bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress-Dependent Characteristics of Coal Permeability in Gasification Zone of Underground Coal Gasification
Authors: Zhao Yufeng , Dong Zhen , Chen Yanpeng , Chen Hao , Xue Junjie , Chen Shanshan , Zhang Mengyuan , Peng Yan 
Published: September 2023

ABSTRACT
Underground coal gasification (UCG) is an environment friendly way to produce coal resource and its efficiency depends on gas flow through porous medium. Therefore, the flow behavior especially the stress-dependent permeability characteristics are important topics for the UCG. The stress-dependent permeability characteristics in combustion zone are widely investigated, while, ones in gasification zone are rarely investigated but they are important for gas flow from injection wells to production wells. In this study, first, permeability tests for coal after heating below 500°C were conducted under various confining pressure. Secondly, microscopic structures of coal samples after heating were observed by the scanning electron microscope (SEM). Finally, the stress-dependent permeability characteristics of coal after heating were discussed and a model involving thermal-mechanical effect was built. The main results show that (1) permeability decreases and then increases with temperature. The increase magnitude of permeability becomes obvious at 200°C and it rises significantly up to 430% at 500°C. (2) the stress-dependent behavior of permeability decreases with temperature. The decrease magnitude can be 60%. (3) samples’ microscopic structures are affected by coal pyrolysis after heating and further affect permeability characteristics. Before 200°C, obvious change of microscopic structure is width increase of existing microscopic fractures. After 200°C, lots of new microscopic fractures are generated and macroscopic fractures may also be generated in some samples. (4) considering impacts of stress, thermal swelling and microscopic fracture generated by coal pyrolysis on permeability, a model is generated and its mean error is less than 4.3%.

INTRODUCTION
Underground coal gasification (UCG) technology, as a cutting-edge technology for clean coal, has developed rapidly in recent years and has also been the focus of academic and industrial circles[1]. This technology can mine deep and ultra-deep coal seams that cannot be mined by ordinary mining technology. The coal reserves of these coal reservoirs are often much higher than those of the middle and shallow coal seams. In addition, since the redox reaction occurs in the formation, the raw coal is converted into clean energy based on CO, CH4, and H2 in the original position[2]. This process leaves the ash produced by gasification in the ground and avoids environmental pollution. It also saves the cost of transporting coal to the ground under normal mining conditions [3].
Elastic Anisotropy of Typical Rocks at Grimsel and Bukov URLs
Authors: Petruzalek M. , Aminzadeh A. , Lokajicek T. , Vavrycuk V. 
Published: September 2023

ABSTRACT
We present the elastic anisotropy of two rock samples from two underground research laboratories (URL) that are focused mainly on the investigation of functionality of deep repositories: (1) BUK sample – migmatized paragneiss, typical for the test site of the URL Bukov, Czech Republic; (2) GRM sample - Central Aare granite, a predominant host rock of the URL Grimsel, Switzerland. We used a detail ultrasonic measurement of P and S wave velocity to obtain a general form of stiffness tensor with 21 independent elastic constants for selected pressure levels from 0.1 to 100 MPa. The transformation of tensor to its principal coordinate systems shows: the Bukov migmatized gneiss is orthorhombic, whereas the Grimsel granite is transversely isotropic under atmospheric pressure. The anisotropy strength of both rocks decreases with applied confining pressure due to closing of preferentially oriented cracks. Grimsel granite becomes almost isotropic at high pressures. A great part of anisotropy in the Bukov paragneiss remains even under high pressures due to its texture. Both rocks are anisotropic under the equivalent of the overburden pressure acting at the in-situ URL conditions.

INTRODUCTION
Rocks, in general, display elastic anisotropy, as a combined effect of preferential orientations of their constituents: crystals, mineral grains and microcracks (eg. Babuska and Cara, 1991). This anisotropy depends on acting stresses, as was demonstrated by the pressure dependence of seismic velocities (eg. Pros et al. 1998). At lower pressures (&lt;50 MPa), the elasticity and its anisotropy is controlled by the cracks with characteristic exponential increase in seismic velocity. Above the crack closing pressure, the velocity/pressure relation becomes linear depending on rock matrix (crack free) properties.
The ultrasonic sounding is a laboratory technique to determine the anisotropic elastic constants for a different symmetry types, most commonly the transverse isotropy (Sarout et al., 2007) or orthorhombic symmetry (Sano et al., 1992). With decreasing level of symmetry, the number of independent elastic constants is increasing up to 21, for the most general case of triclinic symmetry. Lokajicek and Svitek (2015) presented an experimental approach to estimate such a stiffness tensor estimated from the ultrasonic sounding performed on the spherical specimen in 132 independent directions for three waves with different wave polarizations (P, SH, SV). In this experiment, the symmetry type or its orientation does not have to be known/supposed before the experiment, or may even change with the applied pressure (Lokajicek et al., 2020). The obtained general stiffness tensor can be simplified for the higher symmetries by rotation into its principal coordinate system (Aminzadeh et al., 2022).
Stochastic Homogenization of the Elastic Properties of Highly Anisotropic Shales
Authors: Charlton T. S. , Rouainia M. , Aplin A. C. 
Published: September 2023

ABSTRACT
In this paper, we present a stochastic mean-field homogenization model for upscaling the elastic properties of shale from grain-scale to core-scale. The model encompasses several levels, from the solid clay particles to a porous organic-clay matrix to the hard silt-sized inclusions to, finally, a microcracked composite. The uncertainty in the homogenized properties is considered by representing the key model parameters as random variables and quantifying the response through Monte Carlo simulation. We pay particular attention to the anisotropy of the shale elastic response, which we assume is transversely isotropic. The approach is illustrated using a case study of the Fort Simpson shale, which forms the upper fracture barrier in the Horn River Basin of NW Canada and has been shown to be highly anisotropic. The results of a comprehensive nanoindentation testing campaign, oriented both parallel and perpendicular to the bedding plane, are used to obtain the grain-scale, micromechanical statistics. Model predictions are compared with microseismic wave velocities measured in the field and good agreement is found.

INTRODUCTION
The growing momentum in the energy transition is leading to a surge in interest in subsurface energy and decarbonization systems, such as geological storage of CO2 and hydrogen, and the construction of nuclear waste repositories. Shales, or mudstones, represent important components of these technologies as their low matrix permeability makes them ideal for preventing fluid leakage over the long-term. Obtaining geomechanical properties is one of the key technical challenges because it is often problematic to conduct standard rock mechanics tests on shales due to sample recovery and preparation difficulties. The elastic anisotropy of shale is particularly difficult to characterize as it cannot be measured using wireline logs (Worden et al., 2020). Understanding and predicting elastic anisotropy is important in subsurface engineering (Favero et al., 2018), and for the interpretation of seismic reflection data (Sayers, 2005).
Performance of High Energy Absorption (HEA) Panel to Prevent Flyrock
Authors: Saliba E. C. , Nunes A. L. L. S. 
Published: September 2023

ABSTRACT
The biggest environmental impact from excavation by rock blasting and open-pit mining is flyrock. It consists of the projection of a rock boulder or splinter at the blast moment, which may hit a construction, buildings causing damage and being a safety liability to people around. Therefore, slope protection is important in rock blasting operations. This is a successful case study that presents and analyses a new slope protection technique, developed by Nunes (2017), that uses high energy absorption metallic panels known as HEA panels. This technique was designed to be used at rock slope blasting at an industry zone. The case was accompanied and analyzed to verify its behavior during the subsequent blasting events. The analyses showed that the technique had satisfactory development, with the advantage that flyrock is eliminated without the necessity of any other protection and can be used again on each excavation progress and as stabilizing lining to the remaining rock slope after being excavated.

INTRODUCTION
The blasting operations nearby urban and industrial area is sensible and demands extra care due to the infrastructure around them and the possibility of somebody getting injured during the process.
One of the major environmental impacts of an open pit blast is the flyrock which is a fragment of a rock, that can be any size, it flies after the blast with no calculated direction which may hit the surrounding infrastructures or persons, causing damage and it is a risk to those who live nearby.
The main cause of a flyrock is a miscalculation on the detonation plan, especially the reduced bore spaces, higher benches with too deep holes, reduced hole plugging, and excessive explosive loading. Flyrock events may also be influenced by rock mass characteristics. If the rock mass is too fractured with joint spacing at the blast moment most likely will release boulders that may be projected to long distances.
Investigation of Parameters Affecting Seismic Potentials in a Deep Longwall Mine
Authors: Khademian Z. , Van Dyke M. A. , Beale J. , Wickline J. 
Published: September 2023

ABSTRACT
Seismicity can be induced by rock failures or slips along geologic structures around mine workings. Depending on their intensity and proximity to the working area, seismic events may raise safety concerns in underground mining operations. However, the geological and mining parameters leading to destructive seismic events are poorly understood. Monitoring seismic events coupled with geomechanical modeling can be useful tools for understanding underlying mechanisms and main factors causing destructive seismic events. This paper reviews seismic events recorded in a deep longwall mine (&gt;450 m) in Virginia and evaluates the geologic conditions that lead to areas with high seismic event activities (&gt; 1 ML) during mining of longwall panels. Two pseudo two-dimensional models of areas with high and low seismic event activities are constructed in 3DEC software. The variation in the energy content of elastic models is monitored, and potentially damaging events with compression-type and shear-type signatures are identified. The modeling results are compared with historic seismic data to evaluate the model performance in forecasting the seismic potential in each model. The results show the applicability of energy balance calculations for forecasting the approximate location and timing of destructive seismic events.

INTRODUCTION
One source of potential hazards for underground mining operations is mining-induced seismicity. Seismic events during mining are recognized to be violent failure in close proximity to the mining area. The violent failures can occur due to sudden crushing of rock in compression or sudden slip along preexisting weakness planes such as fault and dyke contacts. Deployment of seismic networks and recording the events during the operation has become one of the industry routines for managing risks associated with the seismicity. However, in most cases the main challenge is to find the link between geologic structures, mining parameters, and seismic activities. If no clear link is apparent, it is difficult to design effective proactive measures to reduce seismic potential in a mining design. To better understand the causal mechanism of mining-induced seismicity, seismological and rock mechanics’ analyses need to be mutually investigated.
Following (Salamon, 1970), many studies have shown the energy budget consideration as the missing link between seismology and rock mechanics (Sears, 2009; Garvey, 2013; Khademian & Ozbay, 2018) One possible approach is to use numerical modeling to analyze the state of energy of the rock before and after mining. The occurrence and intensity of a seismic event can be recognized when there is a relatively significant release of energy in the system. However, the uncertainty in the required field data to perform such analyses has limited their applicability.
Temperature Distribution of Heavy Oil Reservoirs Under Radio Frequency Heating and Analysis of Influencing Factors
Authors: Xiao Jiexian , Gao Deli , Dong Xuelin , Feng Chaochao , Wang Zhengxu 
Published: September 2023

ABSTRACT
Heavy oil is increasingly gaining more concerns from all over the world. However, the steam methods applied broadly are gradually being abandoned due to low efficiency and high carbon emissions. Therefore, a radio frequency (RF) heating technology is proposed which mobilizes heavy oil by using RF electromagnetic wave (RF-EMW) rather than steam. To accurately obtain the temperature distribution of heavy oil reservoir, an electromagnetic-thermal coupling model is established initially. The model considers the thermal properties change the heavy oil reservoir with temperature. Afterward, the model is validated by experimental data. Finally, the influence of several key factors on the reservoir temperature are discussed. Calculation results display that the maximum heating radius of the RF heating technology is up to 10m, which indicates that RF heating has obvious technical advantages. The model considering the varying specific heat brings about lower reservoir temperature around the wellbore, and the maximum temperature is obviously higher than that in the case of varying thermal conductivity. In addition, the reservoir temperature can be enhanced by increasing the relative permittivity of reservoir, porosity, electrical conductivity and saturation of water. The research results are intended to provide important guidance for the field application of RF heating technology.

INTRODUCTION
With the decrease of conventional crude oil, heavy oil is being exploited increasingly by a major thrust of petroleum companies. While the high viscosity of heavy oil is the main factor leading to low oil production. Several practices have demonstrated that increasing temperature helps to reduce the crude oil viscosity (Ali S, 2003). Fig. 1 shows the viscosity change with temperature for the heavy oil sample from the WanT 1 Oilfield, Xinjiang of China (Wang et al., 2019).
Current thermal recovery technologies include steam flooding, SAGD and combustion. But those methods have gradually exposed the technique flaws of low profit, high carbon emission and environmental disruption. Therefore, it is urgent to develop new mining technologies. In recent years, RF heating method appears and considered to be a viable technology for extracting heavy oil. It can effectively deliver more thermal energy to reservoir and extract oil from reservoirs cracks where steam method is ineffective. Besides, the RF heating process does not emit carbon dioxide to the atmosphere and its recovery efficiency can be improved to 25-36% compared with a typical steam injection (Abraham et al., 2016; Saeedfar et al., 2016; Hu et al., 2016). Therefore, in order to achieve large-scale and efficient development of heavy oil, it is necessary to carry out in-depth research on this technology.
Vermiculite Particles as an Additive for Oil Well Cement
Authors: Ahmed Abdulmalek , Elkatatny Salaheldin , Adebayo Abdulrauf R. , Mahmoud Ahmed Abdulhamid 
Published: September 2023

ABSTRACT
The process of cementing a well is essential to ensuring the well doesn't collapse. The cement slurry is pumped into the annulus between the casing and the formation. Cement restricts the movement of formation fluids while also supporting the casing. Different types of additives have been used in the design of cement to alter cement properties to meet downhole requirements. This study aims to investigate the impact of vermiculite particles on heavy weighted oil well cement. Base cement and vermiculite cement were prepared and cured under high pressure and high temperature. Viscosity was used to describe the slurry properties, while for the hardened cement samples, the elastic, petrophysical, and strength properties were described by the Poisson's ratio, permeability, and compressive strength, respectively. Moreover, the particles settling was measured by the density variation across the cement column. It was observed from the results that the performance of vermiculite cement is better than the base cement (without vermiculite). Vermiculite cement exhibits excellent properties compared to the base cement, which represents by lower viscosity (reduction of 8%), higher Poisson's ratio (an increase of 7%), lowere Young's modulus (a reduction of 9.4%), minimizing the density variation by 95%, reducing the cement permeability by 46% and improving the compressive strength by 24%.

INTRODUCTION
The process of cementing oil wells has been an integral part of the oil industry for many years. Oil well cementing is a process that is used to form a permanent bond between the wellbore and the casing and to seal or isolate formations that contain oil and gas (Ahmed et al., 2022c). It ensures the structural integrity of the well, as well as provides economic benefits. Oil well cementing has been identified as a critical factor in ensuring the structural integrity of oil wells.
According to Ingraffe et al. (2014), oil well cementing plays a vital role in preventing the migration of hydrocarbons from one formation to another. This is because the cement forms a barrier between the formation and the wellbore, thus preventing any contaminants from entering the wellbore. Furthermore, the cement can also help to prevent the formation of fractures, which can cause a loss of pressure and weaken the integrity of the wellbore. In addition to this, the cement also helps to protect the wellbore from corrosion and other environmental factors that can cause structural damage.
Impact of Production Scheme on Pressure-Sensitive Reservoirs After Hydraulic Fracturing
Authors: Liu Sen , Zheng Leyi , Li Wenjie , He Jiajun , Liang Tianbo 
Published: September 2023

ABSTRACT
Tight oil reservoirs are typically pressure-sensitive, which can affect the well productivity and oil recovery rate when the reservoir pressure decays. In this paper, the pressure-sensitive of reservoir rock is studied using CT-monitored corefloods, during which the change of permeability and porosity of the rock can be determined under different effective stresses; meanwhile, numerical simulations are conducted to understand the conducted to understand the impact of flowback and production schemes on the oil recovery rate in the field scale. After the reservoir rock sample is saturated with the sample oil, different effective stresses are applied on the rock; the oil is continuously flooded through the sample, during which the porosity change is recorded through CT scans, and the pressure change across the rock is recorded to calculate the rock permeability at different time. After the numerical simulation results are history matched with the experimental results, different flowback and production schemes are studied. After fracturing, the bottom pressure was reduced to 15MPa by different steps. The change of permeability and porosity of the rock and its influence on oil recovery rate under different production schemes were observed. During production, the effective stress in the reservoir increases from about 10 MPa to 50 MPa. According to the pressure-sensitive experiment results, the permeability and porosity of the rock decreased to 22% and 89%. When the pressure sensitive effect is considered, the 10-year recovery rate is reduced from 27% to 17%, and the flowback rate is reduced by 13%.The numerical simulation results show that the rapid production scheme has the highest production and flowback rate, increasing the oil recovery rate by 6% and the flowback rate by 5.9% compared with the three or five steps. The change of production scheme has no significant effect on the relief of pressure-sensitivity and the well should be quickly flowback considering the potential effect of water-sensitivity. The change of rock permeability and porosity are firstly quantified in-situ using a CT-monitored coreflood. Combining the experimental and numerical simulation results, the production scheme can be optimized pressure-sensitive reservoirs.
A Study on the CO2 Jet Erosion Natural Gas Hydrate with the Influence of Temperature and Confining Pressure
Authors: Hu Xiao , Zhang Yiqun , Wu Xiaoya , Wang Haizhu , Cui Xu 
Published: September 2023

ABSTRACT
Natural gas hydrate (NGH) has been regarded as important potential energy resource. CO2 jet erosion HBS can be combined with Radial Jet Drilling (RJD) technology to achieve high efficiency and low-cost gas hydrate mining. The replacement of CO2 hydrate and CH4 hydrate can also be used to form a stable cap layer on the hydrate reservoir to achieve CO2 storage. In this study, the Arbitrary Lagrangian Euler (ALE) method is used to establish a heat-liquid-solid coupling model for water/CO2 jet erosion HBS, and the CO2 phase change is considered. The influence of different temperature and pressure on jet erosion effect was studied. The results indicate that confining pressure has an inhibitory effect on jet erosion ability, which gradually weakens as the confining pressure increases from 5-10MPa. At confining pressures ranging from 0.1-2.5MPa, the erosion volume decreases with rising temperature due to the gaseous CO2 in the submerged environment, resulting in reduced resistance. The erosion effect is influenced by the characteristics of the jet. At 2.5-5MPa, the CO2 in the submerged environment undergoes a phase transition from gaseous to liquid. At 5-10MPa, the erosion volume increases with temperature due to the liquid CO2 in the submerged environment, resulting in relatively higher resistance. The erosion effect is affected by the fluid in the submerged environment. Additionally, under equivalent temperature and pressure conditions, CO2 jet exhibits superior erosion effectiveness compared to water jet. This study can provide theoretical basis and technical ideas for using RJD technology to mine hydrate and achieve "carbon peak and carbon neutrality".

INTRODUCTION
Natural gas hydrate is a kind of clean energy with great potential (Sloan, 2003). It is commonly found in marine sediments and permafrost at continental margins, especially in marine sediments (Chong et al., 2016; Michael et al., 2019). The global amount of organic carbon in NGH is twice that of fossil fuels combined (Yu et al., 2019; P. Zhang et al., 2021). So far, many countries in the world have successively formulated the exploitation plan of gas hydrate (Xiao & Zhang, 2021). It can be predicted that the research and exploitation of NGH will remain the focus of global attention for a long time in the future.