akin to the splitting tensile strength test typically performed on concrete, or by using correlations to other mechanical properties like the crack initiation strength, mi from Hoek-Brown, or the Mode I fracture toughness. While the BTS is easier to prepare and more economical, significant uncertainty remains in how the test results correlate to the DTS and the actual behavior in situ. All the major organizations that standardize rock testing are in broad agreement on how to run the BTS however, there is still some room for more detailed guidance about platen shape, the use of a cushion, stress concentrations, and how to use the BTS to estimate the DTS. The goal of this research is to perform laboratory testing on stiff and soft simulated rock to improve understanding about the DTS and BTS tests, how different methods compare, and refine correlations between mechanical properties and the DTS.

1. INTRODUCTION
In order for a robust model to be developed, the anticipated range of behavior of rock when subjected to a variety of loading conditions must be understood and quantified. This range of behavior can be defined by a full strength envelope developed from laboratory testing and up-scaled to the problem of interest.
A full strength envelope for rock is provided in Figure 1, with the typical laboratory tests used to define the various portions of the curve given on the figure (Hoek and Martin, 2014). The tensile strength of rock defines a cutoff value in the overall shear strength envelope, but as indicated above, this value can be difficult to determine. The significantly more common uniaxial and triaxial compression tests are typically used to define the remainder of the envelope past the tensile cutoff.
Meter-Scale Laboratory Earthquakes Triggered by Fluid Injection and the Role of Background Stress in Mediating Runaway Ruptures
Authors: McLaskey Gregory 
Published: August 2024

ABSTRACT:
I present large-scale laboratory experiments where water is injected directly into a stressed fault that is a saw-cut interface in a slab of granite (3 m by 1.5 m and 300 mm thick) in an attempt to examine the earthquake energy budget. The laboratory fault is subjected to 2-10 MPa stress levels, and exhibits slow and aseismic slip within a localized "nucleation zone" prior to rapid dynamic fault rupture. Slow slip associated with the nucleation of dynamic rupture is observed both for cases where water is injected onto the fault and where slip initiates spontaneously due to the external application of shear stress. The 3-m-long sample is long enough that ruptures sometimes arrest within the sample. So, using arrays of sensors, we study the conditions required for rupture arrest, a crucial element in determining whether an earthquake rupture will grow into a large, devastating event, or will remain small and harmless. The rupture can be modeled as a shear crack, and we employ fracture mechanics to explain rupture arrest. Our experiments demonstrate that the initial shear stress plays an important role in an earthquake's size. Another key unknown in earthquake mechanics is the shear fracture energy required to advance rupture. In the lab, we can measure values in the range of 1-10 J/m^2, but it is unclear if shear fracture energy, or, similarly, breakdown work, increases with the rupture size as it propagates into an increasingly rough fault surface. Answering such a scaling question is key to understanding the earthquake energy budget, a major impediment in our ability to accurately model and predict earthquakes.