Seal Analysis Research Articles

Flow Resistance Coefficients of Porous Brush Seal as a Function of Pressure Load

Developments in brush seal analyses tools have been covering advanced flow and structural analyses since brush seals are applied at elevated pressure loads, temperatures, surface speeds, and transients. Brush seals have dynamic flow and structural behaviors that need to be investigated in detail in order to estimate final leakage output and service life. Bristles move, bend, and form a grift matrix depending on pressure load. The level of pressure load determines the tightness of the bristle pack, and thus, the leakage. In the computational fluid dynamics (CFD) analyses of this work, the bristle pack is treated as a porous medium. Based on brush seal test data, the flow resistance coefficients (FRC) for the porous bristle pack are calibrated as a function of pressure load. A circular seal is tested in a static test rig under various pressure loads at room temperature. The FRC calibration is based on test leakage and literature-based axial pressure distribution on the rotor surface and radial pressure distribution over the backing plate. The anisotropic FRC are treated as spatial dependent in axisymmetrical coordinates. The fence height region and the upper region of bristle pack have different FRC since the upper region is supported by backing plate, while bristles are free to move and bend at the fence height region. The FRC are found to be almost linearly dependent on the pressure load for investigated conditions. The blow-down is also calculated by incorporating test leakage and calibrated FRC.

Steady-State Response of a Flexibly Mounted Stator Mechanical Face Seal Subject to Dynamic Forcing of a Flexible Rotor

Mechanical face seals are constitutive components of much larger turbomachines and require consideration of the system dynamics for successful design. The dynamic interplay between the seal and rotor is intensified by recent trends toward reduced clearances, higher speeds, and more flexible rotors. Here, the “rotor” consists of the flexible shaft and the rotating seal seat. The objective here is to, for the first time, determine how the rotor affects the seal performance and vice versa. Thresholds can then be established beyond which the rotor influences the seal but not vice versa (i.e., the rotordynamics can be sent to the seal analysis as an exogenous input). To this end, a model of a flexibly mounted stator face seal is provided including the coupled dynamics of the flexible rotor. The model accounts for axial and angular deflections of the rotor and seal. Coupled rotordynamics are modeled using a lumped-parameter approach including static and dynamic rotor angular misalignments. For expediency, linearized expressions for fluid forces are used, and the resulting steady-state equations of motion are solved analytically to investigate how rotor inertia, speed, and angular misalignment influence the coupled seal dynamics. Importantly, results from the study reveal that in some operating regimes, neglecting the rotordynamics implies healthy seal operation when instead intermittent rub exists between the faces. This work also shows that when the rotor inertia is much larger than the seal inertia, the rotordynamics can be solved separately and used in the seal model as an external input.

Computational Fluid Dynamics and Thermal Analysis of Leaf Seals for Aero-engine Application

Aero-engine gas turbine performance and efficiency can be improved through the application of compliant shaft seal types to certain sealing locations within the secondary air system. Leaf seals offer better performance than traditional labyrinth seals, giving lower leakage flows at design duties. However, for aero-engine applications, seal designs must be able to cope with relatively large off-design seal closures and closure uncertainties. The two-way coupling between temperatures of seal components and seal closures, through the frictional heat generated at the leaf–rotor interface when in contact, represents an important challenge for leaf seal analysis and design. This coupling can lead to leaf wear and loss, rotor overheating, and possibly to unstable sealing system behavior (thermal runaway). In this paper, we use computational fluid dynamics (CFD), finite element (FE) thermal analysis, and experimental data to characterize the thermal behavior of leaf seals. This sets the basis for a study of the coupled thermomechanical behavior. CFD is used to understand the fluid-mechanics of a leaf pack. The leaf seal tested at the Oxford Osney Laboratory is used for the study. Simulations for four seal axial Reynolds number are conducted; for each value of the Reynolds number, leaf tip-rotor contact, and clearance are considered. Distribution of mass flow within the leaf pack, distribution of heat transfer coefficient (HTC) at the leaf surface, and swirl velocity pick-up across the pack predicted using CFD are discussed. The experimental data obtained from the Oxford rig is used to develop a set of thermal boundary conditions for the leaf pack. An FE thermal model of the rig is devised, informed by the aforementioned CFD study. Four experiments are simulated; thermal boundary conditions are calibrated to match the predicted metal temperatures to those measured on the rig. A sensitivity analysis of the rotor temperature predictions to the heat transfer assumptions is carried out. The calibrated set of thermal boundary conditions is shown to accurately predict the measured rotor temperatures.

Elastic and Plastic Analysis of O-Ring Seal for Reactor Pressure Vessel

The elasto-plastic analysis for Reactor Pressure Vessel seal is necessary because of nuclear safety is actively demanded. The existed work based on simplified way to simulate the seal ring, such as uniform stress, spring elements, is too conservative. Therefore, it is necessary to simulate seal ring using 3D solid model considering the elasto-plastc deformation. In this paper, the two-dimensional model is adopted to simulate the compressing and springback character of inconel 718 O-ring using nonlinear isotropic hardening constitutive model and contact algorithm. The simulation approach and constitutive model are validated according to the deformation of seal ring using ANSYS. The seal analysis for reactor pressure vessel is achieved by considering complex loads, such as bolt pre-tightening force and temperature/pressure transient with the usage of an elasto-plastic constitutive model. It is found that the deformation of seal ring obtained by finite element is close to true value. The application of 3D solid model can reduce excessive conservatism effectively and improve the precision of seal analysis compare to the simplified method.

A geometrical model for shale smear: implications for upscaling in faulted geomodels

A new 1D bed-scale model has been built to help model shale smear in interbedded sand–shale sequences using the shale smear factor (SSF). A smear envelope is generated by mapping each potential shale smear onto the fault plane employing five different shale smear geometries. Graphical outputs then focus on the cumulative length of the resultant smears and the remaining sand–sand juxtaposition windows in the predicted shale smear envelope. The smears are evaluated stochastically with lengths that are a randomized function of the estimated Vclay content of the source shale layers, allowing the smear pattern to change with each realization. A new fragmented smear mode is developed that allows discontinuous smears to be distributed randomly on the fault plane and can be used to modify the smear pattern as fault displacement increases. The model has been tested using well data. Results show that windows in the smear envelope are commonly present, and that their frequency and location are dependent on the smear placement model and sand–shale stacking pattern. Smear fragmentation leads to more windows being preserved. The 1D model can also assess the impact of geocellular upscaling on fault seal analysis. Upscaling reduces cross-fault sand connectivity due to the elimination of thin beds. Shale smear envelopes are also reduced in length as fewer shale beds are involved, even though layers are thicker. A fault may or may not appear more sealing dependent on the layer configuration and net-to-gross ratio (NTG). The model offers results that can inform input to fault seal evaluations and allows the effect of geomodel upscaling to be more closely interrogated.

Industrial structural geology: principles, techniques and integration: an introduction

Abstract This volume explores how structural geology can be applied to industrial activities. It includes case studies that exhibit the state of the art and provides an overview of current and future trends in structural geology. The constituent papers cover a wide range of topics, including regional tectonics; trap and prospect definition; fault, fold and fracture analysis; seal analysis; interpretation of geophysical, borehole, core and outcrop data. The volume demonstrates how structural concepts ultimately create value and how academic institutions, specialist consultants and operating companies work together at a variety of scales and in varied geological settings to explore for and produce natural resources for the economic benefit of society.

The application of fault seal analysis at the Solokha field, Dnieper-Donets Basin, Ukraine – case studies

Continued development of world existing production facilities is constitutive to maintaining hydrocarbon production. But every next year in Ukraine is characterized by higher complexity of development and exploration processes than previous one. So it is absolutely vital to unveil each new oil and gas field with fewer risks. One of approaches that may significantly decrease possible risks and enhance the chance of success is Fault Seal Analysis (FSA). It represents a complex research method of integration of high-quality depth processing with seismic structural and stratigraphic interpretation and geological modeling as well. In this paper we show how all of these investigations improve hydrocarbon trap delineation with examples from the central axial part of the Dnieper-Donets Basin.

Using Multiple Investigative Techniques to Assess Flushing of Chip Seal Surfaces

Flushing is a defect that has a damaging effect on the functional performance of chip seal pavements. The reported study was conducted to develop techniques to identify and assess flushed pavements effectively. The main aims of the study were first to investigate the effects of chip seal volumetrics on development of flushing and second to develop a model to forecast flushing of chip seal pavements. The study methodology consisted of mechanical testing of chip seal pavement samples and analysis of pavement performance data. Laboratory testing was conducted on samples obtained from flushed chip seal pavements from four regions in New Zealand. Samples were loaded by using a wheel-tracking device, and imaging techniques were used to assess the effects of micromechanical changes on development of flushing. Data analysis was performed on pavement condition data to identify factors providing the best prediction of flushing, and regression analysis was performed to develop a model to predict the initiation and progression of flushing. Study results revealed a direct relationship between flushing and reduction in air void volume that occurred as a result of loading. Data analysis revealed that the combination of factors providing the best indication of flushing was surface thickness, surface age, rut depth, and grade of aggregates. The flushing initiation model had an accuracy of 76%, and the flushing progression model was robust at predicting the quantity of flushing. By using the study outcomes, a pavement condition assessment guideline was developed to aid with assessing and managing flushed chip seal pavements.

Fault seal analysis of a natural CO2 reservoir in the Southern North Sea

A geomechanical and fault seal analysis of the fault-bound natural CO2 reservoir of the Fizzy Field, Southern North Sea, shows that reactivation of, and leakage along the bounding fault is unlikely. Reservoirs are juxtaposed along the fault but shale-gouge ratio calculations indicate that the fault rock prohibits across-fault leakage of CO2. This study illustrates that, even though the fault is orientated favourably for reactivation relative to present day stress and uncertainties about the geometries remain, fault seal is not the limiting factor in retention of CO2 at the Fizzy field.

Accommodating species identification errors in transect surveys

Ecologists often use transect surveys to estimate the density and abundance of animal populations. Errors in species classification are often evident in such surveys, yet few statistical methods exist to properly account for them. In this paper, we examine biases that result from species misidentification when ignored, and we develop statistical models to provide unbiased estimates of density in the face of such errors. Our approach treats true species identity as a latent variable and requires auxiliary information on the misclassification process (such as informative priors, experiments using known species, or a double-observer protocol). We illustrate our approach with simulated census data and with double-observer survey data for ice-associated seals in the Bering Sea. For the seal analysis, we integrated misclassification into a model-based framework for distance-sampling data. The simulated data analysis demonstrated reliable estimation of animal density when there are experimental data to inform misclassification rates; double-observer protocols provided robust inference when there were "unknown" species observations but no outright misclassification, or when misclassification probabilities were symmetric and a symmetry constraint was imposed during estimation. Under our modeling framework, we obtained reasonable apparent densities of seal species even under considerable imprecision in species identification. We obtained more reliable inferences when modeling variation in density among transects. We argue that ecologists should often use spatially explicit models to account for differences in species distributions when trying to account for species misidentification. Our results support using double-observer sampling protocols that guard against species misclassification (i.e., by recording uncertain observations as "unknown").

Seal Analysis and Optimization of Large Diameter Gate Valve Based on ANSYS

Aiming at the leakage problem on the top of gate valve, the finite element method is used to analyze the gate valves seal face and body, as well as the distributing laws of the stress, deformation and seal pressure are obtained. The shutter is simplified as the circular plate simply supported on the whole circle, and the gate valve is optimized according to the relevant formula to meet sealing requirement. The results show that: the combination of the numerical simulation and theoretical calculation, not only the more accurate theoretical basis for the optimization of the large diameter gate valve can be provided, but also the time of the development and design can be shorten greatly.

Research on Performance of Stern Shaft Mechanical Seal Based on FLUENT

Reasonable assumptions and boundary conditions, the application of CFD method of mechanical seal ring structure analysis and thermal-structural coupling analysis, research on the temperature field and the pressure field distribution of the water flim between moving and the stationary ring . Comparing the change of the maximum temperature and the water film bearing capacity though different inlet velocity and different speed under, known as the fluid inlet speed increases, the maximum temperature of the sealing water film gradually decreased, the bearing capacity gradually increased; as the stern shaft speed increases, the sealing water film maximum temperature gradually reduced, and the bearing capacity of the sealing water film is gradually increased. In this paper, the research to maintain the good performance of the stern shaft mechanical seal has important significance and role.

Three-dimensional structure of experimentally produced clay smears: Implications for fault seal analysis

The geometries of clay smears produced in a series of direct shear experiments on composite blocks containing a clay-rich seal layer sandwiched between sandstone reservoir layers have been analyzed in detail. The geometries of the evolving shear zones and volume clay distributions are related back to the monitored hydraulic response, the deformation conditions, and the clay content and strength of the seal rock. The laboratory experiments were conducted under 4 to 24 MPa (580–3481 psi) fault normal effective stress, equivalent to burial depths spanning from less than approximately 0.8 to 4.2 km (0.5 to 2.6 mi) in a sedimentary basin. The sheared blocks were imaged using medical-type x-ray computed tomography (CT) imaging validated with optical photography of sawn blocks. The interpretation of CT scans was used to construct digital geomodels of clay smears and surrounding volumes from which quantitative information was obtained. The distribution patterns and thickness variations of the clay smears were found to vary considerably according to the level of stress applied during shear and to the brittleness of the seal layer. The stiffest seal layers with the lowest clay percentage formed the most segmented clay smears. Segmentation does not necessarily indicate that the fault seal was breached because wear products may maintain the seal between the individual smear segments as they form. In experiments with the seal layer formed of softer clays, a more uniform smear thickness is observed, but the average thickness of the clay smear tends to be lower than in stiffer clays. Fault drag and tapering of the seal layer are limited to a region close to the fault cutoffs. Therefore, the comparative decrease of sealing potential away from the cutoff zones differs from predictions of clay smear potential type models. Instead of showing a power-law decrease away from the cutoffs toward the midpoint of the shear zone, the clay smear thickness is either uniform, segmented, or undulating, reflecting the accumulated effects of kinematic processes other than drag. Increased normal stress improved fault sealing in the experiments mainly by increasing fault zone thickness, which led to more clay involvement in the fault zone per unit of source layer thickness. The average clay fraction of the fault zone conforms to the prediction of the shale gouge ratio (SGR) model because clay volume is essentially preserved during the deformation process. However, the hydraulic seal performance does not correlate to the clay fraction or SGR but does increase as the net clay volume in the fault zone increases. We introduce a scaled form of SGR called SSGR to account for increased clay involvement in the fault zone caused by higher stress and variable obliquity of the seal layer to the fault zone. The scaled SGR gives an improved correlation to seal performance in our samples compared to the other algorithms.

Fault seal analysis in ‘branched’ fault traps, eastern Gippsland Basin

SummaryThe impact of small-scale and ‘branched’ faults in the assessment of fault-trap integrity often remains unknown or unresolved when risking/evaluating a lead or prospect in regards to its petroleum prospectivity. The following study considered 40 leads in the eastern Gippsland Basin and assessed the overall impact of branch lines on fault trap integrity.Faults and surfaces were interpreted within a 30X50 km area using a 3-D seismic volume, depth-converted using purpose-programmed software and, a fault seal analysis carried out on the top three ranked leads. The fault seal analysis was underpinned by logs from 13 wells located in and adjacent to the leads.It was found that the likelihood of fault reactivation increased for 32% of the branch-line cases considered, reduced for 26% of cases while the change being minimal for the remaining 42%. Overall, modelling of the volume of shale attribute indicated that it is unlikely that sand-onshale windows can be maintained along fault-strike lengths that range up to 20 km.The study conclusively demonstrates that the primary factor affecting fault-trap integrity in the Halibut Subgroup is the high proportion of across-fault sand-onsand windows; by comparison, the contribution of fault tips, ‘branched’ faults and presence of shale smear is secondary. One implication is that the fault-trap integrity for leads located in the eastern Gippsland Basin is more likely to be enhanced closer to the depocentre where the shale content is anticipated to be higher.

Analysis of Vane Hydraulic Damp Dynamic Seal Mechanism and Performance Influencing Factors

In this paper, the force, deformation and other factors of vane hydraulic damp dynamic seal are researched, which is used of theoretical, simulation about the lip seals sealing damping performance factors. In order to improve sealing performance vane hydraulic damp life, dynamic lip seal design, optimization and performance study is to provide the basis for the theory and engineering applications. The factors influencing sealing performance are considered, such as initial compressibility, sealing sping stiffness. The finite element analysis method can be effectively used to solve nonlinear material and sealing failure problem for the seal design, optimization and performance analysis, which provide a new approach and theoretical guidance to the rubber seal research.

Production-induced fault compartmentalization at Elk Hills field, California

Mature and aging clastic-dominated hydrocarbon fields commonly become increasingly difficult to produce, causing lower economic return than initially forecast. A major cause of this reduced economic viability is compartmentalization, defined as limitation on the ability to produce hydrocarbons resulting from permeability barriers within a field. Three primary causes of compartmentalization are structural variations in permeability, stratigraphic variations in permeability, and permeability reduction resulting from compaction adjacent to producing wellbores. Recognition and delineation of compartmentalization permit formulation of development and depletion plans to maximize recovery and economic value. Here, we examine one of 52 reservoir-scale faults that compartmentalize the eastern shallow oil zone (ESOZ), Elk Hills field, California. Using well-log, stratigraphic, structural, and pressure data, we apply standard fault seal analyses to the selected fault. Results are compared with known pressure conditions across the fault and show the fault capable of supporting pressure differentials two to three times those expected from standard static fault seal measures. Although this observation could be used as a basis for local calibration of standard fault seal measures for a dynamic seal, such an approach assumes that these fault seal mechanisms are in fact the cause of sealing behavior. Alternatively, one of the most significant changes in ESOZ reservoir conditions over the production lifetime of the field is the reduction of fluid pressure from approximately 1500 to approximately 200 psi (from ∼10.27 to ∼1.37 MPa). Decreasing fluid pressure would have driven stress states acting on faults in the reservoir from critical (near or at slip) to stable (nonslipping) conditions. Critically stressed faults and fractures are more transmissive than those that are noncritically stressed. We propose that decreasing fluid pressure can cause faults to become less leaky, causing production-induced reservoir compartmentalization.

Seismic attributes and structural interpretation—it takes two to tango...

In this paper, different 3D seismic attributes calculated to improve the accuracy and robustness of structural interpretations in several energy-rich Australian basins are compared. Detailed and precise fault and fracture maps are crucial not only for initial petroleum play assessment, but also for fault seal analysis and reservoir integrity studies. Robust fault and fracture models are also needed to improve the design of reservoir simulation programs and to manage the long-term containment of gas in geological formations. Different attributes (including coherency, dip-steered similarity, dip-steered median filter, dip-steered variance, apparent dip, and dip-steered most-positive and most-negative curvatures) from an array of 3D seismic datasets to better image structural fabrics, such as normal and different fractures patterns, in the North Perth, Cooper, Ceduna, Otway and Gippsland basins have been calculated. The results provide a remarkable improvement in the quality and precision of structural maps using this multi-attribute mapping workflow by comparison with more conventional maps produced, solely using seismic amplitude data. The key to the successful application of multi-attribute structural analysis, however, remains with the ability of the interpreter to identify meaningful structural information from a large volume of data. Thus, the structural expertise of the interpreter remains as the cornerstone to making geological sense of the various seismic processing techniques available.

Single- and two-phase fluid flow properties of cataclastic fault rocks in porous sandstone

Understanding the impact of faults on fluid flow in the subsurface is important for the extraction of oil, gas and groundwater as well as the geological storage of waste products. We address two problems present in current industry-standard workflows for fault seal analysis that may lead to fault rocks not being represented adequately in computational fluid flow models. Firstly, fluid flow properties of fault rocks are often measured only for small-scale faults with throws not exceeding a few centimetres. Large seismic-scale faults (throws >20 m) are likely to act as baffles or conduits to flow but they are seldom recovered from subsurface cores and consequently fault rock data for them is sparse. Secondly, experimental two-phase fluid flow data is lacking for fault rocks and, consequently, uncertainties exist when modelling flow across faults in the presence of two or more immiscible phases. We present a data set encompassing both single- and two-phase fluid flow properties of fault and host rocks from the 90-Fathom fault and its damage zone at Cullercoats Bay, NE England. Measurements were made on low-throw single and zones of deformation bands as well as on slip-surface cataclasites present along the ∼120 m throw main fault. Samples were analysed using SEM and X-ray tomography prior to petrophysical measurements. We show that single deformation bands, deformation band zones and slip-surface cataclasites exhibit dissimilar single- and two-phase fluid flow properties. This is due to grain-size reduction being more pronounced in slip-surface cataclasites and changes in microstructure being fault-parallel for deformation bands but mostly fault-perpendicular for slip-surface cataclasites. A trend of fault rocks with low absolute permeabilities exhibiting lower relative permeabilities than more permeable rocks at the same capillary pressure is evident.

Study on New Bimetal Floating Seal of High Speed Roller Bit Bearing

ANSYS software has been used for high speed rock bit bimetal floating seal finite element analysis, as a result, overlarge pressure of bearing seal, unreasonable pressure distribution and overlarge compression ratio of rubber ring, are main reasons for premature failure of the bearing seal. For this, the optimal design and analysis of bearing seal structure is carried out in this paper. The results showed that: the new structure of the bearing seal has effectively reduced the compression ratio of rubber ring, improved the sealing pressure distribution based on reliable sealing conditions and further reduced the sealing pressure peak. The design of dynamic metal ring flywheel lubrication groove and the application of static metal ring antifriction material surface engineering technology have obviously reduced surface friction factor and wear of metal ring, greatly improved the effectiveness and life of the seal, and further extended the bit’s life.

Carbon dioxide storage leads of the eastern Gippsland Basin, Australia—Terminology, seal and structure considerations in trap integrity assessments

Abstract Geotechnical assessments of carbon dioxide (CO 2 ) storage sites in the Gippsland Basin have mainly focussed on interpreting stratigraphy, reservoir/seal characteristics, and populating geo-models using one dimensional (1D) well data. Less emphasis has been placed on ascertaining the openness of the fluid-flow pathway that could be anticipated for CO 2 migrating within a trap, and using 3D seismic data to interpret any associated faults. This study addresses the structural and seal complexities involved in the assessment of CO 2 storage leads (CO 2 SL) that are proximal to producing petroleum fields where, the data control is optimal and the geology well constrained. The study area is located in the eastern Gippsland Basin, southeast Australia, where we illustrate the concepts introduced and also undertake a fault seal analysis. To assist in the assessment of CO 2 SLs, we also introduce new terminology including flow-path distance, flow-path height, sweep area and fluid-flow cell . In the eastern Gippsland Basin, across-fault sand-on-shale contacts are unlikely to be maintained for fault planes that extend up to 20 km along strike; reservoir intervals are also exceptionally sandy. The trap integrity of the CO 2 SLs studied is likely to be acceptable on condition of a continuous shale smear being present. In the case where sealing by shale smear is considered, mercury injection capillary analyses (MICP) have independently confirmed that the clays of intra-formational seals have mineralogies capable of holding back significant injected columns of CO 2 . The majority of fault azimuths range from 095 to 140 °N and are susceptible to fault reactivation as a result of being sub-parallel to one of the conjugate directions of shear failure; the latter estimated using a maximum shear stress azimuth of 139 °N. However, the sinuous fault planes, possibly rugose in part, have azimuths varying up to ±55°, which could make fault reactivation less likely as a result of increased shear resistance being anticipated. Finally, the low faulting density interpreted within fluid-flow cells provides some assurance for the unimpeded fluid flow of CO 2 .