bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation on the Setting Time Improvement of Geopolymer Cementitious Material Developed for Pumpable Roof Supports
Authors: Motameni S. , Nikvar-Hassani A. , Zhang L.
Published: August 2024

A novel geopolymer cementitious material (GCM) has recently been developed at the University of Arizona for the construction of pumpable roof supports (PRSs) in underground coal mines. The newly developed GCM not only demonstrated superior mechanical properties but also addressed the cracking issues of the traditional CM when exposed to air. However, during the full-scale production and performance evaluation of the GCM, it was observed that the GCM encountered a self-supporting issue. Specifically, the setting time of the GCM was longer than anticipated, leading to slight buckling during the production of the PRSs. The present study explores different additives to adjust the setting time of the GCM, aiming to improve its self-supporting capacity at the very beginning. To achieve the goal, systematic laboratory experiments were conducted to investigate the setting time and self-supporting capacity of the GCM containing different types and dosages of additives. The rheology, compressive strength, tensile strength, and toughness of the GCM at different conditions were evaluated. X-ray diffraction (XRD) analyses were also performed to study the effect of the additives on the phase composition of the GCM. The results show that with the addition of free lime up to a certain amount, the GCM achieves good self-supporting while maintaining its superior mechanical properties and durability.

1. INTRODUCTION

Pumpable roof supports (PRSs) are used in long-wall tailgates and bleeder entries as secondary roof support in underground coal mines (Fig. 1). The main component of a PRS is the cementitious material (CM). The requirements for a CM to be used in the construction of PRSs include high peak UCS and large residual strength (Barczak & Tadolini, 2008). The currently used CMs in practice are either costly or decompose after exposure to air. Finding an alternative CM is therefore essential to meet the PRS requirements (Nikvar-Hassani & Zhang, 2020).

Recently, a new CM, called geopolymer cementitious material (GCM), has been developed in the Sustainable Materials and Recycling Technologies (SMART) Laboratory at the University of Arizona to improve the performance of PRSs. The newly developed CM not only showed enhanced higher mechanical properties like peak and residual UCS, but also addressed the durability issues of the currently used CM (Nikvar-Hassani & Zhang, 2022).
Study on the Fracture Propagation Mechanism in Deep CBM Reservoirs
Authors: Wei S. M. , ShenTu J. J. , Jin Y. , Chen S. Y. , Gao B. C. , Peng F.
Published: August 2024

The matrix permeability of deep coalbed methane (CBM) reservoirs is extremely low, but they are abundant in bedding and cleats structures. Hydraulic fracturing is the most effective method for exploiting deep CBM reservoirs. Due to the characteristics of deep coal seam burial and high construction pressure, there is no mature experience to draw from. The bedding and cleats in coal seams are crucial to the initiation and propagation of fractures in deep CBM reservoirs. The existing stimulation conditions of large displacement and large liquid volume make the high fluid loss characteristics of coal rocks more obvious, highlighting the difference in fracture propagation mechanism between deep CBM reservoirs and conventional reservoirs. Addressing the technical challenge of lacking theoretical guidance on fracture propagation mechanism in the current deep CBM reservoirs stimulation, this paper established a dynamic fracture propagation simulation method based on the discrete element method. The fracture propagation mechanism of deep CBM reservoirs was studied by numerical simulation. Through the analysis of the influence of displacement and viscosity, it is found that the initiation of deep CBM reservoirs involves both shear and tensile failure. Under conditions of low displacement and high viscosity, primary fractures are more likely to form along the direction of the maximum horizontal principal stress, while complex fracture networks are easy to form under high displacement and low viscosity conditions. This paper reveals the dynamic mechanism of hydraulic fracture propagation in deep CBM reservoirs, which helps to understand the construction limits of hydraulic fractures in communicating cleats and bedding, and thereby improves the design method of hydraulic fracturing engineering parameter.

1. INTRODUCTION

China has vast reserves of deep CBM resources. If economically viable exploitation and utilization can be achieved, it will greatly promote and propel the development of China's CBM industry into a new phase. As indicated by Figure 1, the production of CBM in China has experienced nearly linear growth from 2009 to 2018 (Li et al., 2020).

Compared with shallow coal seams, deep coal seams have unique reservoir geological characteristics such as high geostress, high temperature, high pressure, low porosity and low permeability. Large-scale volumetric fracturing of horizontal wells is currently an effective measure for industrialized exploitation of deep CBM reservoirs. The shape and scale of the artificial fracture networks will directly determine the production of CBM.
Investigation into the Rock Mass Response to Pillar Extraction in a Hard Rock Tabular Mine
Authors: Moyo S. , Chikande T. , Zvarivadza T. , Masethe R. T. , Adoko A. C. , Onifade M. , Firoozi A. A.
Published: August 2024

Historically, secondary pillar extraction has been successful in the soft rock mining environment. Several hard rock platinum mines have conducted selective remnant extraction with backfill as a regional support measure. A hard rock tabular platinum mine instigated the extraction within a non-yield pillar layout without backfill support. The mine is situated within the Great Dyke of Zimbabwe in a shallow depth environment of approximately 100m. Pillar extraction without backfill in a hard rock mine is a novel mining method. A study was carried out to make a quantitative comparison between the various design parameters and the rock mass response measurements. The primary mining utilised the mechanised room and pillar mining method to extract ore from the wide tabular reef. Similar, low profile mechanised equipment with additional automated systems were adopted for ore extraction and transportation to the surface crusher. The risks associated with the extraction of pillars include large localised falls of ground due to wide spans, pillar run, high severity injuries due to windblasts and large regional collapses through to the surface. The pre-feasibility study for the mine layout design used MAP3D to assess the expected displacement and stress limits post-extraction. MAP3D uses the boundary element method of analysis and has an in-built CAD system for stress analysis and 3-dimensional visualisation of models. A monitoring strategy consisting of displacement, deformation, stress change, ground motion and groundwater level measurements was put in place to record the variations resulting from the pillar extraction. The rock mass response analysis aimed at trending the monitoring results, conducting a comparison to the design parameters and previous pillar collapse trends. Minor stress, strain, and displacement changes have been recorded within a period of one year since the project began with no visible deformation noted on accessible pillars. The current system was identified as including the hazard identification and first-pass monitoring stages. Real-time monitoring systems with a higher sensitivity are required to ensure long-term data retrieval and timeous emergency response.
Rockfall Occurrence and Precipitation Modeling to Simulate Correlation Patterns
Authors: Williams Frances , Walton Gabriel
Published: August 2024

Rockfalls are naturally occurring geohazards that are frequently associated with steep or vertical slopes. Falling rocks have the potential to disrupt transportation systems, including highway and railway passages. A common trigger known to influence the frequency and severity of rockfall events is precipitation. For many rock slopes, rainfall is considered the primary rockfall trigger. In some cases, the relationship between rainfall amount and rockfall frequency presents as a linear correlation when studied using data averaged over an extended period (i.e. due to monitoring data resolution limitations). However, when considered over smaller timescales, the actual underlying relationship is likely to be non-linear, and may involve step changes in behavior at different levels of rainfall (i.e. threshold-based behavior). The aim of this study is to evaluate the ways in which the apparent relationship between precipitation and rockfall depends on the time period over which data are being compared. We achieve this by developing a simulation that includes several components that overall model rockfall outcomes on a day-to-day basis. Daily precipitation totals are simulated according to a lognormal distribution. Lognormal distributions were also used to represent different ranges of rockfall volumes corresponding to different precipitation thresholds. The model can simulate daily rockfall volume distributions using varying probabilities of occurrence to reproduce the differences in characteristics of various hypothetical rock slopes. Overall, the simulation results are used to interpret how the appearance of correlations between variables averaged over longer time scales depends on the nature of the underlying precipitation-rockfall relationships on a day-to-day basis.

1. INTRODUCTION

Rockfalls represent a significant geohazard, particularly for vertical slopes along transportation corridors. Among the various factors influencing rockfall occurrences, liquid precipitation (rainfall) is a primary trigger (Birien and Gauthier, 2023, Pratt et al., 2018). Studies with a larger monitoring interval often reveal an apparent linear correlation between rainfall and rockfall frequency due to data resolution constraints (Banji et al., 2021; Malsam, 2022; Weidner & Walton, 2021); however, examination on a smaller time scale suggests a non-linear relationship characterized by threshold-based behavior (Schneider et al., 2023). This research aims to explore how the emergent linear correlation between precipitation and rockfall events is influenced by the temporal scale of data analysis through the development of a simulation model incorporating daily precipitation values and corresponding rockfall volumes based on designated thresholds. By simulating scenarios across various hypothetical rock slopes, insights can be derived regarding the interplay between precipitation and rockfall occurrences on day-to-day basis and what would be observed over longer time scales.
Application of Machine Learning Algorithms for Minerals Volume Prediction in Unconventional Reservoirs Using Conventional Well Logs
Authors: Bettir N. , Mellal I. , Dehdouh A. , Rabiei M. , Malki M. L. , Allam L.
Published: August 2024

Quantifying mineral volumes is crucial for accurate characterization of complex and unconventional reservoirs. Multimineral analysis is a technique used to estimate the fractions of minerals and fluids present in a reservoir based on measurements obtained from well logs. This approach assumes that the log response at each depth can be represented as a linear combination of the individual responses of different logging tools to each constituent, with each component weighted by its relative volume fraction. Achieving accurate mineral quantification necessitates having the number of well logs equal to or greater than the number of minerals in the reservoir. However, in complex reservoirs, there are situations where the number of well logs falls short of the number of minerals, resulting in an underdetermined system of linear equations. In such cases, accurate mineral quantification becomes challenging. To address this challenge, we propose the application of machine learning algorithms to predict mineral volumes using quad combo logs, which include gamma ray, deep resistivity, bulk density, and neutron porosity measurements. Four machine learning algorithms — Artificial Neural Networks (ANN), Random Forest (RF), Adaptive Boosting (AdaBoost), and Support Vector Regressor (SVR) — were utilized to generate predictions for mineral volumes. The performance of each machine learning model was assessed using regression statistical measures. RF delivered the best performance with a correlation coefficient of 0.76. Other algorithms yielded correlation coefficients between 0.11 and 0.54 with the SVR having the lowest value. The results show that this approach offers a promising solution for accurate mineral volume estimation in cases where the number of well logs is insufficient compared to the number of minerals in the reservoir.

1. INTRODUCTION

Petrophysical multimineral analysis is indispensable for the effective development of petroleum resources and accurate reservoir characterization. A detailed analysis entails accurate identification of the mineralogical composition as any misinterpretation in mineralogy can significantly impact various processes, spanning from geophysical interpretation to reservoir assessment (Cinintia Finahsan et al., 2014; Klenner et al., 2016).
Búzios Field: Coupled Model to Face the Geomechanical Challenges of the Giant Carbonate Offshore Field
Authors: Falcão F. O. L. , Cordovil A. G. , Maria A. L. M. , Orrico G. , Fidalgo B. , Parcero M. , Alves A. , Fernandes L. F.
Published: August 2024

The Búzios Field, located in the Santos Basin, is a vast offshore pre-salt reservoir with significant oil production potential. Spanning an area of 852 km2 at a water depth of 2000 meters, it lies beneath a 2000 m layer of salt and a 1000 m interval of post-salt sediments. Commerciality was declared in 2013, following its discovery in 2010. To understand the geomechanical effects due to reservoir production, factors such as fault behavior, compaction, subsidence, deformations, and compressibility were considered. A one-way coupling procedure using the GeomecBR, Petrobras' in-house software, assessed the geomechanical response. The developed geomechanical model covered an area of 145 km × 145 km and a vertical length of approximately 10 km, comprising over 50 million elements. It integrated various data and disciplines, involving a multidisciplinary team to calibrate the model and enhance the reliability of future forecasts. This paper outlines the methodology used to construct the geomechanical model for the Búzios Field and highlights its key findings. Understanding the geomechanical behavior improves the safety and efficiency of production operations and contributes to the broader understanding of pre-salt reservoirs in the Santos Basin.

1. INTRODUCTION

Búzios Field, located in the Santos Basin approximately 180 km off the coast of Rio de Janeiro, is a giant pre-salt carbonate reservoir. It covers an area of 852 km2 and has an average net pay of 400 m. Situated at a water depth of 2000 meters, the field is below 2000 m of salt and 1000 m of post-salt sediments. Discovered in 2010, it was declared commercially viable in 2013 after seismic acquisition and testing. With excellent oil production potential and strong reservoir communication, Búzios Field has proven to be a significant asset for Petrobras (Rosa, 2022).

The field is divided into 12 moduli, each produced by a Floating Production Storage and Offloading unit (FPSO). Five FPSOs have already been installed, each with a processing capacity of 150 kbpd. Notably, four of these FPSOs were deployed in less than two years, enabling it to reach the record of 600 kbpd of production in this period. By 2028, when the field will be fully developed with over 170 wells, the total processing capacity is expected to exceed 2 million boed (barrels of equivalent oil per day).
Review of Remedial Cementing: Factors, Design Considerations, and Case Studies
Authors: Youssef Amir Shokry , Mahmoud Ahmed Abdulhamid , Elkatatny Salaheldin
Published: August 2024

Remedial cementing operations in the oil and gas industry are indispensable for ensuring well integrity and mitigating environmental risks. This paper delves into the multifaceted factors that influence the effectiveness of remedial cementing processes, with a dual focus on achieving longevity and minimizing negative environmental impacts while safeguarding groundwater. Through an in-depth examination of various case studies, it offers comprehensive insights into the operational intricacies involved in different remedial applications. The analysis underscores the pivotal role of meticulous planning, precise execution, and the utilization of advanced technologies in achieving successful cementing remediation projects. Moreover, it explores in detail the diverse factors that influence remedial cementing design, including problem identification, cement preparation methodologies, injectivity testing, and cost-benefit analysis. By presenting successful case histories, the paper vividly illustrates how remedial cementing contributes to enhancing well integrity and optimizing production, thereby highlighting the ongoing innovation and refinement in response to the evolving challenges of wellbore construction.

1. INTRODUCTION

Cement serves as a crucial barrier in well construction, primarily aimed at establishing a secure bond around the casing string. Its fundamental role is to furnish the casing with essential mechanical support and to thwart any fluid migration by effectively sealing off potential pathways, including microannuli and fractures, which could undermine well integrity (Chen et al., 2022; Gu et al., 2023). Beyond ensuring mechanical stability, proficient cementing also plays a pivotal role in sealing operations. The capability of cement to seal is paramount in safeguarding groundwater and mitigating environmental risks (Abdelaal & Elkatatny, 2023).

The durability of cement stands as a critical measure, ensuring its resilience against both environmental factors and downhole conditions throughout an extended duration (Bybee, 2015). Additionally, it is imperative to verify the reliability and effectiveness of cement in safeguarding wells, thus contributing to the sustained success of oil and gas operations in the long run (Elhassan et al., 2023).
Drilling Data Based Approach for Real-Time Gamma Ray Prediction in Surface Holes Using Artificial Intelligence
Authors: Youssef Amir Shokry , Elkatatny Salaheldin , Abdulraheem Abdulazeez
Published: August 2024

Gamma-ray (GR) logging involves the measurement of natural formations' radioactivity, serving as a valuable tool for distinguishing various lithologies and correlating zones. A prevalent approach is to record GR data up to the surface through the casing while pulling out of the hole (POOH) using reservoir section logging tools. Although GR measurements are very helpful, they are seldom recorded in the top section. This study utilizes artificial intelligence (AI) techniques—specifically artificial neural network (ANN) and adaptive neurofuzzy inference system (ANFIS)—to predict real-time surface hole GR by leveraging drilling parameters and mud weight data. Training on datasets from six wells with a total of 2,100 data set yielded accurate predictions, with the ANN model slightly surpassing ANFIS in performance. The models were and assessed for accuracy using metrics such as root mean square error (RMSE), average absolute percentage error (AAPE), and correlation coefficient (R). These models offer substantial benefits by providing real-time GR data for analysis, thereby eliminating the necessity for post-drilling recordings. This advancement not only saves time and costs associated with logging but also enhances the efficiency of data-driven decision-making during drilling operations.

1. INTRODUCTION

Gamma-ray (GR) logs stand as pivotal tools in formation evaluation within the petroleum industry, offering direct insights into geological formations. Equipped with detectors that measure the total gamma ray intensity, GR logging tools serve various purposes, notably in distinguishing between shale and non-shale formations. This distinction arises from the distinctive response exhibited by shale formations, correlating closely with the shale content within the formation. Consequently, formations rich in radioactive materials like carbonates and sandstone tend to yield lower GR values, whereas increased shale content results in higher GR values (A. A. A. Mahmoud et al., 2017; K. A. Mahmoud et al., 2019; Wang et al., 2018). Beyond lithology identification and zone correlation, GR logs find utility in shale volume calculations within reservoir rocks, facilitating the precise classification of productive and non-productive zones based on predetermined shale volume thresholds (Ibrahim & Elkatatny, 2022). While GR logs serve as valuable inputs for modeling lithological effects, it's notable that they are not typically recorded during surface hole drilling. Instead, the conventional approach involves recording GR data up to the surface through casing during the pull-out-of-hole (POOH) process using reservoir section logging tools. This underscores the necessity for a real-time model capable of lithology identification by predicting GR logs from surface drilling parameters in addition to the mud parameters.
Numerical Approach to Evaluate Cements Sheath Barrier During Reservoir Compactation in Vertical Oil Wells
Authors: Velilla J. D. U. , Fontoura S. A. B. , Melo D. D. E. F. , Braga J. J. V. , Dias R. , Okama C. S.
Published: August 2024

Reservoir depletion during hydrocarbon production can lead to rock compaction. This compaction is caused by the progressive decrease in pore pressure within the porous matrix. This paper presents an axisymmetric numerical approach to evaluate the integrity of the cement and casings inside the well due to the effect of compaction. A displacement field is used as a model boundary condition and gradually applied during the production stage after the well construction. The construction of the well is considered from the geostatic equilibrium of the materials, followed by the drilling and cementing. Finally, the subsidence stage is created where the applied displacement field displaces the rock column and consequently the cement and casing. The von Mises stress curve for the casing, and the plastification index of the cement and casing were examined. It was observed that areas with the greatest von Mises stresses were proportional to areas with the greatest displacements of the rock column. A significant impact of the top of cementation (TOC) on integrity was observed. The cement acts as a transmitter of displacements to the casing, which can impact the integrity of both the cement and casing in the preceding phases before the production phase.

1. INTRODUCTION

Reservoir depletion during hydrocarbon production can lead to reservoir compaction. The compactation is a densification associated with the rearrangement of the rock matrix when fluids are lost in the porous medium. Such densification affects upper layers, causing deformations that can be observed even on the seabed. These deformations can cause structural problems in oil wells, such as fractures in upper layers, loss of cement integrity, and excessive traction or compression over the casing (Figure 1).

The main goal of this work is to develop a numerical axisymmetric methodology for analyzing the mechanical integrity of casing subjected to subsidence loads. For that purpose, the finite element method will be used. This method allows consideration of several simultaneous effects such, rock-cement-casing contact interactions, different materials within the model, advanced constitutive models, among others.
Real-Time Rate of Penetration Prediction for Motorized Bottom Hole Assembly Using Artificial Intelligence
Authors: Youssef Amir Shokry , Elkatatny Salaheldin , Abdulraheem Abdulazeez , Rahmatullah Idham
Published: August 2024

Efficient drilling operations hinge on accurately obtaining the rate of penetration (ROP), a crucial parameter influencing well delivery costs and overall project timelines. While existing predictive models predominantly cater to rotary and rotary steerable system bottom hole assemblies (BHAs), motorized BHAs have received comparatively less attention. Addressing this gap, our study introduces a pioneering artificial intelligence (AI) model powered by artificial neural networks (ANN) to forecast ROP for motorized BHAs. By integrating surface drilling parameters, mud characteristics, and motor output features, the model undergoes rigorous training, validation, and testing on a comprehensive dataset sourced from six wells in the Middle East, encompassing over 5,800 data points. Robust evaluation metrics, including Root mean square error (RMSE) and correlation coefficient (R), affirm the model's exceptional accuracy (R of 0.97) in predicting ROP. Beyond its predictive capabilities, the ANN-based model provides valuable insights into the impact of diverse drilling parameters on motorized BHA performance, enabling operators to optimize ROP, minimize drilling costs, and enhance overall operational efficiency in the field.

1. INTRODUCTION

Drilling optimization remains a key focus in the quest to boost overall drilling efficiency while minimizing operational time and costs. Among the pivotal tools in this endeavor are downhole mud motors, integral components of the BHA (Koulidis et al., 2023). These motors play crucial roles in both directional and vertical drilling, operating by converting the mud circulation energy from drilling fluid to generate the required revolution and associated torque (El-sayed et al., 2020). Positive displacement motors (PDM) are particularly favored for their operational simplicity, with drilling torque indicated by the differential pressure they create, and motor revolution primarily determined by flow rate (Tschirky, 1978). Extensive case studies worldwide have underscored the efficacy of downhole motor BHAs in enhancing drilling performance, leading to improved ROP, reduced nonproductive time (NPT), shortened drilling cycles, and substantial cost savings (Chen et al., 2018; Feng et al., 2014; Wu et al., 2013; Yin et al., 2014).
Role of Landing Point Selection and Completion Optimization in Stacking and Staggering Decisions – A Multi Domain Integration from Geology to Engineering
Authors: Narasimhan Santhosh , Van Delinder Steve W. , Hewett Tom A. , Arcano Nelson Suarez , Olaoye Olubiyi , Mainali Pukar
Published: August 2024

Unlocking the true potential of unconventional reservoirs requires the integration of multi domain data sets ranging from geology to engineering. Since Niobrara is one of the most heterogenous reservoirs, both vertically and laterally, it requires integrating petrophysics and geomechanics with completion frac modeling to define a proper landing candidate and completion design. This paper discusses the factor(s) that are most important in justifying the good production performances such as landing point interval, thickness, rock type (geology), geomechanics (stress and strength) and completion design. Though many times the answer is the combination of all these factors contributes to the production performance, it becomes essential to prioritize these factors to successfully extract not only the short-term but also the long-term production without compromising the wellbore integrity. This paper discusses the selection of multiple landing points between Niobrara B Marl, Niobrara C Marl and Turner formations initially using the slick water design. Subsequently, Niobrara C Marl zones are tested using the gel design to evaluate changes and improvements in the conductive fracs compared to slick water design without stress shadow in consideration. Since the cost of gel design is significantly higher than the slick water design, improved production needs to be justified. High poro-perm zones such as the Turner are always completed using the gel design. Taking stress-shadow into consideration, NIO C Marl was fracced immediately after fraccing the Turner with minimal bleed off in the pressure. NIO C Marl in-situ (before depletion) conductivity was compared between slick water and gel designs using with and without stress shadow approaches. Overall, this paper will discuss and capture the factors causing NIO C Marl performance using different completion designs and the changes in the conductivity during stress shadowing. This approach brings in depth knowledge for stacking and staggering operational needs.

1. PETROPHYSICS

For a successful source-rock resource assessment, we need to have proper and accurate well logging measurements but also it is necessary to integrate the petrophysical logs with geochemical, petrological and geomechanical parameters. Other geological, reservoir, and fluid analyses are equally important when assessing unconventional resource potential as has been demonstrated in previous studies. This paper applied a phased approach, which is the known most effective method for evaluating a potential hydrocarbon resource, with clearly defined criteria that must be fulfilled prior to further capital expenditures.
Induced Seismicity in Geothermal Settings: Historical Perspective, Enhanced Geothermal Systems, Setbacks, and Future Directions
Authors: Kaven J. Ole
Published: August 2024

Geothermal energy exploration and production has a long history of inducing seismicity, both beneficial and disastrous. Seismicity is common in naturally occurring geothermal systems as they often are co-located in areas with high strain rates, low permeability but fractured rocks, and a shallow brittle-ductile transition. These conditions generally limit the maximum magnitudes of earthquakes, whether tectonic or induced. Furthermore, seismicity often aids in the identification of prominent fluid and heat pathways within the geothermal resource. Engineered or Enhanced Geothermal systems (EGS) need not be located in geologic settings akin to conventional geothermal resources and, thus, may have unknown fault and fracture locations and extents owing to lower tectonic seismicity prior to exploration and thicker crust increasing the likelihood of larger magnitude seismicity. Several EGS projects have experienced earthquakes during the exploration portion of the projects that caused significant damage, e.g. Basel, Switzerland (2006) and Pohang, South Korea (2017). Other more recent EGS projects have experienced little seismicity of concern for the safe operation of reservoir development, e.g. Milford, Utah (2022) and Blue Mountain, Nevada (2022). Both sites benefited from experience gained in previous EGS projects, extensive site characterization, and adherence to Best Practices developed in response to earlier unsuccessful projects. In all cases, probabilistic seismic hazard analyses (PSHA) are crucial steps during planning and stimulation. These generally include a variety of models that can range from simple relationships between expected seismicity and injected volume to detailed geomechanical models of resulting seismicity. Aseismic deformation is seldomly accounted for, although recent research suggests it plays a significant role in the deformation in geothermal resources. Here I will discuss the inclusion of deterministic reservoir models in standard PSHA models and focus on the effects of aseismic deformation in geothermal and EGS settings. Continual improvement in PSHA and reservoir exploration and stimulation that are part of EGS development can ensure that the vast potential of EGS can be unlocked safely.
Calibration of 2D Finite Element Method Rockbolt Models to Fiber-Optic Axial Load Testing Data for Grouted Rebar Rockbolts
Authors: Fischer C. P. , Diederichs M. S. , Forbes B.
Published: August 2024

In modern numerical modelling software, several rockbolt models are available to practitioners for the design of tendon rock support in underground excavations. In this research, two applicable rockbolt models for the modelling of grouted rebar rockbolts are implemented in the 2D Finite Element Method (FEM) modelling program RS2, and compared to the behaviour of fiber-optic instrumented grouted rebar rockbolts in axial pull testing by Forbes (2020). Rockbolt models are assigned strength and stiffness properties based on manufacturer specifications and parameters found in the literature, and model results are compared to Forbes (2020) testing data to assess the fidelity of the rockbolt load development and deformation response. Subsequent model calibration and sensitivity studies are performed, demonstrating considerations for the selection of an appropriate bolt model and bond interface parameters for the design of rebar rockbolts, where pre-yield rockbolt behaviour is of focus.

1. INTRODUCTION

Grouted rebar rockbolts are widely used in civil and mining engineering to control rockmass displacements and improve excavation stability (Kaiser et al. 1996, Hoek 2007). Grouted rebar support is coupled to the rockmass using a cementitious or resin grout material, and generates shear resistance to movement primarily through mechanical interlock between the bolt and the grout, and the grout and the rock. Grouted rebar rockbolts are classified as continuously mechanically coupled support (Windsor 1997).

The numerical simulation of tendon rock support for excavation design can be achieved using material models or structural elements. Structural elements are practical for large-scale problems, as material models require finer mesh that is less computationally feasible for most larger-scale excavation design problems. A multitude of structural elements have been developed across industry numerical modelling programs (e.g. Jalalifar and Aziz 2012, Swoboda and Marence 1991, Marence and Swoboda 1995), incorporating different combinations of parameters to address material and interface strengths and stiffnesses. To properly represent the functioning mechanisms of a rockbolt in a numerical model, an appropriate rockbolt model and appropriate input parameters for the bolt materials and interfaces must be selected. Such parameters control how load is transferred between the rockmass and the modelled support element.
Investigating Mechanical and Acoustic Properties of 3D Printed Materials: A Focus on Printing Orientation
Authors: Ifrene Ghoulem , Pothana Prasad , Egenhoff Sven , Nagel Neal , Hickey James
Published: August 2024

Stereolithography (SLA) 3D printing technology is increasingly applied in geomechanics, petroleum engineering, geothermal, and CO2 storage research, particularly in fracture flow and mechanics. To understand the mechanical characteristics of 3D printed materials, we conducted laboratory experiments examining the effect of printing orientation on the properties of three specimens. These specimens were printed using a FormLabs (3B+) 3D printer at layering angles of 0°, 45°, and 90°, with a resolution of 100μm, and sized 1-inch in diameter and 2-inches in length. We performed triaxial compressive tests, ultrasonic elastic wave velocity measurements, and unconfined compressive strength (UCS) tests using an Autolab 1500 test frame. Incremental confining pressures from 1 MPa to 20 MPa were applied to explore static and dynamic mechanical properties. The UCS tests showed that all samples exhibited ductile behavior with similar stiffness and yield strength across different layering angles, demonstrating a stiffness of approximately 4 GPa and compressional wave velocities between 2555-2580 m/s at zero confining pressure. The findings confirm the mechanical and acoustic consistency of the samples, supporting their suitability for advanced geomechanical applications.

1. INTRODUCTION

Three-dimensional (3D) printing technology, also known as advanced manufacturing (AM), is a rapidly developing field that has revolutionized manufacturing processes across various industries including aerospace (Richter & Lipson, 2011), automotive (Rahim & Maidin, 2014), healthcare (Logan & Duddy, 1998), petroleum engineering (Li et al., 2021), and geomechanics (Phillips et al., 2021). This technology uses computer-aided design (CAD) to create three-dimensional objects by adding material layer by layer using almost any type of material such as polymers, and ceramics. Thermoplastic urethane and metals can also be employed as raw material (Gopinathan & Noh, 2018).

There are several techniques involved in 3D printing, including Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), Digital Light Processing (DLP), Binder Jetting, and Material Jetting. Each technique has its advantages and disadvantages (Jandyal et al., 2022), and the choice of technique depends on the type of object being printed, the desired resolution, and the available materials. With the increasing popularity and availability of 3D printing technology, it is now relatively easy to create custom objects, prototypes, and even entire structures using 3D printing. Among the available techniques, SLA is known for producing high-resolution objects with smooth surfaces. SLA was first developed in the early 1980s by Kodama, 1981 and called Rapid Prototyping (RP).
Assessment of Geomechanical Properties of Fault Damage Zones Based on Numerical Modeling
Authors: Dias F. C. , Quevedo R. , Roehl D. , Carvalho B.
Published: August 2024

Fault zones are generally made of highly deformed rocks composed of a core surrounded by a damage zone. The core is usually formed of an impermeable consolidated material responsible for reservoir compartmentalization. However, the complex architecture of damage zones induces a substantial variability of their properties that can significantly influence fluid flow and geomechanical behavior of oil and gas fields. Therefore, characterizing damage zone properties is relevant during reservoir development, production, and management. Many studies have been carried out to characterize and estimate the structural and hydraulic properties of fault damage zones. Still, relatively few of these studies have aimed at assessing their elastic, strength, and compaction properties. The reason for that is the difficulty in sampling fault damage zones for laboratory testing owing to intense fracturing and poor consolidation. In addition, the sampling protocols face the classical question of the scale effect on the properties of fault rocks. This study uses a numerical methodology to estimate rock properties of fault damage zones through geomechanical modeling based on the finite element method combined with elastoplastic models and softening/hardening laws. The obtained properties can be adopted in further simulations to represent fault damage zones better.

1. INTRODUCTION

Most geologists recognize that faults include subsidiary structures in a region that covers both brittle discontinuities and ductile shear plastic deformation zones (Fossen, 2016). This region, known as the fault zone, consists of two structural domains: the fault core, defined by a central slip surface, and the surrounding volume, named the damage zone. In general, the fault core is a low-permeability zone with a width in the order of millimeters. On the other hand, depending on host rock lithology and fault displacements, damage zone widths can reach dimensions in the order of kilometers. Most damage zones in subsurface faults are characterized by a set of deformation bands and fracture networks, triggering a region with properties significantly different from the undeformed host rock or protolith (Caine et al., 1996; Paul et al., 2007; Hennings et al., 2012; Choi et al., 2016).

For example, permeabilities in the damage zone can be several orders of magnitude higher than those in the protolith during fracturing, while Young's modulus values are usually lower (Cappa, 2009). Some authors have reported that permeability and Young's modulus of fault damage zones can vary in ranges from 1 · 10-14 to 10-16 m2 and 10 to 50 GPa, respectively (Faulkner & Rutter, 2001; Zhang et al., 2008; Cappa & Rutqvist, 2011; Qu & Tveranger, 2016; Treffeisen & Henk, 2020). In addition, frictional properties can be quite different between the host rock and the fault damage zone, with values reduced by up to 65% in the latter (Di Toro et al., 2011).
Laser-Induced Rock Breakage (LIRB) Technology in Mining Engineering - A Review
Authors: Madavi R. P. , Mitra R. , Diwakar P.
Published: August 2024

Mining operations have long relied on conventional methods of rock fragmentation, such as drilling and blasting, for resource extraction. However, as the mining industry faces increasing demands for efficiency, safety, and sustainability, innovative technologies like laser-induced rock breakage (LIRB) have emerged as promising alternatives. LIRB, a cutting-edge technique, employs high-energy lasers to fracture rocks without physical contact, avoiding the use of explosives. This paper provides a comprehensive review, begins by delving into the fundamental principles of LIRB, discussing the various types of lasers used, and highlights the merits of LIRB in terms of safety and environmental impact. Despite the promising advantages of LIRB, this review also addresses the challenges and limitations that researchers and engineers face. These challenges encompass heat management, limited penetration depth, complexity of laser systems, and the development of cost-effective and scalable LIRB systems. Additionally, the need for a thorough understanding of rock properties and behavior is emphasized, as it is critical for achieving successful LIRB outcomes.

1. INTRODUCTION

The first working laser was built by Theodore H. Maiman in 1960 at Hughes Research Laboratories (Bromberg, 1988). Maiman's laser used a synthetic ruby crystal to produce red laser light. This invention marked the beginning of the era of lasers and their widespread applications in various fields. One of these fields was rock breakage and the first experiment in this field was performed in 1969 by United Aircraft Research Laboratories under the Department of Transportation. In this study, the weakening of hard rock by low-power-density laser was considered feasible but not economically viable for tunnel boring machines (TBMs) (Farra, 1969). However, using a high-power-density laser, the laser beam can penetrate the rock which allows the removal of a greater amount of rock (Carstens & Brown, 1971). Various studies by researchers showed that laser-assisted rock cutting has great potential in rock excavation fields (Carstens & Brown, 1971; Jurewicz, 1976; Rui and Zhao, 2021). Apart from traditional drilling and blasting, various other technologies such as thermal rock fracturing (Geller, 1970), high-pressure water jet (Vijay et al., 1993), microwave (Okada et al., 1975), electrical (Andres, 1995), and Soundless Chemical Demolition Agents (SCDAs) (Habib et al., 2022) have been developed for improving rock breakage process.
Estimation of Tunnel Project Completion Time by Combining the CSM2020 Discrete Event Simulation Model with Decision Aid in Tunneling (DAT)
Authors: Khetwal A. , Rostami J. , Einstein H.
Published: August 2024

The decision-making process regarding the uncertainty in the project plan, alignment alternatives, and other project aspects can be accounted for using the Decision Aids in Tunneling (DAT) tool. One of the important input parameters in the DAT is the advance rate, and its accurate estimation can significantly improve the accuracy of the DAT. The advance rate comprises the estimation of the rate of penetration and machine utilization. A few models have been proposed to estimate utilization with different levels of accuracy. The CSM2020, which is a discrete event simulation-based model, has proven to offer a promising estimation of TBM utilization as it incorporates uncertainties in various tunneling activities. The model more reliably allows for the determination of the delays during the tunneling and hence more reliable machine utilization for a given machine type, geological settings, and operational conditions. In the present study, project data were analyzed, and utilization values were estimated using the CSM2020 model and used as input in the DAT to estimate overall anticipated machine performance in a given project. The results include the average completion time that was compared with the actual site data. The accuracy in the completion time shows that a combination of CSM2020 and DAT can be considered to be an effective approach to consider the uncertainties in the various tunnel operations, thereby offering a more accurate and reasonable estimation of completion time for mechanized tunnels.

1. INTRODUCTION AND BACKGROUND

The modern world has given society marvelous underground structures and the comfort of traveling through railways, metros, and road tunnels. These underground spaces provide infrastructure that is difficult or impossible to construct above ground or whose presence above ground is unacceptable, undesirable or simply not feasible. They have the fundamental characteristics of protecting against almost all-natural threats (Goel et al., 2012). With the increasing world population, there is a necessity for sustainable development that does not compromise the future generations' correlations while meeting the present needs, and tunnels are considered a significant contributor to this. They have proven to be an efficient infrastructure in conveying freshwater, disposing of waste products, as a safe and fast conveyance route, functional during extreme weather conditions, and for bulk storage of liquids and gas.
An Assessment of Hydraulic Fracture and Geomechanical Properties on the Compaction and the Productivity of Marcellus Shale Horizontal Wells
Authors: El Sgher Mohamed , Aminian Kashy , Ameri Samuel
Published: August 2024

Declining pore pressure, with reservoir depletion, increases the net stress leading to compaction of the Marcellus shale damaging the formation and hydraulic fracture properties. To accurately predict gas production as net stress increases, geomechanical and fluid flow simulations are required. By analyzing data from Marcellus Shale Energy and Environment Laboratory sites, researchers were able to investigate the impact of shale compaction on gas production. The study was focused on how shale mechanical and fracture properties, as well as operating conditions, influence the productivity of horizontal Marcellus Shale wells with multi-stage fractures. Simulated model results showed that including the compaction in the model resulted in more accurate prediction of production from horizontal wells with multiple hydraulic fracture stages in the Marcellus shale. Young's modulus was observed to have a greater impact on the geomechanical factors and the production performance than for Poisson's ratio. Furthermore, Due to the high gas production rate during early production, compaction has a more dramatic impact which diminishes as production continues.

1. INTRODUCTION

The Marcellus Shale is the largest shale play in the United States, covering a vast geological area of 95,000 square miles. This shale formation, known for holding the largest natural gas deposits in the U.S., is predominantly found in the Permian Basin. The Marcellus Shale, situated in the Appalachian Basin, stands out as the most prominent natural gas-producing play in the country and spans across six states: New York, Pennsylvania, Ohio, West Virginia, Maryland, and Virginia. Characterized as an abundant fine-grained sedimentary rock formed through the compaction of silt and clay-size mineral particles, the Marcellus Shale exhibits the ability to fold into thin layers. Being over 400 million years old, this formation ranks among the largest nationwide and is a top producer of natural gas in the U.S. With the implementation of modern exploration techniques like hydraulic fracturing and horizontal drilling, the Marcellus Shale is estimated to hold around 400 trillion cubic feet of gas, attracting significant attention from the oil and gas industry in the U.S.