This study presents a comprehensive analysis of field data obtained from a substantial hydraulic fracturing campaign in a hard rock mining operation, aiming to enhance prediction, understanding and optimise operational practices through parametric analysis and Machine Learning. Findings reveal that structural control predominates during the initiation stage, limiting the influence of operational parameters, while strong positive correlations emerge between operational variables and achieved pressures as fracturing progresses. Post-fracture shut-in pressure exhibits a moderate positive correlation across all categories, emphasising the importance of considering rock competency in project scheduling and resource allocation. However, seismic event prediction remains challenging, with operational influences showing slight correlations, suggesting the need for further research into understanding and predicting seismic risks. Recommendations for the industry include implementing real-time monitoring systems, incorporating geomechanical considerations into project planning, and investing in research initiatives focused on mining seismicity. Future research should focus on investigating the long-term effects of hydraulic fracturing, exploring advanced modelling techniques, and conducting interdisciplinary studies to optimise practices. This study provides valuable insights for enhancing operational efficiency and risk management in hydraulic fracturing operations.

Non-destructive techniques (NDTs) for stress measurement rely on rock stress memory, which necessitates precise strain and acoustic emission (AE) measurements during uniaxial cyclic loading of rock specimens. This study examined the Kaiser effect under indirect tensile loading, investigated the influence of principal axis rotation, and assessed the potential of full-field strain measurements for accurately determining applied stresses. The tests were performed on Brazilian disc specimens of Adelaide Black Granite and Hawkesbury sandstone, and the deformation was monitored using 2D digital image correlation (DIC) and an AE monitoring system. The effect of rotation of the principal axis was established by rotating the specimens in 15° increments from 0° to 90°. Although the results indicate that the rotation of the principal axis affects the Felicity Ratio (FR) in the first cycle AE analysis, the Kaiser effect can be precisely measured from the second cycle AE analysis. Moreover, the results demonstrate that the preloads can be precisely measured using the Secant Modulus Method (SMM), however, inflection points in the characteristic SMM curves are influenced by the distribution in the specimens. Precise and well-pronounced inflection points are observed from strain measurement in the localisation band even after the rotation of the principal loading axis.

Hydraulic fracture stimulation is one of the most effective methods to recover oil and gas from unconventional resources. In recent years, foam-based fracturing fluids have been increasingly studied to address the limitations of conventional slickwater such as high water and chemical consumption, environmental concerns, and high incompatibility with water-sensitive formations. Due to the gradual breakdown of liquid foams at reservoir conditions, the combination of silica nanoparticles (SNP) and surfactants has attracted a lot of attention to improve liquid foams’ characteristics, including their stability, rheology, and proppant-carrying capacity. This paper investigates and compares the effects of cationic and anionic surfactants on the fracturing performance of SNP-stabilized foams at the reservoir temperature of 90 °C. The experimental results of viscosity measurements were imported into a 3D fracture-propagation model to evaluate the effectiveness of fracturing foams in transporting and distributing proppants in the fracture system. At both ambient and elevated temperatures, cationic surfactant was experimentally found to have better synergistic effects with SNP than anionic surfactant in improving the apparent viscosity and proppant-carrying capacity of foams. The simulation results demonstrate that fracturing with cationic surfactant-SNP foam delivers greater performance with larger propped area by 4%, higher fracture conductivity by 9%, and higher cumulative gas production by 13%, compared to the anionic surfactant-SNP foam. This research work not only helps validate the interrelationship between fluid viscosity, proppant settlement rate, and fracture effectiveness, but it also emphasizes the importance of proppant placement in enhancing fracture conductivity and well productivity.

Abstract:Strip mining is typically preferred for near-surface, tabular deposits such as phosphate. Khouribga, home to Morocco’s largest phosphate deposit, contributs significantly to the nation’s phosphate output. However, a slight dip in the phosphate deposit suggests that strip mining may become less viable in the future. To sustain phosphate production efficiently, transitioning from surface to underground mining through highwall mining could be an effective solution. This method, involving the recovery of phosphate using continuous miners, necessitates stable roof conditions.To evaluate roof stability in highwall mining, both with and without web pillars, we will employ a three-dimensional finite difference method. Firstly, field rock mass properties, including joint frequency, persistency, infills and orientations and mechanical parameters, will be determined for inclusion in the numerical model. The generalized Hoek-Brown failure model, in conjunction with the Geological Strength Index (GSI), will be utilized to analyze rock mass behavior. For intact rock behavior, triaxial tests will be conducted to acquire Hoek-Brown failure parameters. These parameters will inform the construction of realistic 3D models using FLAC3D software, enabling the simulation of various underground working scenarios to identify the optimal mine layout that ensures high production rates and minimizes roof stability issues.An economic analysis will also be conducted to assess the feasibility of this method. This analysis will help in optimizing the dimensions of highwall mining parameters and selecting the best scenario through the Mineable Shape Optimizer (MSO). This planning tool will additionally aid in forecasting the recovery and dilution rates associated with the highwall mining method.Keywords:Highwall mining, Phosphate, Khouribga, Roof stability, GSI, Rock mass classification, HoekBrown failure model, Economic analysis, MSO

The Moroccan High Atlas is a key region for understanding the complexities of tectonic interactions within intracontinental settings. However, the spatial distribution of stress fields and strain partitioning between the basement and cover during the basin inversion remain poorly understood, posing challenges for unraveling the geodynamic evolution of the region and assessing geohazards. This study employs joint paleostress inversion of mesostructures to analyze the spatiotemporal variation of tectonic stresses during the inversion of the High Atlas basin. An initial phase of layer‐parallel shortening occurred between the Eocene and Middle Miocene, characterized by NNE–SSW compression. A subsequent phase of layer‐parallel shortening, with NW–SE compression initiated the main Mio‐Pliocene shortening of the range. Both phases are marked by a prominent strike‐slip tectonic regime. The shift from NNE–SSW to NW–SE compression likely reflects changes in plate kinematics during the Late Cenozoic. A post‐folding NW–SE compression phase, dominated by thrust faulting, occurred during fold tightening in the Late Pliocene‐Quaternary. West of the range, reactivation of basement fault altered the remote stress field, resulting in both clockwise and anticlockwise rotation of σ H , and inducing a pronounced strike‐slip and oblique‐slip regime. Inversion of focal mechanisms data reveals a NW–SE‐striking σ 1 driven by the continuous oblique convergence of Africa and Europe. The consistency of the NW–SE compression determined from the paleo and present‐day stresses suggests uniformity in stress fields from the Neogene to the present. The spatiotemporal evolution of tectonic stresses in the High Atlas is primarily controlled by plate kinematics, while basement fault reactivation induces second and third‐order stresses. In the western segment, stress field modification is facilitated by the obliquity of faults to the remote stress and the presence of hot mantle beneath the range, which promotes friction reduction and reactivation of steeply dipping faults.

The Atlas fold and thrust belt extend from the Atlantic rifted margin of Morocco to Tunisia over a distance of 2500km. Before its inversion in the Cenozoic to the present, the Atlas system evolved initially as a rift basin that opened simultaneously with the Atlantic rift in the west and the Tethys in the north, during the upper Triassic-Jurassic period. The Western High Atlas is believed to be influenced by the Atlantic Ocean (also known as the Atlantic domain), where the Triassic to Early Jurassic strata are considered to be syn-rift, while the Middle Jurassic to Cretaceous deposits are labelled as post-rift. In contrast, the Marrakech High Atlas (MHA), Central High Atlas (CHA), Middle Atlas (MA), and the Eastern High Atlas (EHA) are assumed to be influenced by the Tethys Ocean (also known as Tethyan domain), where the Triassic to Jurassic sediments are considered to be syn-rift. This implies that the Mesozoic rifting along the Atlas was diachronous, making it difficult to determine the exact timing and kinematic of crustal stretching. Constraining the extensional phases in the Atlas system is crucial for understanding how the Atlas crust was stretched and thinned. Our work aims to quantify the magnitude and regional kinematic of stretching in the Atlas system using various methods, namely, thickness variation method, subsidence analysis and palinspatic reconstruction of 2D cross-sections. Our preliminary results indicate that the maximum stretching factor (beta factor) in the Atlas is β = 1.25; and that crustal thinning did not exceed 20%, based on tectonic subsidence analysis. While the palinspatic restoration suggest that the Moroccan Atlas system underwent approximately a uniform stretching with β = 1.11 in EHA (Midelt-Errachidia area), β = 1.08 in CHA (Imilchil area), and β = 1.12 in the East Marrakech High Atlas (EMHA: Demnat area). These values indicate that the Moroccan Atlas crustal thickness has been thinned by 9% in EHA, 8% in CHA, and 11% in EMHA. In addition, the geological context of the High and Middle Atlas regions, where the estimated shortening is reported to be less than 20%, the stretching factor (β) was calculated based on the crust thickness. The initial crustal thickness (IC) of the Meseta block, which constitutes one of the Atlasic rift shoulders, considered an undeformed area, served as a reference. Accounting for the observed shortening, the final crustal thickness was deduced by subtracting the reported shortening value representing 7.8 km from the observed crustal thickness (39 km), resulting in a β value of 1.25, which is consistent with the result obtained from the subsidence analysis. Keywords: Atlas system, extension, stretching factor, Thinning factor,

The Central High Atlas is distinguished by map-scale, sigmoid, and narrow magmatic-cored ridges, which separate wide and open synclines. The origin of these structures has been debated for years. This study addresses this issue from a paleostress perspective, using mesostructural analysis in the Imilchil region and incorporating insights from previous research. Our analysis reveals that the Central High Atlas ridges developed through two main structural stages from the Jurassic to the Cenozoic. The first stage involved an extensional event characterized by NW-SE-oriented a3, coeval with the Early Jurassic Tethyan extension. This was followed by wrench tectonics driven by oblique left- lateral motion of Africa with respect to Europe. This events is marked within the Central High Atlas by ENE- WSW-oriented a1 and NNW-SSE-oriented a3. The basin-scale left-lateral motion likely drove the formation of sigmoid stepovers, facilitating the emplacement of magmatic bodies from the Middle Jurassic to the Early Cretaceous. The second deformation stage is likely associated with the convergence between Africa and Europe and the consecutive Alpine orogeny. In the study area, this stage consists of three events: a pre-folding strike-slip event with NNE-SSW to N-S-oriented a1, and a pre-folding strike-slip event with NW-SE-oriented a1. Near the diapirs, the analyzed mesostructures display syn-to post-folding patterns in some locations, indicating pre-Alpine layer tilting driven by salt tectonics. The final event is marked by significant post-folding NW-SE compression, associated with the Central High Atlas basin inversion and the compaction of pre-existing magmatic-cored salt diapirs. This study highlights the complex deformation history that has influenced the evolution of the Central High Atlas ridges and provides evidence of the significant role of strike-slip tectonics during the post-rift period and magmatic emplacement, as well as in the early phases of basin inversion.

Sustainable ore extraction in cave mining heavily relies on the effective fragmentation or caveability of the orebody. Since cave mining offers substantial benefits, it has gained popularity after preconditioning was introduced to help improve caveability. Therefore, hydraulic fracturing serves as a vital technique for risk management and cave stimulation. The increased rock competency and high stress levels in the rock mass around the orebody significantly influence fracturing and, thus, cavability processes. In order to improve the çefficiency of preconditioning by hydraulic fracturing to specific parts of the non-caving or poorly caving formations, the use of notches as artificial flaws offers an influence on the directionality of fracture propagation; this approach also has the potential to decrease the necessary breakdown pressures, thereby lifting limitations on the design and mechanical capabilities of fracturing campaigns and reducing required breakdown pressures, which could improve hydraulic fracturing capabilities. In this study, we studied the effects of notches on hydraulic fracturing performance under varying stress conditions. A number of hydraulic fracturing experiments were conducted using different notch quantities and spacings. Notches were created parallel to the axis of confining stress, and specimens were then subjected to constant axial loads of 40 MPa under varying confining pressures ranging from 5 to 40 MPa. A supplementary 3-D discrete element method using 3DEC was performed, and the results were compared with the hydraulic fracturing experiment. The 3DEC models incorporated Darcy's Law to describe fluid flow through fractures, and the Mohr–Coulomb softening yield criterion was used to simulate failures on predefined surfaces, providing a thorough hydro-mechanical coupled solution. We found that introducing notches can effectively reduce the pressures needed for fracture initiation and growth. Moreover, with appropriate spacing, fracture direction can be controlled. This knowledge, combined with the use of numerical modelling, has advanced our understanding of fracture behaviour and the influence of notches on propagation paths under different stress regimes. These findings could potentially revolutionise the field of hydraulic fracturing, making it more efficient and sustainable.

The core of sustainable mining is the preservation of the ground stability, and in situ stress measurement is crucial as most of the stability issues are directly associated with the in situ and induced stresses. Deformation rate analysis and acoustic emission are reliable and low-cost methods of stress measurement leveraging stress memory in rocks. However, owing to rock heterogeneity and complex geological stress history, the accurate determination of in situ stresses is often challenging. This study proposes a simple, accurate, and improved method for determining the in situ stresses in rocks called the Secant Modulus Method (SMM). The effectiveness of SMM is determined through uniaxial cyclic loading and unloading experiments on different types of soft and hard crystalline rocks. The influence of the loading modes, strain rates, and time delay is also investigated. Additionally, its utility for in situ stress measurement is explored. The SMM method proved effective in determining both applied and in-situ stresses, with no effect from variations in loading conditions, loading rates, and time delays. Moreover, the in situ stresses measured using the SMM were in good agreement with the overcoring method.

Inherited structures are widely recognized as one of the major factors that govern rift systems localizations, acting as weakening zones and influencing the subsequent inversion style during compression events, as well as controlling the deformation of overburden sediments. The High Atlas intermountain belt in Morocco, interpreted as evolution controlled by Paleozoic inherited structures, comprises Mesozoic and Cenozoic sediments overlying a Paleozoic and Precambrian basement. Exploring these structures is crucial for understanding the evolution of the belts and for assessing seismic hazards. Surface studies are often insufficient to unveil the complete image of the subsurface structural setting, as illustrated by the Mw 7 Al Haouz earthquake, which is interpreted as being linked to a blind fault (William et al., 2023; Cheloni et al., 2024). In this context, geophysical studies are indispensable to bridge this gap. Here, we present a 3D model depicting the morphology of the metasedimentary basement in the Eastern High Atlas and its northern foreland basins. This model is constrained through the inversion of gravity and aeromagnetic data, supported by seismic sections, borehole, and field data. Preliminary findings from fieldwork denote a series of large NE-SW to E-W structures, predominantly comprising reverse and thrust faults that have governed the deformation of Mesozoic-Cenozoic sediments. The depth of both outcropping and non-outcropping structures, along with their tectonic implications during the Alpine inversion, will be derived through the analysis of geophysical data. Keywords: Inherited structures, High Atlas, basement, 3D model, inversion, geophysical data.

Morphotectonic parameters are sensitive to crustal and/or mantle dynamics, especially in young convergent margins and contractional orogenic systems. In northwest Africa, the High Atlas orogen is a natural example where tectonics interact with mantle dynamics to shape the orogen's topography. The High Atlas Mountains are an intracontinental segment of the peri-Mediterranean belt in northwest Africa, formed during the Late Cretaceous-Cenozoic period as part of the Alpine orogeny. An important aspect in the evolutionary history of the High Atlas belt is the presence of uplifted asthenosphere beneath the range, overlaying the Late Cretaceous-Cenozoic crustal shortening. This study aims to investigate the geomorphic and topographic features that reflect the influence of tectonics and mantle dynamics in the High Atlas orogen. A morphotectonic approach is employed, utilizing analysis of geomorphic indices such as relief, slope, channel steepness index, and stream length gradient. Additionally, eleven 30 km wide and 150 to 230 km long swath profiles are constructed to illustrate the variations in topography and geomorphology along the range. The geomorphic indices display a similar pattern of evolution across the High Atlas, with higher values of these indices associated with the primary faults that control the structure of the range. By combining the geomorphic indices and swath profiles, it is evident that the eastern part of the orogen exhibits geomorphic asymmetry, with the northern border experiencing greater neotectonic activity and surface uplift. The central part of the range displays more geomorphic symmetry, while the western part is asymmetrical, characterized by higher elevations and elevated values of geomorphic indices along the southern border. This variation in geomorphology is attributed to the oblique intersection of the High Atlas orogen and a region of thinned lithosphere, which facilitated increased neotectonic activity and surface uplift in the northern part of the Eastern High Atlas and the southern part of the Western High Atlas. In the westernmost portion of the range, the role of structural inheritance is critical in the neotectonic activity. At a local scale, the role of lithology in the drainage reorganization is evident especially in basement exposures such as Mougueur inlier, Skoura inlier and Ouzellarh salient. This study underscores the robustness of tectonic geomorphology as a tool to understand the complex interplay between crustal processes and mantle dynamics, together with surface processes, in young orogenic belts like the High Atlas.

Liquid foams have been increasingly studied and used in hydraulic fracturing application to develop unconventional resources. In recent years, silica nanoparticles (SNP) have been commonly applied to improve foams' thermal stability and performance under reservoir conditions. While liquid foams are highly affected by salt concentration, the influences of salinity on the foams' characteristics have yet to be clearly understood. This paper investigates the effects of salinity on the properties of SNP-surfactant-stabilized foams. The key experiments included the zeta potential and particle size measurements of SNP in surfactant solutions and the foamability, stability, rheology and proppant suspension tests on the studied foams. The results showed that the increase in the NaCl salt concentration reduced the electrostatic repulsion and promoted the aggregation behaviour among the SNP. At higher salinity, the SNP-surfactant-stabilized foams were found to have lower initial volumes, shorter half-lives, reduced apparent viscosity and faster proppant settlement. Furthermore, it was observed that all the studied foams became extremely unstable with very low foamability and had limited proppant suspension capacity when the salinity was increased to 5%. This observation is critical to evaluate the compatibility of fracturing foams when interacting with the formation brine and to improve the process of recycling produced water as a base fluid to generate foams. The outcomes of this study enhance our understanding of the influences of salinity on the properties of liquid foams and contribute to developing a practical guideline for the foam-fracturing application under harsh reservoir conditions.

In the past few years, much attention has been paid to applying liquid foams in hydraulic fracturing due to their significant benefits, including minimal formation damage. In the current literature, the combination of anionic surfactants and nanoparticles (NP) has been thoroughly studied to improve foam-based fracturing fluids' thermal stability and viscosity. On the other hand, very little research has focused on the integration of cationic surfactants and NP, which results in very limited understanding of the effects of this mixture on enhancing the properties of fracturing foams, especially at reservoir temperature. This paper investigates and compares the synergy between cationic/anionic surfactant and silica nanoparticles (SNP) in improving the fracturing foams' stability, rheology and proppant-carrying capacity under ambient and elevated temperature conditions. The experiments involved foamability, bulk static stability, viscosity measurement and proppant settling tests at fixed NP concentration and varied surfactant concentrations. The results showed that as the surfactant concentration increased, the properties of foams were improved considerably until reaching a plateau or a peak at 0.05 - 0.1 wt%. Furthermore, at both ambient and elevated temperature, the foams stabilized by SNP and cationic hexadecyltrimethylammonium bromide (CTAB) surfactant had significantly higher half-life, apparent viscosity and lower proppant settling velocity than those stabilized by SNP and anionic sodium dodecyl benzene sulfonate (SDBS) surfactant. The properties of CTAB/SNP foams were found most outstanding at medium CTAB concentration but declined dramatically at too low or too high surfactant concentration. This study enhances our understanding of the influences of surfactant type and surfactant concentration on the stability, rheology and proppant settling behaviour of the nanoparticle-stabilized foams, which contributes to developing an effective foam system for high-temperature fracturing application.

Identifying potential petroleum traps in petroleum basins is one of the key challenges in petroleum exploration. Specifically, it is the identification of probable petroleum traps within a set of stratigraphic traps of a particular location of source rock and carrier bed. One solution lies in understanding the behaviour of hydrocarbon flow during secondary migration, and the evaluation of the probability of successful transport from the source rock to the trap. Modern reservoir simulators rely on numerical methods to model the oil/gas secondary migration. Using numerical simulators is, however, cumbersome and requires high volumes of data and computation time, which affects successful decision-making in exploration planning. Yet, analytical models are fast and allow for multivariant analysis of hydrocarbon secondary migration requiring only a moderate amount of geological data. This study presents the analytical modelling of hydrocarbon buoyant transport in petroleum basins by including the (i) areal variation of stringers’ cross-section, (ii) chemical reactions including oil biodegradation and (iii) hydrological water flow. The explicit formula is provided for the first and last moments of hydrocarbon arrival at the trap, describing the dynamics of filling of the trap. Field data from Australian and Chinese basins are used to investigate the effects of the above-mentioned parameters on the first and last moments of hydrocarbon arrival at the trap.

<p>Processes such as oblique mid ocean ridge spreading, glacial isostatic adjustment and slope instability provide a highly complex spatial and temporal record of stress in the Fram Strait. The Vestnesa Ridge is a contourite drift bounded by two slow spreading mid ocean ridges located beside a formerly glaciated margin. The total state of stress is difficult to separate into individual components therefore our focus is to ascertain whether there is a stress transfer from the deep crust into the shallow overlying (~200m) sedimentary cover. We use high-resolution P-cable 3D seismic volumes together with 2D seismic, to map deeper faults connecting with near surface deformation. We perform high resolution mapping of the ridge by examining the dip and strike of each distinct fault system. We use a pre trained 3D model to predict faults within each 3D volume and automatically extract faults at multiple intervals to capture temporal stress changes. To minimize noise, the model identifies faults based on edge preserved smoothing for a selection of peak frequencies. In our results we observe fault linkage between parallel faults that may become favourable locations for transtensional and transpressional stress expected in the strike slip regime predicted in the west of the ridge. Our results show that the east of the ridge has a dominant NW-SE fault strike and a present day tensile stress regime while towards the west, the NW-SE assemblage becomes less prominent and multiple fault systems dominate increasing the complexity of the system. We present a high detail comprehensive structural analysis of 3 study sites across the shallow ridge sediments and use our results to investigate differences in the strike and dip between sites to explore the influence of sedimentary faults and ridge geomorphology on the spatial evolution of seafloor seepage at a deep Arctic oceanic basin.</p>

<p>The Atlas system is an intracontinental chain established upon a Paleozoic substratum by the inversion of Triassic basins starting in the late Mesozoic-early Cenozoic. The inversion of the chain is related to the Atlas rift system that was influenced by the opening of the Central Atlantic in the West and the Tethys in the north. This was coeval with a regional exhumation following the Alpine shortening responsible for the continuous uplifting of the chain since Late Cretaceous. The structural history and chronology of events are still matter of debates. To contribute to this, we focus on the Western High Atlas (WHA) aiming a retro enactment of the paleo-stresses states, by analyzing deformation structures at various scales. The geological data were collected at different stratigraphic levels: from the contact Paleozoic basement/Mesozoic cover interface to the Triassic detrital formations of the Argana corridor in the east, to the Jurassic-Cretaceous and Cenozoic plateaus in the west. Preliminary results highlight two major tectonic events: (1)- a first extensive event, with sub-horizontal minimal principal stress σ3 oriented NW-SE, that is linked to the Central Atlantic basin opening. This event is characterized by pull apart basins structured into horsts and grabens. (2)- a second compressive event, marked by NE-SW to NNE-SSW shortening. The later is subdivided into two episodes: i- an early post-rift episode (Middle-Late Jurassic to Early Cretaceous), marked by stylolites and meso-structures that occurred at the beginning of the main uplifting stage. ii- a late compression episode, characterized by a maximum principal stress σ1 mainly oriented NNE-SSW to NNW-SSE, starting at the late Cretaceous and accelerating during the Tertiary, simultaneously with the Africa-Europe collision.</p> <p><strong>Keywords</strong>: Paleo-stress, Structural analysis, Atlas rift system, Tectonic inversion, Western High Atlas Morocco, Alpine orogeny.</p>

ABSTRACT Due to the increased understanding of mining techniques previously uneconomical larger orebodies are becoming viable and block caves are increasingly common. One such technological advance is the use of Hydraulic Fracturing. With the majority of research for hydraulic fracturing being focused on reservoir development, a need to better understand how this translates into mining is required. Exploring how fractures initiate, grow, and the influence of notch spacings and density, more knowledge is gained around prescribing fractures to the mining industry and environments needs. By using multiple perforations, due to coalescing of fractures, more complex fracturing could be through the change in localized stresses. To understand the influence of fracture density, lab work was undertaken looking at how density of notches and notch spacing influence the fracture growth, breakdown pressure, and propagation pressures in Adelaide Black Granite under two different stress regimes. The results show that location of notches has minimal impact on pressures but create changes in the fracture direction. This work confirms that with multiple notches this technique can be used to change fracture propagation. providing solid foundation for designing campaigns with multiple simultaneous injections, and fractures density within the mining industry. INTRODUCTION Block caving is gaining traction as a viable method of mining within hard rock mining environments. As easy shallow depth orebodies are becoming rare and scarcer, then methods to extract deeper orebodies safely has become a need of the industry. Block caving has an initially high outlay of costs and slow turn around in producing tons relative to Sub Level Caving methods, but in the long term requires less active development and low running costs alongside the ability to design footprints to meet the needs of the stresses, structures and environments, it equates to an economically sound, customizable, and relatively simple mining method. The challenges faced with the block cave mining method, and future caves that are established at depths are mostly related to the higher stress environment and cave propagation and stalling. A way to mitigate these risks is through the use of hydraulic fracturing. By inducing fractures in a favorable manner into the environment stress can be redistributed, highly stressed zones can be activated, and competent rocks weakened for the promotion of cave growth

ABSTRACT Rock bursts and spalling are major concerns for the design of deep underground structures under high in-situ stress conditions. A full constrain of in-situ stress magnitude and spatial distribution is therefore essential for managing the occurrence and severity of such phenomena. In recent decades, non-destructive stress measurement methods have been developed as a reliable alternative to traditional methods. These methods are based on rock stress memory and rely on accurate measurements of strain and acoustic data during uniaxial cyclic loading of specimens. In this study, several non-destructive stress measurement methods based on strain measurement and acoustic emission were evaluated. Uniaxial cyclic loading and unloading tests were performed on cylindrical specimens of Hawkesbury sandstone, and the deformation was monitored using strain gauges, Linear Variable Differential Transformer (LVDTs), Digital Image Correlation (DIC) and high-speed acoustic emission (AE) system. The strength and capability of each method in determining the applied stresses were evaluated by analyzing the strain and acoustic data collected during uniaxial cyclic loading. Although all methods were found effective in determining the applied stresses, our results indicate that the DRA and SMM methods were more precise and consistent. INTRODUCTION The Kaiser effect is a phenomenon observed in rock specimens when a uniaxial cyclic loading is applied in a laboratory. Acoustic emission (AE) activity begins just after the applied stress exceeds the peak of previously applied maximum stress to the specimen (Lavrov, 2002). This memory of previously applied stresses is found not only as a change in AE activity but also in the strain rate of rock specimens under a constant loading rate, known as the stress memory (Yamamoto et al., 2009). Kuwahara et al. (1990) proposed a model for the inelastic deformation of rock specimens under axial loading of compression to explain the mechanism of the Kaiser effect. According to Kuwahara et al. (1990) there are many potential micro-cracks in a rock specimen, and the strength of the specimen depends on potential cracks and applied stress to the specimen. If the applied stress is increased to a certain magnitude, all the potential micro-cracks with strengths smaller than the applied stress should initiate or propagate (Hoek and Martin, 2014). When the specimen is subjected to stress again after unloading, new micro-fractures hardly occur at first, and the pre-existing crack produced in the previous loading steadily moves with an increase in applied stress until the applied stress reaches the peak of the previously applied stress. New micro-fractures begin to occur only after the applied stress has reached the previous stress.

Summary Understanding the behaviour of the hydrocarbon flow during secondary migration greatly helps geologists and petroleum engineers to identify the potential hydrocarbon traps in geological basins in the exploration stage. Basin modeling is, therefore, necessary to curtail resource-consuming challenges such as dry-hole drilling. However, building accurate basin models to predict secondary migration and dynamics of trap filling is still a formidable problem due to the complexities associated with hydrocarbon movement at large time scales. Despite several commercial basin simulators for modelling secondary migration, they are primarily based on numerical algorithms and require high volumes of data and computation time, adversely affecting effective exploration decision-making. Analytical models, yet, are fast and require moderate data for multivariant analysis of the secondary migration of hydrocarbons while accounting for relevant geological and physical factors. The analytical models proposed in literature for secondary migration offer limited precision when evaluating the combined effects of physical, chemical, and biological reactions. This study proposes novel analytical models that simulate the dynamics of hydrocarbon propagation below seals and accounts for; (i) chemical reactions including oil biodegradation, (ii) areal variation of cross-section of stringers, and (iii) hydrological water flow below the migrating hydrocarbons for cases of pulse and continuous expulsions.