Fluid Pressure Research Articles

Investigation of long-term pressure on primary packaging materials and a biologic drug product for injection with a novel autoinjector concept.

Gerresheimer and Midas Pharma have developed a novel cartridge-based autoinjector concept in which the cartridge as primary packaging is under constant pressure. In this article standard cartridge primary packaging material of five different companies were analyzed for their behavior under long-term pressure. Materials of 3 glass manufacturers and 2 manufacturers for cartridge rubber parts were considered. Within the test program septum stability, septum piercing, glide forces (GF), break-loose forces (BLF), glass breaking as well as a regulatory approved and marketed antibody drug product under pressure were subject to analysis. Under pressure the cartridge septum bulge grew within the first 14 days and then relevantly slowed down. An accelerated study in different atmospheric conditions allowed to extrapolate values for 24 months storage, not showing any signs of decay or problematic septum bulge increase. Pierce forces were in normal ranges and septum rupture could not be observed at the end of 42 days of pressurization. GF and BLF were within acceptable ranges and changes due to pressure could not be observed. Lowest glass breaking pressures at 4922kPa turned out to be at least 3.5 times higher than pressures used in the autoinjector concept. Degradation of the Adalimumab antibody drug product due to pressure or device fluid pathway could not be observed with size exclusion chromatography, electrophoresis or sub-visible particles tested as a release testing in a GMP setting.

Using continuous electronic urine output monitoring for the management of acute cardio-renal syndrome in patients with acute decompensated heart failure

Abstract Funding Acknowledgements None. Background Patients admitted for acute decompensated heart failure (ADHF) are at high risk for type I cardio-renal syndrome (CRS) related to venous congestion and diuretic resistance. Positive fluid balance has been associated with adverse outcomes including acute kidney injury (AKI) and mortality. In critically ill patients urine output (UO) is used both to assess deterioration of renal function as well as for management of fluid balance .We investigated the possible effect of real-time UO monitoring, fluid balance, renal outcomes and 30-day mortality of patients admitted to the cardiac intensive care unit (ICU) with ADHF. Methods We performed a case series of 50 patients admitted to the cardiac ICU from July 2021 and June 2023 with ADHF. Their standard foley catheter was connected to an electronic monitoring system that continuously monitors UO in real-time. Its technology is described elsewhere (1). The UO monitoring system displays UO trends on the consoles that are updated in real-time. UO trends were utilized to guide an individualized approach for the pharmacologic management of each patient, based on blood pressure, hourly UO and total fluid balance. Daily and accumulated fluid balance was registered at up to 72 hours following admission. Patient outcomes included change in fluid balance, incidence of AKI and 30-day mortality. The case series group was than compared to a historical group of 50 matched controlled patients admitted between 2019-2020. Patients were matched according to cause of admission, age and glomerular filtration rate. Results In the study cohort the median age was 71±12 years, and 36 (72%) were men. In the historical cohort the median age was 71±13 years, and 36 (72%) were men. Patients in the electronic urinary monitoring cohort demonstrated significantly more negative daily and cumulative fluid balance as compared to the historical cohort, (P<0.001 for all, Figure 1). Incidence of AKI and the combined endpoint of AKI and 30-day mortality was significantly lower in the electronic UO monitoring cohort (24% vs. 46%, p=0.0197 and 40% vs 78%, P<0.0001 respectively). These changes were more prominent in the subgroup of patients with chronic kidney disease (Figure 2). Conclusion We demonstrated that real time monitoring of UO was associated with better prevention of fluid overload and the management of type I CRS in patients with ADHF. Further studies on larger populations are required to validate the potential utility of UO trending in the management of critically ill patients with ADHF.Fluid balance renal senseAKI and 30-day mortality

Design, fabrication, and evaluation of a novel highly sensitive tuning fork pressure sensor for precise liquid level measurement

This article investigates the under-explored potential of utilizing a thin stainless-steel diaphragm coupled with a quartz tuning fork sensor for liquid depth measurements. The focus is on monitoring molten salt fluid levels in nuclear reactors and concentrated solar power systems. Addressing a literature gap, the research explores cantilever-type configurations of a double-ended quartz tuning fork resonator, with a no-load resonance frequency of 17.37 kHz, on thin stainless-steel diaphragms for fluid depth measurement at room temperature. As the fluid depth increases, hydro-static pressure acting on a 20 μm diaphragm causes deflection, bending a tuning fork. The resulting change in resonance frequency correlates with fluid depth. Experimental setups assess the tuning fork’s sensitivity to strain and bending, revealing strain sensitivity of 7.83 Hz/μ strain (450.78 ppm/μ strain) and bending sensitivity of 0.09 Hz/μm (5.18 ppm/μm). The pressure sensor assembly, tested in a water tank, exhibits a sensitivity of −0.28 Hz/mm (−16.12 ppm/mm) in a single cantilever-type configuration. Despite a limited linear range, it effectively measures water depth changes as small as 0.7 mm. Exploring a double cantilever-type configuration yields a sensitivity of 0.07 Hz/mm (4.03 ppm/mm) with a broader linear range. The article discusses the reasons for opposite sensitivity and highlights the advantages of each configuration. Beyond molten salt level monitoring, the technology’s applications may extend to fluid depth and pressure measurements in industrial and domestic settings.

Brushing Up on Cartilage Lubrication: Polyelectrolyte-Enhanced Tribological Rehydration.

This study presents new insights into the potential role of polyelectrolyte interfaces in regulating low friction and interstitial fluid pressurization of cartilage. Polymer brushes composed of hydrophilic 3-sulfopropyl methacrylate potassium salt (SPMK) tethered to a PEEK substrate (SPMK-g-PEEK) are a compelling biomimetic solution for interfacing with cartilage, inspired by the natural lubricating biopolyelectrolyte constituents of synovial fluid. These SPMK-g-PEEK surfaces exhibit a hydrated compliant layer approximately 5 μm thick, demonstrating the ability to maintain low friction coefficients (μ ∼ 0.01) across a wide speed range (0.1-200 mm/s) under physiological loads (0.75-1.2 MPa). A novel polyelectrolyte-enhanced tribological rehydration mechanism is elucidated, capable of recovering up to ∼12% cartilage strain and subsequently facilitating cartilage interstitial fluid recovery, under loads ranging from 0.25 to 2.21 MPa. This is attributed to the combined effects of fluid confinement within the contact gap and the enhanced elastohydrodynamic behavior of polymer brushes. Contrary to conventional theories that emphasize interstitial fluid pressurization in regulating cartilage lubrication, this work demonstrates that SPMK-g-PEEK's frictional behavior with cartilage is independent of these factors and provides unabating aqueous lubrication. Polyelectrolyte-enhanced tribological rehydration can occur within a static contact area and operates independently of known mechanisms of cartilage interstitial fluid recovery established for converging or migrating cartilage contacts. These findings challenge existing paradigms, proposing a novel polyelectrolyte-cartilage tribological mechanism not exclusively reliant on interstitial fluid pressurization or cartilage contact geometry. The implications of this research extend to a broader understanding of synovial joint lubrication, offering insights into the development of joint replacement materials that more accurately replicate the natural functionality of cartilage.

Achieving deep intratumoral penetration and multimodal combined therapy for tumor through algal photosynthesis

BackgroundElevated interstitial fluid pressure within tumors, resulting from impaired lymphatic drainage, constitutes a critical barrier to effective drug penetration and therapeutic outcomes.ResultsIn this study, based on the photosynthetic characteristics of algae, an active drug carrier (CP@ICG) derived from Chlorella pyrenoidosa (CP) was designed and constructed. Leveraging the hypoxia tropism and phototropism exhibited by CP, we achieved targeted transport of the carrier to tumor sites. Additionally, dual near-infrared (NIR) irradiation at the tumor site facilitated photosynthesis in CP, enabling the breakdown of excessive intratumoral interstitial fluid by generating oxygen from water decomposition. This process effectively reduced the interstitial pressure, thereby promoting enhanced perfusion of blood into the tumor, significantly improving deep-seated penetration of chemotherapeutic agents, and alleviating tumor hypoxia.ConclusionsCP@ICG demonstrated a combined effect of photothermal/photodynamic/starvation therapy, exhibiting excellent in vitro/in vivo anti-tumor efficacy and favorable biocompatibility. This work provides a scientific foundation for the application of microbial-enhanced intratumoral drug delivery and tumor therapy.Graphical

Modeling dynamic crack branching in unsaturated porous media through multi‐phase micro‐periporomechanics

AbstractDynamic crack branching in unsaturated porous media holds significant relevance in various fields, including geotechnical engineering, geosciences, and petroleum engineering. This article presents a numerical investigation into dynamic crack branching in unsaturated porous media using a recently developed coupled micro‐periporomechanics (PPM) paradigm. This paradigm extends the PPM model by incorporating the micro‐rotation of the solid skeleton. Within this framework, each material point is equipped with three degrees of freedom: displacement, micro‐rotation, and fluid pressure. Consistent with the Cosserat continuum theory, a length scale associated with the micro‐rotation of material points is inherently integrated into the model. This study encompasses several key aspects: (1) Validation of the coupled micro‐PPM paradigm for effectively modeling crack branching in deformable porous media, (2) Examination of the transition from a single branch to multiple branches in porous media under drained conditions, (3) Simulation of single crack branching in unsaturated porous media under dynamic loading conditions, and (4) Investigation of multiple crack branching in unsaturated porous media under dynamic loading conditions. The numerical results obtained in this study are systematically analyzed to elucidate the factors that influence crack branching in porous media subjected to dynamic loading. Furthermore, the comprehensive numerical findings underscore the efficacy and robustness of the coupled micro‐PPM paradigm in accurately modeling dynamic crack branching in variably saturated porous media.

Numerical modelling of earthquake sequences involving valving and pumping of fluids

Summary Faults in the upper crust are sometimes thought to act as self-sealing valves, episodically releasing highly overpressured fluids trapped at greater depth during earthquakes. They are also often considered to be capable of actively pumping fluids into or out of faults in response to coseismic volumetric strain, thermal pressurisation or other mechanisms. In this study we investigate how these different types of behaviour (i.e., valve versus pump) are manifested in earthquakes. We do this using a two dimensional plane strain model where frictional sliding on a thrust fault that is fed by a fluid source at its base is coupled to porous flow, thermal pressurisation and strong variations in permeability. Our results show that thermal pressurisation leads to dramatic dynamic weakening that produces earthquakes that propagate as slip pulses producing large stress drop, large slip and high slip velocities. On the other hand, valve-type behaviour typically produces smaller, less energetic earthquakes that commonly arrest before rupturing the entire fault. In some valve-models, we observe complex compound ruptures and swarm activity, which is linked to the ascent of a propagating fluid pressure pulse driven by a large increase in permeability during sliding. Both pump and valve mechanisms can produce anomalously weak faults, though they are each associated with distinctly different fluid pressure and strength evolution over the seismic cycle and during rupture. Our models highlight the complex way in which fluids may interact with earthquakes, especially if valve and pump models coexist.

Intra-plate Jal Az-Zor Strike-Slip faulting deciphering the enigma of local earthquakes in Kuwait

Abstract Kuwait National Seismic Network (KNSN) data shows the clustering of earthquakes in northern and southern clusters. Spatial correlation between these clusters and oil fields led previous studies to declare that oil production/injection triggered earthquakes, but some suggested the possibility of tectonic causes. This study addresses the genuine objective of uncovering the origin of Kuwait earthquakes by analyzing relationships between earthquake spatial and temporal patterns, oil production/injection, structural and tectonic setting, and subsurface fluid pressures. A kinematic model of the Jal Az-Zor dextral-slip fault was presented as a decipherer to the earthquake's origin. The northern and southern clusters represent leading quadrants, where increased mean stress causes earthquakes. Dibdibah Trough and Kuwait Bay represent trailing quadrants with decreased mean stress and a lack of earthquakes. The small percentage of earthquakes falling outside clusters are caused by the concentration of regional compressive stresses related to Arabian Plate motion on pre-existing faults. Triggering earthquakes by oil field operations requires 10% pressure increase above the original pressures, which never occurs in Kuwait oil fields. The results of this study emphasize the significance of understanding fault kinematics to assess earthquake hazards and the need to focus on engineering requirements for developments in the leading quadrants areas.

Comparative examine of fluid pressure within microchannel through integrated cantilevers for microfluidic applications

This paper aims to explore the concept of a microfluidic pressure sensing mechanism across a microchannel, integrated with different structures of microcantilevers. Various structures of microcantilevers are integrated into a microchannel where laminar fluid flows and the microcantilever senses the fluid velocity and pressure. The different structures of the microcantilever include rectangular, T-shaped, and Pi-shaped designs, which are placed at the centre of the microchannel. The 2D microchannel has a length of 4000 μm and a height of 840 μm, while the microcantilever is positioned at a distance of 2000 μm from the inlet of the microchannel. The analysis of the fluid sensor is observed by plotting graphs of velocity, pressure, displacement of the microcantilever, Reynolds number, and friction factor with respect to the time domain. An inlet velocity of 8.33 µm/s is applied at the microchannel, and the fluidic sensor shows a significant change in the fluid characteristics, comparing them across all types of microcantilevers. The simulation results show that the T-microcantilever has a maximum displacement of 4.97 µm compared to other microcantilevers, with a maximum pressure of 1.58 Pa for the Pi-cantilever. The integrated device is suitable for healthcare applications, measuring fluid pressure in syringes, where the T-microcantilever proves to be more compatible than the other two microcantilevers (R-cantilever and Pi-cantilever). The design and simulation of the microfluidic pressure sensing process are conducted using the FEM tool COMSOL Multiphysics.

Optimization design of plugging agent dosage and application of deep shale gas inner-diversion fracturing

China boasts abundant deep shale gas resources with considerable development potential. However, the weak brittleness and large horizontal stress contrast of deep shale rock may restrain the complex fractures network extension during hydraulic fracturing. To address this challenge, the inner-diversion fracturing technique is widely employed, facilitating the formation of a complex fractures network. Numerous theoretical studies emphasize the pivotal role of plugging pressure exerted by temporary plugging agents within fractures in enhancing deep shale stimulation performance. However, various types of temporary plugging agents with different plugging performances make it difficult to determine the optimal dosage of temporary plugging agents before fracturing operation. This study considered the dynamic propagation of fractures affected by the coupling of the induced stress from clustered fractures and the fluid pressure within the fractures into the mathematical model, based on rock mechanics theory. Subsequently, the inner-diversion capability testing instrument was utilized to evaluate the critical plugging pressure of several common temporary plugging materials. By integrating on-site data from temporary plugging and inner-diversion fracturing operations in the Southern Sichuan deep shale gas reservoir with this approach, the optimal dosage of temporary plugging agents in the operational scheme was refined. The fracturing operation curves demonstrate that the temporary plugging and inner-diversion pressure significantly increased after pumping the temporary plugging agent, indicating the hydraulic fractures successful plugging and a large-scale complex fractures network extension. This underscores the potential effectiveness of the temporary plugging dosage optimization method for inner-diversion fracturing. Furthermore, this study not only provides important guidance for optimal design but also mitigates the operational risks of inner-diversion fracturing in deep shale gas horizontal wells.

Generic low-density corrections to the equation of state of chain molecules with repulsive intermolecular forces

Molecular-based equations of state for describing the thermodynamics of chain molecules are often based on mean-field like arguments that reduce the problem of describing the interactions between chains to a simpler one involving only nonbonded monomers. While for dense liquids such arguments are known to work well, at low density they are typically less appropriate due to an incomplete description of the effect of chain connectivity on the local environment of the chains’ monomer segments. To address this issue, we develop three semi-empirical approaches that significantly improve the thermodynamic description of chain molecules at low density. The approaches are developed for chain molecules with repulsive intermolecular forces; therefore, they could be used as reference models for developing equations of the state of real fluids based on perturbation theory. All three approaches are extensions of Wertheim’s first-order thermodynamic perturbation theory (TPT1) for polymerization. The first model, referred to as TPT1-v, incorporates a second-virial correction that is scaled to zero at liquid-like densities. The second model, referred to as TPT1-y, introduces a Helmholtz-energy contribution to account for correlations between next-nearest-neighbor segments within chain molecules. The third approach, called TPT-E, directly modifies TPT1 without utilizing an additional Helmholtz energy contribution. By employing TPT1 at the core of these approaches, we ensure an accurate description of mixtures and enable a seamless extension from chains of tangentially bonded hard-sphere segments of equal size to hetero-segmented chains, fused chains, and chains of soft repulsive segments (which are influenced by temperature). The low-density corrections implemented in TPT1 are designed to preserve these good characteristics, as confirmed through comparisons with novel molecular simulation results for the pressure of various chain fluids. TPT1-v exhibits excellent transferability across different chain types, but it relies on knowing the second virial coefficient of the chain molecules, which is non-trivial to obtain and determined here using Monte Carlo simulation. The TPT1-y model, on the other hand, achieves comparable accuracy to TPT1-v while being fully predictive, requiring no input besides the geometry of the chain molecules.

Thermal accumulation effects modelling of investigate radial shaft seal wear and lubrication transition mechanism

A radial shaft seal (RSS) model is established to reveal mixed thermal lubrication (MTL) and wear performance at speeds ranging from 3000r/min to 7000r/min. The model takes into account the initial temperatures of the oil medium and the running time of the RSS to investigate the transition limit of lubrication. Then a thermal fluid-solid method was developed to simulate the lubrication performance of RSS, which shows lubrication transition boundaries through rough micro convex bodies for wear deformation. The RSS deforms wedge-shaped during the wear process and a localized fluid pressure is created on the convex bodies. Considering the wear deformation of the convex bodies due to the wedge effect, the micro performance of the RSS can fully describe the mechanism of the leakage rate. As the dynamic pressure decreases and the leakage rate increases with the temperature of the medium, the RSS lubrication gradually transitions from MTL to EHL. Thus, the initial medium temperature should be considered to maintain the RSS under the mixed lubrication regime with low friction.

An efficient multi-field dynamic model for 3D wave propagation in saturated anisotropic porous media

An efficient multi–field coupled dynamic model for saturated anisotropic porous materials is proposed here. The mathematical formulation of the dynamic deformation–diffusion problem is developed starting from the mixture theory and the definition of the effective stress for anisotropic poro–elasticity, taking into account also the fluid phase compressibility and anisotropic permeability. The effective stress principle is properly extended through the Biot tensor to predict the coupling between the shear stress of the solid skeleton and the pore fluid pressure. Numerical solution of the coupled problem is obtained by inf-sup stable Finite Element spaces. A fundamental issue for the computational efficiency of the coupled model is the numerical solution of the resulting large–size and non–symmetric discrete problem. In this work, we develop a fully implicit monolithic solver based on the Bi–Conjugate Gradient Stabilized (Bi-CGStab) algorithm accelerated via an ad–hoc Multi–Physics Reduction (MPR) preconditioning technique. The proposed advances are implemented in the 3D GeoMatFem research code and several numerical analyses are performed to test the potential and computational efficiency of the proposed tool. In particular, we focus on 3D wave propagation applications in fully saturated single and multi-layered anisotropic media. Numerical results show that our implementation is able to identify the shear wave splitting phenomenon due to the different degree of material symmetry between the solid phase and the whole porous material.

Near-infrared Light-Triggered Size-Shrinkable theranostic nanomicelles for effective tumor targeting and regression

Most nanomedicines with suitable sizes (normally 100–200 nm) exhibit favorable accumulation in the periphery of tumors but hardly penetrate into deep tumors. Effective penetration of nanomedicines requires smaller sizes (less than 30 nm) to overcome the elevated tumor interstitial fluid pressure. Moreover, integrating an efficient diagnostic agent in the nanomedicines is in high demand for precision theranostics of tumors. To this end, a near-infrared light (NIR) −triggered size-shrinkable micelle system (Fe3O4@AuNFs/DOX-M) coloaded antitumor drug doxorubicin (DOX) and biomodal imaging agent magnetic gold nanoflower (Fe3O4@AuNFs) was developed to achieve efficient theranostic of tumors. Upon the accumulation of Fe3O4@AuNFs/DOX-M in the tumor periphery, a NIR laser was irradiated near the tumor site, and the loaded Fe3O4@Au NFs could convert the light energy to heat, which triggered the cleavage of DOX-M to the ultra-small micelles (∼5 nm), thus realizing the deep penetration of micelles and on-demand drug release. Moreover, Fe3O4@AuNFs in the micelles could also be used as CT/MRI dual-modal contrast agent to “visualize” the tumor. Up to 92.6 % of tumor inhibition was achieved for the developed Fe3O4@AuNFs/DOX-M under NIR irradiation. This versatile micelle system provided a promising drug carrier platform realizing efficient tumor dual-modal diagnosis and photothermal-chemotherapy integration.

Designing & Developing a Porous based Box-Type Heat Exchanger for Enhanced Heat Transfer Rate

Abstract: The shell-and-tube heat exchanger's geometric configuration is optimized during the design development phase by taking into account various aspects like baffle spacing, tube arrangement, and overall system integration. Incorporating a blower into the system results in improved air circulation and effective heat transfer. By placing the band heater in a strategic location, air is heated precisely and locally, which helps to create a more responsive and controlled heating process. One essential tool for assessing the system's thermal and fluid dynamics is CFD analysis. The heat exchanger, blower, and band heater components' fluid flow patterns, temperature distributions, and pressure gradients are investigated through simulations. The CFD analysis provides valuable insights that guide design modifications aimed at optimizing heat transfer rates, minimizing pressure drops, and improving the integrated system's overall performance

Developing meshing workflows in Gmsh v4.11 for the geologic uncertainty assessment of high-temperature aquifer thermal energy storage

Abstract. Evaluating uncertainties of geological features on fluid temperature and pressure changes in a reservoir plays a crucial role in the safe and sustainable operation of high-temperature aquifer thermal energy storage (HT-ATES). This study introduces a new automated surface fitting function in the Python API (application programming interface) of Gmsh (v4.11) to simulate the impacts of structural barriers and variations of the reservoir geometries on thermohydraulic behaviour in heat storage applications. These structural features cannot always be detected by geophysical exploration but can be present due to geological complexities. A Python workflow is developed to implement an automated mesh generation routine for various geological scenarios. This way, complex geological models and their inherent uncertainties are transferred into reservoir simulations. The developed meshing workflow is applied to two case studies: (1) Greater Geneva Basin with the Upper Jurassic (“Malm”) limestone reservoir and (2) the 5° eastward-tilted DeepStor sandstone reservoir in the Upper Rhine Graben with a uniform thickness of 10 m. In the Greater Geneva Basin example, the top and bottom surfaces of the reservoir are randomly varied by ± 10 and ± 15 m, generating a total variation of up to 25 % from the initially assumed 100 m reservoir thickness. The injected heat plume in this limestone reservoir is independent of the reservoir geometry variation, indicating the limited propagation of the induced thermal signal. In the DeepStor reservoir, a vertical sub-seismic fault juxtaposing the permeable sandstone layers against low permeable clay-marl units is added to the base case model. The fault is located in distances varying from 4 to 118 m to the well to quantify the possible thermohydraulic response within the model. The variation in the distance between the fault and the well resulted in an insignificant change in the thermal recovery (∼ 1.5 %) but up to a ∼ 10.0 % pressure increase for the (shortest) distance of 4 m from the injection well. Modelling the pressure and temperature distribution in the 5° tilted reservoir, with a well placed in the centre of the model, reveals that heat tends to accumulate in the updip direction, while pressure increases in the downdip direction.

A new framework to characterize and unify the impact load exerted by flow-type mass movements

AbstractA wide range of flow-type mass movements occur in nature. Depending on the solid fraction of these flows, they can be characterized as stream flows (flash floods), hyper-concentrated flows (debris floods), debris flows, and dry debris avalanches. A key scientific challenge in mitigating these hazards is estimating the impact force that they exert on protection structures. In this study, a new framework (Nfric - Fr2 - $$\alpha$$ α  relationship) is proposed to characterize and unify the impact behavior for a wide spectrum of flow-type mass movements. The friction number Nfric characterizes the ratio of grain-contact to fluid-viscous stresses for the wide range of flow types. Solid–fluid interaction regulates the pore fluid pressure, thereby governing the rheology of the flows and the degree of static loading exerted on a barrier. The Froude number Fr2 (in squared form) macroscopically characterizes the flow inertia relative to the earth’s gravitational field. Finally, the dynamic pressure coefficient $$\alpha$$ α is used to quantify the impact force in a dimensionless manner. As compared to existing guidelines, which recommend a wide range of $$\alpha$$ α without considering the flow composition, the newly proposed framework in this study estimates the dynamic impact force by considering the effects of solid–fluid interaction. Findings from this study could further enhance the design of flow-type mass movement mitigation structures.

Exploring the Multifaceted Dynamics of Cartilage: A Comparative Modeling Study

Cartilage numeric models play a vital role in advancing our understanding of cartilage mechanics, disease progression, and the development of clinical interventions. The aim of this study is to investigate the influence of different mathematical models on cartilage mechanical behavior over time. A comparative analysis was conducted across three scenarios: the single-phase, biphasic, and fibril-reinforced poroelastic models. To understand how cartilage behaves over time, a 1000-second ramp relaxation displacement was applied. The findings reveal that the single-phase model falls short of capturing the time-dependent characteristics of cartilage. Conversely, the inclusion of fluid and collagen fibrils within the cartilage model significantly enhances cartilage resilience and enables the cartilage to behave non-linearly. The results presented herein make a substantial contribution to a deeper and more holistic comprehension of cartilage's dynamic behavior under compressive loads, shedding light on the intricate interplay between fluid pressure and fibril reinforcement.

Brittle sedimentary strata focus a multimodal depth distribution of seismicity during hydraulic fracturing in the Sichuan Basin, Southwest China

The number of background earthquakes (ML ≥ 0) in the southern Sichuan basin, southwest China, has increased thirtyfold as a result of hydraulic fracturing. Background events are originally deep (4–6 km) within the sedimentary section but build into a multimodal distribution both at depth and in the shallow stimulated reservoir (2–4 km) - representing a counterpoint to the usual triggering of seismicity on deep sub-reservoir basement faults. Surprisingly, the largest events (ML ≥ 3) evolve in the deep sedimentary strata (4–6 km) that are hydraulically isolated from the injection zone (2–4 km) by low permeability layers. We evaluate the friction-stability rheology of the strata within the full stratigraphic section to define the feasibility of nucleation within these shallow and deep strata. These show velocity-neutral to velocity-weakening behavior in the shallow reservoir transitioning to more strongly velocity-weakening with increase in both depth and temperature. Poroelastic stress calculations confirms that stress transfer, rather than transmitted fluid pressures, are capable of directly reactivating critically-stressed faults at depth, with fluid pressures the triggering source within the shallow reservoir.

Effect of Gas-Oil Ratio on Oil Production for a Niger Delta Well

This study delves into the intricate relationship between gas-oil ratio (GOR) and oil production rate in a vertical well within the framework of reservoir engineering. The investigation employs advanced reservoir modeling techniques, drawing insights from Prosper software simulations and well data analysis. A comprehensive methodology involving PVT data, inflow performance relationship data, and sensitivity analysis guides the exploration of GOR's impact on oil rate. The selected well configuration, a vertical well, serves as the experimental canvas for this study. Through meticulous analysis of reservoir and well data, an Inflow Performance Relationship (IPR) curve emerges. This curve is developed using the Darcy reservoir model available within the Prosper software, reflecting the intricate interplay between fluid dynamics, pressure gradients, and production behavior. Further expanding the analysis, the study explores the IPR-Vertical Lift Performance (VLP) curve, spotlighting the well's behavior at a top node pressure of 250 psig. Subsequently, the study dives into the realm of sensitivity analysis, seeking to unravel the nuanced connection between oil rate, GOR, and well head pressure. The captivating findings are encapsulated, a visual testament to the intricate dance of fluid dynamics. The results paint a vivid picture of the GOR's role in oil rate modulation. The correlation between GOR and oil rate is revealed to be a delicate balance, illustrated by a crescendo and diminuendo as GOR rises beyond the bubble point. Above the bubble point, the gas's continuous expansion within the solution propels oil production. The study's intricate examination of well head pressure offers further illumination. The result further exposes the inverse relationship between well head pressure and oil production rate, as heightened well head pressure curtails pressure drawdown and subsequently reduces the amount of oil lifted to the surface. The study concluded that Oil production rate increases with increase in gas-oil ratio up to a maximum above which oil production starts decreasing. The decrease in oil production starts when gas is released from the oil. An increase in well head pressure led to a decrease in oil production. This is attributed to a decrease in pressure drawdown between the bottom of the well and the well head.