Geological faults are key discontinuities in sedimentary basins and strongly influence the hydraulic and mechanical behavior of hydrocarbon reservoirs. Fault zones typically contain a low-permeability core and a more permeable damage zone, generating sharp contrasts in petrophysical and mechanical properties. Stress variations from production, injection, or geological storage may induce fault reactivation, dilatancy, and permeability enhancement, yet many numerical studies still treat faults as homogeneous features. This study develops a two-dimensional coupled hydro-mechanical framework that explicitly represents fault-core and damage-zone domains incorporating viscoelastoplastic behavior through a Mohr–Coulomb model with Perzyna viscoplasticity. The novelty of this approach lies in integrating realistic geological architecture with explicit core-damage-zone contrasts and coupled viscoelastoplastic analysis under production and injection scenarios in compartmentalized reservoirs. Based on seismic interpretation of the Laurentian Basin (offshore Canada), CODE_BRIGHT simulations model single-phase flow in a deformable reservoir to evaluate stress redistribution, permeability evolution, and deformation. Sensitivity analyses indicate that an injection pressure of 6.5 MPa triggers fault reactivation, causing dilation-induced permeability increases and establishing hydraulic communication between the deep reservoir and the overlying aquifer previously sealed by Faults 01 and 02. Fault reactivation induces an asymmetric deformational field, with horizontal displacements of approximately + 25 cm along Fault 02 and − 13 cm along Fault 01, and a distortional vertical response characterized by a dip-slip response with differential block-scale subsidence and uplift, with a maximum subsidence of 7 cm. Shear stresses concentrate mainly along Faults 01 and 02, particularly near their tips, indicating stress redistribution toward Fault 03. These results underscore the importance of internal fault-zone heterogeneity in controlling deformation, stress evolution, and transmissivity, with implications for CO2 storage, geothermal systems, industrial injection, and geotechnical applications.

This study aimed to evaluate the effects of chemical dissolution on the properties of reservoirs by matrix acidizing, using synthetic carbonate rocks with and without fractures, prepared with limestone powder, epoxy resin (chemically inert) and fractures represented by non-woven geotextile strips positioned perpendicular to the fluid flow direction, to check their influence on the dissolution process. A system was developed using an acid injection cell to carry out acidizing tests, applying a solution of acetic acid and distilled water at constant pressure, to observe the organic acid-rock interaction for contact times of 36, 72 and 108 h. Chemical and petrophysical tests, as well as image analyses using X-ray micro-computed tomography were conducted to characterize the acidizing effects. Changes in rock properties were observed as the contact time increased, particularly the increase in porosity and permeability. Was observed the formation of CO2 and calcium acetate as reaction products between calcite and acid solution. Ramified wormhole and uniform dissolution patterns were noted; moreover, fractures influenced the dissolution in regions where they were inserted, increasing the branches present along their structure and deviating the fluid flow to a perpendicular direction to the injection direction, especially observed at 72 h, highlighting the use of geotextile as a material that reproduces the fractures' transmissivity in synthetic samples. The methodologies used contributed to presenting the effects of mineral dissolution on the properties of reservoir rocks post-stimulation, emphasizing the importance of chemical/petrophysical aspects and the contribution of fractures to better understand the matrix acidizing efficiency in field.

This research presents a methodology to evaluate the water potential of the Serra dos Martins Sedimentary Formation, which is part of the Barreiras geological group, and has an important occurence in the municipalities of Araruna and Cacimba de Dentro – Paraíba State. The adopted method involves multidisciplinary integration: hydrogeophysical studies, near surface geophysical methods, petrophysical relationships used to link geophysical properties to hydrological properties and state variables, data inversion, and generation of three-dimensional models through spatial data interpolation methods. This work quantitatively and qualitatively characterized the groundwater of the investigated region. A 3D model for the investigateds area was generated and a 85 million m³ of groundwater reserve was estimated. The methodology here proposed can be applied in any region with similar geological characteristics.

This study aimed to evaluate the geomechanical changes in carbonates after matrix acidizing via acetic acid at different contact times (36/72/108 h). Synthetic carbonate rocks without fractures and with fractures were produced and subjected to matrix acidizing tests. X-ray microcomputed tomography, porosity and permeability tests were performed to identify the dissolution processes. Unconfined compressive strength tests (UCS) were performed on acidified and nonacidified samples to compare their stress–strain behavior, Young’s modulus and Poisson’s ratio before and after acidification. Petrophysical changes, such as increased porosity and permeability caused by the dissolution of the rock matrix with increasing injected acid, promote the formation of wormholes, affecting their structure. The samples exhibited a gradual decrease in mechanical strength with increasing contact time with acid; they were classified as moderately hard to hard (41.32 MPa to 50.80 MPa for nonacidified rocks) to soft (12.45 MPa to 24.18 MPa) after 36 h of testing; they also progressed from soft to very soft (4.61 MPa to 11.20 MPa and 4.12 MPa to 6.69 MPa) after 72 h and 108 h of acidification, respectively; and they exhibited a change in elastic behavior (brittle) to plastic (ductile) and a reduction in stiffness, as evidenced by a decrease in Young’s modulus, in addition to a reduction in Poisson’s ratio. Evaluating the impact of acid treatment on rock mechanics is essential for determining mechanical degradation after acid treatment to ensure that the stimulation technique does not compromise the integrity of the reservoir to the point at which its collapse.

The accelerated growth and urban expansion in Brazil without proper planning have resulted in informal settlements in areas susceptible to landslides, intensifying landslide risks due to anthropogenic interventions and the increased frequency of extreme weather events. This study investigates the stability of urban slopes in Nova Descoberta, Recife, Brazil, incorporating extreme rainfall events and anthropogenic actions. Using the limit equilibrium method and the finite element method, the research evaluates the stability of the Córrego do Joaquim slope, considering rainwater infiltration, pipeline leaks, and the presence of a water supply tank. Field and laboratory tests, along with recent surface data obtained via drone photogrammetry, enabled the development of a geological-geotechnical planialtimetric model of the study area for numerical modeling. The results show a general agreement between the methods but highlight discrepancies in the factor of safety in specific scenarios, underlining the need for multiple methods. Rainwater infiltration significantly impacted stability, while plastic tarps did not ensure safety according to Brazilian standards. Pipeline leaks presented stability risks even with waterproofing against rain. In this analysis, the shear strength reduction method demonstrated advantages over the limit equilibrium method in detecting rupture progression.

The structural characterization of fractures is crucial to understand the processes of fluid flow in tight reservoirs. This contribution focuses on the role played by vertical fractures on the permo-porosity properties of the Aptian tight carbonate sequence of the Crato Formation, Araripe Basin (NE Brazil). The study performed a structural analysis in two different scales: reservoir scale (approximately 19.000 m2) and outcrop scale (approximately 125 m2), focusing on the fracture networks in lacustrine laminates, which have been investigated as an analogue of carbonate facies observed within the pre-salt reservoir sequence of the marginal basins in Brazil. This study employed a combination of systematic outcrop-based fracture characterization involving digital outcrop models and mechanical stratigraphy analysis. To evaluate the influence of vertical fracture systems in the fracture porosity and the equivalent permeability we performed DFN (Discrete Fracture Network) models. We focused on vertical calcite-filled fractures, oriented in two principal directions: set 1 NNW-SSE and set 2 NE-SW. Each set shows different vertical linkage patterns due to the influence of the mechanical intervals. Results of the outcrop scale model show similar behaviour for both fracture porosity and equivalent permeability, indicating that storage capacity and fluid flow may not be affected by vertical linkage of fractures. The reservoir scale DFN models show that the fracture porosity was greater in models which consider through-going continuous fractures than in models that consider the segmentation (discontinuity) of vertical fractures. Considering the vertical connectivity of fractures, the equivalent horizontal permeability (Kxx and Kyy) showed similar values in both scale models. This implies that vertical segmentation of fractures does not impact fluid flow in horizontal directions. The calculated values of equivalent vertical fracture permeability (Kzz) at reservoir scale are one order of magnitude higher in the DFNs that consider continuous fractures. Our results suggested that vertically continuous fractures enhance preferential flow pathways allowing greater vertical fluid flow than segmented fracture networks in tight carbonate reservoirs.

In recent decades, faster and more affordable methods for characterizing reservoir rocks in environmental and geological studies have gained importance, particularly for hydrocarbon exploration and resource management. One promising method is X-Ray Computed micro-Tomography (XR-?CT), enabling non-destructive analysis of rock properties. However, this technique presents challenges related to image interpretation, property characterization below the voxel scale, and result comparison across configurations. In this study, laminated limestones from the Crato Formation, analogs to the pre-salt Barra Velha Formation, were analyzed using XR-?CT to estimate density and porosity. These rocks serve as substitutes for actual reservoir conditions, addressing the challenge of limited subsurface samples. This study assessed the feasibility of XR-?CT for characterizing these properties and understanding the impact of millimeter-scale laminations on their distribution. Calibration values for calcite, the primary mineral, were used to ensure accuracy and repeatability. The results demonstrate that XR-?CT is a viable tool for environmental and geological characterization. Laminations due to stratification influenced porosity distribution in the axial direction, with higher concentrations in certain sections of the samples. The porosity values calculated using XR-?CT align relatively well with the gas porosimetry results, with most samples showing a relative difference of less than 10%. However, exceptions were observed in LM4 and T10.2, where the relative difference reached -15.90% and -12.80%, respectively. Despite these challenges, qualitative analysis was achieved. The study highlights the necessity of accounting for mineralogy and calibration in XR-?CT to ensure reliable comparisons across different tomographic systems, enhancing the method’s applicability in environmental and geological studies.

Na análise de sistemas de fraturas em geologia e engenharia, a técnica scanline é passível de viéses, podendo repercutir incertezas nos resultados. Para sanar essa fragilidade, foi desenvolvida uma ferramenta computacional de código aberto chamada Lindiwe. Assim, o objetivo deste estudo é descrever o funcionamento da ferramenta Lindiwe, desenvolvida para otimizar a análise de fraturas geológicas com base na técnica scanline. A ferramenta foi utilizada em uma simulação a partir de afloramento na Praia de Itapuama, sobre o qual foram realizados cálculos manuais pertinentes da técnica de scnaline, e fornecidas informações para a ferramenta proceder na análise. Os resultados validaram o Lindiwe, evendenciando que a ferramenta representa um avanço na análise de fraturas geológicas, proporcionando uma solução eficiente e precisa.

Characterization and development of hydrocarbon reservoirs depends on the classification of lithological patterns from well log data. In thin reservoir units, limited vertical data impedes the efficient classification of lithologies. We present a test case of petrofacies classification using machine learning models in a thin interval of finely laminated limestones using pseudo-well data created over outcrops (radiometric and unconfined compressive strength logs). We tested Gaussian naïve Bayes (GNB) and support vector machine (SVM) techniques to classify eight petrofacies types, divided into two groups. The objective was to observe the capacity of some well-known models to classify petrofacies with a high-frequency vertical variation of diagenetic heterogeneities in an extreme scenario within a thin sedimentary interval. The GNB was less effective (F 1 score of 0.29), and the SVM achieved the best results in classifying the main facies patterns (F 1 = 0.47). However, the GNB performed better when the analysis was focused on distinguishing the two main groups of petrofacies. The results demonstrate that high-frequency facies variations present a challenge to the automatic identification of lithofacies, mainly due to local variations in horizontal heterogeneities (on the mm- to cm-scale) created by depositional and diagenetic processes, which impact the flow in porous media.

Carbonate rocks are important for the petroleum industry, as they contribute significantly to hydrocarbon reserves, although their analysis is complex due to the high cost of core sampling and their high heterogeneity; for this, synthetic rocks aim to provide relatively homogeneous samples with analogous characteristics to natural rocks. In this research, synthetic carbonate rocks were produced by mixing a fixed ratio between limestone powder, obtained from limestone mining waste, and epoxy resin as a cementing material, using compaction energy for consolidation. The work aimed to produce homogeneous samples with high strength, reproducing the intergranular pore system for future applications in rock–fluid interaction analysis. The characteristics and structure of the samples were investigated through X-ray computed microtomography, petrographic images, petrophysical, chemical and geomechanical tests. Results showed a direct increasing relationship between porosity and permeability and a tendency for mechanical strength (UCS) to decrease with increasing porosity. When compared with the natural carbonate rocks, these presented similarities in their mechanical properties and petrophysical measurements, showing that the methodology can be considered as an alternative for the obtention of a realistic material that can be used for future experiments regarding rock mechanics and rock–fluid interaction for prediction of carbonate rocks’ behavior.

We use a two-dimensional finite-element modeling approach to investigate the structural evolution of strike-slip faults under five different confining pressures and determine how their damage zone widths vary depending on the kinematic. Three representative fault segments are modeled, accounting for movement obliquity forming in pure strike-slip, oblique convergence and oblique divergence scenarios. The elastoplastic constitutive model (Drucker-Prager) was employed to couple an associated flow rule into the initial stress state of a geostatic stage. We applied two empirical methods for determining the width of the damage zone from progressive model response. The first method involves using the plastic strain distribution curve's inflection points, to mathematically fixate the width. The second method uses the standard deviation obtained from a trend Gaussian/ Normal probability distribution, with over 98% fit to the plastic strain curve data, simplifying the inference of the strain propagation along the model. The simulation results indicate inverse proportional relationships between confining pressure and both porosity and plastic strain intensity, while showing a direct proportional relationship with the damage zone width. For fault zone width quantification, results show convergence between the methods, revealing widths of 2.46-2.65 m for oblique divergence (displacement of 0.20 m), 2.65-3.55 m for pure strike-slip (displacement of 0.20 m), and 4.36-4.46 m for oblique convergence zones (displacement of 0.70 m). The pure strike-slip and the oblique convergence damage zone width results align well with outcrop observations of faults with similar kinematics from the literature, underscoring the significance of numerical modeling as a valuable tool for measure and study the mechanics of characterizing the nucleation of fault zones and quantifying the width of the damage zone.

Abstract The main objective of this study is to evaluate the hanging wall stability of the mining stopes resulting from the open stope underground mining method, taking into account the exposure time of the wall sans any support, through numerical simulation, using an elasto-viscoplastic model formulated for the finite element method. In order to carry out the simulation, a real application case was chosen: the extraction of a mining block from the underground zinc mine of Nexa Resources, in the municipality of Vazante-MG, which operates through the open stope mining method, where the values of unplanned dilution are known. The stability of the stope’s hanging wall was analyzed through two instability indicators, the horizontal displacements and the minor principal stress, simulated in a two-dimensional perpendicular section and in the center of the stope. The results obtained in the simulations were coherent with the real results that occurred in the stope, and with the rheological behavior of the rocks, since the unstable regions increase with the exposure time without any type of support used, which shows that the model used is a good alternative for prediction of the dilution and the evolution of instability areas of the stope wall according to its exposure time.

Oil production in offshore regions involves the transportation of oil and gas in submarine pipelines, which are vulnerable to geological processes triggered by subsurface oil production like fault reactivation. The fault reactivation process can lead to phenomena that impact the seabed, like subsidence and fluid exudation, and can trigger instability of submarine slopes, which can result in environmental and economic damage. The present work addresses a coupled hydromechanical numerical modeling of a hypothetical case involving fault reactivation caused by oil reservoir production and its impact on an overlying submarine slope. The hypothetical case was simulated using a finite element model. The case involves a reservoir which is cut by a fault zone that reaches the seabed. The slope instability studied was induced by the injection and production of fluids in the reservoir. The fault zone is assumed to be a sealing region and a geomechanical and pressure field discontinuity within the reservoir. Int this work was used the Mohr-Coulomb elastoplastic model with Perzyna viscoplastic regularization to represent the behavior of the fault zone and the overlying submarine slope. Results showed that the fault reactivation, caused by the reservoir production, developed shear stress and shear plastic strain along the fault and through the submarine slope, causing horizontal and vertical displacements in the slope mass and acting as a trigger factor for slope stability. Pore pressure increase at the bottom of the slope structure correlated with the injection pressure artificially increased into the reservoir.

Deformation bands can influence fluid flow within reservoirs, mainly acting as flow barriers. This study aims to characterize deformation bands and evaluate the influence of these structures on fluid flow through 2D modeling and numerical simulation using the equivalent permeability tensor computed numerically through a flow-based upscaling procedure in siliciclastic reservoirs. To do so, we analyze arkosic sandstones of the Antenor Navarro Formation in the Rio do Peixe Basin, NE Brazil. The characterization of deformation bands involved: 1) acquisition of aerial imagery using a drone; 2) conducting direct field-based structural analysis along one scanline (frequency of deformation bands/m); and 3) collection of samples in the field to perform petrophysical (porosity and permeability) tests. After the characterization phase, we built a 2D geological model using the previously acquired parameters and performed a single-phase numerical flow simulation of water using finite element code. We simulated four different horizontal and vertical flow scenarios for both measured and exaggerated host rock permeability. Our structural analysis demonstrated that the deformation bands preferentially strike NE–SW, with secondary E–W– to N–S–orientations. Our petrophysical analysis showed that samples affected by deformation bands have lower porosity (by up to two orders of magnitude) and permeability (by up to four orders of magnitude) values than samples collected in the host rocks. The numerical fluid flow simulation allowed us to conclude that the deformation bands act as partial flow barriers where the hydraulic head can indicate the barrier effect intensity. Pressure drops between host rock regions separated by deformation bands reached values from 10 to 40%, depending on the fluid flow direction, especially for cases with a high contrast between the permeability values (three orders of magnitude) of the deformation bands and the host rock. The results of this study focus on the importance of contrasts in permeability measurements between deformation bands and host rocks, which could help to enhance understanding of the behavior of the deformation bands as partial fluid flow barriers, as well as their implications for hydraulic properties in deformed siliciclastic reservoirs.