In hospitals, a medical computed tomography (CT) scan is used to detect damage to infected areas of the human body. Using this technology, scientists and engineers have found a way to detect the internal pore connections and characterize rock samples of oil and gas reservoirs in the petroleum industry. Nowadays, the micro-CT scan technique is gaining considerable interest in reservoir rock characterization and in situ monitoring of fluid flow through porous media during different flooding experiments. Along with this digital rock physics (DRP) idea, images have been used to accurately describe and model for simulations of rock samples. In this review, the application of micro-CT and medical-CT scanning in the oil and gas industry has been thoroughly discussed. Recent improvements in DRP and modern imaging techniques in the oil and gas industry have been modeled using both experimental and simulation work. The combination of a DRP study and a CT scan has also been discussed as a unique idea for the current scenario of research work in this field. The available literature shows that the modern imaging technique and the DRP concept can enable an understanding of the pore network model. It has also been observed that the visualization of fluid flow behavior through porous media is now possible during fluid movement through the core samples. This review contributes to the new research area and aids those in this field in quickly gaining an understanding of applied image techniques in the oil and gas industry.

Predicting rock blasting outcomes in mining has been crucial since its inception. Blasting remains the most energy- and cost-efficient method for rock breaking and is often the only practical option. However, the mechanism is complex, influenced by various rock properties, explosives, and blast design parameters, making their effects difficult to quantify. Traditional stress-based models struggle with many parameters, such as stress and Poisson's ratio, which are challenging to measure in the field. Empirical models, though simpler, often oversimplify blast conditions. Both types of models are limited to simulating a few blastholes and cannot handle full-scale blasts involving hundreds of blastholes. However, modeling full-scale blasts with all blast design parameters is most required for modern mining applications. This paper presents a novel strain-based modeling approach for blasting and geomechanical applications, utilizing measurable variables such as particle velocity, strain, and displacement. By bypassing complex constitutive relations, strain-based models capture critical blasting trends and simulate full-scale blasts with full-blast design parameters with minimal calibration. The framework encompasses field strain measurements, model construction based on measurable variables, and laboratory-derived strain-failure criteria, each offering potential for future enhancement. Additionally, a standardized field test for site characterization is recommended. The approach is demonstrated through the Multiple Blasthole Fragmentation model, which simulates rock fragmentation and fragment strain during blasting, highlighting the practicality and effectiveness of strain-based modeling for multiple blasthole blasts. Moreover, this approach extends beyond blasting, with potential applications in highwall stability monitoring and other geomechanical applications. Strain-based modeling provides a simplified yet effective solution, avoiding the complexities of rock constitutive relations and field stress measurements while enabling full-blast design simulations for large-scale field blasts.

Considering the expansion of mining operations into increasingly deeper areas, it is imperative to assess the influence of dynamic disturbance loads on the security of deep tunnels. Here, via AUTODYN finite difference software, a numerical analysis of the fracture characteristics of a fractured tunnel was employed under the coupled action of in-situ stress and dynamic disturbance loads. The experimental setup comprised a tunnel model with “I-shaped” cracks, and a drop impact device (DID) was employed to generate dynamic wave loads. A crack fracture test (CFT) was utilized to gather information on the fracture process, including initiation time and average propagation rate. A series of combined scenarios were subsequently simulated to replicate various in situ stress levels (ranging from 0.5 to 2.5 MPa) and dynamic loads. The results indicate that with increasing in situ stress, the crack propagation rate, crack propagation length, and crack break time (CBT) decrease; moreover, the circumferential tensile stress concentration factor in the tunnel also decreases, enhancing tunnel stability. Finally, changes in ground stress influence the propagation path of cracks.

The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters. In this article, the dynamic compression test of anthracite under five strain rates is carried out, the evolution law of three kinds of crack characteristic stress is analyzed, and a prediction model of the crack characteristic stress threshold considering the strain rate effect is established. Then, the rationality of crack characteristic stress under dynamic loading is discussed from the damage evolution standpoint, and the crack extension response mechanism during dynamic compression of anthracite is discussed. The result shows that the crack characteristic stress threshold is significantly influenced by the strain rate. The three characteristic stress thresholds are positively correlated with the strain rate, but the ratios to the crest stress gradually decrease. The increase in the strain rate strongly contributes to the crack extension behavior of anthracite. In the crack unstable extension phase, because of the increase of the strain rate, anthracite shows more energy dissipation under the same deformation in association with the stress concentration effect and the dynamic strength enhancement effect. The crack propagation rate is increased, the crack propagation path of the section is more complex, and more severe damage occurs before the dynamic failure of anthracite, which leads to even more severe damage.

The vibration caused by blasting excavation of rock mass frequently poses a threat to the stability of adjacent tunnels. Previous research is limited by the simplification of a rock mass as a homogeneous elastic medium, without considering the wave attenuation caused by viscoelasticity and wave separation induced by rock discontinuities, as well as plane waves while neglecting geometric attenuation of near-field nonplane blast waves. This paper establishes a theoretical model of cylindrical P-wave propagation across a fault to an adjacent existing tunnel. Based on the time-domain recursive method, vibration equations and peak particle velocity on the adjacent existing tunnel wall caused by a cylindrical wave passing through a fault are derived. The rock mass and fault are assumed to satisfy Kelvin viscoelastic bodies, and contact interfaces between fault and rock mass follow a nonlinear hyperbolic deformation model in the normal direction and a linear model in the tangential direction. The results show that tunnel vibration caused by the blast cylindrical P-wave is primarily induced by transmitted P-waves. With the increase of the fault dip angle, vibration on the upper side of the adjacent existing tunnel gradually decreases, while vibration on the lower side increases. The closer the vibration to the upper and lower sides, the stronger the shear effect on the tunnel wall, and the closer the vibration to the middle, the stronger the pressure effect on the tunnel wall. Larger fault thickness and higher initial blast wave frequency result in weaker vibration of the adjacent tunnel. The deeper the burial depth, the stronger the vibration of the adjacent tunnel wall. Findings of this study provide insight into the dynamic response of rock construction and safety evaluation in engineering service.

Deep mining of natural resources, like coal, is increasingly utilizing directional blasting technology with slit charge for rock blasting at greater depths. This study, based on numerical simulation methods, analyzes the dynamic behavior of slit charge blasting in three aspects: slit tube dynamic response, hoop stress evolution, and crack propagation. According to research findings, the failure mode of the slit tube mainly manifests as a tensile fracture of the inner wall and a shear fracture at the end connection, where the end connection of the slit tube is the weak point of the overall structure. The dynamic response of the slit tube mainly exhibits radial response in the vertical direction of the slit and hoop response in the slit direction. The hoop tensile stress plays a crucial role in determining the spread of cracks caused by explosions. As the in situ stress increases, the peak hoop tensile stress reduces, and the peak hoop compressive stress increases. This hinders the propagation of cracks. In addition, the directional impact is most pronounced in the middle of the borehole, with the longest primary directional crack observed. Conversely, the directional impact is least favorable near the bottom of the borehole. When the in situ stress reaches 60 MPa, the purpose of directional fracture has not been achieved, suggesting combining presplit blasting for in situ stress relief to improve rock breaking efficiency.

In coal mines, dynamic disasters such as rock bursts seriously threaten the safety of mining activities. Exploring the dynamic behaviors and disaster characteristics in the impact failure process of coal serves as the basis and prerequisite for monitoring and warning rock bursts. In this context, impact failure tests of coal were carried out under different axial static loads and impact velocities to analyze the dynamic behaviors and acoustic emission (AE) response characteristics of coal. The results show that the dynamic behaviors of coal under combined dynamic and static loads are significantly different from those under static loads, and the stress-strain curve displays double peaks without an obvious compaction stage. As the axial static load grows, the dynamic strength and peak strain both have a quadratic function with the axial static load. When the coal damage intensifies instantaneously, the AE count and energy parameters both witness pulse-like increases and reach their peak values. The damage effect of axial static loads on coal, though limited, has an extreme point. In contrast, the impact velocity can strengthen the response of AE signals and has linear function relationships with the peak values of AE count and energy. This plays a leading role in the damage to samples and sets a critical point for coal failure and fracture. Compared with the analysis results of stress and strain, the responses of AE signals are more accurate and reliable. Based on AE response characteristics, the damage evolution process of coal under the combined dynamic and static loads can be identified more accurately to reveal the moment corresponding to coal damage and the characteristics of coal failure. The research results are conducive to the further application of AE monitoring methods to early warning of rock burst disasters in coal mining sites.

Grouting with water-cement mixtures is the most widely used and cost-effective method for managing excess water inflow during tunnel construction. Due to uncertain geological and hydrological conditions, current grouting design relies heavily on the experience of onsite engineers. Recent advances in machine learning offer a promising alternative to traditional design to predict grout volume and improve grouting efficiency. Here, an artificial neural network (ANN) model was developed using the data set from an operation tunnel of Jurong Rock Caverns in Singapore to showcase an efficient and physics-guided training strategy. The ANN model was refined by incorporating the spatial scenarios, including the number of grouting holes in four quadrants of tunneling faces, the sequence of grouting screens along the tunnel axis, and the order of grouting rounds on the tunneling faces. The results indicate that an improved training strategy should encompass the grouting process, from Round 1 with grouting holes uniformly distributed around the tunnel periphery, to Round 2 with grouting holes drilled midway between neighboring first-round holes, and to Round 3 with grouting holes determined by onsite engineers. This model, trained based on the order of grouting rounds, performs better than the other models, highlighting the importance of establishing machine learning models grounded in physical principles. The finding was verified by the data set from another operation tunnel and concluded with a perspective on future grouting research.

Hydrochloric acid (HCl) extensively exists in deep underground projects, arising from the transportation of industrial raw materials or fracturing fluids of petroleum engineering. It results in corrosion, which can significantly impact the stability of surrounding rock structures. Therefore, in-depth analysis of the degradation of rock corroded by the HCl solution is an essential task for underground engineering. In this study, the granite specimens are initially treated with the HCl solution with various concentrations. Then, the tests and analyses, such as electrical conductivity (EC) measurements, mineral composition assays, and Brazilian splitting tests, are employed to investigate the corrosion mechanism of the HCl solution. Our results and findings are generally as follows: (1) As the immersion time increases, the EC exhibits a relatively high level at pH value of 1, a decreasing trend at pH value of 3, and an increasing trend at pH value of 5 and 7. (2) The HCl solutions with various concentration have different effect on mineral composition, characterized by an increase in proportion of SiO₂ and a reduction in proportion of Na₂O, Al₂O₃, K₂O, MgO, and CaO, as the solution pH value decreases. (3) After immersion in the solutions with pH values of 1, 3, and 5, the tensile strength of the granite decreases by 23.85%, 20.84%, and 20.24%; the average stiffness of the specimen decreases by 29.29%, 23.43%, and 11.97%; the proportion of releasable energy increases by 6%, 4%, and −2%; the releasable energy decreases by 54.96%, 26.09%, and 14.52%; and the dissipated energy decreases by approximately 68.85%, 41.39%, and 5.41%, respectively. (4) The evolution of physical and mechanical properties of the immersed granite specimen can be analyzed from a chemical aspect. The corrosive action of HCl cleaves Si-O and Al-O chemical bonds within the granite, particularly altering the tetrahedral structures of its silicate components. This process involves breaking existing chemical bonds and the formation of new ones, ultimately destroying the silicate molecular structures. As the concentration of HCl increases, the rate of these reactions accelerates, progressively weakening the chemical bonds and consequently deteriorating the mechanical characteristics of the granite. These findings can deepen our knowledge about the corrosion effect of HCI solutions on natural surrounding rocks and serve as references for further research on rock corrosion mechanisms in underground engineering.

The deformation and failure of coal walls in front of a working face cause significant difficulties during mining operations. This study reveals the nonuniform distribution of bearing pressure in front of coal walls based on in situ monitoring data and numerical simulation. Therefore, an eccentric compression mechanical model was established to study the deformation and failure characteristics of a coal wall. The slenderness ratio of the compression bar is introduced to define coal walls. The results showed that instability failure occurs when λ > λ_c and material failure occurs when λ ≤ λ_c. The instability failure-type coal wall spalling was related to the mining height, eccentricity of roof pressure, the horizontal force, and the reaction moment of the floor. The material failure-type coal wall spalling was related to the cohesion, the internal friction angle of the coal, the upper pressure, and the horizontal force of coal walls. Unstable and destructive coal wall peeling usually occurs at a height of 0.5-0.6 times the mining height, while material damage to coal wall peeling is determined to occur within the range of 0.4-0.6 times the mining depth. The findings contribute to the understanding of the deformation and failure of coal walls.

Wellbore drilling disturbs the equilibrium stress state in the rock mass, resulting in stress redistribution around the opening. Wellbore stability in the altered stress state is vital for engineering applications, as the wellbore instability results in cost overrun. Accurate estimation of rock mechanical properties, in-situ stresses, and required mud pressure is crucial for safe drilling. If the mud pressure is lower than required, the shear failure of the rock takes place, and conversely, if the mud pressure is higher than the upper limit, tensile failure occurs. A strength criterion that can accurately predict the mud pressure may help significantly reduce non-productive time and cost in well drilling. The commonly used Mogi-Coulomb (MGC) failure criterion for estimating critical mud pressure neglects the few fundamental aspects of rock failure characteristics observed in the laboratory, such as nonlinear strength response in major-minor principal stress space and prediction of multiple failure stress values near the triaxial axial extension boundary. The present study uses the Modified Mohr-Coulomb true-triaxial failure criterion (MMC_TT), which predicts the strength of rock better than the MGC in laboratory true-triaxial tests to overcome the limitations. Moreover, based on the data from previously published five vertical wells in the Krishna-Godavari basin (K-G basin), an empirical relationship is proposed to obtain the strength parameters for the MMC_TT criterion for shaley sedimentary rocks as the existing correlations do not cater for the parameters required for MMC_TT criterion. The comparative study of the MMC_TT with MGC, Modified Mohr-Coulomb triaxial, and Mohr-Coulomb failure criteria, showed that for most of the K-G basin wells, the MMC_TT criterion predicted close to the MGC. However, for well-13, the MMC_TT criterion results are closer to the mud pressure used in actual drilling than the MGC.

Understanding the microscopic time-dependent mechanical behavior of shale is critical for assessing macroscopic creep and engineering applications. Grid nanoindentation experiments and nanoindentation creep tests were systematically conducted to investigate microscopic creep behaviors in shale. The indentation creep displacements and creep rates of the shale's soft, intermediate, and hard phases showed the same evolution patterns. The creep deformation was much higher in the soft phase than in the other two phases. However, the difference in the steady-state creep rates between the three mechanical phases was negligible. A linear relationship was observed between the microscopic contact creep modulus and the microscopic Young's modulus, hardness, creep displacement, and creep rate. The primary mechanism of microscopic creep in shale revealed by the creep strain rate sensitivity parameter was the extension and closure of microcracks. The differences in the microscopic creep parameters derived from the experimental data using the deconvolution methods and representative point methods were evaluated, and the applicability of the two methods was described. The performances of commonly used creep models to predict the microscopic creep behaviors were evaluated. The Burgers model provided the best performance in predicting the steady-state creep deformation and creep rate. The ability of the Mori-Tanaka and Voigt-Reuss-Hill models to derive macroscopic parameters from microscopic mechanical parameters was compared. Both methods provided macroscopic Young's modulus values close to the experimental values; however, neither could predict macroscopic creep parameters based on microscopic creep parameters.

Conventionally, foundations have been classified as shallow or deep in routine civil engineering practice. However, due to recent developments, two other approaches, semi-deep and ground modification foundations, are now available, complicating foundation categorization. Accordingly, a new concept for foundation categorization is introduced in this paper based on insights into the theory of structure analysis. Based on the form aspect, foundation systems can be categorized as one-dimensional (linear), two-dimensional (planar), and three-dimensional (volumetric). Based on the load transfer aspect, foundations can also be categorized as vector-acting (piles), section or surface-acting (rafts and shells), and block-acting (piled rafts). As a step toward implementing this new categorization scheme, a database of 22 cases has been compiled, symbolizing novel introduced foundation systems. This compilation involves structures such as offshore jackets, high-rise buildings, towers and storages, and diverse geomaterials. Among them, a few have been selected for detailed evaluation, emphasizing influential factors in foundation selection, comprising superstructure, subsoil condition, foundation system, circumferential conditions, and supplementary considerations, that is, constructional and sustainability-based issues. Lessons learned from experience and these knowledge-based cases have described for foundation selection and implementation. Geotechnical and practical aspects with critical components have been realized as major performance assessment and comparison factors. Foundation systems have been compared and ranked using the improved analytic hierarchy process approach. Finally, four categories of buildings, from low-rise to towers and four prevailing levels of soil strength, from soft to very hard, have been considered to propose a perspective for building substructure implementation, adapted via relevant cases. Overall, the introduced categorization is recognized as an efficient algorithm for the experimentation of appropriate foundations for specific structures and subsoil conditions.

The Jinping Underground Laboratory is the deepest and largest underground laboratory in the world, with a maximum buried depth of approximately 2400 m. The objective is to study the brittle-ductile transition of marble through a combination of experimental research and constitutive modeling. Triaxial compression and triaxial cyclic loading tests are initially conducted to explore the accumulation of pre-peak plastic strain and the deterioration of stiffness of the marble. Then, a specific constitutive model is developed to accurately reflect the pre-peak plastic hardening and post-peak strain softening behaviors based on the deformation and failure mechanism of the marble. The incremental constitutive relationship of the proposed model is subsequently derived in detail, and the model parameters are calibrated using data obtained from the test results. Finally, the effectiveness of the proposed model is assessed by comparing its results with the experimental results of the marble. The findings show that the proposed model accurately predicts the behavior of the marble, and its results are in good agreement with the test data.

Pores among particles provide the main space for the storage and migration of deep underground fluids (such as oil, gas, groundwater, and unconventional natural gas). The pores form a pore structure with complex morphology which is mainly dominated by the shape and distribution of particles. Therefore, the reconstruction of the pore structure or granular porous media and the evaluation of particle roundness have become an important foundation for the study of fluid flow through deep underground rock mass. This research proposes a novel approach for the multi-scale model with angular vertexes. The fractal topology theory and Voronoi space segmentation technology are combinedly used for the reconstruction of fractal granular porous media. The angular shapes are smoothed by using a modified B-spline technique and the particles with varying degrees of roundness are generated. To validate the superiority of our approach, the roundness based on the Wadell roundness calculation method is calculated and compared with the roundness obtained from particles smoothed using the vertex rounding substitution method. Results show that the roundness of particles smoothed with the modified B-spline technique closely aligns with the corresponding set rounded level (a nondimensional variable). Conversely, the vertex rounding substitution method is limited to a single dimensionally rounded radius. This innovative approach can offer a new method for the construction of granular porous media for the fluid flow study in deep underground rock mass.

Prediction of permeability changes in surrounding rock induced by engineering disturbances is crucial for mitigating tunnel water inrush accidents. This study investigates the progressive failure characteristics and permeability evolution of hard and soft rocks subjected to triaxial compression. A series of laboratory tests were conducted at confining pressures ranging from 4 to 20 MPa. Experimental results demonstrate that rock permeability variation with strain shows three distinct stages: an initial decrease, a stage of rapid mutation, and a postpeak increase. The concept of critical permeability barrier strength is introduced, representing the stress level at which continuous fracture formation enables significant seepage. Furthermore, two generalized permeability-stress models are developed for soft and hard rocks. The predicted permeability values obtained from these models align well with the experimental data. These findings offer valuable insights into the hydro-mechanical coupling behavior of rocks, providing a foundation for safe construction practices in underground engineering.

Intermittent joints are common in rock masses and are subjected to cyclic shear loads from seismic events, environmental factors, and human activities. In this study, we conducted cyclic shear tests to investigate the effect of joint geometry (persistence, overlap, and spacing) on the cyclic shear behavior of intermittent joints under constant normal stiffness conditions. Our results revealed step-path failure surfaces comprising tensile and shear failure surfaces. Shear failure surface controlled the degradation of shear properties, with shear strength decreasing progressively with cycles, ranging from 74.07% to 97.94%. Intermittent joints exhibited significant compressibility, with dilation predominant in early cycles and compression in later ones. Shear strength and dilation were more sensitive to joint persistence and spacing than overlap. Friction coefficients showed nonmonotonic variations with cycle number. High persistence, moderate overlap, and small spacing were identified as the most destabilizing combination. These findings offer valuable insights for stability assessment and deformation characterization in deep rock engineering.

Comprehending the flow behavior of deep-sea mining plumes is paramount for precise predictions of their propagation range and holds immense significance in advancing the commercial exploitation of deep-sea minerals. As deep-sea mining plumes propagate, they can transition from high-density non-Newtonian fluids to low-density Newtonian fluids. However, a comprehensive rheological model capable of accurately describing this intricate evolutionary process is currently lacking. This study explores the variations in rheological properties observed during the propagation of deep-sea mining plumes, utilizing rheological test data obtained from kaolin clay plumes. Utilizing the Power Law model, we established a power exponential function correlating the plume rheological parameters (consistency index and flow behavior index) with a density range from 1.00 to 1.50 g/cm³ through data fitting, developing a rheological model of deep-sea mining plumes considering the variations in plume density. Subsequently, taking into account the differences in sediment properties, the effects of clay content and clay mineral composition on the rheological parameters of natural sediment plumes were compared and analyzed. This model provides a reference for understanding the rheological properties of deep-sea mining plumes during their propagation.

Carbonate reservoirs are vital energy storage spaces, including for oil, shale gas, geothermal, and hydrogen energy. Accurate prediction of reservoir characteristics such as permeability and saturated fluid types through noninvasive approaches is crucial for optimal storage capability. In this paper, we combine a linear Boolean model and a discrete Fourier transform approach to generate pore- and fracture-pore-type carbonate rocks. Elastic wave velocity information is necessary to predict permeability in different rock geometry models. Permeability is calculated using the lattice Boltzmann method, and the elastic wave velocity is calculated using a finite element method based on a minimal energy approach. Saturated fluids that contain oil and gas were both considered. Our simulated results reveal that, for pore-type carbonate, empirical formulas were proposed to estimate permeability through elastic data. However, in fracture-pore carbonate rocks, the precision of the empirical formula is compromised due to the presence of significant conductive channels within the rock matrix. We also find that using S-wave velocity and permeability relationships to distinguish oil and gas is better than using P-wave velocity and permeability relationships under low-porosity conditions.

During geothermal resource exploitation, the potential deterioration of mechanical properties in high-temperature granite subjected to cooling poses a significant safety concern. To address this, the present study investigates the coupled thermo-mechanical behavior of granite during heating and cooling through a combination of laboratory tests and finite difference method analysis. Initial investigations involve X-ray diffraction, thermal expansion test, thermogravimetric analysis, and uniaxial compression test. Results show the significant variations of granite properties under different thermal conditions, attributed to temperature gradients, water evaporation, and mineral phase transitions. Subsequently, a model considering temperature-dependent parameters and real-time cooling rates was employed to simulate linear heating and nonlinear cooling processes. Simulation results indicate that the thermal cracking predominantly occurs during the heating stage, with tensile failure as the primary mode. Additionally, a faster real-time cooling rate at higher temperatures intensifies the thermal cracking behavior in granite. This study effectively elucidates the thermo-mechanical coupling behavior of granite during heating and cooling processes, providing insights into the mechanisms of mechanical property changes with rising or decreasing temperatures.

Oil and gas resources serve as the driving force for economic and social development. This rapid development of science and technology has accelerated the exploration, development, and utilization of oil and gas resources, and thus led to spurts in related research. However, the research trends in global oil and gas exploration vary with the progress of science and technology as well as social demands. Accordingly, they are not easily captured. This study explores the research trends in global oil and gas exploration through the bibliometric analysis of 3460 articles on oil and gas exploration collected from the Web of Science database and published from 2013 to 2023. The research hotspots, objects, regional distribution, methods, and evaluation methods in oil and gas exploration are analyzed, and the direction of development of oil and gas exploration is presented on this basis. The research characteristics of four major countries or regions related to oil and gas exploration were further investigated and compared. The results show that the number of publications on oil and gas exploration research has been continuously increasing in the past decade, with China ranking the top in terms of publications. Given the continuously evolving global energy demand, exploration of unconventional oil and gas, application of digital technology, deep and emerging regional resource exploration, and environmentally friendly and low-carbon source exploration will be future research hotspots.