bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non-Cubic Law Fracture Flow Phenomena
Authors: Gee B. , Gracie R. 
Published: September 2022

ABSTRACT:
Hydraulic fracture and fracture flow simulations are almost exclusively based on Poiseuille flow (the cubic law). A key assumption embedded in our models is that flow is steady, inertial effects are negligible, the fracture surfaces are parallel and the rate of change of the fracture aperture does not impact flow. However, in many practical applications most and sometimes all of these assumptions are violated. In this paper, we will discuss various phenomena that may be observed in experiments and the newly derived Reduced Dimension Fracture Flow (RDFF) model which are not captured by simulations based on the cubic law. These include (1): fracture fluid flow induced by seismic waves, (2) phase shifts between pressure, aperture, and flux fields, (3) non-Darcian flow in the direction of positive pressure gradients, (4) negative near well bore fluid pressures induced by high velocity radial flow.

1 INTRODUCTION
Modern large-scale simulations of fracture flow and hydraulic fracture operations are based almost exclusively on the cubic law (also known as Poiseuille flow). The cubic law is popular because it provides a constitutive relationship between the fluid flux and the fluid pressure, but this model is accompanied by a number of limiting physical assumptions. The cubic law is the analytical solution to flow through rigid parallel plates and makes the assumptions: a) that flow is steady, b) inertial effects are negligible, c) fracture surfaces may be locally approximated using parallel plates, d) that flow is laminar, and e) that the rock mass is impermeable. In many applications of the cubic law, most and sometimes all of these assumptions are violated. The recently derived Reduced Dimension Fracture Flow (RDFF) model (Gee and Gracie, 2022b) provides an alternative to the cubic law. The RDFF model is derived from the Navier-Stokes equations by integrating over the fracture aperture and making simplifying assumptions about the flow behaviour to generate a model that, at the cost of increased model complexity, is not subject to the same physical limitations as the cubic law. The RDFF model is capable of capturing inertial and transient flow behaviours, and has been shown to conserve energy in fractures of varying aperture where the cubic law does not.
Coupled Effect of Glass Microfiber Reinforcement and Temperature Elevation to the Swelling and Compressibility Characteristics of Bentonite
Authors: Calaunan J. M. F. , Eun J. , Kim S. , Kim Y.-R. 
Published: September 2022

ABSTRACT:
The deep geological repository is one of the most preferred disposal methods in many countries for high-level radioactive waste materials and spent fuel after nuclear energy production. The engineered barrier system (EBS) in the repository holds the nuclear waste-containing canister in place. However, it is known that the EBS can be readily dried near the canister due to the heat emitted from the spent fuel inside the canister, which could induce the generation of cracks in the EBS. Inorganic microfiber can be an alternative to mitigate such cracks, and thus, enhance the performance of the engineered buffer material. This study investigated the coupled effect of glass microfiber reinforcement on the swelling and compressibility characteristics of sodium bentonite at both ambient (22°C) and elevated (50°C) temperatures. By using the one-dimensional consolidation test setup with temperature controls, the swelling pressure test was performed to investigate the swelling pressure, compression, and swelling indices for 0.0% and 3.0% glass fiber contents by weight. A unique coupled relationship between the fiber inclusion and temperature elevation for the bentonite can better explain the engineering performance of the deep geological repository to safely store the high-level radioactive waste materials and spent fuel.

1. INTRODUCTION
Nuclear energy is one of the main sources of energy utilized across the globe. According to the U.S. Energy Information Administration (2021), the United States of America generated 809 BkWh of total annual nuclear electricity last 2019. This amount translates to 30.5% of the total world nuclear electricity generation. At present, the United States has 94 nuclear reactors in operation, in which 30 of its states house many commercial nuclear power plants (U.S. Energy Information Administration, 2021).
According to the U.S. Environmental Protection Agency (2022), fossil fuel accounts for 65% of global greenhouse gas emissions. On the other hand, nuclear power currently represents more than half of all low-carbon electricity generation in the U.S. and 30% of the world’s low-carbon electricity (Hsu, 2021). With that, nuclear energy is gaining traction due to its non-production of greenhouse gas emissions during operation (World Nuclear Association, 2022). However, given the national and global reliance on this energy, its production entails a huge amount of nuclear waste generated afterward.
Geological and Geomechanical Analyses for Hydrogen Storage in Salt Caverns, Central Kansas
Authors: Meng Jingyao , Hasiuk Franek , Holubnyak Eugene , Raney Jennifer 
Published: September 2022

ABSTRACT:
The H-2-SALT study aimed to assess the feasibility of a power-to-hydrogen system utilizing salt cavern storage of hydrogen in Kansas. Two specific sites were evaluated in this study, including Gordon Evans Energy Center (GEEC), located near Colwich, KS; and the Hutchinson Energy Center NG-EGU (HEC), located northeast of Hutchinson, Kansas. The existing well and Kansas Department of Health and Environment (KDHE) salt cavern data were collected at the two sites and adjacent area to develop a hydrogen storage potential database for site characterization efforts. The Hutchinson Salt Member, a bedded salt formation, exists in central to western Kansas, dipping towards the west and providing prospective potential for hydrogen storage in designed salt caverns. GEEC and HEC contain 200-300 ft (61-91 m) Hutchinson salt under the 300-450 ft (91-137 m) overburden formation. Little or no major stability issue is existed at the study area. Potential stability issue such as cavern closure, roof collapse, interbed slip, and tensile fracturing can be avoided by limiting the cavern parameters during the hydrogen storage operation. Pressure, size limitation, and distribution of potential salt caverns for each site were determined to meet the criteria of cavern stability. Future research should focus on obtaining core and log data, and 2D or 3D seismic surveying to characterize the salt formation and mechanical behavior for pre-FEED (front end engineering and design) studies.

1. INTRODUCTION
Natural, bedded salt formations can be considered as host rocks for cavern storage of hydrogen produced by the conversion of excess energy to hydrogen via electrolysis. There are three active facilities in the US and one facility in the UK stores hydrogen in salt caverns (Zivar et al., 2021). Thick salt deposits underlie south-central Kansas (Sawin and Buchanan, 2002; Walters, 1978). Kansas has a mature salt industry, including traditional mining, solution mining, and underground liquid hydrocarbon storage in salt caverns. A comprehensive understanding of the geology and geomechanics principles is vital to understanding site selection, sizing, and designing a hydrogen storage facility. The H-2-SALT study aimed to assess the feasibility of a power-to-hydrogen system utilizing salt cavern storage of hydrogen in Kansas. Sponsorship of this study was provided by the National Energy Technology Laboratory, US Department of Energy.
Permeability and Water Saturation Characterization and Prediction in Wellington Oil Field Using Core Analysis and Seismic Inversion
Authors: Esmaeilpour S. , Ispas I. 
Published: September 2022

ABSTRACT:
Reservoir permeability is a critical parameter for the evaluation of hydrocarbon reservoirs. It is often measured in the laboratory from reservoir core samples or evaluated from well test data. The prediction of reservoir rock permeability utilizing well log and seismic data is important because the core analysis and well test data are usually only available from a few wells in a field and are associated with high coring and laboratory analysis costs. In this work, a joint inversion strategy based on Multi Attribute Analysis (MAA) and Deep Feed-forward Neural Networks (DFNNs) algorithm was applied to predict the spatial variations of key petrophysical parameters (porosity, permeability, and saturation) for inter-well regions. In this method, acoustic impedance (AI) models are computed from post-stack seismic amplitude data by seismic inversion in the time domain with measured log density and velocity as constraints. The obtained results reveal that the proposed strategy, which combines MAA and PNNs, leads to the optimization of lateral and vertical facies heterogeneities and accurate prediction of reservoir parameter distribution. The time slice maps of inverted porosity and permeability at various time intervals indicate a reasonable calibration with the measured core and well log data. The methodology proposed in this study may be considered useful for other basins in Kansas with similar geological settings and anywhere in the world for reservoir characterization, particularly for carbonate Cambrian-Ordovician formations and variable depositional environments.

1. INTRODUCTION
Recently, acoustic impedance (AI) mapping, which is derived from the inversion of poststack seismic amplitude data, has emerged as a widely used technique for predicting spatial reservoir properties. It has been proposed that the inverted models of AI, i.e., P-impedance, S-impedance, and density, can be used to estimate lithofacies, petrophysical, and elastic parameters (Singha and Chatterjee 2014; Leiphart and Hart 2001; Pramanik et al. 2004; Calderon 2007; Kumar et al. 2016; Kumar et al. 2016; Walls et al. 2002). Based on the literature, several researchers have developed geological features and petrophysical properties using particular seismic attributes. For example, Russell et al. (2004), demonstrated how seismic attributes may be used to estimate the porosity cube. They employed stepwise regression and neural network approaches to create the porosity cube. De Groot and Aminzadeh (2004) employed the seismic attribute to discover faults, cracks, gas chimneys, and salt bodies in the ground.
Effect of Rock Elastic Anisotropy on Hydraulic Fracture Containment in the Bakken Formation
Authors: Chellal H. A. K. , Merzoug A. , Rasouli V. , Brinkerhoff R. 
Published: September 2022

ABSTRACT:
In this study, a special focus was dedicated to the effect of elastic anisotropy of shales on the in-situ stress contrast between different layers and its implications on the vertical containment of hydraulic fractures (HF) and how they relate to the widely observed fracture driven interaction (FDI) phenomena and undesirable HF height growth. The reported elastic and mechanical properties of the main members of the Bakken petroleum system in the Williston Basin (i.e. Upper and Lower Bakken Shale, Middle Bakken, and Three Forks) were used to estimate the in-situ stresses based on anisotropic rock properties and use the minimum horizontal stress profile for HF modeling. The estimated stress profile appeared to be very different from the one calculated based on the isotropic formation assumption. The anisotropic stress model, as reported by other researchers, is more realistic in transversely isotropic rocks and rocks with a high volume of clay and TOC and generated more reliable results that conform better with other indicators and observations from other types of data associated with HF geometry.

1. INTRODUCTION
Accurate estimation of the minimum principal in-situ stress is a milestone in the successful design of hydraulic fracturing (HF) jobs (Ganpule et al., 2015). The role of accurate stress variations with depth becomes more pronounced where HF is performed in different horizons to explore what is called stacked pay. Estimation of in-situ horizontal stresses is mainly attributed to the inherently simplistic assumptions of the commonly used stress models (Zoback, 2007). However, the revolution in the oil and gas industry due to production from Shale plays indicated the necessity of using anisotropic, or what is so-called as transverse isotropic (TI) assumption for the different geological layers for improved estimation of the horizontal stresses. In this study, we showcased the importance of laboratory characterization of the elastic and mechanical properties for accurate prediction of stress profiles and how they can change our designs and improve the profitability of our investments by generating more reliable stress models that are coherent with what is indicated by other types of data. This can serve as a strong base for improved planning. This is proved through our case study performed using data from the Bakken petroleum system in the Williston Basin. It was found that the HF geometries predicted from simulation using a well-calibrated anisotropic stress model strongly agreed with HF geometries observations from microseismic data reported in many other studies such as McKimmy et al. (2022) and Lorwongngam et al. (2018).
The Effect of Fracture Aperture on Fracturing Fluid Imbibition into Gas-Saturated Rocks
Authors: Li Guanlin , Liu Yuetian , Cheng Ziyan , Xue Liang , Kong Xiangming 
Published: September 2022

ABSTRACT:
During well shut in after hydraulic fracturing, a large amount of fracturing fluid enters the formation through imbibition, which significantly reduces the recovery of injected water. However, the capillary pressure of fractures is usually ignored, and the effect of fracture aperture on this process is not clear. We examined the imbibition characteristics between fractures and matrix in the capillary-controlled gas-water flow. The focus is on the flow behavior and effects caused by capillary pressure of fractures. The imbibition experiments were carried out under different fracture apertures (50-950 μm). The results show that fractures within a certain opening range accelerate water imbibition by providing a plane source. The water flows rapidly in the fractures, then being absorbed by the matrix on both sides. The water imbibition rate of fractures is mainly affected by the fractures aperture, which controls the fracture capillary pressure and permeability. The overall trend is that the imbibition rate is inversely proportional to the fracture aperture. This indicates that the small aperture fractures without proppants can quickly transport water to the interior of the matrix. The research is significant to understand the law of fracturing fluid imbibition in the formation.

1. INTRODUCTION
Horizontal wells with multistage hydraulic fracturing are an important technical means for developing unconventional gas reservoirs (Fazelipour, 2011; Yu and Sepehrnoori, 2013; Lei et al., 2022). A large volume of water-based fracturing fluid such as slick water is injected into the formation to form a complex fracture network (Barati and Liang, 2014; Cai et al., 2017). Field practice shows that the flowback rate of fracturing fluid is generally low (Alkouh and Wattenbarger, 2013; Osselin et al., 2018). Spontaneous water imbibition is considered to be one of the main reasons for this phenomenon (Almulhim et al., 2014; Ge et al., 2015; Al-Ameri et al., 2018). The fracturing fluid spontaneously imbibes into the matrix from fractures, which could increase water saturation and reduce the gas phase relative permeability, affecting the production of gas reservoirs (Saini et al., 2021). The study of spontaneous imbibition mostly focuses on the capillary pressure of matrix pores and related problems (Makhanov et al., 2012; Dehghanpour et al., 2013; Roychaudhuri et al., 2013; Sadjadi and Rieger, 2013; Mason and Morrow, 2013; Shi et al., 2018). But spontaneous imbibition in unsaturated water fractures also deserves attention. There are different scales of fractures in the complex fracture network formed by artificial and natural fractures (Yushi et al., 2016). Studying the effect of fracture aperture on fracturing fluid imbibition into gas-saturated rocks has significance for improving fracturing technology and enhancing recovery.
Determining Elastic Constants and Indirect Tensile Strength from a Single-Orientation Core of Transversely Isotropic Rock by the Uniaxial Compression and Brazilian Tests
Authors: Yim Juhyi , Lee Yoonsung , Hong Seungki , Min Ki-Bok 
Published: September 2022

ABSTRACT:
A practical method determining five elastic constants of a transversely isotropic rock is proposed by the uniaxial compressive strength test and the Brazilian test using specimens from a single-orientation core. The indirect tensile strength of the Brazilian test can be obtained through this suggested method. The simple iterative procedure based on the least square method was suggested. While suggested method works best for inclined cores in determining five independent elastic constants, horizontally or vertically layered cores require the empirical relation to determine the second shear modulus. Validation against Asan gneiss shows that the proposed method determines five elastic constants with acceptable variation in comparison with those determined by the conventional method using multiple cores. The indirect tensile strength of the Brazilian test can be evaluated with the determined elastic constants as inputs, but it can differ depending on the method determining elastic constants. According to the observed variations in the experiment results, the better understanding of the mechanism of the Brazilian test and the further experimental validation are recommended.

1. INTRODUCTION
Rock deformation and failure are often dependent on loading direction; as such, considering the mechanical anisotropy of rock is important in various civil, mining, and petroleum engineering applications. The anisotropic elastic constants have to be considered for in-situ stress measurement by the overcoring method (Van Heerden, 1983), design of underground structure (Sanio, 1985), and numerical modeling of hydraulic fracturing (Kahn et al., 2012). The tensile strength needs to be carefully determined for the stability analysis for mine roof (Nova and Zaninetti, 1990) and the design of drilling or rock excavation (Yarali and Kahraman, 2011); therefore, accurate determination of tensile strength is important. The transversely isotropic (TI) model has been commonly used to characterize anisotropic rock owing to its applicability and simplicity (Amadei, 1996; Exadaktylos, 2001).
Revisiting Rockburst Predictive Models for Seismically Active Mines
Authors: Kulgatov A. , Adoko A. C. 
Published: September 2022

ABSTRACT:
Rockburst is a mining-induced seismic event characterized by a sudden explosion of rock due to the release of strain energy stored in rock mass, often occurring in high geo-stress and other unfavorable geological conditions. The prediction of the rockburst damage potential (RDP) is essential in mining as this phenomenon causes damage to excavations, leading to dire consequences that include economical losses, injuries, or casualties of miners. Despite the existence of a large number of rockburst predictive models and other empirical tools, a reliable prediction of RDP still remains challenging. Hence, the aim of this paper is to revisit some existing studies and propose practical RDP charts based on basic machine learning algorithms such as artificial neural network classifier. Historical records of rockburst compiled from Australian mines were employed for this purpose. Overall, the results of this study showed good consistency with the field data and outperformed those of some existing studies. It is concluded that the proposed charts could be used for the excavation vulnerability assessment and, therefore, assist in managing ground prone to rockburst in seismically active mines.

1. INTRODUCTION
Rockburst is commonly defined as a rock explosion that occurs primarily in high geo-stress conditions and other unfavorable geological conditions in underground excavations due to the sudden release of strain energy stored in rock mass (Xue et al., 2020). In underground mines, it occurs in the form of mining-induced seismic events. The consequences of this phenomenon have the potential to be extremely destructive causing significant damage to equipment and underground structures as well as injuries and fatalities among mine workers. As early as in 1738, when it was first mentioned in a tin mine in Great Britain (Zhou et al., 2012), rockburst has been associated with numerous accidents and casualties throughout the mining industry around the world. Rockburst was the main reason of the mine disaster in South Africa, where 73 employees died during underground gold extraction in 1975 (Cai, 2016). Many similar cases have been recorded in China, with an increase of cases every year as mines go deeper (Pu et al., 2019). These few examples illustrate the devastating consequences of rockburst and the urgent need to study ways of predicting or controlling its severity.
Capillary Imbibition of Fracturing Fluid in Unconventional Reservoirs: The Impact of Velocity-Dependent Dynamic Contact Angle
Authors: Gao Yanling , Wu Keliu , Chen Zhangxin , Tian Weibing , Li Jing , Bi Jianfei , Huang Ziyang 
Published: September 2022

ABSTRACT:
In this work, we compare experimental data with different kinds of dynamic contact angle (DCA) models firstly, rationality of the values of fitting parameters are then analyzed. Based on the combined model, we modify the classic L-W equation further to consider the influence of DCA in the process of water imbibition in micro and nanoscale hydrophilic capillaries. Besides, the effects of static wettability and pore dimension are investigated. Results show that: 1) The velocity dependences of DCA predicted by different kinds of DCA models are similar to each other and they can all fit well with the experimental data due to the existence of fitting parameters. 2) DCA deviates from equilibrium contact angle (ECA) more in capillaries with larger dimensions, which is due to the lower flow resistance and higher imbibition velocity. 3)With the decreases of the ECA, the deviation between DCA and ECA increases, this is because energy dissipation in the meniscus is higher in more hydrophilic capillaries due to the stronger fluid-wall interaction. 4) For spontaneous water imbibition in hydrophilic capillaries, the influence of DCA is more obvious in capillaries with larger sizes or smaller ECA, where it should be considered for more accurate recovery prediction.

1. INTRODUCTION
Capillary imbibition is an interesting and ubiquitous phenomenon in nature, and plays a significant role in many industries (Feng et al. 2018b), such as ultrafine filtration process, irrigation engineering, energy conversion/storage, powder engineering, etc. (Zhang and Pei 2020, Feng et al. 2018b). Specially, in petroleum engineering, imbibition in porous media has important applications in the flowback of fracturing liquid and the huff-puff development of oil and gas field (Tian et al. 2021a). During the imbibition process, fracturing fluid, which is made up of as much as 97 percent water, imbibes into the matrix from the fracture, expelling oil and gas there and is favorable to the final recovery when the pore surface is water-wet (Tian et al. 2021b). Therefore, the imbibition process has great prospects in the development of fractured and unconventional oil and gas reservoirs and the recovery enhancement (Yha et al. 2020).