Increase In Fluid Pressure Research Articles

High-Temperature Hydrothermal Fluid Evolution, Archean Alkalic Intrusion-Related Mineralization, Karari-Whirling Dervish Gold Deposit, Western Australia

Abstract Genetic models that propose a magmatic-hydrothermal source for the gold ore fluid in Archean gold deposits hosted by, or spatially associated with, felsic to intermediate magmas are contentious. The Archean Karari-Whirling Dervish gold deposit (>1 Moz at approximately 3 g/t Au), Kurnalpi terrane, Yilgarn craton, Western Australia, provides an opportunity to test such models because it is hosted by quartz-poor, volcaniclastic metasedimentary rocks that were intruded by Neoarchean oxidized syenitic magma. A carapace of hydrothermal alteration in felsic to intermediate volcaniclastic rocks that overlie the eastern intrusive complex evolved from pervasive potassic (biotite) alteration through structurally controlled tabular zones of sodic (albitic) alteration to localized potassic (K-feldspar) alteration within the albitized rocks; the last of these was directly associated with gold. Low-grade gold was deposited with hydrothermal K-feldspar in a pervasive fracture network as nanoparticles or crystallographic substitution in disseminated pyrite, probably as a result of redox reactions between an oxidized, potassic ore fluid and reduced, sodic host rocks. Subsequent fracturing of the volcaniclastic host rocks, under increasing fluid pressure, produced biotite-rutile-pyrite stringers and quartz-pyrite veins with K-feldspar-dolomite-pyrite alteration selvages. Pyrite associated with both of these events contains numerous inclusions of native gold and constitutes the high-grade component of mineralization (>3 g/t Au). Geothermometric data (biotite-apatite, Ti-in-biotite, Zr-in-rutile) indicate that these hydrothermal events took place at temperatures between 500° and 650°C; other mineral compositional (biotite, rutile) and S isotope data (δ34S is –11 to 0 per mil) show that the hydrothermal fluids responsible for potassic (biotite) and potassic (K-feldspar) alteration were moderately to strongly oxidized. The ∆33S signature of pyrite indicates a mantle source, and allows only minor or no crustal involvement, for the ore fluid. The fluid responsible for high-temperature, oxidized hydrothermal alteration and gold mineralization is identified as the magmatic-hydrothermal phase that exsolved from spatially associated syenitic magmas. On the basis of this interpretation, Karari-Whirling Dervish is classified as an alkalic intrusion-related gold deposit.

Managing Induced Seismicity Risks From Enhanced Geothermal Systems: A Good Practice Guideline

AbstractGeothermal energy is a green source of power that could play an important role in climate‐conscious energy portfolios; enhanced geothermal systems (EGS) have the potential to scale up exploitation of thermal resources. During hydraulic fracturing, fluids injected under high‐pressure cause the rock mass to fail, stimulating fractures that improve fluid connectivity. However, this increase of pore fluid pressure can also reactivate pre‐existing fault systems, potentially inducing earthquakes of significant size. Induced earthquakes are a significant concern for EGS operations. In some cases, ground shaking nuisance, building damages, or injuries have spurred the early termination of projects (e.g., Basel, Pohang). On the other hand, EGS operations at Soultz‐sous‐Forêts (France), Helsinki (Finland), Blue Mountain (Nevada, USA), and Utah FORGE (USA) have adequately managed induced earthquake risks. The success of an EGS operation depends on economical reservoir enhancements, while maintaining acceptable seismic risk levels. This requires state‐of‐the‐art seismic risk management. This article reviews domains of seismology, earthquake engineering, risk management, and communication. We then synthesize “good practice” recommendations for evaluating, mitigating, and communicating the risk of induced seismicity. We advocate for a modular approach. Recommendations are provided for key technical aspects including (a) a seismic risk management framework, (b) seismic risk pre‐screening, (c) comprehensive seismic hazard and risk evaluation, (d) traffic light protocol designs, (e) seismic monitoring implementation, and (f) step‐by‐step communication plans. Our recommendations adhere to regulatory best practices, to ensure their general applicability. Our guidelines provide a template for effective earthquake risk management and future research directions.

Wireless and Battery-Free Sensor for Interstitial Fluid Pressure Monitoring.

Congestive heart failure (CHF) is a fatal disease with progressive severity and no cure; the heart's inability to adequately pump blood leads to fluid accumulation and frequent hospital readmissions after initial treatments. Therefore, it is imperative to continuously monitor CHF patients during its early stages to slow its progression and enable timely medical interventions for optimal treatment. An increase in interstitial fluid pressure (IFP) is indicative of acute CHF exacerbation, making IFP a viable biomarker for predicting upcoming CHF if continuously monitored. In this paper, we present an inductor-capacitor (LC) sensor for subcutaneous wireless and continuous IFP monitoring. The sensor is composed of inexpensive planar copper coils defined by a simple craft cutter, which serves as both the inductor and capacitor. Because of its sensing mechanism, the sensor does not require batteries and can wirelessly transmit pressure information. The sensor has a low-profile form factor for subcutaneous implantation and can communicate with a readout device through 4 layers of skin (12.7 mm thick in total). With a soft silicone rubber as the dielectric material between the copper coils, the sensor demonstrates an average sensitivity as high as -8.03 MHz/mmHg during in vitro simulations.

A laboratory perspective on accelerating preparatory processes before earthquakes and implications for foreshock detectability

Dynamic failure in the laboratory is commonly preceded by many foreshocks which accompany premonitory aseismic slip. Aseismic slip is also thought to govern earthquake nucleation in nature, yet, foreshocks are rare. Here, we examine how heterogeneity due to different roughness, damage and pore pressures affects premonitory slip and acoustic emission characteristics. High fluid pressures increase stiffness and reduce heterogeneity which promotes more rapid slip acceleration and shorter precursory periods, similar to the effect of low geometric heterogeneity on smooth faults. The associated acoustic emission activity in low-heterogeneity samples becomes increasingly dominated by earthquake-like double-couple focal mechanisms. The similarity of fluid pressure increase and roughness reduction suggests that increased stress and geometric homogeneity may substantially shorten the duration of foreshock activity. Gradual fault activation and extended foreshock activity is more likely observable on immature faults at shallow depth.

Micro-fracture propagation and numerical simulation of fracture propagation under thermal simulation experiment of organic-rich shale: Chang-7 source rock in Yanchang, Ordos Basin

Organic-rich shale as a high-quality source rock which is usually deposited in a high-temperature and high-pressure environment, and its internal organic matter will gradually transform into hydrocarbon and be discharged from shale. However, shale has polar porosity and permeability, making it difficult for hydrocarbon to be discharged from the shale through the pore throat. The latest research suggests that due to the strong hydrocarbon generation potential of shale rich in organic matter, the pressure generated by hydrocarbon can cause micro-fracture in the shale, leading to the expulsion of hydrocarbon from the micro-fracture. Therefore, this article uses hydrocarbon generation simulation experiments and Comsol Multiphysics to analyze the mechanical characteristics and damage propagation of micro-fracture during shale hydrocarbon generation process. The results show that with the increase of temperature and fluid pressure, micro-fracture of different lengths have different initial fracture pressures, and during the diffusion of micro-fracture, the stress inside the shale matrix and micro-fracture exhibits different diffusion characteristics.

Modelling of water injection-induced shear stimulation and heat extraction in hot fractured reservoirs

Hydroshearing has been proposed as an effective technique for enhancing the permeability of fractured geothermal reservoirs. This approach involves complicated thermo-hydro-mechanical (THM) coupling, but the shear behaviour and its effect on flow and heat transfer are often simplified. In this study, Barton–Bandis (BB) joint behaviour is extended to include nonlinear rock joint deformation, shear dilation and post peak softening and healing behaviours. Two models of field-scale fractured geothermal reservoirs are considered. In addition, the widely used Mohr-Coulomb (MC) model is also incorporated into the THM coupled model for comparison. The results show that cold water injection-induced high-temperature rock contraction and fluid pressure increase, reducing the effective stress and promoting fracture shear deformation and irreversible slip. Moreover, shear dilation, shear softening, and nonlinear fracture opening notably alter reservoir permeability. The two models exhibit entirely different behaviours due to different pathway evolutions and consequent pressure build-up. The BB model displays a larger shear disturbance zone than the MC model, significantly enhancing the permeability and heat extraction within the fractured reservoirs. Accurate descriptions of the mechanical behaviour of rock fractures in hydroshearing models are crucial, suggesting the potential of these models to enhance fractured reservoirs and regulate fracturing for improved geothermal heat extraction.

Effect of thermal maturation and organic matter content on oil shale fracturing

The Pabdeh Formation represents organic matter enrichment in some oil fields, which can be considered a source rock. This study is based on the Rock–Eval, Iatroscan, and electron microscopy imaging results before and after heating the samples. We discovered this immature shale that undergoes burial and diagenesis, in which organic matter is converted into hydrocarbons. Primary migration is the process that transports hydrocarbons in the source rock. We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion. Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons, but as catagenesis progressed, the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release. The transformation of solid kerogen into low-density bitumen/oil increased the pressure, leading to the development of damage zones in the source rock. The Pabdeh Formation’s small porethroats hindered effective expulsion, causing an increase in pore fluid pressure inside the initial microfractures. The stress accumulated due to hydrocarbon production, reaching the rock’s fracture strength, further contributed to damage zone development. During the expansion process, microfractures preferentially grew in low-strength pathways such as lithology changes, laminae boundaries, and pre-existing microfractures. When the porous pressure created by each kerogen overlapped, individual microfractures interconnected, forming a network of microfractures within the source rock. This research sheds light on the complex interplay between temperature, hydrocarbon generation, and the development of expulsion fractures in the Pabdeh Formation, providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings.

Relation between earthquake swarm activity and tides in the Noto region, Japan

The Noto region in Japan has been experiencing earthquake swarm activity since mid-2018, with repeated rises and falls in activity. Crustal deformation (expansion and uplift) observed there since the end of 2020 has been connected to crustal fluids. Studies in other regions have suggested that tides are related to earthquake swarm activities associated with crustal fluids. Therefore, we investigated whether tides are also involved in the Noto earthquake swarm activity. Our results suggest a tidal correlation only at greater depths in the southern part of the analyzed area (‘region Sd’). There, we inferred that an increase in pore fluid pressure caused by the inflow of deep fluids may have led to a decrease in fault fracture strength, making the local seismicity relatively susceptible to the effects of tidal forces. The significantly high value in region Sd of the scaling parameter b\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$b$$\\end{document} of the Gutenberg–Richter law (describing the earthquake magnitude–frequency distribution) and observed crustal deformation are consistent with this interpretation.Graphical

Examining the Connections Between Earthquake Swarms, Crustal Fluids, and Large Earthquakes in the Context of the 2020–2024 Noto Peninsula, Japan, Earthquake Sequence

AbstractEarthquake swarms are most commonly composed of small‐magnitude earthquakes. However, a recent study by Yoshida, Uchida, et al. (2023, https://doi.org/10.1029/2023GL106023) analyzed a swarm beneath the Noto Peninsula in Japan that, after more than two years of moderate‐magnitude seismicity, triggered the moment magnitude (Mw) 6.2 Suzu mainshock in May 2023. Based on high‐precision earthquake locations and a slip inversion of the mainshock, these authors found that the Mw 6.2 Suzu earthquake occurred on the updip extension of a fault that was active during the swarm, likely driven by increased fluid pressure. After publication of that paper, a much larger and more destructive Mw 7.5 event occurred nearby on 1 January 2024. These events underscore the potential for swarms to be precursors to large, damaging earthquakes. Forecasting the eventual evolution of swarms is currently very challenging but could be aided in the future by new observations and models.

Simultaneous optimization of crude oil refinery vacuum distillation column and corresponding ejector system

A vacuum distillation unit (VDU) is a relatively complex crude oil refining process that usually overlooked in researches. A detailed review of the corresponding literature reveals that most of the limited existing researches focus on either the study of the vacuum tower alone or its vacuum creating ejector system. For the first time, the combination of VDU tower and corresponding ejectors are studied in this article by resorting to coupling of Aspen-HYSYS simulation software with Ansys-FLUENT computational fluid dynamic. Both simulations were initially validated by using two sets of experimental and industrial data, borrowed from literature.Optimization of an industrial unit improved its process economics by boosting the heavy vacuum gasoil production around 38% and reducing the less valuable cut of vacuum residue by 28%, which increases the overall earnings of the optimal VDU column economics over 140 MM$/year. Furthermore, sensitivity analysis of the VDU ejector system revealed that the primary steam cost does not depend on the corresponding temperature, while, it rapidly rises, when the motive fluid pressure increases. The overall simulation results of the VDU tower and corresponding ejector system concluded that the lower primary steam pressures are more favorable both from operational and economical standpoints.

Origin and geological significance of the first discovered seafloor oil seepage in the Beikang Basin, southern South China Sea

Seafloor oil seepage, resulting from fluids migration from depth, provides valuable insights into the characteristics of potential source rocks and hydrocarbons. For the first time, seafloor seepage oils were obtained by piston coring in the Beikang Basin, southern South China Sea (SSCS). Based on integrated analysis of the seismic data, core sediments, porewater, headspace gas and heat flow, the geochemical characteristics of seafloor seepage oils and their geological implications were elucidated. Results indicate that deep-sourced hydrocarbons intruded into subsurface sediments via paleo-uplift-related faults, fluid seepage pipes and mixed with in-situ modern marine sediments. Biomarkers suggest the presence of both marine and terrestrial organic matter, as well as a diverse range of thermal maturity levels from immature to mature. The seafloor seepage oil was most likely originated from coal-related source rocks in the Oligocene-Lower Miocene. Deep hydrocarbons were expelled through fractures induced by hydrocarbon-generating overpressure, as well as source rock-connecting faults and finally accumulated atop the paleo-uplift beneath the T3 unconformity. The gradually increased fluid pressure ultimately leads to the fracturing of overlying caprocks, resulting in the formation of fluid seepage pipe and the occurrence of oil seepage on the seafloor. Seafloor oil seepage and the accompanied high methane flux caused biogeochemical process, elements cycling and shoaled the depth of sulfate-methane transition zone (SMTZ), which provides valuable information in indicating gas hydrates occurrence. This study offers significant geological and geochemical information to reveal potential origin of source rocks and hydrocarbons, particularly in the case of limited drilling wells in the SSCS. In addition, this study also advances the understanding of gas-bearing fluids activity and the coupling relationship between deep and shallow strata under a focused fluid seepage background.

Sealing Performance of Ethylene Propylene Diene Monomer Seals for Proton Exchange Membrane Fuel Cells

The reliability of the sealing system of a proton exchange membrane fuel cell (PEMFC) is a prerequisite for ensuring the efficient and safe operation of the cell stack. In consideration of the actual assembly process, a local model of single‐cell sealing structure is constructed using a rounded corner rectangular sealing gasket structure. Apart from that, the effects of fluid pressure, bipolar plate offset, sealing gasket size, steady‐state temperature field, and seal structure on the sealing performance of PEMFC are investigated. As shown by results, with the increase of fluid pressure and sealing gasket width, the contact pressure is increased and the sealing performance is also improved. However, the increase of sealing gasket height is unfavorable to the stability and sealing performance of the stack. Meanwhile, excessive offset error leads to a sharp decrease in contact length and contact pressure at the sealing interface, which reduces the stability of the stack. With the increase of the operating temperature, the thermal expansion of the gasket increases and the contact performance improves significantly. Seals with rectangular structure have some advantages in terms of contact stability and standard deviation of contact pressure.

EVIDENCE OF THE INVOLVEMENT OF STRUCTURAL PREDISPOSITIONS OF THE CRYSTALLINE BASEMENT IN THE OBSERVATION OF MICROEARTHQUAKES IN THE WADI FIRA IN EASTERN CHAD

The seismically active regions of the world are modelled on zones where the crust is constantly evolving, subduction zones or seismically active zones such as the East African Rift. Chad is not one of these zones, because towards the end of the Precambrian, Chad's crustal evolution came to an end and it became part of a stable zone. Nevertheless, micro-earthquakes of up to magnitude four have been recorded in the Wadi-Fira region thanks to the Abéché ABC seismological station. The signals recorded have been processed and located in an area of very uneven high basement at the surface. Their origin is thought to be linked to the dynamics of the aquifer in relation to the rate of weathering, which plays an important role in the infiltration of water, causing the hydrostatic pressure to vary considerably. This variation in pressure can lead to a change in the state of stress in pre-existing faults. An increase in fluid pressure in the rock mass can create fault instability. The largest recorded event is located on the N30°E direction corresponding to the direction of an old non-active fault representing the Volcanic Line of Cameroon.

Evolution of shallow volcanic seismicity in the hydrothermal system of La Soufrière de Guadeloupe following the April 2018 Mlv 4.1 earthquake

La Soufrière de Guadeloupe volcano is characterized by seismo-volcanic activity dominantly linked to an active hydrothermal system. This microseismicity is shallow, mainly triggered in swarms and characterized by repeating earthquakes. Four recurrent families of Volcano-Tectonic (VT) repeaters have been identified and the main repeater accounts for 80% of detections. Stacking repeating seismic waveforms produces MASTER events with a high Signal-to-Noise Ratio (SNR) and thanks to the deployment of a temporary seismic nodal array, their absolute locations can be better constrained. Because we observe systematic positive residuals of P-wave arrival times at almost all stations, we investigate potential bias in the velocity model in the shallow part of the dome. By increasing the P-wave velocity and decreasing the VP/VS ratio from 1.8 to 1.69, we reduce these residuals and improve the local velocity model. We use this new velocity model to locate each VT event relatively to is own MASTER hypocenter. This procedure offers a new image of the hydrothermal seismic activity that we locate under the acid lake of the summit Tarissan crater, along a sub-vertical conduit. We also define a linear relationship between the logarithm of the peak amplitude of seismic events and their duration to obtain a pseudo local magnitude. The approach enables to accurately and automatically estimate the magnitude during the event detection. We show that after the occurrence in April 2018 of the largest earthquake (Mlv 4.1) since the last phreatic eruption in 1976–1977, the swarm frequency and amplitude increased significantly, and a new family of VT repeater emerges, accounting for up to 14% of detections. We show a quiescence in the main repeaters activity in the month following the April 2018 earthquake, suggesting a significant stress release within the volcanic system, which is likely related to dynamic stress changes rather than static stress variations caused by the earthquake. Moreover, we detect the emergence of a new family of repeaters 3 months after the event, located ∼100 m above the main repeater family, that could be related to a fluid pressure increase induced by the regional hydrological cycle, superimposed to the internal forcing driven by the hydrothermal system. Finally, using a statistical approach, we highlight seasonal periodicities in the number of events and the released seismic moment at La Soufrière de Guadeloupe, with a dominant peak of seismic activity in October–November and a second, less significant, peak of in April.

Sensitivity Analysis of Wellbore Mud Pressure towards Anisotropic Shale Properties, Pore Fluid Pressure and Far Field Stresses

The paper investigates the mud pressure to maintain the stability of wellbores drilled in transversely isotropic shale through sensitivity analyses, carried out with analytical and numerical modeling (FLAC). To this end, we interpreted the anisotropic strength of the Tournemire shale with the Weakness Plane Model (WPM) and the modified Hoek–Brown criterion (HBm). The sensitivity analyses of synthetic case studies indicated a different trend in mud pressure for the two criteria. In some cases, the WPM predicts mud pressures higher than those predicted by the HBm and vice versa. The mud pressures predicted by the HBm resulted in being more sensitive to the increase in the anisotropy of the far field stresses for all the inclinations of the weakness planes. In this context, the WPM predicts some anomalous low mud pressures in a wide range of inclinations of the weak planes. The change in the frictional component of strength decreases with an increase in the pore fluid pressure for both criteria. The mud pressure predicted by the WPM resulted in being more sensitive to the change in frictional strength. The change in trend of the two criteria with change in input data suggests caution in the “a priori” selection of the strength criterion. A simple solution is proposed to predict a safe and reliable mud pressure with a small number of lab tests.

Semi-analytical dynamic modeling and fluid-structure interaction analysis of L-shaped pipeline

The traditional semi-analytic modeling is mainly aimed at the straight pipeline with simple boundary conditions. In contrast, the actual aero-engine pipeline needs to consider the effects of complex configuration, boundary and multiple clamps, so proposing an improved semi-analytic method to model an arbitrary fluid-conveying L-shaped pipeline is challenging. Based on the Hamiltonian principle, the differential equations of the L-shaped pipeline are derived. Then, the modal shape functions are determined under the conditions that the elastic support points and the joints of the straight pipeline and the curved pipeline meet the deformation coordination requirements. The proposed semi-analytical model is verified by comparing the natural frequencies and mode shapes obtained from the finite element method using ANSYS and experiment; the error of each order natural frequency is less than 5 %. In addition, the model is verified under various working conditions: different center angle and boundary conditions (clamp position and pipeline end constraints). The effects of the fluid velocity and pressure on the natural characteristics of the L-shaped pipeline are also analyzed. The results show that under the critical pressure of 60.51 MPa and the critical velocity of 247 m/s, the natural frequency decreases with the increase of fluid velocity and pressure. The proposed method can provide theoretical support for efficient and accurate modeling of complex spatial pipeline systems.

Effect of Inhaled Sevoflurane on Pediatric Cerebrospinal Fluid Pressure During Lumbar Puncture; Implications for Intracranial Hypertension.

Objective: To determine influence of sevoflurane on changes in cerebrospinal fluid pressure in children presenting for lumbar puncture. Methods: Cerebrospinal fluid pressure, end tidal carbon dioxide, and end tidal sevoflurane concentration measurements were obtained at 2-minute intervals for a total of 10 minutes (T0 to T5). Because of concerns regarding patient safety and comfort, the study measurements were completed at the end of the lumbar procedure, starting with the closing pressure and when sevoflurane was stopped. Results: As end tidal sevoflurane concentration decreased, cerebrospinal fluid pressure initially increased up to T2 before decreasing back to around the initial point. There was no significant correlation between sevoflurane level and cerebrospinal fluid pressure. Both weight status and presence or absence of optic edema did not have a significant impact on pressure over time. However, there was a statistically significant difference in the cerebrospinal fluid pressure over time between those with spontaneous respirations compared to those without. Conclusions: There was no significant correlation between the end tidal sevoflurane concentration and cerebrospinal fluid pressure. Assisted ventilation did produce a statistically significant increase in cerebrospinal fluid pressure and suggests that the most accurate measurements are in those with spontaneous respirations.

Improved imaging of ground deformation and brine seepage around abandoned flooded salt mines by joint inversion of multiphysics data

Centuries of bad mine-flooding practice have left a legacy of underground salt mine collapse and contaminated discharges, the scale of which is only slowly being revealed now that ground processes have caused instability over decades to >100 years. Geophysical methods are used for mapping ground subsidence and groundwater contamination at such sites but suffer individually from non-uniqueness and with the underlying mechanism and processes not being well understood. Here, to reduce uncertainty and maximize accuracy we recover subsurface models with structural similarity enforced via crossgradients joint inversion of seismic refraction and dc resistivity data for the top 40 m at former mining areas in Carrickfergus region of Northern Ireland. The models in combination with multispectral image fusion, enable us to identify hitherto unknown mechanism of deformation and compositional changes consistent with the Chebotarev geochemical evolution of groundwater. We found evidence of concealed gravitational slump structures interpreted as being caused by water ingress weakening the gypsum-bearing marl bedrock (via gypsum dissolution and increased fluid pressures within marl) and leading to gravitational gliding deformation, expressed as curved subsidence bands and stepped thrusts coincident with surface zones of brine-mud seepage and sinkhole collapse. Our results have wide-ranging implications for best-practice assessment and management of abandoned flooded salt mines and the hazards they pose to ground stability and water resources world-wide.

CO2 storage: threshold capillary pressure estimate in a remoulded caprock specimen

CO2 storage: threshold capillary pressure estimate in a remoulded caprock specimen

Effect of fluid pressure on adhesive wear of spherical contact

Lubrication with fluid between two rough surfaces has been extensively studied, while the present work provides an additional principle for its effect on adhesive wear reduction associated with the fluid pressure. In this work, a finite element model for elastoplastic spherical contact with fluid pressure applied on surface is established, considering the realistic ductile failure criteria. It is found that as the fluid pressure increases, the location of fracture nucleation in the front contact region moves towards the contact surface. Two wear modes, namely the detaching and scratching modes, are identified by defining a critical dimensionless fluid pressure. Accordingly, the wear coefficient decreases as the fluid pressure increases, serving as the additional principle for wear reduction in lubrication systems.