bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deciphering the Tensile Fracturing Process Using Acoustic Emission
Authors: Wu Shan , Yang Hui , Zhao Qi , Su Boyang , Cai Guanglei 
Published: August 2024

ABSTRACT:
We simulated the tensile fracturing process, capturing both microseismic events (acoustic emissions) and the dynamics of fracture propagation through high-speed photography. To record the millisecond-level fracture propagation, a synchronization circuit was employed, designed to align the 10 MHz acoustic emission recordings with high-speed images taken at a rate of 200,000 frames per second. This setup enabled us to precisely record fracture propagation within a 1.5-microsecond period. Our findings show that the relocated acoustic emission events align closely with the locations of macroscopic tensile fractures. We observed a microsecond-level time delay between the fracture propagation process and the clustering of acoustic emissions. This delay indicates that the clustering of acoustic emissions is related to the fracture nucleation process, while the high-speed photography records the coalescence and growth of fractures, reflecting the development of macroscopic cracks. Considering the temporal and spatial alignment between the acoustic emissions and the propagation of tensile fractures, it is evident that microseismic monitoring primarily captures the early stages of crack formation. Our research indicates that current microseismic monitoring results lack interpretation of the relationship between the nucleation stage and macroscopic fractures, as well as the relationship between microseismic clouds and fracture networks.

1. INTRODUCTION
Microseismic monitoring represents a field technique in observing hydraulic fracturing cracks(Baig and Urbancic, 2010; Cipolla et al., 2012). While it is understood that hydraulic fracturing generates a mix of tensile and shear fractures(Busetti et al., 2014; Fischer and Guest, 2011; Wu et al., 2019), tensile fractures play a more significant role due to their greater contribution to permeability enhancement. This fact highlights the need to better understand tensile fractures. However, most established theories on microseismic inversion are based on traditional seismology(Eisner et al., 2011; Vavryčuk et al., 2008), which predominantly concentrates on shear fractures or slips. Such a concentration restricts the application of microseismic data in interpreting hydraulic fractures. Key challenges include determining whether microseismic events originate from hydraulic tensile fractures(Maxwell, 2011; Warpinski et al., 2013), understanding the relationship between the spatial extent of microseismic clouds and hydraulic fracture zones(Mayerhofer et al., 2010; McKean et al., 2019), and correlating microseismic event magnitudes with the geometric parameters of fractures(Wu et al., 2019).
Optimizing Recovery in Unconventional Reservoirs by Advancing Fishbone Drilling Technology in the Bakken Formation, Williston Basin
Authors: Dehdouh A. , Bettir N. , Khalifa H. , Kareb A. , Al Krmagi M. 
Published: August 2024

ABSTRACT:
The integration of multi-stage hydraulic fracturing and extended horizontal drilling has markedly advanced oil extraction from the Bakken tight oil reservoir, a prominent unconventional reservoir in the United States. Despite these technological strides, the primary recovery rates from this tight formation have remained suboptimal, leaving a considerable volume of oil unrecovered. This challenge underscores the necessity for innovative Enhanced Oil Recovery (EOR) methods tailored to the unique conditions of the Bakken formation. While CO2 injection has been explored, its effectiveness is limited by the formation's heterogeneity. This study introduces an innovative approach through the application of Fishbone Drilling (FbD) technology, aimed at enhancing recovery efforts in the Bakken formation. Our investigation reveals that FbD, characterized by multiple minor holes branching from the main wellbore, significantly improves hydrocarbon recovery by enhancing reservoir contact and exploiting the existing natural fractures more effectively than traditional methods. The findings indicate that FbD not only promises an increase in hydrocarbon flow but also, through optimization of design parameters, aligns with economic viability over time despite higher initial costs. This paper presents a comprehensive analysis of FbD's optimal design and its efficacy in the Bakken formation, supported by data-driven insights that validate the technology's potential to revolutionize EOR strategies in unconventional reservoirs. Through detailed numerical simulations and comparative analyses, this study highlights the superior performance of FbD over conventional drilling and fracturing methods, proposing a promising avenue for future exploration and development within the unconventional reservoirs.

1. INTRODUCTION
The quest for enhanced oil recovery (EOR) techniques in unconventional reservoirs has been a pivotal focus within the energy sector, driven by the imperative need to optimize hydrocarbon extraction from formations like the Bakken tight oil reservoir (Almousa et al., 2023a). Located in the Williston Basin, one of the United States' most expansive unconventional reservoirs, the Bakken formation presents a unique set of challenges and opportunities for EOR strategies (Helms et al., 2023). Hydraulic fracturing and re-fracturing contributed heavily in the oil and gas production in the Bakken as reported by (Dehdouh et al, 2023a). Despite the significant strides made through the integration of multi-stage hydraulic fracturing and extended horizontal drilling, these conventional methods have only marginally improved the primary recovery rates in such tight formations. This scenario underscores the substantial volume of oil that remains untapped, highlighting the critical need for innovative approaches to EOR as detailed by Merzoug et al. (2024).
Quantifying Anisotropic Viscoelastic Parameters Using In-Situ Pressuremeter Testing in Shale
Authors: Liu L. , Trzeciak M. , Xie X. , Chalaturnyk R. 
Published: August 2024

ABSTRACT:
Shale exhibits a certain degree of anisotropy in its deformation properties. This anisotropy is important to consider in rock engineering problems. Pressuremeter (or dilatometer) testing, as an in-situ method to determine geomechanical parameters, has revealed its potential in characterizing this anisotropy with the borehole deformation measured by calipers oriented at multiple diametric axes. In this work, a transversely isotropic viscoelastic model is proposed to predict the anisotropic borehole deformation for pressuremeter testing in the boreholes drilled perpendicular and parallel to the bedding of the shale. The determination of the model parameters is demonstrated using the data obtained from two pressuremeter test cases in Opalinus Clay, a shale with strong anisotropy. The elastic parameters of the model are determined with the model fit on the data from the unloading step while the stiffness relaxation parameters are determined using the model fit on the borehole creep deformation measured during the pressure hold step. The stiffness relaxation parameters determined from the two test cases are considerably different, implying the altered viscoelastic properties in the local borehole damage zone induced in the test case when the borehole is drilled parallel to bedding.

1. INTRODUCTION
Shales play a critical role in various subsurface engineering projects, including petroleum extraction, geological sequestration of CO2, and construction of underground gas storage and radioactive waste disposal facilities. Accurate measurement of their geomechanical properties is important for the successful design and implementation of these projects. A key aspect of shale behavior under subsurface conditions is its tendency to undergo creep deformation when subjected to loading or unloading (Sone & Zoback, 2013). The principle of linear viscoelasticity has been used to model the creep of shale (Trzeciak et al., 2018). Due to its fine-grained texture and laminated structure, shale also exhibits a certain degree of anisotropy in its geomechanical properties. This anisotropy is important to consider in predicting and managing the behavior of shale formations in various engineering applications such as wellbore stability and caprock integrity assessment.
An Improved Time-Dependent Convergence Confinement Method for Estimation of Tunnel Support Loads in Squeezing Ground Conditions
Authors: Arora K. , Gutierrez M. 
Published: August 2024

ABSTRACT:
In tunnel construction, the total tunnel wall displacement increases due to face advancement and the time-dependent behavior of the surrounding rock mass. The convergence confinement method (CCM) is one of the approaches used to analyze the interactions between tunnel wall displacement and support load. CCM utilizes either analytical closed-form solutions or empirical Longitudinal Displacement Profiles (LDP); however, it usually neglects the influence of time-dependency of ground response and associated gradually increasing deformations even after the excavation stage. Designing the tunnel support system without consideration of the time-dependent deformation may result in a false selection of the installation time and the support system type, causing safety issues, cost overruns, and project delays. This paper focuses on discussing a revised CCM to estimate the tunnel's support system loads in a geomaterial with squeezing characteristics and tunnel wall converges significantly with time. The proposed methodology is based on the outcomes of the physical model test results and observations from the tunnels that have experienced squeezing in different parts of the world. The initial section of this paper elucidates the Convergence Confinement Method (CCM) and outlines enhancements aimed at broadening its applicability to squeezing tunnels. The subsequent portion of the paper details the validation process of proposed method, followed by a systematic approach to designing tunnel support systems in squeezing ground.

1. INTRODUCTION
Tunnels in squeezing ground experience significant deformations even after the excavation (Barla, 1995). The load the converging rock mass/soil imposes on the tunnel support system also increases gradually. The support required to stabilize the tunnel boundary in squeezing ground can be two to three times the thickness/stiffness of the support for the same tunnel in non-squeezing conditions (Jethwa et al., 1984). Estimating the deformations due to squeezing beforehand is vital to ensure safe, efficient, and economical tunnel construction (Barla, 2001).
The primary reason for the squeezing ground conditions is the presence of clay minerals in a geological unit with a low strength ratio to the in-situ stress at the tunnel location (Terzaghi, 1946; Wood, 1972). Some of the notable examples of such tunnels include the John Street Pumping Station Tunnel in Canada (Lo et al., 1987), the Still Water Tunnel in the United States (Phien-wej & Cording, 1991), the Uluabat Project Tunnel in Turkey (Bilgin & Algan, 2012), and the Laodongshan Tunnel in China (Cao et al., 2018).
Well Integrity Analysis During CO2 Injection in a Depleted Chalk Field
Authors: Amour F. , Hajiabadi M. R. , Hosseinzadehsadati S. , Nick H. M. 
Published: August 2024

ABSTRACT:
The present study is part of the Bifrost project and aims at assessing the feasibility of storing CO2 in chalk reservoirs by using the depleted Harald East gas field located in the northern part of the Danish North Sea as a showcase. Chalk is a singular rock with a high compressibility and the resulting pronounced compaction during hydrocarbon exploitation and possibly during CO2 storage raises questions on the integrity of cement surrounding the legacy, monitoring, and injector wells. In this context, the study carries out a well stability analysis of a well present in the field. The strain and stress distribution computed by a full-field coupled thermo-hydro-mechanical model is used as input data in a finite element model, which captures the properties and mechanical behavior of a near wellbore area (formation, cement, and casing) located in the seal interval of the field. The results show negligible deformation in the cement during hydrocarbon production and CO2 storage, thereby suggesting low risk of leakage along the studied well.

1. INTRODUCTION
Complying with the ambitious objectives of the intergovernmental panel on climate change in terms of amount of greenhouse gas emission reduction requires the quick implementation of multiple carbon capture storage (CCS) projects worldwide (IPCC, 2005). In this context, the re-use of pre-existing oil and gas infrastructures and fields that were thoroughly studied for decades represents a time- and cost-efficient opportunity associated with a relatively low risk of leakage due to a proof of containment at least at pre-production time (Schmelz et al., 2020). In the Danish North Sea, over 800 Mt of CO2 storage capacity was estimated within mature chalk fields (Bonto et al., 2021). Assessing the possibility of storing CO2 in chalk deposits is currently based on laboratory studies such as batch-reactor and flow-through experiments combined with triaxial tests. Exposures of the rock to CO2 in supercritical and gas phase under temperature and pressure conditions relevant for the subsurface of the North Sea indicate no to minor mechanical alteration of the elastic, shear, plastic, and time-dependent properties (Alam et al., 2014; Ditlevsen & Christensen, 2010; Liteanu et al., 2013; Schroeder et al., 2001).
Probabilistic Analysis of Compressed Air Energy Storage Cavern Stability Considering Rock Mass Property Uncertainties
Authors: Lu Hui 
Published: August 2024

ABSTRACT:
Compressed Air Energy Storage (CAES) in caverns is gaining prominence for its role in ensuring grid stability by storing surplus energy and releasing it as needed, thus addressing the intermittent nature of renewable energy sources. However, existing research on CAES caverns stability often overlooks inherent uncertainties in rock masses, approaching stability evaluations deterministically. This study addresses this gap by incorporating uncertainties in rock mass properties, conducting a probabilistic analysis of the mechanical responses during both the excavation and air-charging stages using numerical modeling with the point estimate method. Specifically, rock mass yield zone development and cavern displacement distributions have been obtained to assess cavern stability. Additionally, the effects of cavern depth, cavern size and the COV of rock mass deformation modulus on cavern stability have been investigated. The probabilistic analyses shed light on the impact of rock mass property uncertainties on cavern stability, offering valuable insights for a more systematic and rational approach to the CAES cavern design.

1. INTRODUCTION
Wind and solar energy are emerging renewable energy sources being developed globally. However, wind and photovoltaic power generation exhibit intermittent and random fluctuations, urgently necessitating large-scale energy storage technologies to absorb renewable energy and to "smooth out" peaks and troughs in energy demand, thereby addressing technical bottlenecks in the development of renewable energy sources. Pumped hydro storage technology is mature and highly efficient, yet its implementation is constrained by factors such as site selection, ecological and environmental protection, and lengthy construction periods. Compressed air energy storage (CAES) is a promising technology solution that can store energy generated at one time for use at another time using compressed air. The CAES system operates by utilizing surplus electrical energy from the grid during periods of low demand to drive compressors that store air in storage containers. During peak electricity demand, this compressed high-pressure air is released from storage and expanded through a turbine to perform work, driving a generator to produce electricity for grid use. It can offer advantages including energy storage, grid stability and renewable integration by storing surplus energy from wind and solar and releasing it for later use during peak demand period (Qin et al., 2023, 2024).
Where Does the Energy Go in Percussion Drilling? FDEM's Answer
Authors: Yang X. , Xiang J. , Naderi S. , Wang Y. , Latham J. , Aising J. , Gerbaud L. , Ugarte I. 
Published: August 2024

ABSTRACT:
A drilling system incorporating percussive action is generally preferred for very hard rock to propagate significant cracking and fragmentation. Therefore, improving energy utilization efficiency becomes crucial for increasing the drilling rate. In this study, 3D FDEM simulations were employed to model the piston-bit-rock interaction in percussive drilling, revealing how the impact energy is partitioned and consumed during the impact process. To ensure the accuracy of energy analysis, rigorous validation against experiments was conducted, comparing the bit indentation and rebound velocity, fragment mass, and the range of rock cracking after impact. The results revealed that, for both St Anne limestone and Rhune sandstone, during a single impact, only 2.4-2.6% of the energy was utilized for crack propagation, while 30-70% of the energy was consumed by friction between fragments. As the piston impact energy increases, there is no significant change in the proportion of fracture energy, while the energy lost to friction gradually increases, then remains unchanged.

1. INTRODUCTION
With the increasing demand for underground mineral resources and green energy (i.e., geothermal energy), efficient drilling technologies are crucial for reducing the cost of drilling (Zappa et al., 2019). When drilling into hard brittle rock formations, impact-assisted drilling methods achieve faster drilling rates compared to purely cutting drilling technologies. Therefore, for percussion drilling, achieving faster drilling rates to reduce drilling costs has become a focus of many engineers and researchers (Aldannawy et al., 2022; Kahraman et al., 2003). It also becomes crucial to fully understand the cracking mechanism and energy transition during the multi-body interaction (i.e., piston-bit-rock interaction), to improve the drilling rate and the energy utilization efficiency.
Several experimental studies have been conducted at various scales to study the rock fragmentation efficiency (i.e., fragment mass per impact) of percussion drilling. Factors such as insert geometry (Qin et al., 2014), impact energy (Saksala et al., 2014), "weight on bit" (Aldannawy et al., 2022) and rock confinement pressure (Li et al., 2021) have been studied for their impact on the rock fragmentation process.
Machine Learning (ML) Model for Blasting and Seismic Event Classification on Chilean Copper Mines
Authors: Otaíza J. R. , Jimenez O. , Vera M. , Sartori R. 
Published: August 2024

ABSTRACT:
In this paper, the support vector machine model (SVM) was used to classify the earthquakes and blasting from the files recorded by an open pit copper mine seismic network. The database cleaning of false positive records (vibrations records not from blasting) must be supervised. This implies spending several hours of highly skilled engineers doing this routine task. Changing to an unsupervised classification method, based on AI, has shown an extremely high overall accuracy (as high as 0.97 over the validation dataset), allowing to perform the database filtering on real time while the vibration events are recorded by the seismographs.

1 INTRODUCTION
In open pit mining, it is a very common practice to implement a seismographers network into the pit to monitor 24/7 any vibration on the ground that exceed a certain limit and especially to record the vibrational event generated by blasting. These records are extremely important to understand and model the vibrational behavior of the rock mass and guarantees the operation safeness for workers and equipment. Due to the heterogeneously of the rock mass and the pit it self, the existence of unstable areas in the pit are a extremely likely scenario. It must be watched carefully and the vibrations generated by the blasting reported on real time to avoid risks.
To model the rock mass vibrational response, the "tendency behavior" is widely used that means to model the Peak Particle Velocity (PPV) as function of "Scalar distance", the distance from the sensor to the closest blasthole, scaled by the explosive load of the blasthole.
On the other hand, the database housekeeping is a highly time consuming process that must be performed by a well trained engineer and the main cause of that time expending is the matching between the blasting information given by the mining company (date, time and blast pattern position) to guarantee that all registered database is in fact blasting induced vibrations. As above mentioned, it is quite important to differentiate the vibration from blasting or by any other source, in particular seismic events.
A Casing Force Prediction Method with a Missing of Cement Sheath Based on Cementing Displacement Efficiency
Authors: Liu Jinlu , Li Jun , Li Yingjie , Li Hui , Yang Hongwei , Liu Gonghui 
Published: August 2024

ABSTRACT:
Due to the low cementing displacement efficiency(CDE), the cement sheath around the casing is prone to be missing, and the casing deformation problem occurs frequently during the subsequent hydraulic fracturing process. Aiming at this problem, a casing force prediction method is proposed in this paper. Firstly, a prediction model of replacement efficiency was established to analyze the influence of different factors on CDE, which can predict the geometry of the cement sheath at different well depths, and is used to characterize where and to what extent the cement sheath is missing in the wellbore. Subsequently, a casing-cement sheath-formation finite element model was established to study the distribution law of casing stress at different degrees of cement sheath missing and calculate the corresponding casing safety coefficient. Based on the safety coefficient, it can be judged whether the casing at the depth of the current well meets the requirements for safe production. Taking well A in Changqing oilfield in China as an example, the method was utilized. The results show that the upper well section is highly susceptible to casing deformation due to the low CDE, the large degree of missing casing, and the low safety coefficient. According to the method proposed, field workers can predict the casing stress in advance.

1. INTRODUCTION
It is well known that cementing quality has a large impact on wellbore integrity (Yan, et al., 2018; Liu, et al., 2022). Due to the low cementing displacement efficiency(CDE) during cementing, the cement ring around the casing is prone to defects, and the casing deformation problem occurs frequently in the subsequent hydraulic fracturing process (Li, et al., 2019; Yan, et al., 2019; Jiang, et al., 2020; Liu, et al., 2023).
Casing eccentricity and low displacement are the main reasons for low CDE. There are more research results on the displacement efficiency, and most of them are calculated by numerical simulation software (Zulqarnain, et al., 2016; Yang, et al., 2021; Xue, et al., 2022). However, fewer research results have been applied to the field of cement ring integrity(Vefring, et al., 1997; Mirjalili, et al., 2017).