bluuebunny/crossref_metadata_2025_split huggingface dataset:
Definition Please – A Rock Engineering Dictionary
Authors: Yang B. , Li Y. , Ambah E. , Elmo D. 
Published: August 2024

ABSTRACT:
definition /def-i-ni-tion/ noun a statement of the meaning of a word, commonly found in a dictionary. Every discipline has its own language – domain specific terminology that allows practitioners to better understand the problem and communicate with one another. While some words and phrases are only found in one specific discipline, there are others that are found in a variety of related disciplines and subdisciplines. Examples in disciplines related and/or adjacent to rock engineering include the terms validation (which has differing definitions in machine learning compared to numerical modelling) and fines (which has differing definitions in soil mechanics compared to cave mining). Confusion may arise when these terms with differing discipline definitions are not defined in their specific context in the literature. Adding to this confusion is the misuse of certain terms in rock engineering, such as accuracy, precision, and quantifying. The goal of this paper is to clarify the definitions of rock engineering terms that are found in other related disciplines, as well as clarify the definitions of rock engineering specific terms. By providing this dictionary of rock engineering terms, we hope to standardize rock engineering vocabulary, allowing for clearer communication among practitioners and students.

1. INTRODUCTION
For any rock engineers who competed in spelling bees in their childhood, the phrase "definition please" may ring a bell. During spelling bees, contestants are able to ask for the definition of a word ("definition please?") to help them spell it. While spelling bees are no longer an aspect of our lives after elementary school, asking for the definition of a word remains an important aspect of research and professional development. Every discipline has its own language – domain specific terminology that allows practitioners to understand the problem in greater detail and to better communicate with one another. Rock engineering language consists of its own terminology (such as rock mass rating or geological strength index) and terminology overlapping with other disciplines, such as with soil mechanics, statistics, and numerical modelling. Confusion may arise when terms are not defined in their specific context, especially those overlapping with other disciplines. This confusion is further exacerbated by the tendency of rock engineers to both misuse certain terminology (such as accuracy, precision, and quantity) and use others interchangeably when they do not have the same definition (such as imbalanced data/skewed data and calibration/validation). As a result, there is a clear need to clarify the definitions of certain rock engineering terms.
Hyperparameter Tuning of an Artificial Neural Network (ANN) for Laboratory Acoustic Emission Source Location
Authors: Xiong Q. , Johnson E. K. , Wu C. S. , Hampton J. C. 
Published: August 2024

ABSTRACT:
Acoustic emission (AE) testing, a technique that has been extensively applied in experimental rock mechanics, traditionally requires source location analysis with both pre-processing and post-processing steps. Performing real-time decision-making that relies on in-situ rock fracture information is hindered by this primarily post-testing analysis technique. This paper examines the potential for using an artificial neural network to replicate the algorithm and output near instantaneous raw source locations; through hyperparameter tuning, this raw output can be improved to approach the accuracy of the standard algorithm. On-disk waveform features are extracted by a trained convolutional neural network (CNN) signal processing model and passed to the ANN through an interlayer. This architecture not only provides the potential for parallel processing but also the ability to directly "read out" raw source locations from the on-disk data. The results of this model provide promising source location predictions despite being only a conceptual example of an ANN for this problem. A further developed model may contain a trained CNN for extracting important waveform features; however, this topic exceeds the scope of this paper and will be the theme of future work.

1. INTRODUCTION
Acoustic emission (AE) testing has been extensively used for delineating the rock fracture process in a variety of scientific and engineering applications [1-6]. This technique uses piezoelectric AE sensors to detect energy releases from rock fractures. Arrival times of AE signals and sensor coordinates can be passed to an optimization function, based on the time delay of wave propagation, for locating the source of an energy release. Procedures within laboratory AE source location analysis, in general, include steps of pre-processing, source location, and post-processing as depicted in Fig. 1. Such procedures have been well-established and practiced for decades. During pre-processing, signals are recorded onto the disk and the signal processing codes are applied to the recorded signals for extracting the arrival times and other features. The results of pre-processing (i.e. the arrival times of AE signals) are then fed into a source location algorithm. This algorithm first produces raw results of source locations and then refines them by filtering out disqualified locations based on the physical principle [7] or mathematical (i.e., error or residual) feature [8]. After completing the previous two steps, source locations can be further used for visualizing the rock fracture propagation path, source type classification [6, 9-11], clustering/declustering analysis [12, 13], and other advanced analysis [14-17].
Kick Warning and Pressure Inversion Method Based on Wellhead Pressure Signal
Authors: Duan Shiming , Song Xianzhi , Yao Xuezhe , Xu Zhengming , Zhou Mengmeng , Zhu Zhaopeng , Cui Yueqi 
Published: August 2024

ABSTRACT:
Kick detection seriously restricts safe and efficient drilling, so accurate and timely warning and analysis are very important. This paper is based on drilling data and optimizes parameters of wavelet analysis such as mother wavelet function, data frequency, and data length. Using the wavelet analysis method, the wellhead pressure signal undergoes decomposition. The obtained signals are combined with logic rules to constrain the intelligent kick warning model, and the final model accuracy reaches 90.08%. To further analyze the kick parameters, spectral analysis is used to quantitatively extract the wellhead kick pressure fluctuations which is used to set the wellhead boundary. By integrating perturbation theory with the governing equation, an analytical solution for pressure propagation and attenuation in the liquid phase is proposed. This analytical solution is applied to the flow model, enabling real-time solutions and analyses of bottom-hole kick fluctuation pressure and volume. The final model demonstrates a relative error of 0.4%. This model is expected to provide new methods for the detection and control of kick.

1. INTRODUCTION
Drilling is the only way to create oil and gas channels, and the process is complex and changeable. Due to factors such as inaccurate formation information prediction and improper operations, drilling risks such as the kick, lost circulation, and blowout can easily occur (Vandenbussche et al., 2012). Among them, kick is one of the common drilling risks. The fundamental reason for the kick is that the bottom hole pressure is lower than the formation pressure during the drilling process. Then the formation fluid invades the wellbore, causing the volume of fluid in the wellbore to instantly increase and kick from the wellhead. When a kick occurs, if it is not detected in time or dealt with too late, it is likely to induce a blowout accident(Aime et al., 1967; Han et al., 2017). In addition, when there is gas in the invading fluid, the bottom hole gas continues to rise with the drilling fluid, the pressure and temperature decrease, and the gas expansion accelerates. As a result, the closer to the wellhead, the greater the drilling fluid flow rate, and the more difficult it is to control the wellbore pressure (Alhuthali et al., 2010). For example, the "12.23" blowout accident in Kaixian, Chongqing, China(2003), and the blowout in the Gulf of Mexico in the United States(2010), both caused serious consequences such as equipment damage, casualties, environmental pollution, and scrapping of oil wells (Rathnayaka et al., 2012). Therefore, kick has become one of the recognized high-frequency and high-risk accidents in the drilling industry (Fu et al., 2015). Rapidly detecting kick signals and analyzing the kick process are important means to help quickly deal with kick risks.
Assessment of Thermal Effects on the Formation Breakdown Gradient in APB Mitigation Scenarios
Authors: Souza B. S. P. , Souza C. O. , Fontoura S. A. B. 
Published: August 2024

ABSTRACT:
This work aims to investigate the influence of temperature variation on the formation breakdown gradient in scenarios of annular pressure build-up (APB) mitigation during well production. In subsea well projects, it is common to mitigate the effect of APB through the open shoe method, which involves allowing formation fracture below the casing shoe. In this analysis, the fracture gradiente obtained through leak-off tests conducted in the field is typically used. However, the breakdown pressure tends to be higher than the fracture gradient and can be further augmented by temperature increase, potentially resulting in undersizing of well structure elements and eventual integrity failure. To assess the potential implications in well design, a 1D geomechanical model was developed, and thermo-hydraulic simulations were conducted for two wells located in the Brazilian coast. Then, the breakdown gradient calculations were performed, considering variations in pressure and temperature in the confined annuli, primarily comprising shale layers. As a result, variations of up to approximately 19% were observed in the breakdown gradient. Significant reductions in the casing safety factors were observed for the analyzed wells, approximately 37% reduction in the burst safety factor and 25% in the triaxial safety factor.

1. INTRODUCTION
The Theory of Thermo-Poro-elasticity has been widely discussed and presented in various wellbore stability and reservoir stimulation works. The stress concentration around the borehole is strongly affected by temperature. In scenarios of narrow drilling windows, for instance, cooling induced by fluid circulation can lead to losses to the formation due to the reduction in stress concentration, and consequently, the breakdown pressure (as well as the collapse pressure). Conversely, heating tends to increase the breakdown pressure. Rizvi et al. (2022) presented some case studies where the bottom hole temperature was affected by operational drilling parameters variation leading to fluid loss. The same effect is described in many others works (Maury and Idelovici, 2015, Li et al, 1998, Liu and Zhu, 2018, Tao and Ghassemi, 2010). As a point of view from reservoir stimulation, Azevedo et al. (2023) demonstrated that the minor in situ horizontal stress can be reduced by cooling of the rock during cold fluid injection through numerical analysis and evidence of field cases.
High Temperature Triaxial Direct-Shear Testing for FORGE and Field Scale Implications
Authors: Frash L. P. , Iyare U. C. , K C B. , Meng M. , Smith M. , Kroll K. 
Published: August 2024

ABSTRACT:
Rock fractures are the most important element of Enhanced Geothermal Systems (EGS) but we lack the necessary data to predict the combined effect of temperature, flow, mechanics, and chemistry on the forecasted effectiveness of these fractures for heat extraction and power production. Here, we seek to quantify the strength, deformation, and hydraulic conductivity of rock fractures before and after shear slip, at geothermal reservoir conditions. This information enables evaluation of the likelihood that hydraulically induced shear slip will improve the performance of EGS. This data can also aid risk forecasting for injection induced seismicity. Concurrent effluent analysis yields insights regarding the chemical reactivity of fresh shear fractures. Our measurements were obtained using triaxial direct-shear experiments conducted at conditions replicating well 16A(78)-32 at the Frontier Observatory for Research in Geothermal Energy (FORGE) in Milford, Utah. We also implement these measurements into reservoir models to evaluate their impact on predicted reservoir performance relative to prior estimates.

1. INTRODUCTION
Geothermal energy retains promise to supply clean stable electrical power and heat (Hamm et al., 2018), as well as flexible power to accommodate the intermittency of wind and solar energy (Ricks et al., 2024). Predicting the behavior of rock fractures is key to expansion, especially for Enhanced Geothermal Systems (EGS) because of its requirement for fractures to facilitate fluid flow and heat extraction (Tester et al., 2006; Brown et al., 2012). However, the properties of fractures at hot and deep conditions are not well known, especially if the effects from stimulation, chemistry, and mechanics are to be considered. The Frontier Observatory for Research in Geothermal Energy (FORGE) is an opportunity to better understand such processes by comprehensive scientific assessment of a hot dry rock (HDR) geothermal resource (Podgorney et al., 2023), along with the performance of technologies needed to access and harvest the heat.
Here, we present laboratory experiments to characterize thermal, hydraulic, mechanical, and chemical (THMC) coupled processes related to the stimulation of and flow of fluid through shear-induced fractures. Results from this work reveal insights into the potential of hydraulic shear stimulation to enhance flow and quantify key properties for fractures, including strength, frictional properties, dilation tendencies, and chemical reactivity; the details of which are included herein.
A Conceptual Subsurface Risk Management and Measurement, Monitoring and Verification Design for an Offshore Carbon Capture and Storage Site in Japan
Authors: Nii K. , Nakayama S. , Ohira A. , Ashida T. , Qiu K. , Lee H. , Wada N. , Yamabe H. 
Published: August 2024

ABSTRACT:
This paper presents a case study on the conceptual subsurface risk management and measurement, monitoring, and verification (MMV) design for an offshore CCS carbon capture and storage (CCS) site in Japan. Based on the available geological and carbon dioxide (CO2) numerical simulation results, preliminary risk assessment and risk management analyses were conducted for this site. This risk management analysis identified the key monitoring tasks of MMV. The MMV design was subsequently conducted to develop a site-specific and risk-based MMV plan to proactively address the potential subsurface risks for the given site. The paper describes the workflow of conceptual subsurface risk management and MMV design, summarizes the key considerations and findings, and sets examples for conducting similar evaluations for other CCS projects.

1. INTRODUCTION
The Government of Japan announced the goal of achieving carbon neutrality by 2050, and carbon capture and storage (CCS) is considered a critical part of the overall solution to achieve the goal. In 2023, seven potential offshore CCS projects were selected by the government as the first initiative for the CO2 storage feasibility study toward the commencement of commercial CCS operations by 2030.
Subsurface risk management and related MMV design are critical parts of the feasibility study, as the success of a CCS project relies on the long-term containment of the injected CO2 in the storage complex.
In this context, conceptual subsurface risk management and MMV design were conducted at one of the candidate sites located offshore Japan by leveraging the enriched knowledge of worldwide CCS guidelines and regulations on CCS subsurface risk management and MMV planning.

2. INTRODUCTION OF THE STORAGE SITE
The offshore carbon storage site, located around the Tokyo metropolitan area, was selected by INPEX for potential CCS operations. CO2 will be transported by onshore and offshore pipelines from emitters located in the metropolitan area. The injection operation is planned to start in 2030 and continue for more than 30 years, with a target injection rate of approximately 1.0 million tonnes per annum (Mtpa). Considering the water depth around the potential CCS site, the platform injection concept was selected. The target storage aquifer in the site employs a continuous and thick, deep- and shallow-water marine sedimentary succession.
Development of Hydraulic Fracturing Evaluation Techniques Using Chemical Adsorption Mechanics
Authors: Zhang Shang , Zheng Danzhu , Yu Mengjiao 
Published: August 2024

ABSTRACT:
In order to identify problems during the fracturing job and optimize the hydraulic fracturing design for future development, an effective method for monitoring and evaluating the hydraulic fracturing operation is needed. Due to the complex nature of the process, most of the existing techniques for hydraulic fracturing diagnostics and evaluation are limited.
In this research, a direct far-field measurement method was also developed in this research by utilizing chemical adsorption mechanics. A specially designed surfactant was tested in laboratory experiments for its ability to adsorb on the fracture surfaces. The advantage of this method is it can bypass the difficulties of assuming the fracture geometry and directly translate the fracture surface area into stimulated reservoir volume (SRV). It will be especially useful in naturally fractured reservoirs, where the hydraulic fracture will interact with the existing natural fractures. A dynamic adsorption model was developed for the proposed evaluation method in field scale.
Furthermore, a hydraulic fracturing efficiency improvement method was proposed using the same surfactant. An economic analysis was conducted using the comprehensive hydraulic fracturing model developed in this research. The results showed that the efficiency of hydraulic fracturing could be significantly improved using surfactant adsorption.

1. INTRODUCTION
Hydraulic fracturing is a process that could improve the recovery of hydrocarbons from formations, especially for low permeability formations. A successful hydraulic fracturing operation is the key to enabling economic production from low permeability reservoirs. Because of lacking affordable data acquisition technologies during the operation, it has been a "black-box" tool for the industry for decades, although many researchers have tried to measure or numerically describe the hydraulic fracturing process (Warpinski et al., 1994; Cipolla & Wright, 2000).
One of the reasons for this situation is the difficulty of verification. The actual fracture geometry that is located at extreme in-situ conditions thousands of feet under the surface is nearly impossible to obtain directly. Another reason is that the whole process is extremely complex. A poorly designed operation or problems during the fracturing job, such as inadequate fluid volumes, inappropriate proppant selection, and insufficient treatment stages, would result in a less efficient fracture network, contributing to the flow in the production phase (Sinha & Ramakrishnan, 2011). If no proper evaluation techniques were deployed during the fracturing operation, operators could not realize the underperformance of the well until it had been put into production for a while. Since then, a workover or re-fracturing job has been needed to optimize production, which would cause a considerable amount of extra cost and an enormous amount of non-productive time (NPT).
Effect of the Stress Regime on Injection-Induced Seismicity
Authors: Xiao Y. , Haitao Y. 
Published: August 2024

ABSTRACT:
The distribution of local stress regime has a significant influence on natural earthquakes, while its role in controlling injection-induced fault reactivation and associated seismicity remains poorly understood. This paper investigates the relationship between fault aseismic slip, seismic slip and seismicity magnitude under different stress regime. Results show that the seismic slip zone will exceed the pressurized area with the increase of initial slip tendency under the strike-slip-faulting stress regime. Compared with fluid pressure, the seismic slip is mainly determined by a sudden increase of the shear stress at the aseismic slip zone boundary. In addition, the location of the microseismic events moves towards the fluid pressure propagation front. The larger slip area and seismicity magnitude are easier to be induced under strike-slip-faulting stress regime than thrust-faulting stress regime. The tensile failure and higher permeability of the fault induced at injection phase for normal-faulting stress regime leads to a greater seismogenic hazard at the shut-in stage.

1 INTRODUCTION
In recent years, induced seismicity events have been increased rapidly due to the injection of large volume fluid into reservoir formations (Rutqvist et al., 2015; Ellsworth, 2013). These earthquakes are triggered by reactivating critically stressed faults. The fault reactivation process is highly dependent on the stress regime, the pore pressure, the hydrological properties of the fault and surrounding rock. The range of geological reservoirs may reached up to several kilometers and the in-situ stress and fault geometry experience obvious variation. A large number of geophysical observations have shown that the regional reservoir stress is a key control factor for fault slip behaviour (Sheikholeslami et al., 2021). The magnitude and frequency of the natural earthquakes have a strong relationship with stress regime (Scholz, 2015). It is postulated by Amini and Eberhardt (2019) that a critical fault in strike-slip fault stress regime respond differently than that in a normal or thrust fault stress regime. However, the effect of stress regime on spatiotemporal evolution of injection-induced fault reactivation and seismicity is still not clear.