bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Evaluation of Flow Heterogeneity in Enhanced Geothermal Systems (EGS)
Authors: Villaquiran Vargas A. P. , Knippel E. P. , Xiong Q. , Hampton J. C. 
Published: September 2023

ABSTRACT
Enhanced Geothermal Systems (EGS) are unconventional reservoirs with significant stored thermal energy and low hydraulic connectivity e.g., Hot Dry Rocks. To take advantage of these resources as a sustainable option, it is necessary to create and/or enhance existing fractures to achieve economic production rates. Laboratory-scale tests can assess critical knowledge gaps by conducting research under controlled conditions, allowing to understand mechanisms and then extrapolate them at the field scale, especially those contributing to, and controlling, flow heterogeneity. To that end, we use novel equipment that allows drilling, casing, stimulation, and multi-physics monitoring all under in-situ stress and temperature conditions, with multiple oriented wellbores and complex fracture networks connecting them. The laboratory EGS environments are assessed through acoustic emissions, foil strain gauges, fiber optic sensing, and tracer injection/recovery, measuring changes in stress, pressure, flow, and temperature, where fast-flowing channels that may lead to early thermal breakthrough affecting the heat recovery process can be identified and characterized. The experimental approach to mitigate the effects of flow channeling, is to design and evaluate different circulation schemes that minimize short-circuiting flow paths by adjusting specific operational parameters. During this first experimental stage, only surface control will be used since other strategies such as mechanical and chemical conformance control may not be suitable for EGS conditions. This paper provides a snapshot of a work-in-progress of the experimental results showing a single wellbore stimulation and hydraulic characterization in an unconfined Dakota granite.

INTRODUCTION
Geothermal Energy is considered a renewable energy resource since the rate of consumption is smaller than the renewing process rate - i.e., Just 1% of the total heat available in the Earth's crust is necessary to meet global energy needs; therefore, geothermal resources can provide energy to the planet for 2800 years at a constant consumption rate. Considering that this resource is continuously being renewed by various forms of heat received, it is a sustainable energy (Olasolo et al., 2016).
Benchtop Experimental Studies of Stick-Slip Mitigation Methods
Authors: Hilborn H. , Jorgenson H. , Su J.-C. , Mazumdar A. 
Published: September 2023

ABSTRACT
Drilling vibrations can cause inefficient drilling and accelerated damage to system components. Therefore, reducing or eliminating such vibrations is a major focus area for natural gas and geothermal drilling applications. One particularly important vibration mode is stick-slip. Stick-slip occurs when the bottom-hole angular velocity starts oscillating while the top hole angular velocity remains relatively constant. This not only causes poor drilling, it is also difficult to detect using surface sensors. In this work, we describe the development and testing of a benchtop drilling system for studying stick-slip dynamics and mitigation. We show how this system can produce stick-slip oscillations. Next, we use this data to formulate a data-driven rock-bit interaction model. This model can be combined with linear systems analysis to predict stick-slip and understand mitigation methods. We describe out instrumentation that enables closed-loop control under simulated communications constraints. We conclude by providing preliminary experimental data on bench-level stick-slip.

INTRODUCTION
Exploration via autonomous drilling processes for geothermal resources is an important focus area for drilling research. However, to fully realize the clean-energy promise of geothermal energy, key challenges still need to be resolved.
Issues arising in the drilling process often originate from a drillstring's increased susceptibility to vibrational oscillations as depths increase. Some examples of drilling vibrations include stick-slip (Navarro-Lopez and Suarez, 2004), bit-bounce (Spanos et al., 1995), and whirl (Jansen, 1991). Torsional oscillations are the focus of this work.
Torsional vibrations result in a destructive phenomenon known as stick-slip. Initiated at the bit-rock surface, the drillstring bit experiences large angular velocity oscillations not seen at the surface (Pavone and Desplans, 1994; Besselink et al., 2011; Kessai et al., 2020). Stick-slip results in premature bit wear and drillstring fracture.
Stick-slip is a fundamentally nonlinear and unpredictable phenomena. Stick-slip results from the combination of bit-rock interactions and drillstring compliance. As a result, there is a key need for experimental studies of stick-slip dynamics and mitigation.
Numerical Simulation of Hydraulic Fracturing of Hot Dry Rock Based on Coupled THM Model
Authors: Xie Zixiao , Huang Zhongwei , Wu Xiaoguang , Long Tengda , Yang Rui , Wu Sitong , Huang Pengpeng 
Published: September 2023

ABSTRACT
One of the challenges of developing an enhanced geothermal system (EGS) is to create connected fracture networks by hydraulic fracturing between the injection well and the production well. However, limited work has been conducted on studying the fracture initiation and propagation of hot dry rock. To have a clear understanding of how the temperature differences between the rock and the fluid influence hydraulic fracturing, numerical simulations were conducted under different temperature conditions (100°C-300°C) based on the FDEM approach. The results indicate that the increase in the temperature difference between the rock and the injected fluid could induce the larger fracture tortuosity and fracture apertures effectively. The breakdown pressure decreased by 52% as the initial rock temperature rise from 100°C to 300°C. The present study is expected to provide an in-depth understanding of the reservoir stimulation in EGS.

INTRODUCTION
Geothermal energy is widely distributed across the world and is rapidly gaining interest globally as it shows great potential to decrease carbon consumption. Hot Dry Rock (HDR) is a kind of geothermal resource where no water or only a small amount of fluid exists inside the rock and the average temperature of HDR is typically above 180°C(Li et al., 2022). Enhanced Geothermal System (EGS) is currently considered the most efficient way to develop HDR reservoirs, which applies the hydraulic fracturing technique to create the fluid flow path, enabling the working fluid to pass through the fracture network transferring heat from underground to the surface(Xie et al., 2022; Mcclure and Horne., 2014).
The main difference in hydraulic fracturing of the hot dry rock and other types of reservoirs is that strong thermal stress would be induced by cold water contacting with the hot rock mass, which plays a crucial role in the initiation and propagation of the hydraulic fracture(Li and Tang., 2022; Li et al., 2022). It has been investigated that the mechanical properties of the granite derogated substantially after the specimens are subject to cyclic heating and cooling(Wu et al., 2019). The large temperature difference between hot rock and cold fluid leading to a larger thermal stress contributes to damaging the granite. Therefore, it is necessary to study how thermal stress influences the hydraulic fracturing of hot dry rock.
Investigation of Long-Term Casing Strength Degradation Prediction Method Under "Thermal Stress – Corrosion" Combined Effect in Cyclic Steam Injection Wells
Authors: Zhang Binqi , Deng Jingen , Li Fuli , Zhang Jingru , Yan Wei , Zhang Binqi , Lin Hai 
Published: September 2023

ABSTRACT
Steam huff and puff is the main production mode of heavy oil, but the casing damage problems during the cyclic thermal injection process are very serious. The casing damage of thermal recovery wells is an important factor affecting oilfield production and economic benefits. The conventional casing strength calculation method does not consider the effect of corrosion and thermal degradation in terms of long-term casing strength designing. The establishment of a long-term casing strength prediction method to check and optimize casing strength is an important guarantee for the safe production of heavy oil thermal recovery wells. In this paper, the strength degradation characteristic of two kinds of casing steels (N80 and TP100H) are tested under the cyclic thermal effect using a High Temperature Tensile Testing Machine. The heat temperature is from 30˚C to 350˚C, and heating cycles are 1, 3, 5 respectively. The results show that the N80 casing strength decreases by 18.2% in the first thermal cycle, and the average damage of each subsequent thermal cycles are about 0.88%. However, the TP100H decreases by 13.7% in the first cycle and subsequently with 0.31% degradation averagely. The long-term corrosion rates of N80 and TP100H were measured in HTHP autoclave, which are 0.43m/a and 0.3m/a respectively. Combining the obtained experimental results with the standard casing strength calculation formulas, a newly prediction method of casing long-term strength for cyclic thermal injection well is presented. This method has been successfully used in Lvda 21-2 block of Bohai oil field CNOOC, which provides a technical basis for casing strength design in cyclic thermal injection wells.

INTRODUCTION
Casing damage in oil fields has now become a pressing problem worldwide, and many fields have encountered casing damage during development. The factors affecting casing damage are extremely complex. Steam injection is the most widely used and effective method in the exploitation of heavy oil reservoir. However, in the process of steam huff and puff, the high temperature steam injected in circulation makes the casing undergo great alternating stress, and the residual stress increases constantly, reducing the casing strength. In addition, after steam injection, thermal cracking of heavy oil produces acidic gas and the casing is in a corrosive environment. This leads to the casing strength decay and reduces the casing service life. Therefore, casing damage is a difficult problem in the development of heavy oil reservoir.
Study on the Variation Law of Rock Mechanical Properties with Depth in Deep/Ultra-Deep Layers-Taking Shunbei Oilfield as the Rresearch Object
Authors: Mingming Geng , Hui Zhang , Zhuoxin Dong , Yufei Chen , Kerou Liu 
Published: September 2023

ABSTRACT
At present, the development of petroleum industry is gradually developing from shallow oil layer to deep/ultra-deep layer, but with the increase of well depth, the rock strength is also getting higher and higher, which hinders the drilling work. In this paper, based on the well logging data, the variation of rock strength characteristics with well depth is analyzed, and the uniaxial compression model is established using the global cohesive element. The reason why the rock is difficult to be destroyed in the deep layer is analyzed, and the relationship between the numerical simulation results and the confining pressure and the well depth is analyzed. The results show that the confining pressure can greatly increase the mechanical strength characteristics of rock, and the rock strength increases faster and faster with the increase of well depth.

INTRODUCTION
Oil and natural gas are the main raw materials for obtaining energy in the world today. With the improvement of the development level of oil and natural gas, the depth of recoverable oil reservoirs is getting deeper and deeper, and the depth and number of deep/ultra-deep wells are also increasing. (Wang HG, Huang HC, Bi WX, et al. 2021). For these deep/ultra-deep wells, the traditional drilling methods cannot effectively drill, and it is difficult to meet the needs of rapid deployment of well patterns in the oilfield. (Tian S, Huang Z, Niu J, et al. 2009). Therefore, it is necessary to further study the influence of bottom hole confining pressure on deep/ultra-deep layers.
Now, some studies have proved that confining pressure has an effect on rock mechanical properties. When the strain rate remains stable, the confining pressure can improve the compressive strength of rock. (Christensen et al, 1972;Hokka et al, 2016). Under the condition of dynamic loading, the strength characteristics of rock are still affected by the confining pressure. (Wang SM, et al., 2018).
In order to study the influence of confining pressure on rock mechanical properties, many scholars have carried out sufficient theoretical research work from the microscopic field. From their research contents, it can be seen that confining pressure can reduce the initiation of cracks and hinder the expansion of cracks, and increase the energy required for crack expansion to cause block fragmentation. (Zhou et al., 2016; Zhou & Yang, 2007; Zhou et al., 2004).
3D Numerical Manifold Method for Modeling Heat Conduction and Thermo-Mechanical in Quasi-Brittle Materials
Authors: Tong Defu , Yi Xiongwei , Tan Fei , Han Zhenyu 
Published: September 2023

ABSTRACT
Thermal fractures are common in natural rock masses, and numerous works are concentrated on this topic at present. Comprehending the failure mechanism of thermo-mechanical problems is crucial for enhancing the effectiveness and safety of engineering applications. Despite considerable endeavors to experimental results, precisely simulation 3D thermo-mechanical coupling remains a formidable challenge. This paper proposes a novel thermo-mechanical coupling model (3DNMM-TM) that integrates a heat conduction algorithm with the numerical manifold method (NMM) to effectively simulate problems related to heat conduction and thermo-mechanical coupling. The discrete equations for the system equation are derived using a variational method, and the penalty method is utilized to solve the crucial boundary conditions. The accuracy of the proposed 3DNMM-TM model is verified through numerical tests which compares with analytical solution. The results show that the proposed heat conduction model can effectively capture the effect of cracks on heat conduction as well as the sudden temperature change across the cracks. The model can be used as a robust tool to study the whole process and basic mechanism of thermodynamic behavior in quasi-brittle materials.

INTRODUCTION
The field of engineering frequently utilizes quasi-brittle materials, including but not limited to concrete, ceramics, and rock. The thermal conductivity within these solids is a crucial factor to consider (Ezekoye, 2016). Any temperature variation could potentially modify the thermal and mechanical characteristics of quasi-brittle materials (Gautam et al., 2018; Tan et al., 2022), leading to material degradation and engineering mishaps. For example, when a fire breaks out in a tunnel, its temperature can swiftly escalate to 700 °C or beyond within a brief period (Shen et al., 2023). A significant temperature gradient within concrete can result in thermal cracking (Committee, 2007). During CO2 geological sequestration, the injection of CO2 into the brine stratum at a depth ranging from 1000 to 2500 m may give rise to shrinkage or even fracturing of the adjacent saline rocks owing to the frigidity of the CO2 (Taylor & Bryant, 2014). In the subterranean repository of nuclear waste, the thermal energy generated by nuclear decay may elevate the temperature of the surrounding rock, leading to thermal cracking, and incidents involving nuclide leakage may transpire (Kim et al., 2011). Consequently, it is imperative to investigate the interdependent thermal-mechanical impact.
Influence of Local Grain Size Distribution on Damage Development in X-Ray CT Images of Boise Sandstone Deformed by Confined Compression
Authors: Louis L. , Boyd P. , Hofmann R. , Saxena N. 
Published: September 2023

ABSTRACT
MicroCT imaging is performed before and after confined compression testing on a minicore of Boise sandstone in order to extract quantitative information regarding the microstructural controls on compaction initiation and distribution, with the ultimate goal of formulating compressibility predictions at in situ conditions. In contrast with traditional compaction studies, our analysis focuses on local statistics among regions of a given sample as opposed to global statistics in a sample set. The original workflow includes a segmentation strategy and the definition of a series of metrics that are evaluated throughout the entire image volumes before and after testing. The results suggest that local porosity and sorting are the main controls on local strength, whereas neighborhoods with larger mean grain size do not appear to be more prone to yielding. This is consistent with previous findings on confined comminution which emphasize the tendency of grain size distributions to become self-similar through the elimination of same size neighbors at all scales.

INTRODUCTION
The limited ability to predict the onset and development of compaction at the pore scale in high porosity reservoir rocks undergoing depletion represents a substantial barrier to the optimization of appraisal and production planning. Compaction may be potentially beneficial as a pressure support mechanism but can also be a hindrance to overall flow properties through reservoir compartmentalization and fines production/migration. This topic has been the focus of many studies both within industry and academia (Fatt, 1958; Zhang et al., 1990a; Schutjens et al., 1998; Wong and Baud, 1999; Olsson et al., 2002). Beyond conventional reservoir operations, better understanding of the mechanical behavior of confined granular aggregates is of interest in many other subsurface applications from 4D seismic interpretation to storage and subsidence, but also across industries in environmental and civil engineering domains.
As a powerful extension of traditional microscopy work, non-destructive X-ray CT imaging has been enabling investigations that were not previously possible. An example is the in-situ monitoring of 3D microstructural changes occurring in materials under active loading, with the continuous introduction of ever more sophisticated setups (e.g. Renard et al., 2016; Voltolini et al., 2019; Shahin et al., 2022; Francois et al., 2022).
Study on Sealing Integrity Mechanism of Salt Cavern Hydrogen Storage Under Alternating Load
Authors: He Aiguo , Ma Qingyuan , Liu Tianen , Li Jingcui , Zhang Hong , Dai Kun , Lu Yunhu 
Published: September 2023

ABSTRACT
The sealing integrity of salt cavern hydrogen storage is an important technology and safety index of hydrogen storage. In the process of injection and production, the surrounding rock of hydrogen storage chamber is in the state of alternating load stress, and there is the risk of fatigue failure and leakage. Analysis of dynamic rock mechanics characteristics of surrounding rock of salt cavern hydrogen storage chamber under alternating load is the key to study the sealing integrity mechanism of salt cavern hydrogen storage chamber. Uniaxial tests, triaxial tests, cyclic loading and unloading tests and creep tests were carried out on rock samples from salt layer, interlayer and cap layer of hydrogen storage reservoir of Jintanmao 17 well by means of rock mechanics experimental machine RTR-1500. The deformation and failure characteristics, permeability, porosity, breakthrough pressure and other parameters of rock samples under alternating loads were discussed. Based on the results of the creep test, the Burgers creep model parameters for this block were fitted. The results show that: (1) in the triaxial cyclic loading and unloading experiment, the cyclic loading and unloading before the yield point decreases the porosity and permeability of the rock sample, while the cyclic loading and unloading after the yield point increases the porosity and permeability of the rock sample.(2) In the process of cyclic loading and unloading, the dissipative energy of cap rock is greater than that of interlayer, and with the increase of cycle times, the dissipative energy first decreases and then becomes stable.(3)Burgers creep model can well reflect the creep law of salt formation in the target block, and can be used to study the long-term stability of hydrogen storage cavity. The research results provide a scientific basis for the design and operation of salt cavern hydrogen storage.

INTRODUCTION
Salt rock has been used in the construction of hydrogen storage because of its low porosity, low permeability and damage recovery. Sealing integrity is very important for a salt cavern hydrogen storage tank. Only by maintaining the sealing integrity of the salt cavern hydrogen storage tank can the salt cavern hydrogen storage tank run stably.
Effect of Dilatancy in Weak Mechanical Discontinuities on Their Interaction with Fluid Driven Fractures
Authors: Smilovich D. , Celleri H. , Serebrinsky S. , Manzanal D. 
Published: September 2023

ABSTRACT
Fluid driven fracturing plays a key role in several industrial applications, such as stimulation of O&G reservoirs, development of enhanced geothermal systems, and geological carbon storage, to name a few.
In previous works we have introduced Y-FRAC®, a fluid driven fracture and rock mechanics simulation platform which makes use of the Discontinuous Galerkin method and a cohesive zone model to describe the deformation and fracture processes that take place in the rock, and standard finite elements to model the corresponding fluid flow inside the fractures during stimulation.
In this work, we expand the previously used constitutive models in order to include the effects of dilatancy during shear deformation. We then evaluate the effect of dilatancy in some cases of practical interest, particularly for the hydraulic fracturing of unconventional reservoirs.

INTRODUCTION
The role of fluid driven fractures and their interaction with weak discontinuities in subsurface phenomena is of significant interest for many industrial applications, such as geothermal energy production, O&G reservoir stimulation and CO2 storage, among several others Kneafsey et al. (2018); Zimmermann and Reinicke (2010).
Shale formations are characterized by having an extremely low permeability, in the order of hundreds of nD.. For this reason, hydraulic stimulation is required in the O&G industry in order to generate conductive channels between the formation and the well, thus making extraction commercially viable. In the context of CO2 geological storage, they are considered as seals.
Weak mechanical discontinuities play an important role in the development of O&G fields in Argentina due to the highly variable presence of sub-vertical and sub-horizontal natural fractures Rodrigues et al. (2009); Ukar et al. (2017, 2019a,b). It is known that these weak interfaces can potentially act as preferential propagation paths, locally altering the fracture propagation direction Gale et al (2018), or even restricting its height Weng et al. (2018); Xu et al. (2019); Celleri and Sánchez (2021).