bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigations on the Effect of High Temperature and Pressure on the Mechanical Properties and Drillability of Granite
Authors: Fu Xinkang , Huang Zhongwei , Wu Hongzhi , Shi Huaizhong , Zhang Jiawei , Ji Guodong 
Published: September 2023

ABSTRACT
Hot Dry Rock (HDR) is an important clean energy resource. However, there are many problems in the exploration of HDR, which are closely related to the geological environment and properties of HDR. The representative lithology of HDR is granite. Granite has the characteristics of poor drillability, high hardness and strong abrasive property in underground high-temperature and high-pressure environment. Therefore, the effect of temperature and pressure on physical and mechanical properties and drillability of granite was explored with deep water pore pressure servo system and rock drillability tester. The result shows that Young's modulus and compressive strength increase with the increase of confining pressure. High temperature weakens the mechanical properties of granite under the same confining pressure. The specific manifestation is that density, mass, longitudinal wave velocity and drillability grade value decrease with the increase of temperature, while mass loss rate decreases by 2.2‰ and longitudinal wave velocity decreases by nearly 74%. The drillability grade value of granite increases with the increase of confining pressure, especially at room temperature. This study has certain guiding significance for revealing the mechanical properties of granite after heating under high pressure and efficient drilling in the exploration of HDR.

INTRODUCTION
At present, HDR is a new clean energy, which is a reliable energy resource (Goldstein et al., 2008). HDR is a dense high-temperature rock mass with a temperature between 150 °C and 650 °C, and buried at 3-10 km underground, with little or no liquid (Ma et al., 2022). The most typical reservoir rock of hot and dry rock is granite (H. Liu et al., 2020). However, there are many problems during drilling, such as high confining pressure, high rock hardness and poor drillability (Rossi et al., 2020). The physical and mechanical properties of granite have changed considerably under the influence of high temperature and high pressure (S. Liu & Xu, 2015). Therefore, it makes sense to study the effect of high temperature and pressure on the mechanical properties and drillability of granite.
Lau et al. (1995) heated the granite from 75 °C to 125 °C, and found that the Young's modulus decreased slightly, and the decrease amplitude increased under low confining pressure. In addition, temperature seems to have no effect on Poisson's ratio. Dwivedi et al. (2008) explored various thermodynamic properties of Indian granite at temperatures ranging from 30 to 160 °C, mainly including Poisson's ratio, uniaxial compressive strength, Young's modulus and creep behavior, and scanned micro-cracks generated in the rock due to high temperature by scanning electron microscope (SEM).
Development of a Low Cost Environmentally Friendly Proppant with High Buoyancy for Hydraulic Fracturing Operations
Authors: Haydar Raz Rzgar , Fakher Sherif 
Published: September 2023

ABSTRACT
Proppants are one of the main components/ingredients used in hydraulic fracturing for reservoir stimulation in order for fractures to have conductivity and maintain it. In hydraulic fracturing, usually when dealing with high parting pressure or harsh environment, high strength durable proppants are used that are expensive and require more expensive fracture fluids. Thus, the idea of developing a new type of proppant that has high compressive strength, high durability, resistant to corrosion and erosion, and economical became the focus of this research. Fly ash, a by-product from any combustion process, and a very prominent by-product from cement production, was used to develop a new type of proppant that is durable, is environmentally friendly. Sodium metasilicate and water were used in the mix designs. The samples were subjected to high temperature, pressure, acidic, and alkaline environments to test their durability. The samples showed high durability and minimum erosion, with no corrosion in all of the environments that were subjected to. 20% binder mix design showed the best results having minimum to no deterioration of the samples.

INTRODUCTION
As the industry of petroleum engineering is developing and more technologies are being introduced to optimize the production, stimulating the reservoirs has been an area of development and research that is gaining more attention and attraction, especially with the rise of unconventional reservoirs. The global production ratio of conventional to unconventional reservoirs is 2:8, and in unconventional reservoirs, stimulation is a default practice (Lan et al., 2020). One way to stimulate the reservoir is by hydraulic fracturing, in which proppants are used where the rock is ductile, meaning there is high clay content, closing the fractures that are made. Proppants come in different shapes and sizes being angular, such as natural sand, spherical or rods (Ba Geri et al., 2019). The shape of the proppant is connected to the way it will be placed and arranged inside of the fractures, which the better placement the proppant has the better conductivity the fracture will have, thus better and higher production rate for a long period of time (Wang et al., 2022; Li, 2021).
A Microscale Thermo-Hydro-Mechanical (THM) Model for Thermal Recovery of Shale Gas
Authors: Gao Qi , Han Songcai , Shi Xian , Cheng Yuanfang , Yan Chuanliang , Han Zhongying 
Published: September 2023

ABSTRACT
Studies have shown that up to 85% of total shale gas-in-place could be adsorbed gas. Thus, how much more adsorbed gas can be extracted will significantly impact the ultimate gas recovery. In recent years, the concept of using thermal stimulation to enhance shale gas recovery has been proposed as more gas desorbs under the higher temperature conditions. In this paper, a fully coupled THM model is developed to characterize gas transport and extraction in shale matrix from the microscopic perspective during thermal treatment. A set of partial differential equations are defined to model the processes involved: (1) geomechanical deformation of heterogenous shale matrix; (2) gas sorption and flow in heterogenous shale matrix; and (3) thermal transport in heterogenous shale matrix. All these processes are linked together through the porosity and apparent permeability models. This microscale THM model is verified against an analytical solution available in the literature. The verified model is then applied to investigate rock and fluid responses in shale matrix during thermal treatment and the impacts of operational and rock physical parameters on gas recovery. Simulation results indicate that a greater thermal treatment temperature enhances ultimate gas recovery; and that shale thermal properties and matrix permeability impact initial gas recovery but does not impact ultimate gas recovery.

INTRODUCTION
Gas shale is naturally tight and fine-grained sedimentary rock with methane trapped in its nanopores. Commercial extraction of gas in shale requires the application of horizontal drilling and hydraulic fracturing techniques (Kumar and Ghassemi, 2018; Gao et al., 2019). When hydraulically fractured, shale gas reservoirs can be divided into two sections. One section is the stimulated zone where massive hydraulic fractures are created with natural fractures being activated. The other section is unstimulated zone which mainly consists of unactivated natural fractures and matrixes. Once the production initiates, gas in hydraulic fractures will first flow out into the wellbore. Then, gas in natural fractures will migrate into hydraulic fractures. Finally, gas in matrix will transfer into natural fractures to sustain the production (Zhang et al., 2017). Although fracturing technique has been widely applied, the overall shale gas recovery rate still remains at a low level around 20% (Neil et al., 2020). The main reason is that up to 85% of shale gas-in-place could be adsorbed gas (Darishchev et al., 2013; Zhou et al., 2022) and most of the adsorbed gas is still unattainable after fracturing. Thus, stimulation techniques that can alter gas desorption behavior have the great potential to enhance shale gas recovery.
Geomechanics Analysis of the Phosphate Ore Mining Using the Hoek-Brown Model
Authors: Wang Suifeng , Wang Tao , Fan Bowen , Hu Suoao 
Published: September 2023

ABSTRACT
Phosphate rock is an essential non-renewable resource for both food production and phosphorus chemical production. Located in Yichang City, China, the Houping Phosphate Mine (HPM) poses significant challenges due to its complex topography and geological structures. In this study, we conducted a geomechanical analysis of the mining layer at HPM utilizing the Hoek-Brown model. First, we calibrate the Hoek-Brown parameters through uniaxial compression tests in FLAC3D. Then, we calculate the stress distribution of the rock mass around the stope, the subsidence and displacement law of the roof and floor, and the plastic zone distribution. We find that the shallow-hole room-pillar method with anchor roof protection has poor pillar stability, while the filling method is more stable, lastly. Our results offer valuable insights into efficient phosphate ore mining practices and provide technical support through numerical calculations.

INTRODUCTION
Phosphate rock is not only an important chemical mineral material but also a non-renewable and irreplaceable resource. With much mining in recent years, the shallow phosphate resources have been gradually exhausted, and the mining of underground phosphate layers with larger buried depths has become the focus of research, one of the biggest problems is the mining research of gently inclined medium-thick ore bodies underground. Underground mining will form goaf, goaf destroys the initial stress balance of the mine, redistributes its internal stress, affects the stability of slope rock mass, and cause a series of engineering geological disasters, such as surface subsidence, caving, landslide, etc. In 1980, unreasonable mining of the Yanchihe phosphate Mine in Yuan’an County, Hubei Province led to the collapse of the mountain, which destroyed and buried the entire mining area, resulting in 284 deaths and heavy losses (Li et al., 2016). In order to prevent the occurrence of similar accidents, we should do the safety analysis of mining in advance to ensure the safety of people's lives and property.
Delaying of Bottom-Water-Coning Oriented Hydraulic Fracturing Design and Optimization: Numerical Simulation and Field Case Study
Authors: Jv Liu , Hui Liu , Hongtao Liu , Hongqiang Zhang , Wenjing Lv , Dengfeng Ren 
Published: September 2023

ABSTRACT
Is usually used hydraulic fracturing to enhance the productivity of tight gas sandstone formations. If basal water layers were connected to the upper gas formation via hydraulic fractures, the gas productivity of the stimulated wells would be reduced drastically. It is crucial to postpone the bottom-water-coning effect by meticulous hydraulic fracturing design and operation parameters optimization. Temporary plugging could be a potential solution for controlling hydraulic fracture extension in the vertical direction. This paper proposed a basal water-avoiding hydraulic fracturing design and optimization methodology and procedures to solve this problem. The geological and geo-mechanical models were built based on the characteristics of the gas layer, natural fracture, and basal water layer analysis. Hydraulic fracture propagation simulation conducted pump rate, Hydraulic fracture propagation simulation considered pump rate, frac-fluid volume, frac-fluid viscosity, temporary plugging material volume, proppant concentration, and proppant volume. Hydraulic fracture vertical height and distance to the basal water layer were used as the primary indicators to optimize the frac-fluid volume, pump rate, and temporary plugging material volume. Then simulated fracture area and fracture propped area were used as significant parameters to identify the optimal frac-fluid viscosity, proppant concentration, and proppant volume. KS field is an ultra-deep tight gas sandstone formation with basal aquafers. The fracture propagation model of the KS-X well was established to delay bottom-water-coning-oriented hydraulic fracturing design and optimization. Results showed that the optimal frac-fluid volume, pump displacement, and temporary plugging material quality are 950 m3, 4.5 m3/min, and 300 kg, respectively. The optimal proppant volumes of 70/140 mesh, 40/70 mesh, and 30/50 mesh ceramic proppant are 6 m3, 38 m3, and 9 m3, respectively. After hydraulic fracturing, the gas production rate of the KS-X well is as high as 290,000 m3/day without any water production for one month, indicating the effectiveness of the proposed basal water-avoiding hydraulic fracturing design and optimization methodology. The proposed design and optimization procedures can be further used in other basal aquifer gas fields.
Deep Coal Seam In-Situ Stress Evaluation Through the Integration of Sonic Logging and Micro-Indentation Methods
Authors: Yang Qi , Li Jianchuan , Li Liang , Zhou Libo , Mei Wenbo , Wu Jian , Jiang Yao , Lv Wenjing , Li Ben , Li Hui 
Published: September 2023

ABSTRACT
The porosity and permeability of deep coal seams are usually as low as 5% and 0.1mD, respectively, thus requiring hydraulic fracturing to obtain an economic coalbed methane production rate. In-situ stress evaluation is fundamental to the hydraulic fracturing design. However, the conventional in-situ stress calculation methods could not be used directly due to the specific structure and rock mechanic features of deep coal seams. The in-situ stress of deep coal seam should be interpreted with full consideration of deep coal geology, logging, coal petrology, and elastic mechanics. This paper proposed a modified in-situ stress interpretation method that integrated sonic logging and micro-indentation methods. Sonic logging provides the compressive and shear velocity of the coal seam, and micro-indentation provides the compressibility coefficient of the coal cleats, coal bedding, and principal minerals that are used to identify the effective stress coefficient. Firstly, the dynamic Young's modulus and dynamic Poisson's ratio are calculated by acoustic logging and density logging data, and the correlations of dynamic - static Young's modulus and dynamic - static Poisson's ratio are obtained in combination with indoor core mechanic experiments. Then, the minimum horizontal principal stress estimated from 9 wells of hydraulic fracturing operation data (LX field China) is used to figure out the maximum and minimum horizontal structural coefficients. The micro-indentation of the deep coal seam is used to calculate the effective stress coefficient modifier. Results showed that the Poisson's ratio of the up and bottom layers is slightly smaller than that of the coal seam, and Young's modulus of the up and bottom layers is 6.15 times larger than that of the coal seam. Indicating that there are significant differences in the mechanical properties of the coal seam and the up and bottom layers. In terms of stress prediction results, the LX coal seam has a large interlayer stress difference with the up and bottom layers. The vertical stress is the maximum in the three-dimensional stress, which belongs to the normal fault type in-situ stress type. The proposed method can be used to evaluate the in-situ stress and mechanical properties of the coal seam and can be further used for other coal seams’ in-situ stress and mechanical property evaluation.
Experimental Investigation on the Threshold Transportable Concentration of Temporary Plugging Materials of Different Sizes of Slide Sleeves
Authors: Long Wang , Xiaotong Xie , Xiong Zhang , Bing Zhao , Tunhao Chen , Chunyue Li , Wenjing Lv , Yu Xia , Hui Li , Ben Li 
Published: September 2023

ABSTRACT
The uncased horizontal wellbore is widely used in high-strength formation, especially in low porosity and low permeability carbonate reservoirs to enlarge the drainage area around the whole horizontal section. Multi-staged fracturing and temporary plugging technology are usually used to create complex fracture networks for enhancing well productivity. However, due to the complex geological environments in hydraulic fracturing operations, the sliding sleeve cannot be always fully opened. It is crucial to figure out the threshold concentration of temporary plugging materials at which the temporary plugging materials can be transported through different sizes of slide sleeves. This paper provides an innovative experiment apparatus and experimental procedures to evaluate the transportability of various temporary plugging mixtures concentrations. The proposed sliding sleeve transportability device consists of a 3D migration simulation system, a sliding sleeve simulation device, and a video recording device. The sizes of the sliding sleeve determined by the similarity criterion (the same Reynolds number) are 60mm × 14mm, 45mm × 14mm, and 30mm × 14mm, which can be used to simulate the different degrees of opening the sliding sleeve. Similar criteria that convert filed operation parameters such as pump rate and flow regime to indoor experimental conditions were also proposed. SH-1 well, an uncased horizontal well in the S carbonate reservoir, in China, was used as an example to explore the upper limits concentration of temporary plugging mixtures. The filed temporary plugging displacement is 3m3/min and the carrying fluid viscosity is 12mPa.s. Serial and rigorous experiments were designed to explore the transportability threshold of different sizes of sliding sleeve sizes under different hydraulic fracturing conditions. Results show that the threshold transportability concentration of the temporary mixtures for 60mm×14mm, 45mm×14mm, and 30mm×14mm slide sleeve sizes are 3.2% 4-6mm fiber +2.4% 1-2mm particle, 2.4% 4-6mm fiber +2.0% 1-2mm particle, and 2.0% 4-6mm fiber +1.6% 1-2mm particle, respectively. The proposed experimental apparatus and procedures can be further used to explore the threshold concentrations of temporary plugging materials for other uncased horizontal wells and can provide a theoretical basis for the design of temporary plugging displacement and carrying fluid viscosity.
Experimental Investigation of Methods for Measuring the Permeability of Dry and Water-Saturated Ultra-Deep Tight Sandstones
Authors: Zebo Yuan , Shengxian Pu , Jueyong Feng , Xiwu Yang , Jiangyu Liu , Yesong Li , Jiang Jing , Qiang Wang , Ben Li , Hui Li 
Published: September 2023

ABSTRACT
Ultra-deep tight sandstone reservoirs have extremely low permeability and porosity due to extremely deep burial depth, and extremely high in-situ stress. Therefore, hydraulic fracturing is widely used to create diversion fractures to improve oil well productivity. Incompatible fracturing fluids can severely damage the permeability and fracture surface of the tight sandstone matrix. Rigorous evaluation of formation sensitivity and fracturing fluid compatibility is critical before hydraulic fracturing operations. There are three types of permeability experimental evaluation methods: steady-state permeability method, pressure pulse decay method, and pressure transmission method. In this study, a series of comparative experiments were designed to accurately evaluate the sensitivity and compatibility of injected fluids in ultra-deep tight sandstones. CT scanning and 3D reconstruction techniques were used to obtain digital data on pore space and pore-throat connections of downhole cores. Through statistical regression analysis, a modified correlation between the pressure pulse decay method and the pressure transmission method is proposed. The proposed experimental and regression methods can also be used to validate permeability measurements in other types of reservoirs.

INTRODUCTION
With the development of oil exploration, people pay more and more attention on deep and ultra-deep strata. Since the 21st century, China has made a series of breakthroughs in deep oil and gas exploration, especially in the central and western basins (Li et al., 2023). Unlike conventional reservoirs, ultra-deep tight sandstone reservoirs are characterized by large buried depth, complex structure, tight matrix, and strong heterogeneity. Rocks with extremely low permeability are more affected by stress than those with high permeability (Jones., 1997). Due to the extremely low permeability and porosity (Li et al., 2019; Li et al., 2020), hydraulic fracturing is widely used to create diversion fractures to increase well productivity of tight reservoirs (Li et al., 2018). The fracturing fluid used in hydraulic fracturing can significantly alter some formation properties. Due to the high temperature and pressure, tight reservoirs are susceptible to stress, flow rate, and output, especially in the case of deep and ultra-deep tight sandstonereservoirs (Gilicz., 1991). Therefore, it is critical to evaluate formation sensitivity and fracturing fluid compatibility before hydraulic fracturing (Zhang et al., 2019).
Measuring Poromechanical Properties of Berea Sandstone Relevant to Underground Hydrogen Storage
Authors: K C B. , Frash L. P. , Meng M. , Iyare U. , Madenova Y. , Neil C. , Carey J. W. , Gross M. 
Published: September 2023

ABSTRACT
Seasonal fluctuation in electricity generation is a major set-back for the integration of renewable energy sources such as solar and wind into a national grid. Temporary storage of ‘green’ hydrogen in underground porous reservoirs could be a cost-effective solution to balance renewable energy fluctuations to stabilize the energy grid. However, due to the novelty of Underground Hydrogen Storage (UHS) in deep porous reservoirs, our knowledge about the interaction between hydrogen and host reservoir rock is limited. It is crucial to develop the fundamental understanding of these interactions and their impact on the reservoir rock for successful deployment of UHS. In this study, we measure the poromechanical properties, such as bulk compressibility, in-situ porosity, Biot's effective stress coefficient, and P-wave velocity of Berea sandstone specimen at in-situ reservoir stress condition i.e., depth of ∼ 1.25 km. Results showed decrease in bulk compressibility, porosity, and Biot's coefficient due to increase in effective stress. Considered together, results from this study infer change in stress regime in UHS reservoir due to multiple injection/extraction cycles could alter the reservoir capacity and transport properties. In addition, P-wave velocity increased with the effective stress. However, it remained insensitive to different gas (i.e., air and Argon) saturated pores at same effective stress.

INTRODUCTION
Renewable energy is a focal point in our effort to achieve global net zero emission target by 2050. However, seasonal fluctuation in electricity generation is a major set-back for the integration of renewable energy sources such as solar and wind into national grid. As such, surplus energy produced from renewable sources during the period of low demand can be used to produce ‘green’ hydrogen, which can be stored for future consumption to stabilize the grid when the demand is higher. Hydrogen is an ideal energy storage option due to its low carbon footprint and versatility to be used in different sectors such as transportation, industry, residential, and others (e.g., IEA, 2019). Hydrogen has higher specific energy capacity compared to other gases such as methane but, due to its low density very large volume is required to store energy at the scale of GWhr to TWhr needed to balance seasonal fluctuations. Such large-scale volume is available in underground geological formation such as salt caverns, saline aquifer, and depleted oil and gas reservoir (e.g., Heinemann et al., 2021; Zivar et al., 2021; Chen et al., 2022).