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Rock pore structure coupled with fluid pressure plays an important role in controlling fault slip behavior. Observation of fluid-induced seismicity in geoenergy extraction has raised fundamental questions about the physics of fault rock structure and fault frictional stability in the presence of fluid. Here, we change the pore structure of faults by thermal treatment and report on the frictional stability of granite faults with pore evolution and pore fluid pressure in velocity stepping experiments under the rate-and-state framework, where the variation of pore fluid is monitored. The experiments under constant fluid pressure show that pore structure propagation leads to an increase in friction coefficient from 0.71 to 0.78. As the degree of pore propagation increases, the drained fault exhibits a transition from velocity strengthening to weakening behavior. The decrease in frictional stability could be caused by the coupling between the pore fluid and the well-connected pores, namely “fluid oscillation”. Pore pressure overpressurization could develop and cause non-uniform stress distribution along the fault surface due to pore fluid oscillation at velocity steps. The time required to equilibrate fluid pressure could be prolonged by fluid oscillation, leading to intrinsic velocity strengthening behavior appearing as velocity weakening. The decrease in rate-and-state parameter with elevating pore fluid pressure on high-porosity fault corroborates the fluid-induced fault destabilization. The fluid oscillation at the greater pore pressure could be responsible for fault reactivation. Therefore, the coupling effect of rock pore structure with pore fluid could be a potential mechanism governing fault frictional stability. [ABSTRACT FROM AUTHOR]

Adsorption and capillarity, in the order of high free energy to low, are the two soil–water interaction mechanisms controlling the hydro-mechanical behaviour of soils. Yet most of the poroelasticity theories of soil are based on capillarity only, leading to misrepresentations of hydro-mechanical behaviour in the low free energy regime beyond vaporisation. This inability is reasoned to be caused by two major limitations in the existing theories: missing interparticle attraction energy and incomplete definition of adsorption-induced pore-water pressure. A poroelasticity theory is formulated to incorporate the two soil–water interaction mechanisms, and the transition between them – that is, condensation/vaporisation, by expanding the classical three-phase mixture system to a four-phase mixture system with adsorptive water as an additional phase. An interparticle attractive stress is identified as one of the key sources for deformation and strength of soils induced by adsorption and is implemented in the poroelasticity theory. A recent breakthrough concept of soil sorptive potential is utilised to establish the physical link between adsorption-induced pore-water pressure and matric suction. The proposed poroelasticity theory can be reduced to several previous theories when interparticle attractive stress is ignored. The new theory is used to derive the effective stress equation for variably saturated soil by identifying energy-conjugated pairs. The derived effective stress equation leads to Zhang and Lu's unified effective stress equation, and can be reduced to Bishop's effective stress equation when only the capillary mechanism is considered and to Terzaghi's effective stress equation when a saturated condition is imposed. The derived effective stress equation is experimentally validated for a variety of soil in the full matric suction range, substantiating the validity and accuracy of the poroelasticity theory for soil under variably saturated conditions. [ABSTRACT FROM AUTHOR]

A rigorous analytical solution is developed for undrained cavity expansion problems in non-associated Mohr–Coulomb soil, based on a novel graphical analysis approach and on the Lagrangian description through tracking only the responses of a soil particle at the cavity surface. The mathematical difficulties involved with the flow rate calculation when the stress state lies on the corner/edge of two adjacent (Mohr–Coulomb) yield surfaces, for both cylindrical and spherical cases, are tackled by using the generalised Koiter theory for non-associated plasticity. In particular, through the unique geometrical formulation, the effective stress path pertaining to the cylindrical cavity problem can be very conveniently directly determined, and is found to consist of simple, piecewise straight lines in the deviatoric stress plane with the orientations dependent of the relative magnitude of Poisson's ratio and the friction angle. This thus renders possible the removal of the stringent intermediacy assumption for the vertical stress that is commonly adopted in previous formulations, and hence the development of a complete cylindrical cavity expansion solution in Mohr–Coulomb soil under undrained loading conditions. The stress and deformation responses of the cavity, including the typical pressure–expansion curves and limiting cavity pressure, are finally analytically obtained along with the Lagrangian form of the radial equilibrium equation in completely explicit forms. The closed-form solution provided in this paper is the first rigorous one of its kind, thus completing the analytical analysis of the cavity expansion problem with the classical Mohr–Coulomb model; this is deemed to be essential for the interpretation of in situ test results pertaining to cohesive-frictional soils. [ABSTRACT FROM AUTHOR]

In the South China Sea, a significant amount of methane hydrate exists in the sediment containing fine-grained soil. Increasing temperature and/or decreasing pore pressure can remarkably degrade the mechanical characteristics of this methane hydrate–bearing fine-grained sediment (HBFS). In this study, several compression tests under triaxial stress condition on HBFS are performed with changing temperature and pore pressure. The experimental results reveal that the HBFS specimen has an enhanced stiffness and failure strength characteristic under lower temperature and/or higher pore pressure conditions. An improved phase state parameter H is presented as a characterization for the temperature and pore pressure condition, which considers the capillary effect for HBFS with wide pore size distribution. The secant modulus and failure strength tend to linearly increase with the rising improved phase state parameter H. The internal friction angle is independent of the temperature and pore pressure, while the cohesion exhibits a significantly linear increase with the rising improved phase state parameter H. In addition, the shear–dilatancy curve shifts to the right with the rising improved state parameter H owing to the enhanced cementing strength of hydrate–soil cluster. These research findings are beneficial for grasping the mechanical behavior of HBFS. Furthermore, this research also provides data support for building the constitutive model of HBFS during methane hydrate recovery. [ABSTRACT FROM AUTHOR]

This study aims to investigative the relationship between the pore pressure and the explosive spalling of polypropylene (PP) fiber reinforced concrete when subjected to high temperature. Using the vapor pressure gauge, the moisture measuring sensor, and the thermocouple to measure the vapor pressure, moisture content, temperature, and the temperature on the heated surface of slab specimen, and observing the explosive spalling for the specimens of cylinder and slab made of PP fiber concrete. Test results showed that only the cylindrical specimen without PP fiber and 100% moisture content was apparently subjected to explosive spalling. Comparing with the test results of the slab specimen, the moisture content of the cylinder specimen had a significant effect on the occurring of explosive spalling. On the other hand, the effect of PP fiber on explosive spalling was obviously improved. The control slab specimen without fiber presented explosive spalling on the fire-exposed surface, causing the steel bar to be exposed to air, while the internal temperature rose faster than the PP fiber slab specimen without explosive spalling. The non- PP fiber slab specimen is affected by explosive spalling, the heat trend effect of temperature showed more obvious, and its moisture movement was more rapid than the slab specimen with PP fiber. Under similar moisture content, the slab specimen without PP fiber started sooner to explosive spalling with a serious explosive failure, on the contrary, the slab specimen with 0.1% PP fiber was completely without explosive spalling, indicating the significant effect of anti-explosive spalling by adding PP fiber in concrete. [ABSTRACT FROM AUTHOR]

Predicting pore pressure is critical in every exploration venture because it prompts safe drilling, fluid design, casing emplacements, improved wellbore dependability, and water driven cracking enhancement. Hence, the objective of this paper was to predict and evaluate the pore pressure characteristics of a selected field in the Niger Delta Basin of Nigeria using appropriate standard methods. The results of the 1D pore pressure model from the Eaton and Bower's sonic techniques revealed that the deviation from Normal Compaction Trend started at about 8350 ft as a result of overpressure. The determined break angle from the Fracture gradient formular, utilizing the Effective Stress Ratio (ESR), Overburden Pressure (OVP) and the anticipated Pore Pressure (PP) was estimated to be between 0.65 psi/ft and 0.725 psi/ft. Due to the use of overbalanced drilling in the Niger-Delta, wellbore pressure should be higher than the Hydrostatic pressure, but not as high as the fracture pressure. Therefore, the safe drilling window should likely be from 0.613 psi/ft to 0.645 psi/ft for the study area. [ABSTRACT FROM AUTHOR]

Wave erosion of slopes can easily trigger landslides into marine environments and pose severe threats to both the ecological environment and human activities. Therefore, near-shore slope monitoring becomes crucial for preventing and alerting people to these potential disasters. To achieve a comprehensive understanding, it is imperative to conduct a detailed investigation into the dynamics of wave erosion processes acting on slopes. This research is conducted through flume tests, using a wave maker to create waves of various heights and frequencies to erode the slope models. During the tests, seismic signals, acoustic signals, and pore pressure generated by wave erosion and slope failure are recorded. Seismic and acoustic signals are analyzed, and time-frequency spectra are calculated using the Hilbert–Huang Transform to identify the erosion events and signal frequency ranges. Arias Intensity is used to assess seismic energy and explore the relationship between the amount of erosion and energy. The results show that wave height has a more decisive influence on erosion behavior and retreat than wave frequency. Rapid drawdown may potentially cause the slope to slide during cyclic swash and backwash wave action. As wave erosion changes from swash to impact, there is a significant increase in the spectral magnitude and Power Spectral Density (PSD) of both seismic and acoustic signals. An increase in pore pressure is observed due to the rise in the run-up height of waves. The amplitude of pore pressure will increase as the slope undergoes further erosion. Understanding the results of this study can aid in predicting erosion and in planning effective management strategies for slopes subject to wave action. [ABSTRACT FROM AUTHOR]

This paper presents two case studies dealing with undesirable impacts of overburden drilling of casings for end-bearing piles to bedrock. Monitored pore-water pressures and ground settlements are used to document and assess the influence from rotary percussive drilling with "down-the-hole" (DTH) hammers. The studies show that drilling with high-pressure air-driven DTH hammers may cause considerable erosion and soil volume loss adjacent to the drill bit and along the casing, resulting in settlements of the surrounding ground. The risk of soil volume loss increases when the drilling is carried out in erodible soils such as silt and fine sands. The volume loss is found to be caused by a combined air-lift pump effect and a Venturi suction effect. Monitoring pore pressures in the vicinity of the drilling may be used to reduce soil volume loss and prevent damaging settlements. Results from drilling with water-driven DTH hammer showed significantly less ground settlements and influence on pore pressures compared to using an air-driven hammer. The study suggests that the drilling parameters flow rate and penetration rate, and the cross-sectional area of the pile casing can be combined in a non-dimensional methodology to assess the mass balance of drill cuttings when drilling with water flushing. A design framework is suggested to guide overburden drilling in urban settings to reduce potential impact on the surroundings. [ABSTRACT FROM AUTHOR]

AbstractMost studies of the wave interaction with pipeline were conducted on a flat seabed. This paper presents the results from the numerical modelling simulation to investigate the wave induced response around a half-buried pipeline on a sloping seabed. The numerical model is validated using the experimental data of the wave-pipeline-seabed interaction. The validated model is then applied to simulate the wave generated pore pressure distribution around the pipeline buried in the sloping seabed. Effects of the pipeline buried depth, the pipeline position and the slope gradient on the wave generated residual pore pressure as well as the potential soil liquefaction within the sloping seabed are simulated and analyzed. Results demonstrate that the pipeline location on the sloping seabed can significantly affect the residual pore pressure within the sloping seabed. This is particularly true when the pipeline is placed at the junction between the flat seabed and slope. [ABSTRACT FROM AUTHOR]

Abstract—The hydrogeology of fault zones, especially at considerable depth, is perhaps a most underdeveloped field in earthquake source mechanics. This is due to both the lack of the data on the filtration characteristics of the geomaterial at large depths and to the complexity of the processes of mass transfer, fracture formation and healing under high temperatures and pressures. In this case, the strong influence of fluid on both the friction characteristics and the stress conditions in the vicinity of the slip zone is obvious. Fluids are carriers of dissolved matter and thermal energy, an effective catalyst for various types of metamorphic transformations. According to some models, fluid flows can be triggers for the initiation and arrest of seismogenic ruptures. The current trend in world seismology to constructing a complex computational model that adequately describes the processes of preparation, initiation, and arrest of various fault slip modes requires developing the ideas about fluid dynamics of seismogenic faults. This review considers the information on hydrogeology of fault zones obtained in recent years. Models and ideas involving field data, laboratory and field experiments and numerical calculations regarding the role of fluids at different stages of the seismic cycle are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive computational model for analyzing thermo‐hydro‐mechanical coupled processes in unsaturated porous media under frost actions. The model employs the finite element method to simulate multiphase fluid flows, heat transfer, phase change, and deformation behaviors. A new soil freezing characteristic curve model is proposed to consider the suctions from air‐water capillary pressure and water‐ice cryosuction. A total pore pressure with components from liquid water pressure, air pressure, and ice pressure is used in the effective stress law. Vapor and dry air are considered miscible gases, utilizing the ideal gas law and Dalton's law. The governing equations encompass the linear momentum balance equation, the energy balance equation, and mass conservation equations for water species (ice, liquid, and vapor) and dry air. Weak forms are formulated based on primary variables of displacement, water pressure, air pressure, and temperature. The spatial discretization is achieved through the finite element method, while temporal discretization employs the fully implicit finite difference method, resulting in a system of fully coupled nonlinear equations. To verify the proposed computational model, a numerical implementation is developed and validated against a set of experimental data from the literature. The successful verification demonstrates the robustness of the model. A detailed discussion of the contributions from phase change strain and different sources of pore pressure is also addressed. [ABSTRACT FROM AUTHOR]

The discovery of gas in Groningen in 1959 has been a massive boon to the Dutch economy. From the 1990s onwards, though, gas production has led to induced seismicity. In this paper, we carry out a comprehensive exploratory analysis of the spatio-temporal earthquake catalogue. We develop a non-parametric adaptive kernel smoothing technique to estimate the spatio-temporal hazard map and to interpolate monthly well-based gas production statistics. Second- and higher-order inhomogeneous summary statistics are used to show that the state-of-the-art rate-and-state models for the prediction of seismic hazard fail to capture inter-event interaction in the earthquake catalogue. Based on these findings, we suggest a modified rate-and-state model that also takes into account changes in gas production volumes and uncertainty in the pore pressure field. [ABSTRACT FROM AUTHOR]

In undrained triaxial tests, membrane penetration varies with the change of effective confining pressure. Membrane compliance correction is a necessary step to accurately obtain the dynamic characteristics of soils in geotechnical tests. In this paper, a real-time instrument compensation equipment was adopted to eliminate membrane compliance The influence of membrane compliance on pore pressure was explained from experimental perspective, and a two-stage formula was proposed to establish the relationship between the optimized membrane correction coefficient Cm and the normalized pore pressure U/σ0′. C, which is the constant value of Cm in the stationary segment, is analyzed under different confining pressures, relative densities, consolidation ratios, and gravel contents, and the power function of C with the characteristic particle size d50 is proposed. Based on Cm, a series of predictions of pore pressure development without membrane compliance are implemented, which are basically consistent with the actual experimental results. The method to predict the pore pressure development without membrane compliance based on Cm is accurate and effective, and a large amount of experimental workload can be reduced for practical engineering applications. [ABSTRACT FROM AUTHOR]

In undrained triaxial tests, membrane penetration varies with the change of effective confining pressure. Membrane compliance correction is a necessary step to accurately obtain the dynamic characteristics of soils in geotechnical tests. In this paper, a real-time instrument compensation equipment was adopted to eliminate membrane compliance The influence of membrane compliance on pore pressure was explained from experimental perspective, and a two-stage formula was proposed to establish the relationship between the optimized membrane correction coefficient Cm and the normalized pore pressure U/σ0′. C, which is the constant value of Cm in the stationary segment, is analyzed under different confining pressures, relative densities, consolidation ratios, and gravel contents, and the power function of C with the characteristic particle size d50 is proposed. Based on Cm, a series of predictions of pore pressure development without membrane compliance are implemented, which are basically consistent with the actual experimental results. The method to predict the pore pressure development without membrane compliance based on Cm is accurate and effective, and a large amount of experimental workload can be reduced for practical engineering applications. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Determination of pore pressure and minimum horizontal stress are the first steps in geomechanical studies, and they are critical for hydrocarbon exploration, drilling, and production operations. The right quantity of pore pressure and minimum horizontal stress can enhance the quality of decisions taken and the economics of the oil and gas industry operations. Recent studies indicate that machine learning methods can be suitable for estimating the pore pressure and minimum horizontal stress, but it still needs to analyze different datasets, especially complex data to emphasize the accuracy of the results. Thus, the purpose of this article is to provide a robust machine-learning method to estimate the pore pressure and minimum horizontal stress using well-log data. The machine learning method includes multi-layer perceptron (MLP) and radial basis function (RBF). The performance of the MLP and RBF is dependent on the number of hidden layers and the number of neurons. To overcome this problem, the Genetic Algorithm (GA) is used to compute the number of hidden layers and number of neurons in each layer. A dataset of nine wells with 75,123 data points on the Volve oil field with various reservoir rocks is used to develop the predicted models. The results show the reliability of the machine learning methods to estimate the pore pressure and minimum horizontal stress from well-log data. It shows similar prediction accuracy when using unseen data. The comparison of MLP and RBF models presents that the MLP model for predicting and estimating pore pressure and minimum horizontal stress has higher accuracy than the RBF model. [ABSTRACT FROM AUTHOR]

Wellbore instability occurs when an open well cannot maintain its size, shape, or structural stability. It is a common issue especially in shale sections and can be caused by both mechanical factors, such as poor drilling technique or weak rock, and chemical factors, such as interactions between the rock and drilling fluid. This problem can lead to costly and dangerous complications. In this study data from three wells in Nahr Umr Oil Field (NR-10, NR-12, and NR-14) in southern Iraq were analyzed to determine pore pressure and rock strength parameters, as well as in situ horizontal stresses. The results showed an increase in pore pressure and horizontal stress in shale units, and various geomechanical parameters were also estimated. The study showed the fault regime in the area is a strike-slip fault and suggested the estimated pore pressure values while drilling hole sections to prevent problems at abnormal and subnormal formations. [ABSTRACT FROM AUTHOR]

The undrained shearing behavior of the Jhelum Riverbed sands and the effect of fines content on their overall response and their static liquefaction potential are still elusive. In this context, the present study aims to understand the undrained shearing response and static liquefaction potential of Jhelum riverbed sands through a series of isotropically consolidated undrained compression (CIUC) triaxial tests. The effect of sand type and fines content were established through CIUC triaxial tests conducted on clean sands obtained from three different locations (Khanabal, Rajbagh, and Sopore) along the Jhelum River and sand-silt mixtures. Results showed that volumetric compressibility (mv) decreased by 67, 65, and 46% as the relative density increased from 15 to 50% for KS, RS, and SS sands, respectively. Compared to clean sands, an increase of 23 and 15% in mv was observed with the addition of 7 and 14% non-plastic fines, respectively. An increase in the undrained shearing resistance by factors of 2.12, 3.08, and 1.98 for KS, RS, and SS, respectively, is observed as the relative density increases from 15 to 50%. An increase in undrained strength by 79.2% is observed when the initial effective confining pressure ( p i ′ ) is increased from 50 to 150 kPa. It was also observed that Jhelum sands follow normal behavior of increasing contractile tendency as p i ′ increased from 50 to 150 kPa. Specimens with larger mean grain diameter (D50) and lower coefficient of uniformity (CU) values exhibited higher undrained strength as well as higher liquefaction resistance. Higher roundness and sphericity values facilitate a higher generation of excess pore water pressure, resulting in higher liquefaction potential. With the addition of non-plastic fines, the Sopore Sand-silt mixture exhibited higher liquefaction potential, more strain-softening behavior, and higher excess pore pressure, resulting in 83 and 51% reduction in p i ′ at 7 and 14% fines content, respectively. A unique critical state line in q - p ′ space is observed for sand silt mixtures. [ABSTRACT FROM AUTHOR]

As a waterless fracturing fluids for gas shale stimulation with low viscosity and strong diffusibility, supercritical CO2 is promising than the water by avoiding the clay hydration expansion and reducing reservoir damage. The permeability evolution influenced by the changes of the temperature and stress is the key to gas extraction in deep buried shale reservoirs. Thus, the study focuses on the coupling influence of effective stress, temperature, and CO2 adsorption expansion effects on the seepage characteristics of Silurian Longmaxi shale fractured by supercritical CO2. The results show that when the gas pressure is 1-3 MPa, the permeability decreases significantly with the increase in gas pressure, and the Klinkenberg effects plays a predominant role at this stage. When the gas pressure is 3-5 MPa, the permeability increases with the increase in gas pressure, and the influence of effective stress on permeability is dominant. The permeability decreases exponentially with the increase in effective stress. The permeability of shale after the adsorption of CO2 gas is significantly lower than that of before adsorption; the permeability decreases with the increase in temperature at 305.15 K-321.15 K, and with the increase in temperature, the permeability sensitivity to the temperature decreases. The permeability is closely related to supercritical CO2 injection pressure and volume stress; when the injection pressure of supercritical CO2 is constant, the permeability decreases with the increase in volume stress. The results can be used for the dynamic prediction of reservoir permeability and gas extraction in CO2-enhanced shale gas development. [ABSTRACT FROM AUTHOR]

To explore the feasibility of geogrid reinforcement as a promising countermeasure to improve the liquefaction and post-liquefaction resistance of calcareous sand, extensive undrained monotonic and multi-stage triaxial tests were performed on unreinforced and geogrid reinforced calcareous sand with different relative densities. The test results illustrate that pore pressure generation curves of unreinforced and reinforced calcareous sand gradually evolve from S-shaped to hyperbolic-shaped with the increase in relative density, cyclic stress ratio, and effective confining pressure. Following this, a pore pressure model applicable to both unreinforced and reinforced calcareous sand is proposed. The liquefaction resistance of calcareous sand increases with the increase in relative density, whereas an elevated cyclic stress ratio increases its liquefaction susceptibility. A virtually unique relationship can be observed between the liquefaction resistance normalized to the product of phase transformation strength ratio and relative density against the number of cycles for triggering liquefaction, providing an effective means of early assessing sand liquefaction resistance. Moreover, the geogrid exhibits excellent reinforcement efficiency in enhancing the liquefaction resistance of calcareous sand at relative densities of 50% and 70%. During the post-liquefaction stage, increasing relative density and geogrid reinforcement can accelerate the recovery of stiffness and strength for liquefied calcareous sand and improve the post-liquefaction strength. In general, geogrid reinforcement is considered a good alternative to densification for improving the engineering properties of calcareous sand and offers great application prospects in marine engineering construction. • The effects of geogrid reinforcement and relative density on the liquefaction and post-liquefaction behaviors of calcareous sand are investigated. • A pore pressure model applicable to both unreinforced and reinforced calcareous sand is proposed. • The inclusion of geogrid enhances the liquefaction resistance of calcareous sand. • Increasing relative density and geogrid reinforcement accelerate the recovery of stiffness and strength for liquefied calcareous sand and improve the shear strength during the post-liquefaction stage. • Geogrid reinforcement is considered a good alternative to densification for improving the engineering properties of calcareous sand and offers great application prospects in marine engineering construction. [ABSTRACT FROM AUTHOR]

The paper is devoted to a study of factors that provide the nonlinear mechanical influence of pore fluid on the stress state, strength, and fracture of permeable brittle materials. Two key factors are considered: pore pressure and viscous stresses in the interstitial fluid. Using a coupled dynamic model implemented in the numerical method of homogeneously deformable discrete elements, we verified for the first time that Stefan's viscous stress is responsible for the nontrivial and widely discussed effect of a significant increase in the dynamic strength of brittle solids in a fluid-saturated state compared to the dry state. Considering watered high-strength concrete, a quantitative estimate of the dimensionless factor of Stefan's stress was derived. The contributions of shearing and tearing-off fracture mechanisms to the total damage of a concrete sample under uniaxial compression with different strain rates are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents measurements of total pressures and pore pressures in the mixing chamber, the pore pressures in the soil in front of an earth pressure balance (EPB) at the Botlek Rail tunnel, as well as laboratory tests on foam infiltration behavior from foam–sand mixture to saturated sand. It shows that the plastering effect at the tunnel face is less effective for an EPB shield than for a slurry shield, as the pressure fluctuations are greater in the mixing chamber for an EPB shield, suggesting a higher water leakage at the tunnel face. The difference in the development of excess pore pressure at two different locations of the EPB shield suggests the influence of the soil permeability. Foam infiltration at the tunnel face can result in a low permeable layer that restricts the ground water flow. Results from laboratory tests suggest that foam infiltration will be influenced by foam injection ratio and soil permeability. As the foam infiltration length is only limited, no low permeable layer can be formed during drilling for fine sand conditions. While a larger foam infiltration length can be expected for medium sand condition. Field measurements on the development of pore pressures in the soils at the two different locations show agreement with the conclusions from laboratory tests. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petroleum Research & Studies is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rates of seismicity in the Delaware Basin of Texas and New Mexico increased from 10 earthquakes per year of local magnitude (ML) 3.0 and above in 2017 to more than 185 in 2022, coincident with increasing oil and gas production and wastewater re‐injection into strata shallow or deeper than producing intervals. Events of large magnitude—up to ML 5.4 to‐date—occur on faults extending into formations above the basement that have received more than four billion barrels of injection. Here, we demonstrate the link between injection geology, pore pressure evolution, fault stability, and induced seismicity in this region. We find that the injection targets are largely dolomitized platform carbonates with low (<5 vol.%) matrix porosity and fracture‐enhanced permeability with inherent heterogeneity in flow properties. A comprehensive, three‐dimensional geological model populated with reservoir properties is used for fluid flow modeling, with global calibration supplemented by dynamic injectivity data. Pore pressure changes with deep injection are up to 5 MPa from 1983 to 2023, increasing the native pore pressure state by 10% locally. Modeling results show that earthquakes occurring at distances of up to 30 km from deep injection have experienced small (<0.1 MPa) pore pressure increases, indicating that the faults hosting these earthquakes are highly sensitive to changes in effective stress and have lower frictional stability than the 0.6 generally assumed. These results serve as a critical step in understanding the stress changes that induce earthquakes in one of the most seismically active and geologically complex basins in the US. Plain Language Summary: Earthquakes have become more frequent in areas with historically little seismicity and are coincident in space and time with an increase in oil and gas production and the re‐injection of wastewater. Larger‐magnitude earthquakes occur on deep faults and generally within the crystalline basement. They are likely caused by wastewater injection into carbonate rocks above the basement, causing changes in pressure and stress on nearby faults. Results from this modeling work show that deep fluid injection increases pressure by up to 10% near deep injection wells. Key Points: Injection of oil field wastewater into deep strata in the Delaware Basin causes pore pressure changes of up to 5 MPaEarthquakes occurring in crystalline basement are likely induced by pore pressure diffusion associated with regional deep injectionMany basement‐rooted faults hosting earthquakes are optimally oriented, sensitive, and slip with small pore pressure perturbations [ABSTRACT FROM AUTHOR]

The semi-circular breakwater (SBW) has been implemented at numerous global locations due to its outstanding wave dissipation effectiveness and high structural performance. This study extends prior research by investigating the seabed dynamic response and hydrodynamic response characteristics around perforated SBWs. A coupled numerical model is developed to integrate waves, a semi-circular breakwater, and a sandy seabed. Wave behavior is simulated using Reynolds-averaged Navier–Stokes equations with a k-ε turbulence closure scheme, and the seabed response is numerically simulated using Biot's full-dynamic (u-w) equations. After verifying computational accuracy, a series of tests is conducted to explore the effects of marine environments and SBW characteristics. Test results reveal a positive correlation between seabed response and wave height, wave period, and perforation number, while showing a negative correlation between seabed response and water depth and perforation rate. The basic perforation type is more effective than front and rear perforation types in maintaining a stable flow field and seabed response. These findings provide insights for designing SBWs for effective wave dissipation and seabed stability in complex marine environments, offering valuable recommendations for future designs. [ABSTRACT FROM AUTHOR]

Predicting pore pressure is critical in every exploration venture because it prompts safe drilling, fluid design, casing emplacements, improved wellbore dependability, and water driven cracking enhancement. Hence, the objective of this paper was to predict and evaluate the pore pressure characteristics of a selected field in the Niger Delta Basin of Nigeria using appropriate standard methods. The results of the 1D pore pressure model from the Eaton and Bower’s sonic techniques revealed that the deviation from Normal Compaction Trend started at about 8350 ft as a result of overpressure. The determined break angle from the Fracture gradient formular, utilizing the Effective Stress Ratio (ESR), Overburden Pressure (OVP) and the anticipated Pore Pressure (PP) was estimated to be between 0.65 psi/ft and 0.725 psi/ft. Due to the use of overbalanced drilling in the Niger-Delta, wellbore pressure should be higher than the Hydrostatic pressure, but not as high as the fracture pressure. Therefore, the safe drilling window should likely be from 0.613 psi/ft to 0.645 psi/ft for the study area.

Abstract A two-dimensional unsteady seepage model for coal using a finite element program is developed, and the temporal variations of key factors such as water pressure and hydraulic gradient are analyzed in this paper. Additionally, the triaxial rock mechanical experiment and utilized pneumatic fracturing equipment on raw coal samples to investigate both hydraulic and pneumatic fracturing processes are conducted. Through these experiments, the relationship between pressure and crack formation and expansion are examined. The analysis reveals that the pore pressure gradient at the coal inlet reaches its peak during rapid surges in water pressure but diminishes over time. Conversely, the pore pressure gradient at the outlet side exhibits a gradual increase. Hydraulic fracturing is most likely to occur at the water inlet during sudden increases in water pressure. Besides, as the permeability of coal decreases, the duration for seepage stabilization prolongs due to the intensified pore pressure gradient resulting from sudden increases in water pressure. Moreover, an extended period of high hydraulic gradient further increases the risk of hydraulic fracturing. The experimental findings indicate that coal samples initially experience tensile failure influenced by water and air pressure. Subsequently, mode I cracks form under pressure, propagating along the fracture surface and becoming visible. The main types of failure observed in hydraulic and pneumatic fracturing are diametrical tensile failure, and the development of fractures can be categorized into three distinct stages, which contains the initial stage characterized by slight volume changes while water pressure increases, the expansion stage when pressure reaches the failure strength, and the crack closure stage marked by little or even decreasing volume changes during pressure unloading. The acoustic emission signal accurately corresponds to these three stages.

Objective The MS 6.8 earthquake that struck Luding County, Sichuan Province, on September 5, 2022, and its aftershocks have drawn widespread attention, especially concerning the potential risks of induced seismicity associated with the construction of high-dam reservoirs in regions with high seismic intensity. Previous studies have explored the possible link between reservoirs and seismic activity, without reaching a definitive conclusion. This study aims to assess the impact of water storage in the Dagangshan Reservoir on the surrounding strata and its correlation with recent seismic events. Methods Numerical simulation methods were employed using high-precision digital elevation model (DEM) data, fault data, and reservoir water level information to develop a three-dimensional poroelastic finite element numerical model extending from the surface to a depth of 25 km. By analyzing the hydrogeological conditions, lithology of rock masses, and groundwater dynamic changes, this study evaluated the seismic hazard risk of major faults, such as the Moxi Fault, and calculated variations in Coulomb stress and strata pore pressure at the hypocenter during the occurrence of the earthquake. Results The study indicates that, during the MS 6.8 Luding earthquake on September 5, 2022, the pore pressure at the epicenter reached 5 kPa, and the Coulomb stress increased by 3.6 kPa, suggesting that the impoundment of the Dagangshan Reservoir contributed to an increased risk along the Moxi Fault on the northwestern side of the reservoir. Using the source parameters of the MS 5.6 aftershock that occurred on January 26, 2023, it was observed that the impoundment caused a change in Coulomb stress at the epicenter of -0.69 kPa and a pore pressure of approximately 0.32 kPa. It is evident that the reservoir impoundment had a relatively minor impact on the fault activity where the MS 5.6 aftershock occurred and even exhibited a certain inhibitory effect. Moreover, seismic activity was mainly concentrated in two areas on the western side of the reservoir, with both the seismicity and expected magnitudes in these regions reflecting a higher risk of earthquakes. Conclusion This study demonstrates a correlation between the impoundment activities of the Dagangshan Reservoir and the occurrence of the Luding County earthquake and its aftershocks. The spatial distribution characteristics of the earthquakes align with the geological stress adjustment patterns following the reservoir impoundment, which played a promotive role in the occurrence of the MS 6.8 main shock, leading to an increased risk of earthquakes in the Moxi Fault region. This finding is significant for understanding the mechanisms of reservoir-induced earthquakes, subsequent aftershock analyses, and earthquake disaster prevention and mitigation efforts. Significance The results of this study provide new insights into the complex relationship between reservoir water storage and seismic events. This study offers a scientific basis for future assessments of seismic risks of reservoir design and operation, contributing to improved accuracy in earthquake early warnings and efficiency in disaster prevention and mitigation efforts.

Purposes Increasing the permeability of coal reservoirs is a key technology to improve the recovery rate of coalbed methane, and in-situ thermal injection mining is an effective method to enhance coalbed methane production. Methods In order to explore the change rule of coal reservoir permeability under the coupling of heat, fluid, and solid, pyrolysis seepage experiments of anthracite with different burial depths and temperatures were conducted, and theoretical analysis and research were conducted on the experimental results. Findings The results showed that: 1) Under three-dimensional effective stress, the permeability of pyrolysis anthracite varies with temperature and pore pressure in a "V" shape, with a significant rebound phenomenon, which decreases with the increase of burial depth. When the pore pressure is less than the critical pore pressure and the temperature is lower than 70 ℃, the permeability of the coal body mainly depends on the slippage effect. When the pore pressure is greater than the critical pore pressure and the temperature is higher than 70 ℃, the permeability mainly depends on thermal expansion and the opening degree of pore pressure on the fracture, and the impact of thermal stimulation on the permeability is much greater than that of pore pressure. 2) The critical pore pressure is between 1 and 1.5 MPa, the influence of slippage effect on permeability gradually decreases with the increase of temperature, and the gradient of influence reduction increases with the increase of burial depth. 3) The fracture opening coefficient increases with the increase of temperature and burial depth, but the higher the temperature, the smaller the change in the sensitivity of permeability to pore pressure under different burial depths. Conclusions These research results further enrich the theory of in-situ thermal injection mining of coalbed methane, and provide valuable data reference for enhanced permeability of coalbed methane.

Deep rock is under a complex geological environment with high geo-stress, high osmotic pressure, and strong dynamic disturbance, under the action of the three, the rock body is more prone to damage and rupture, inducing sudden water surges, seepage, blowouts and other engineering geologic hazards. Therefore, investigating the rock dynamics of the rock under hydraulic-mechanical coupling is one of the prerequisites for conducting rock engineering construction. In recent years, many scholars have obtained some fruitful research results in the study of rock dynamics properties under the consideration of water and different stress states. In order to provide more comprehensive guidance for engineering construction and facilitate the subsequent research, the above work is reviewed and summarized in terms of experimental setups, test results, and the mechanism of the confining pressure and water content. Firstly, the basic principle of the split Hopkinson pressure bar (SHPB) system and the device improvements used to simulate the deep rock storage environment are introduced, including the confine-ment-coupled SHPB system and pore-pressure (osmotic pressure)-coupled SHPB system. The advantages and shortcomings of each type of device in the study of rock dynamics under hydraulic-mechanical coupling are briefly analyzed. Secondly, the dynamic mechanical response characteristics of rocks hydraulic-mechanical coupling considering different stress states (uniaxial confining, triaxial confining) are summarized. The dynamic mechanical response of deep rocks under fixed preset pore pressure and osmotic pressure coupling and its law of variation with pore water pressure and osmotic pressure are described in detail. Subsequently, the mechanism of confining pressure on the dynamic properties of the rock is outlined, and the influence law under different stress states is analyzed. The strengthening and weakening microscopic mechanism and quantitative expression of the dynamic mechanical properties of the rock by water are recapped. Finally, the dynamic response of deep rocks under hydraulic-mechanical coupling is summed up, and the further experimental research work and the research direction of deep rock dynamics are proposed.

Abstract To further investigate the weakening effect of pore water pressure on intact rock mechanics properties and characteristics of fracture surface after failure, direct shear tests of sandstone were conducted under different pore pressure. A 3D scanner was employed to digitize the morphology of the post-shear fracture surface. The variogram function was applied to quantify the anisotropic characteristics of post-shear fracture surface. The relationship between deformation during shear failure of intact rock and quantitative parameters of fracture surface after shear failure was initially established. It can be found that amplitudes of the sinusoidal surface determine the maximum value of variogram, and period affect lag distance that reach the maximum value of variogram. Test results revealed that the increase of pore pressure has obvious weakening effect on shear strength and deformation of rock. Moreover, the increase of pore pressure makes the shear fracture surface flatter. It can be obtained that both Sill max and Range max are positively related to shear strain, but negatively related to normal strain.

Episodic Tremors and Slip (ETS) are highly susceptible and sensitive to external stress perturbations. The tidal and remote triggering phenomena of tremors are well-documented globally, however, the significance of the delayed triggering mechanism remains elusive. In this paper, the possibilities of the tremor modulation by the Lamb waves induced from the Hunga Tonga-Hunga Ha’apai volcanic eruption (SW Pacific) on 15 January 2022 have been explored. The increasing activity of tremors after eruption has been explored at the study region of Cascadia subduction zone where such tremor do not correlate with tidal stress perturbations or remote triggering by far-off or near-by earthquakes. The increasing tremor activities are observed during the propagation of the Lamb wave cycles (L1, L2, L3, L4) and more interestingly during inter-ETS period. From the seismic waveform analysis, we observe two coherent packets of teleseismic energy on 15 January 2022, which corresponds to arrival of surface and Lamb waves, respectively. The delayed triggering of tremors may be linked either with the teleseismic surface waves or Lamb waves from the volcanic explosion, or both. Although we cannot rule out coincidence, the delayed triggering by Lamb waves appears to be consistent with magnitude-dependent time delay and 2-D coupled pore pressure induced diffusion model.

A two-dimensional unsteady seepage model for coal using a finite element program is developed, and the temporal variations of key factors such as water pressure and hydraulic gradient are analyzed in this paper. Additionally, the triaxial rock mechanical experiment and utilized pneumatic fracturing equipment on raw coal samples to investigate both hydraulic and pneumatic fracturing processes are conducted. Through these experiments, the relationship between pressure and crack formation and expansion are examined. The analysis reveals that the pore pressure gradient at the coal inlet reaches its peak during rapid surges in water pressure but diminishes over time. Conversely, the pore pressure gradient at the outlet side exhibits a gradual increase. Hydraulic fracturing is most likely to occur at the water inlet during sudden increases in water pressure. Besides, as the permeability of coal decreases, the duration for seepage stabilization prolongs due to the intensified pore pressure gradient resulting from sudden increases in water pressure. Moreover, an extended period of high hydraulic gradient further increases the risk of hydraulic fracturing. The experimental findings indicate that coal samples initially experience tensile failure influenced by water and air pressure. Subsequently, mode I cracks form under pressure, propagating along the fracture surface and becoming visible. The main types of failure observed in hydraulic and pneumatic fracturing are diametrical tensile failure, and the development of fractures can be categorized into three distinct stages, which contains the initial stage characterized by slight volume changes while water pressure increases, the expansion stage when pressure reaches the failure strength, and the crack closure stage marked by little or even decreasing volume changes during pressure unloading. The acoustic emission signal accurately corresponds to these three stages. [ABSTRACT FROM AUTHOR]

Pore pressure prediction is fundamental when drilling deep and geologically complex reservoirs. Even in relatively well-characterized hydrocarbon reservoir fields, with a considerable number of drilled wells, when located in challenging geological environments, poor prediction of abnormal pore pressure might result in catastrophic events that can cause harm to human lives and infrastructures. To better quantify drilling risks, the uncertainty associated with the pore pressure prediction should be integrated within the geo-modelling workflow. Leveraging a challenging real case from the Brazilian pre-salt, the work presented herein proposes a seismic-driven gradient pore pressure modelling workflow, which combines machine learning and geostatistical co-simulation to predict high-resolution gradient pore pressure volumes. First, existing angle-dependent seismic reflection data are inverted for P- and S-wave velocity and density. Then, K-nearest neighbor is used to create a regression model between pore pressure gradient and P- and S-wave velocity, density and depth based on the well log information. The trained model is applied to predict a three-dimensional gradient pore pressure model from the models obtained from geostatistical seismic inversion. This gradient pore pressure model is a smooth representation of the highly variable subsurface and is used as secondary variable in stochastic sequential co-simulation with joint probability distributions to generate multiple high-resolution realizations of gradient pore pressure. The ensemble of co-simulated models can be used to assess the spatial uncertainty about the gradient pore pressure predictions. The results of the application example show the ability of the method to reproduce the spatial patterns observed in the seismic data and to reproduce existing gradient pore pressure well logs at two blind well locations, which were not used to condition the gradient pore pressure predictions. [ABSTRACT FROM AUTHOR]

A growing number of large data sets have created challenges for the oil and gas industry in predicting reservoir parameters and assessing well productivity through efficient and cost-effective techniques. The design of drilling plans for a high-pressure tight-sand reservoir requires accurate estimations of pore pressure (Pp) and reservoir parameters. The objective of this study is to predict and compare the Pp of Huizhou Sag, Pearl River Mouth Basin, China, using conventional techniques and machine learning (ML) algorithms. We investigated the characteristics of low-permeability reservoirs by observing well-logging data sets and cores and examining thin sections under a microscope. In the reservoir zone, the average hydrocarbon saturation is 55%, and the average effective porosity is 11%. The tight sandstone reservoirs consist of fine- to extremely fine-grained argillaceous feldspathic sandstone. The mean absolute error for reservoir property prediction is 1.3%, 2.2%, and 4.8%, respectively, for effective porosity, shale volume, and water saturation. Moreover, the ML algorithm was employed to cross-check the validity of the prediction of Pp. Combining conventional and ML techniques with the core data demonstrates a correlation coefficient (R2) of 0.9587, indicating that ML techniques are the most effective in testing well data. This study shows that ML can effectively predict Pp at subsequent depths in adjacent geologically similar locations. Compared to conventional methods, a substantial data set and ML algorithms improve the precision of Pp predictions. [ABSTRACT FROM AUTHOR]

Concrete subjected to fire loads is susceptible to explosive spalling, which can lead to the exposure of reinforcing steel bars to the fire, substantially jeopardizing the structural safety and stability. The spalling of fire-loaded concrete is closely related to the evolution of pore pressure and temperature. Conventional analytical methods involve the resolution of complex, strongly coupled multifield equations, necessitating significant computational efforts. To rapidly and accurately obtain the distributions of pore-pressure and temperature, the Pix2Pix model is adopted in this work, which is celebrated for its capabilities in image generation. The open-source dataset used herein features RGB images we generated using a sophisticated coupledmodel, while the grayscale images encapsulate the 15 principal variables influencing spalling. After conducting a series of tests with different layers configurations, activation functions and loss functions, the Pix2Pix model suitable for assessing the spalling risk of fire-loaded concrete has been meticulously designed and trained. The applicability and reliability of the Pix2Pix model in concrete parameter prediction are verified by comparing its outcomes with those derived from the strong coupling THC model. Notably, for the practical engineering applications, our findings indicate that utilizing monochrome images as the initial target for analysis yields more dependable results. This work not only offers valuable insights for civil engineers specializing in concrete structures but also establishes a robust methodological approach for researchers seeking to create similar predictive models. [ABSTRACT FROM AUTHOR]

Excessively high pore water pressure presents unpredictable risks to the safety of rock tunnels in mountainous regions that are predominantly composed of limestone. Investigating the creep characteristics and permeability evolution of limestone under varying hydrated conditions is crucial for a better understanding of the delayed deformation mechanisms of limestone rock tunnels. To this end, this paper initially conducts a series of multi-stage triaxial creep tests on limestone samples under varying pore water pressures. The experiment examines how pore water pressure affects limestone's creep strain, strain rate, long-term strength, lifespan, and permeability, all within the context of hydraulic-mechanical (HM) coupling. To better describe the creep behavior associated with pore water pressure, this paper proposes a new nonlinear fractional creep constitutive model. This constitutive model depicts the initial, steady-state, and accelerated phases of limestone's creep behavior. Finally, the proposed model is applied to the numerical realization of deformation in limestone tunnel, validating the effectiveness of the proposed constitutive model in predicting tunnel's creep deformation. This research enhances our understanding of limestone's creep characteristics and permeability evolution under HM coupling, laying a foundation for assessing the long-term stability of mountain tunnels. [ABSTRACT FROM AUTHOR]

Purpose: The paper aims to clarify the distribution of excess pore pressure during cone penetration in two-layered clay and its influence on penetrometer resistance. Design/methodology/approach: An arbitrary Lagrangian–Eulerian scheme is adopted to preserve the quality of mesh throughout the numerical simulation. Simplified methods of layered penetration and coupled pore pressure analysis of cone penetration have been proposed and verified by previous studies. The investigation is then extended by the present work to study the cone penetration test in a two-layered clay profile assumed to be homogeneous with the modified Cam clay model. Findings: The reduction of the range of pore pressure with decreasing PF will cause a decrease of the sensing distance. The PF of the underlying soil is one of the factors that determine the development distance. The interface can be obtained by taking the position of the maximum curvature of the penetrometer resistance curve in the case of stiff clay overlying soft clay. In the case of soft clay overlying stiff clay, the interface locates at the maximum curvature of the penetrometer resistance curve above about 1.6D. Research limitations/implications: The cone penetration analyses in this paper are conducted assuming smooth soil-cone contact. Originality/value: A simplified method based on ALE in Abaqus/Explicit is proposed for layered penetration, which solves the problem of mesh distortion at the interface between two materials. The stiffness equivalent method is also proposed to couple pore pressure during cone penetration, which achieves efficient coupling of pore water pressure in large deformations. [ABSTRACT FROM AUTHOR]

Pore pressure (PP) information plays an important role in analysing the geomechanical properties of the reservoir and hydrocarbon field development. PP prediction is an essential requirement to ensure safe drilling operations and it is a fundamental input for well design, and mud weight estimation for wellbore stability. However, the pore pressure trend prediction in complex geological provinces is challenging particularly at oceanic slope setting, where sedimentation rate is relatively high and PP can be driven by various complex geo-processes. To overcome these difficulties, an advanced machine learning (ML) tool is implemented in combination with empirical methods. The empirical method for PP prediction is comprised of data pre-processing and model establishment stage. Eaton's method and Porosity method have been used for PP calculation of the well U1517A located at Tuaheni Landslide Complex of Hikurangi Subduction zone of IODP expedition 372. Gamma-ray, sonic travel time, bulk density and sonic derived porosity are extracted from well log data for the theoretical framework construction. The normal compaction trend (NCT) curve analysis is used to check the optimum fitting of the low permeable zone data. The statistical analysis is done using the histogram analysis and Pearson correlation coefficient matrix with PP data series to identify potential input combinations for ML-based predictive model development. The dataset is prepared and divided into two parts: Training and Testing. The PP data and well log of borehole U1517A is pre-processed to scale in between [-1, þ1] to fit into the input range of the non-linear activation/transfer function of the decision tree regression model. The Decision Tree Regression (DTR) algorithm is built and compared to the model performance to predict the PP and identify the overpressure zone in Hikurangi Tuaheni Zone of IODP Expedition 372. [ABSTRACT FROM AUTHOR]

Analyzing the mechanical deformation of the hydrate-bearing layer during hydrate exploitation requires the establishment of a robust model for the isotropic compression behavior of methane hydrate-bearing sediment (MHBS), which is of utmost importance. However, few research involves developing the isotropic compression model. In this paper, a novel simplified isotropic compression model of MHBS is developed according to the isotropic compression characteristics of MHBS. To address the effect of temperature and pore pressure condition (P-T condition) on the isotropic compression curve (ICC) of MHBS, the phase state parameter, as a representative for P-T condition, is used to characterize the ICC of MHBS with varying P-T condition. The fact that the predicted and measured ICCs display a strong agreement indicates that the simplified compression model developed in this study can effectively capture the isotropic compression behavior of MHBS under various hydrate saturation, temperature, and pore pressure conditions. • A novel simplified isotropic compression model is developed for MHBS. • The influences of hydrate saturation on ICCs are addressed. • The effects of temperature and pore pressure on ICCs are addressed. [ABSTRACT FROM AUTHOR]

The High Dam is one of the world's biggest embankments dams. Moreover, the new city of Aswan, which locates on the western side of the Nile River, is one of the cities that was established to overcome the growing population problem. Therefore, the detailed geophysical studies for the active faults are of more importance for assessing the seismic stability for both of them. Indeed, the emergency spillway fault was documented as a normal and inactive fault. While, a moderate earthquake (ML = 4.6) was recorded along this fault in 2010, about 4.5 km away from the Dam. Hence, its activity must be re-evaluated. The seismic activity along the fault and its extension has been studied. The seismicity distributions and the fault plane solution indicate normal faulting with a strike-slip component and shallow focal depth. Moreover, pore pressure and fluid diffusion play an essential role in fault activation process. On the other hand, the magnetic data for the research area was subjected to a detailed analysis. 2D spectrum analysis and 3D Euler deconvolution methods, were used to analyze and interpret the aeromagnetic anomaly data so as to better understand the tectonic framework of the study region. Finally, the integrated geophysical data delineate the trend of the emergency spillway fault which extends NW–SE. This fault could assist in updating the current seismic source model around the High Dam and new Aswan city for evaluating the seismic hazard for both of them. [ABSTRACT FROM AUTHOR]

Pore pressure prediction is a critical parameter in petroleum engineering and is essential for safe drilling operations and wellbore stability. However, traditional methods for pore pressure prediction, such as empirical correlations, require selecting appropriate input parameters and may not capture the complex relationships between these parameters and the pore pressure. In contrast, artificial neural networks (ANNs) can learn complex relationships between inputs and outputs from data. This paper presents a new empirical correlation for predicting pore pressure using ANNs. The proposed method uses 42 datasets of well log data, including temperature, porosity, and water saturation, to train ANNs for pore pressure prediction. The trained model, with the Bayesian regularization backpropagation function, predicts the pore pressure with an average absolute percentage error (AAPE) and correlation coefficient (R) of 4.22% and 0.875, respectively. The trained ANN is then used to develop a new empirical correlation that relates pore pressure to the input parameters considering the weights and biases of the optimized ANN model. To validate the proposed correlation, it is applied to a blind dataset, where the model successfully predicts the pore pressure with an AAPE of 5.44% and R of 0.957. The results show that the proposed correlation provides accurate and reliable predictions of pore pressure. The proposed method provides a robust and accurate approach for predicting pore pressure in petroleum engineering applications, which can be used to improve drilling safety and wellbore stability. [ABSTRACT FROM AUTHOR]