Search Results (18)

Deep coalbed methane (CBM) development faces significant challenges due to extreme geological conditions (high stress, elevated pressure, high temperature) that differ fundamentally from shallow reservoirs. Traditional productivity models developed for shallow CBM often fail to accurately predict deep reservoir performance. The complex “stress-desorption-flow” multi-field coupling mechanism, intensified under deep conditions, critically controls production dynamics but remains poorly understood. This study develops a multi-layer, commingled, coupled geomechanical-flow model for the Hujiertai deep CBM block (2140~2170 m) in Xinjiang, China. The model, integrating gas-water two-phase flow, Langmuir adsorption, and transient geostress evolution, was validated against field production data, achieving a low relative error of 1.2% in the simulated average daily gas rate. Results indicate that: (1) Geomechanical coupling is critical. The dynamic competition between effective stress compaction and matrix shrinkage limits fracture porosity reduction to ~2%, enabling a characteristic “rapid incline, 1–2-year plateau, gradual decline” production profile and significantly enhancing cumulative gas production. (2) Porosity (10~30%) is positively correlated with productivity: a 10-percentage-point increase raises the peak gas rate by 2.1% and cumulative production by 2.8%. Conversely, high initial cleat permeability boosts early rates but accelerates geomechanical damage (cleat closure), lowering long-term productivity. (3) Stimulation parameters show a trade-off. SRV only dictates short-term, near-wellbore production. Higher fracture permeability (peak rate +17% per 500 mD) boosts early output but accelerates depletion and stress-induced closure. The multi-field coupling mechanisms revealed and the robust model developed provide a theoretical basis for optimizing fracturing design and production strategies for analogous deep CBM plays. Full article

This study evaluates the technical, design, and economic feasibility of large-scale hydrogen storage in deep water-bearing geological formations (aquifers), presenting it as a scalable solution for seasonal energy storage within the European Union’s decarbonization framework. A techno-economic model was developed for a 1 BCM facility, integrating geomechanical, microbial, and thermodynamic criteria. The results indicate a recoverable hydrogen fraction of 70–85%, with dissolution and microbial conversion losses limited to below 10% under optimized operational regimes. Geochemical and microbiological modelling demonstrated that sulfate-reducing and methanogenic bacterial activity can be reduced by 80–90% through controlled salinity and pH management. The proposed design, incorporating high-permeability sandstone reservoirs (100–300 mD), hydrogen-resistant materials, and fibre-optic monitoring ensures stable containment at 60–100 bar pressure and enables multi-cycle operation with minimal leakage (<0.05% per year). Economically, the baseline Levelized Cost of Hydrogen Storage (LCOHS) for aquifers was found to be ~0.29 EUR/kWh, with potential reductions to ~0.18 EUR/kWh through optimized drilling, modularized compression systems, and microbial mitigation. The lifecycle carbon footprint (0.20–0.36 kg CO₂-eq/kg H₂) is competitive with other geological storage methods, while offering superior scalability and strategic flexibility. Full article

This paper presents a hybrid methodology for predicting rock mass deformation and roadway loads induced by longwall mining. The approach combines the classical Budryk–Knothe influence function model with numerical simulations in the FLAC3D finite difference environment. Instead of explicitly reproducing large-scale excavation and caving, the impact of mining is introduced through analytically derived displacement boundary conditions applied to the numerical model. This allows detailed analyses of the rock mass deformation state while significantly reducing computational effort compared with conventional geomechanical models. The methodology involves deriving displacement components from the Budryk–Knothe influence function, implementing them through Python 3.6.1 scripts in FLAC3D 7.00, and performing stepwise simulations of longwall advance. Results show that the proposed approach reduces the number of finite difference zones by nearly an order of magnitude, achieving more than a tenfold decrease in computation time. At the same time, the displacement and stress distributions obtained remain consistent with both the analytical Budryk–Knothe solution and those from the classical numerical model. The study demonstrates that this methodology provides a reliable and efficient tool for assessing stress redistribution and deformation around roadway excavations influenced by mining. Its application enhances the accuracy of deformation predictions, supports support system design, and improves safety and efficiency in underground mining operations. Full article

To meet the demand for simulative materials exhibiting suitable hydraulic characteristics in geomechanical model tests, this research developed a type of simulative material using iron powder, quartz sand, and barite powder as aggregates, white cement as binder, and silicone oil as additive. An orthogonal experimental design L₁₆(4⁴) was employed to prepare 16 distinct mix proportions. Advanced statistical methods, including range analysis, residual analysis, Pearson correlation analysis, and multiple regression performed with SPSS 27.0.1, were applied to analyze the influence of four factors—aggregate-to-cement ratio (A), water–cement ratio (B), silicone oil content (C), and moisture content (D)—on physical and mechanical parameters such as density, uniaxial compressive strength, elastic modulus, angle of internal friction, and permeability coefficient. Range analysis results indicate that the aggregate-to-cement ratio serves as the primary controlling factor for density and elastic modulus; moisture content exerts the most significant effect on compressive strength and permeability; while the water–cement ratio is the dominant factor influencing the internal friction angle. Empirical formulas were established through multiple regression to quantitatively correlate mix proportions with material properties. The resulting similitude materials cover a wide range of mechanical and hydraulic parameters, satisfying the requirements of large-scale physical modeling with high similitude ratios. The proposed equations allow efficient inverse design of mixture ratios based on target properties, thereby supporting the rapid preparation of simulative materials for advanced model testing. Full article

Blast-induced airblast poses a significant environmental and operational issue for surface mining, affecting safety, regulatory adherence, and the well-being of surrounding communities. Despite advancements in machine learning methods for predicting airblast, present studies neglect essential geomechanical characteristics, specifically rock mass strength (RMS), which is vital for energy transmission and pressure-wave attenuation. This paper presents a capuchin search algorithm-optimized multilayer perceptron (CapSA-MLP) that incorporates RMS, hole depth (HD), maximum charge per delay (MCPD), monitoring distance (D), total explosive mass (TEM), and number of holes (NH). Blast datasets from a granite quarry were utilized to train and test the model in comparison to benchmark approaches, such as particle swarm optimized artificial neural network (PSO-ANN), multivariate regression analysis (MVRA), and the United States Bureau of Mines (USBM) equation. CapSA-MLP outperformed PSO-ANN (RMSE = 1.120, R² = 0.904 compared to RMSE = 1.284, R² = 0.846), whereas MVRA and USBM exhibited lower accuracy. Sensitivity analysis indicated RMS as the main input factor. This study is the first to use CapSA-MLP with RMS for airblast prediction. The findings illustrate the significance of metaheuristic optimization in developing adaptable, generalizable models for various rock types, thereby improving blast design and environmental management in mining activities. Full article

Understanding the in situ stress state and mechanical properties of rock masses is essential for ensuring the stability and safety of quarrying operations. This study aims to estimate the natural stress state of rock using the CSIRO HI (Hollow Inclusion) triaxial overcoring method; we also conducted numerical modelling by applying the Distinct Element Method (DEM) for stability assessments in quarry environments. The investigation provided comprehensive insights into the geomechanical properties of the rock mass and the stability of quarry fronts. Precise measurements and analyses of in situ stress contributed to a detailed understanding of stress distribution within the rock. Additionally, biaxial compression tests further characterized the mechanical behavior of the rock, which was essential for accurate modelling and simulation. Numerical modelling using DEM facilitated an in-depth stability analysis, allowing evaluation of potential failure mechanisms and proposal of effective mitigation strategies. The 3D numerical model was calibrated using in situ measurements from CSIRO HI data and was employed to simulate future excavations. DEM modelling was particularly crucial because of the fractured nature of the rock mass, which necessitated thorough stability verification in excavation design simulations. This research advances the scientific understanding of stress distribution and mechanical behavior in jointed rock masses, ultimately contributing to the development of safer and more efficient quarrying practices. Full article

The deep shale gas resources of the Sichuan Basin are abundant and constitute an important component of China’s natural gas production. Complicated by fault zones and other geostructures, the in situ stress state of the deep shale gas reservoirs in the Luzhou block remains poorly understood. This study integrated multiple datasets, including acoustic logging, diagnostic fracture injection testing (DFIT), imaging logging, and laboratory stress measurements, for calibration and constraint. A high-precision geomechanical model of the Luzhou block was constructed using the finite element method. This model characterizes the geomechanical properties of the reservoir and explores its applications in optimizing shale gas horizontal well placement, drilling processes, and fracture design. The study findings indicate that the Longmaxi Formation reservoir demonstrates abnormally high pore pressure, with gradients ranging from 16.7 to 21.7 kPa/m. The predominant stress regime is strike-slip, with an overburden stress gradient of 25.5 kPa/m and a minimum horizontal principal stress gradient ranging from 18.8 to 24.5 kPa/m. Based on a three-dimensional geomechanical model, a quantitative delineation of areas conducive to density reduction and pressure control drilling was conducted, and field experiments were implemented in well Y65-X. Utilizing an optimized drilling fluid density of 1.85 g/cm³, the deviated horizontal section was completed in a single trip, resulting in a 67% reduction in the drilling cycle compared to adjacent wells. Similarly, the Y2-X well demonstrated a test daily output of 506,900 cubic meters following an optimization of segmentation clustering and fracturing parameters. Studies indicate that 3D geomechanical modeling, informed by multi-source data constraints, can markedly enhance model precision, and such geomechanical models and their results can effectively augment drilling operational efficiency, elevate single-well production, and are advantageous for development. Full article

To increase natural gas storage capacity and further utilize salt mine resources, salt cavern gas storage in the Yunying salt mine, Hubei Province, China, was simultaneously constructed in two different mining layers (K3 and K4). The purpose of this study was to investigate the long-term feasibility of operating salt caverns for gas storage in two mining layers. Based on the geological conditions and sonar test results, the geometric parameters for the salt caverns in the two mining layers were designed, and a 3D geomechanical model was built to predict the cavern stability. The corresponding evaluation index included the displacement, volume shrinkage rate, equivalent strain, and dilatancy factor. The results show that simultaneously operating salt cavern gas storage in two mining layers is feasible, and the operational pressures for the salt caverns in mining layers K3 and K4 should be no less than 4–9 and 7–12 MPa, respectively, to satisfy the stability requirements. The surrounding rock of the salt caverns presents a larger displacement and volume reduction compared with cases in which the salt caverns are operated in a single mining layer. Increasing the injection–withdrawal frequency increases the deformation of the surrounding rock. Full article

Reliable regional-scale permeability data and minimum sustained injectivity rate estimates are key parameters required to mitigate economic risk in the site selection, design, and development of commercial-scale carbon sequestration projects, but are seldom available. We used extensive publicly available disposal well data from over 4000 disposal wells to assess and history-match regional permeability estimates and provide the frequency distribution for disposal well injection rates in each of 66 disposal formations in the Alberta Basin. We then used core data and laboratory analyses from over 3000 cores to construct 3D geological, geomechanical and petrophysical models for 22 of these disposal formations. We subsequently used these models and the history-matched regional permeability estimates to conduct coupled geomechanical and reservoir simulation modeling (using the ResFrac™, Palo Alto, CA, USA, numerical simulator) to assess: (i) well performance in each formation when injecting carbon dioxide for a 20-year period; (ii) carbon dioxide saturation and reservoir response at the end of the 20-year injection period; (iii) reliability of our simulated rates compared to an actual commercial sequestration project. We found that: (i) the injection rate from our simulations closely matched actual performance of the commercial case; (ii) only 7 of the 22 disposal formations analyzed appeared capable of supporting carbon dioxide injectors operating at greater than 200,000 tons per year/well; (iii) three of these formations could support injectors operating at rates comparable to the successful commercial-scale case; (iv) carbon dioxide presence and a formation pressure increase of at least 25% above pre-injection pressure can be expected at the boundaries of the (12 km × 12 km) model domain at the end of 20 years of injection. Full article

The discrete fracture networks (DFN) have become indispensable tools for geomechanical modelling of jointed rock masses. The technology creates a three-dimensional (3D) representation of fracture geometry used in the construction of surface and subsurface engineering projects in mining, civil engineering, and fracturing of the reservoir in the oil and gas industry. The approach depends on the accuracy of the data obtained during site investigation to create models that represent the fracture geometry of the structure. The better the acquired information available, the better the stochastic analysis that determines the engineering applications and designs that can be carried out. Therefore, it is important to use instruments that can capture fracture distribution characteristics such as fracture intensity, fracture orientation, spatial distribution, fracture length, fracture aperture, and size. This study provides a detailed review of the recent advances in the application of a DFN for modelling jointed rock masses in different engineering applications. The paper shows the principles of modelling in a DFN, including various data-capturing methodologies, and the general application of DFN in various fields. Several case studies where the DFN method was applied are presented in the paper. These include evaluation of slope in an open pit mine, modelling of discontinuity in tunneling, stability evaluation of coal seam longwall, the design of high-level radioactive waste, prediction of groundwater flow, fracturing of petroleum reservoirs, and geothermal cracking of shale gas in the coal bed. However, despite the versatility of the DFN technique, there are still some limitations and challenges to the integration of complexities encountered in rock masses within DFN models. Full article

Geomechanical model tests provide an intuitive and convenient method for observing physical phenomenon due to their easy implementation compared to in situ tests and prototype tests. The success of model tests depends heavily on the appropriate selection of model materials and proportions. Therefore, a new similar material is developed by utilizing the orthogonal experimental design method to conduct a series of proportioning tests. The new material is mixed with barite powder, iron ore powder, quartz sand, liquid paraffin, rosin, gypsum powder, and water. The physical and mechanical properties are studied through uniaxial compressive tests, Brazilian splitting tests, and direct shear tests. The influences of various raw material factors on the parameters of the similar material are systematically studied through range analysis. The results demonstrate that the mechanical parameters of similar materials have wide variation ranges; the adjustment range is 42.0–279.0 MPa for the elastic modulus, 0.37–5.37 MPa for the uniaxial compressive strength and 2.23–2.65 g/cm³ for the density. The new similar material has illustrated advantages in terms of performance stability, low price, and convenient production, which can simulate the similar relationship with different geomechanical model tests. The similar material is applied to a 3D geomechanical model test of the foundation pit excavation of Shenzhen metro station, which proves that the similar material can realistically reflect the change of earth pressure in the excavation process. With the deepening of excavation, the earth pressure curve shows significant fluctuations, and as the retaining structure is displaced, the parts with large earth pressure changes should be strengthened. The research methods and results can provide reference for further geological engineering research. Full article

The main objective of this research work was the wellbore stability evaluation of oil and gas wells based on a 3D geomechanical model, which as constructed using seismic inversion in a southeastern Algerian petroleum field. The seismic inversion model was obtained by using an iterative method and Aki and Richards approximation. Since the correlation between the inversion model and the log data was high at the wells, the reservoir was efficiently characterized and its lithology carefully discriminated in order to build a reliable 3D geomechanical model. The latter was further used to suggest the drilling mud weight window for the ongoing wells (well 5) and to examine the stability of four previously drilled wells. The main contribution of this study is providing a 3D geomechanical model that allows the optimization of drilling mud weight parameters so that a wellbore’s stability is guaranteed, on the one hand, and, on the other hand, so that the reservoir damage brought about by excessive surfactant use can be prevented. Indeed, the mud parameters are not just important for the drilling process’s effectiveness but also for logging operations. Since the tools have limited investigation diameters, with excessive use of surfactant, the invaded zone can become larger than the tools’ investigation diameter, which makes their logs unreliable. Hence, the 3D geomechanical model presented here is highly recommendable for the proposition of new wells, entailing less exploration uncertainty and more controllable productivity. Full article

Hydraulic fracturing (HF) has been used for years to enhance oil and gas production from conventional and unconventional reservoirs. HF in enhanced geothermal systems (EGS) has become increasingly common in recent years. In EGS, hydraulic fracturing creates a geothermal collector in impermeable or low-permeable hot dry rocks. Artificial fracture networks in the collector allow for a continuous flow of fluid in a loop connecting at least two wells (injector and producer). However, it is challenging to assess the fracability of geothermal reservoirs for EGS. Consequently, it is necessary to design a method that considers multiple parameters when evaluating the potential of geothermal development. This study proposes an improved fracability index model (FI) based on the influences of fracability-related geomechanical and petrophysical properties. These include brittle minerals composition, fracture toughness, minimum horizontal in-situ stress, a brittleness index model, and temperature effect to quantify the rock’s fracability. The hierarchical analytic framework was designed based on the correlation between the influencing factors and rock fracability. The results of the qualitative and quantitative approaches were integrated into a mathematical evaluation model. The improved fracability index model’s reliability was evaluated using well logs and 3D seismic data on low-permeable carbonate geothermal reservoirs and shale gas horizontal wells. The results reveal that the improved FI model effectively demonstrates brittle regions in the low-permeable carbonate geothermal reservoir and long horizontal section of shale reservoir. We divide the rock fracability into three levels: FI > 0.59 (the rock fracability is good); 0.59 > FI > 0.32 (the rock fracability is medium); and FI < 0.32, (the rock fracability is poor). The improved FI model can assist in resolving the uncertainties associated with fracability interpretation in determining the optimum location of perforation clusters for hydraulic fracture initiation and propagation in enhanced geothermal systems. Full article

Underground structures in earthquake-prone zones should be designed to withstand both static overburden pressures and earthquake shocks. This paper presents a case study on a large-span powerhouse cavern. With seismic data selected from past earthquake records, lab and in situ tests of the cavern’s geological and geomechanical conditions were performed to analyze the static and dynamic stability of the cavern through the continuum modeling approach. Performance analyses via both 2D and 3D modeling were carried out under seismic conditions and for selected design ground motions. The dynamic response of the surrounding rock mass and of the reinforcement system was detected. The results obtained will facilitate future stability analyses of large underground caverns constructed in the past on the basis of seismic design analyses and input data from post-earthquake records that were recently made available on the site. Full article

Small-spacing twin-well (SSTW) salt caverns have an extensive application prospect in thin or bedded rock salt formations due to their good performance, while they are rarely used in ultra-deep formations. The target strata depth of Pingdingshan salt mine is over 1700 m, and it is planned to apply an SSTW cavern to construct the underground gas storage (UGS). A 3D geomechanical model considering the viscoelastic plasticity of the rock mass is introduced into Flac^3D to numerically study the influence of internal gas pressure, cavern upper shape and well spacing on the stability of an SSTW salt cavern for Pingdingshan UGS. A set of assessment indices is summarized for the stability of gas storage. The results show that the minimum internal gas pressure is no less than 14 MPa, and the cavern should not be operated under constant low gas pressure for a long time. The cavern with an upper height of 70 m is recommended for Pingdingshan gas storage based on the safety evaluation and maximum volume. The well spacing has a limited influence on the stability of the salt cavern in view of the volume shrinkage and safety factor. Among the values of 10 m, 20 m and 30 m, the well spacing of 20 m is recommended for Pingdingshan gas storage. In addition, when the cavern groups are constructed, the pillar width on the short axis should be larger than that on the long axis due to its greater deformation in this direction. This study provides a design reference for the construction of salt cavern gas storage in ultra-deep formations with the technology of SSTW. Full article