Seal Capacity Research Articles

Estimates of scCO2 Storage and Sealing Capacity of the Janggi Basin in Korea Based on Laboratory Scale Experiments

Laboratory experiments were performed to measure the supercritical CO2 (scCO2) storage ratio (%) of conglomerate and sandstone in the Janggi Basin, which are classified as rock in Korea that are available for CO2 storage. The scCO2 storage capacity was evaluated by direct measurement of the amount of scCO2 replacing the pore water in each reservoir rock core. The scCO2 sealing capacity of the cap rock (i.e., tuff and mudstone) was also compared by measuring the scCO2 capillary entry pressure (Δp) into the rock core. The measured average scCO2 storage ratio of the conglomerate and the sandstone were 30.7% and 13.1%, respectively, suggesting that the scCO2 storage capacity was greater than 360,000 metric tons. The scCO2 capillary entry pressure for the tuff ranged from 15 to 20 bar and for the mudstone it was higher than 150 bar, suggesting that the mudstone layers had enough sealing capacity from the aspect of hydromechanics. From XRF analyses, before and after 90 d of the scCO2-water-cap rock reaction, the mudstone and the tuff were investigated to assure their geochemical stability as the cap rock. From the study, the Janggi Basin was considered an optimal CO2 storage site based on both its high scCO2 storage ratio and high capillary entry pressure.

Pore pressure estimation in salt-sealed formations

Abstract Many conventional methods for pore pressure estimation are challenged by conditions below salt, and this is especially true in isolated sediments. However, for Gulf of Mexico salt allochthons – and potentially for other settings where sediments were sealed by salt early in their burial histories – a simple consideration of seal capacity provides useful insight into possible pressures. Data from several such confined settings are presented here and compared to two simple sealing models. The resulting observations are also compared to regional mudrock trends and intra-salt data to evaluate the potential implications. Together, the data suggest the salt seal fails at a constant pressure below the base-salt minimum confining stress, and pressure in sediments below that point increases at a constant gradient. The field data shown here indicate a consistent behavior over a large area of the Gulf of Mexico, despite substantial variability in salt thickness, water depth, etc. The proposed model provides estimates that agree with observed pressures within salt, at base salt, and through salt-sealed sediments below salt. A simplified version of the model can also provide a map of pressure or effective stress across base salt; while not fully accounting for sub-salt structure, such maps can be valuable in assessing relative drill-site risk to guide more detailed site-specific work.

Sealing capacity of clay-cap units above the Cerro Pabellón hidden geothermal system (northern Chile) derived by soil CO2 flux and temperature measurements

Cerro Pabellón is a hidden high-enthalpy geothermal system (reservoir temperature up to 250°C) located in the Pampa Apacheta (northern Chile), where the first geothermal power plant in South America is currently operating. A fumarolic field, located on the summit of Apacheta Volcano, about 3.5kmW of Pampa Apacheta, is the only evidence of the presence of a degassing magma connected to the surface. CO2 soil flux and temperatures, on a grid of ~430 points, were measured to understand the absence of any other thermal manifestations. More than 90% of the measured CO2 flux values were below background, estimated at 1.35g·m−2·day−1 whereas the associated soil temperatures (mean value=19.4°C) carried out at ~10cm depth were related, at least partially, to an endogenous, though weak, thermal anomaly. No spatial correlation was observed between soil CO2 flux and temperature measurements, suggesting a minimal role played by the volcano-tectonic structures in the circulation of geothermal fluids. Soil temperature gradients measured on a grid of 85 points in the active fumarolic field (where acid waters and magmatic gases are discharged) revealed the only strong thermal anomaly (temperatures up to ~83°C) of the area. The thick argillic clay-cap (~300m) located above the geothermal reservoir, has a pivotal role in preventing the resurgence of fluids, whereas an efficient interaction between the rising magmatic fluids and the liquid-dominated reservoir favours acidic gas scrubbing processes, thus allowing the ascent of a steam depleted in magmatic compounds. This steam interacts with the shallower, discontinuous aquifer(s) below Pampa Apacheta, with the consequent nearly complete dissolution of CO2 and H2S, and heating of the shallow groundwater. This results in low CO2 fluxes and extended slight thermal anomaly at the surface. Finally, an integrated conceptual model using our results and available geological, mineralogical, geochemical and geophysical data of the Cerro Pabellón hidden geothermal system is presented, with the aim of providing criteria for geothermal exploration of similar high-enthalpy geothermal systems in the Andes that also exhibit a lack of thermal surface features.

Characterization and Impact of Seal Heterogeneity on its Sealing Capacity for a CO2 Storage

Characterization and Impact of Seal Heterogeneity on its Sealing Capacity for a CO2 Storage

Deformation Mechanism and Vertical Sealing Capacity of Fault in the Mudstone Caprock

The petrophysical property of mudstone often transforms from ductile to brittle in the process of burial-uplift. The deformation mechanism of fault in brittle and ductile mudstone caprock is different, which leads to the formation of different types of fault zone structure. Different methods are required to evaluate the sealing mechanism of those fault zones. Based on the caprock deformation mechanism, fault sealing mechanism, quantitative evaluation method of vertical fault sealing capacity is put forward in this study. Clay smear is formed in the process of plastic deformation and its continuity controls the sealing capacity of fault. The outcrop and oil field data have confirmed that when sealing parameter SSF is less than 4-7, the clay smear becomes discontinuous and then oil and gas go through the caprock and migrate vertically. Quantities of fractures are formed in mudstone in the process of brittle deformation. The fracture density increases with the increase of the fault displacement. When the fractures are connected, oil and gas go through the caprock and migrate vertically. The connectivity of fault depends on the displacement and the thickness of caprock. On the basis of the above, a method is put forward to quantify the connectivity of fault with the juxtaposition thickness of caprock after faulting. The research on the juxtaposition thickness of caprock after faulting of the member Ⅱ of Dongying Formation in Nanpu depression and the distribution of oil and gas indicates when the juxtaposition thickness of caprock is less than 96.2 m, the fault becomes leaking vertically. In the lifting stage, with the releasing and unloading of the stress, the caprock becomes brittle generally and then forms through going fault which will lead to a large quantity of oil and gas migrate vertically.

Technology Focus: Natural Gas Processing and Handling (April 2019)

Technology Focus To cater to the seasonal highs and lows in demand throughout a year, natural gas is stored in underground storage facilities. The need for such facilities arose because increasing (or decreasing) gas production to mirror changes in demand is neither practical nor economical. Therefore, gas is produced and stored during low-demand times and retrieved to meet the highs during winters. This cyclic trend can be observed also in gas-storage inventories [as reported by the Energy Information Administration (EIA)]. The northeast US has the highest concentration of such storage facilities, close to the biggest market. Most of the underground gas-storage facilities are depleted reservoirs, but aquifers and leached salt caverns are also used. The US and Canada were the pioneers in realizing the potential of depleted reservoirs for gas storage and, hence, have several well-developed facilities. What makes depleted reservoirs attractive is the presence of existing wells used to produce the reservoir, plus the geologic and engineering knowledge acquired during the development of the field. All that information is leveraged when repurposing the field for gas storage. Depleted reservoirs also contain some amount of gas already in the reservoir, which decreases the requirement to inject gas as cushion gas. (Cushion gas is immobile gas that remains in the reservoir and allows the reservoir to be used for storage.) Depleted reservoirs are also the most abundant. I would be remiss not to touch upon the Aliso Canyon incident of 2015. Aliso Canyon was the second-largest storage facility in the US at the time. The industry learned a harsh lesson about the repercussions when containment is lost for such facilities. The loss of containment was because of the casing failure of one of the wells (along with having subsurface safety valves removed in the past). This led to 109,000 tonnes of methane emissions by some estimates. One measure that was proposed to reduce such risks is to use offshore reservoirs nearing abandonment for gas storage (instead of onshore ones that are close to populated urban areas). At the time of this writing, the week-to-week change in the natural gas storage inventory was –237 Bcf, and levels remained lower than the 5-year historical average, according to the EIA. This withdrawal from the inventory was less than most forecasts based on the extreme cold temperatures faced by the US. The Henry Hub natural gas prices reached highs of more than $4.5/million Btu in 2018 because of record gas demand. The price has since dipped to $2.57/million Btu because of abatement in the extreme weather leading to lower demand for heating. To learn more, visit the SPE Annual Technical Conference and Exhibition in Calgary, 30 September–2 October, and the Gastech Exhibition and Conference in Houston, 17–19 September. Recommended additional reading at OnePetro: www.onepetro.org. SPE 190838 Comprehensive Evaluation of the Dynamic Sealing Capacity of Clayey Caprocks in a Large Underground Gas Storage by Junchang Sun, PetroChina, et al. SPE 192961 Maintaining Flare-Tip Health by Venugopal Bakthavachsalam, ADNOC, et al. SPE 192783 Cutting-Edge Solutions for Sour-Gas Treatment: A Retrospective Study by Kuwait Oil Company by Fahad Al-Ghanem, Kuwait Oil Company, et al.

Sealing capacity of siderite-bearing strata: The effect of pore dimension on abundance and micromorphology type of siderite in the Lopingian (Late Permian) coal-bearing strata, western Guizhou province

We conducted a series of core observation, thin section evaluation, and integrated with low-temperature nitrogen adsorption/desorption, porosity, permeability, breakthrough pressure analysis of the siderite-bearing strata. This paper aims to discuss the sealing capacity of siderite-bearing strata as a function of siderite abundance andmicromorphology type. The siderite-bearing strata can be potential gas barrier layers in multiply-superposed gas-bearing systems. In the transitional Lopingian coal-bearing succession of western Guizhou, the siderite content of siderite-bearing mudstone is 18.6–90.7% (wt.), with an average 53.4% (wt.). There are three morphologies of siderite, including S1 (gelatinous aggregates), S2 (microcrystal-silt size crystal aggregates), and S3 (sphaerosiderites). It shows that different abundance of siderite and type of siderite micromorphology affected the pore structure. The sealing capacity of siderite-bearing mudstone at the study area is somewhat or significantly larger, and the sealing capacity of the siderite-free mudstone is moderate. The development of siderite-bearing strata is controlled by the stratigraphy of the sequence.

Experimental Validation and Numerical Simulation of Static Pressure in Multi-Stage Ferrofluid Seals

With the development of science technology, ferrofluid seal has been intensively applied in mechanical industry, but more and more larger sealing stages are needed. At present, the literature mostly concentrated on numerical analysis with few pole pieces ferrofluid seals and focused on the critical pressure value in one-stage magnetic fluid seal, lacking of numerical simulation and experimental validation on the static pressure of multi-stage ferrofluid seals. On this basis, the analysis of larger number of sealing stages is presented. And numerical simulation along with experiment investigation was used to study the seal capacity of ferrofluids in different seal gaps and different seal stages in this paper. The results show that the theoretical value is well coincident with experimental value when the sealing gap is less than 0.2 mm. Increase the number of the pole tooth can significantly improve the seal capacity of ferrofluid seal, but the sealing pressure of ferrofluids does not increase linearly with the addition of the number of pole teeth. For the new structure, the pressure of one-stage pole tooth has more than doubled as the sealing clearance is 0.2 mm and 3.5 times increase when the sealing gap is 0.3 mm.

Seismic imaging of complex geometry: Forward modeling of sandstone intrusions

Sandstone intrusions form large bedding-discordant sandstones that intruded into finer grained, less permeable host strata. They form naturally sand-propped hydraulic fractures that constitute a connected network of permeable conduits through which fluids escape to the Earth's surface. Saucer-shaped sandstone intrusions are among the largest volume intrusions and are commonly resolved on seismic data. Outcrop analogues of seismically-resolved saucers-shaped intrusions reveal that many attendant intrusions, in particular dikes, are undetected in seismic data. Seismic forward modeling of a detailed outcrop description of a saucer-shaped intrusion demonstrates that intrusions steeper than 45° are undetected and that up to 40% of the entire volume of sandstone intrusions is not seismically imaged. Wedge geometry – associated with discordant contacts between different lithologies – causes constructive and destructive amplitude interference, creating imaging artefacts of sandstone thickness and geometry. Comparison of the outcrop seismic models with 3D seismic data from Volund oilfield demonstrate both the similarity of the saucer-shaped intrusions and the distribution and quantity of dikes that may be undetected (ca. 78%) using subsurface data. Lack of detection of dikes has direct implications on the valuation of upward migration of fluids and an overestimation of seal capacity. This therefore has major implications when using seismic data to evaluate waste sequestration or to execute hydrocarbon or groundwater exploration and production.

Numerical Analysis on Boundary and Flow Regime of Magnetic Fluid in the Sealing Clearance With a Rotation Shaft

The magnetic fluid seal is one of the best known and widely used technical applications of magnetic fluid. However, the boundary and the flow regime with the rotation shaft cannot be observed by the experiment method. This paper presents a novel numerical simulation method to obtain the boundary and the velocity of the fluid in seals. The magnetic field of the seal is solved by the finite-element method, and the Navier–Stokes equations of the magnetic fluid based on the influence of magnetic force are solved by the finite-volume method. The two-phase flow is solved by the volume of fluid method. The seal capacities of the rectangle tooth and the trapezoid tooth with different rotation velocities are obtained. The result shows that the seal capacity decreases with the increase in the rotation velocity.

Numerical Analysis and Experimental Study on Magnetic Fluid Reciprocating Seals

Magnetic fluid is a new type of functional materials. The seal of reciprocating shaft is a typical application of the magnetic fluid. However, there is little research on the magnetic fluid reciprocating seals, thus improving the sealing life and seal capacity is the key problem of studying the reciprocating seals. This paper presents a structure of the seal to test the sealing life and other characteristics. The magnetic field of the seal is estimated using the finite-element method. The thickness of the magnetic fluid on the surface of reciprocating shaft and the flow rate of magnetic fluid are obtained theoretically. The experimental result shows that the static seal capacity is related to the fluid volume. The static seal capacity obtained by experiment is approximately equal to the value through the simulation with sufficient magnetic fluid. The relationship between sealing life and the motion of the reciprocating shaft is obtained experimentally. The sealing life decreases rapidly with the increase of the stroke and velocity.

Evaluation of sealing potential near gas chimneys–the Gippsland Basin, Australia

Gas chimneys are geological features that are associated with seal bypass systems. Knowledge of the capacity of the seal is important for the evaluation of the petroleum systems and Carbon Capture and Storage (CCS) studies. The seal is breached when the capillary pressure threshold is exceeded by the underlying buoyancy pressure. The chaotic seismic character that is generally associated with the gas chimneys has been studied previously to evaluate the origin and geometry of the chimneys. Seismic attributes have also been used to determine the character of the gas chimneys and the potential association of hydrocarbon fields. However, it is important to evaluate the sealing potential of the cap rock in the vicinity of the gas chimney. This paper demonstrates that the chimney can be used as a calibration point and, with the use of seismic attributes, variations of sealing capacity can be evaluated. Out of many existing seismic attributes, understanding the shale structure is crucial to narrow the search criteria for the right class of attributes. Using the most useful stream of seismic attributes, the average sealing potential of the Lakes Entrance Formation is estimated. The sealing capacity map across the field is then shown to help evaluate the prospectivity of the area of study and may upgrade subsequent play fairway maps.

Study on sealing capacity of packing element in compression packer

Sealing capacity of packing element is of great importance for compression packer. In this study, constitutive experiments and friction experiments of rubber material were carried out. Pressure penetration criterion was applied to numerical simulation model. In addition, a visible indoor experimental setup was established to verify the simulation model. Compressive deformation magnitude and sealing pressure difference capacity of packing element were obtained and compared in numerical simulation and experiment, which shows that the result in numerical simulation aligned with the experimental result. Compressive deformation magnitude and sealing pressure difference capacity both increase with the increase in axial load, but their growth trends are in different way. The study can offer some advices in predicting and improving the sealing capacity of packing element in compression packer.

Generation, migration, entrapment and leakage of microbial gas in the Dutch part of the Southern North Sea Delta

Understanding the shallow gas system is critical for assessing its potential as an energy source, for evaluating the possible hazard of shallow gas for drilling and wind farm locations and for evaluating the effect of gas emissions at the seabed on marine ecosystems and climate. This paper presents the key elements and processes of the microbial shallow gas system in the Plio-Pleistocene Dutch Southern North Sea Delta based on recent findings from different projects. Geochemical and carbon isotopic composition of shallow gas occurrences in the delta are indicative of a microbial origin of the gas. Shallow gas mainly occurs in stratigraphic traps and stacked anticlinal structures above salt structures, as indicated by identified direct hydrocarbon indicators on seismic, such as bright spots. Organic matter in the delta deposits is of predominantly land plant origin with TOC values varying between <1% and 5%, and mostly between 1 and 2%. Simulations of temperature and burial history in combination with dedicated 1D simulations of microbial gas generation reveal that gas generation in the delta started in Early Pleistocene Calabrian times and is still ongoing. Simulated volumes of gas generation are more than enough to fill published estimated volumes of shallow gas prospects in the delta. The geometry of the E-W prograding delta sequences and the close interbedding of interglacial silty/sandy and glacial clayey/silty sediments focus gas migration updip through the foresets towards the topsets of the delta sequences, and ultimately into the anticlinal stacked traps. Grain-size based calculations of the permeability and capillary seal capacity of clayey/silty seals of the stratigraphic and anticlinal traps provided first estimates of permeability values ranging from 2.8E-20 m2 to 1.1E-18 m2 and capillary seal capacity values between 10m and 24m. Comparison of gas column heights derived from grain-size based calculations, cross plots of neutron and density logs and pressure measurements, with trap heights derived from seismic bright spots suggests that many traps in stacked bright spots are not filled to structural spill point. This suggests that filling of the stacked reservoirs is not related to fill-spill migration, but rather to leakage through the top seal. In absence of fault and fracture zones crossing the seal, this leakage is related to the capillary seal capacity and permeability of the top seal. The leakage extends, locally, to the seabed. The microbial gas system in the delta today is a highly dynamic system driven by ongoing burial of the delta sediments and microbial gas generation. © 2018

Numerical Analysis and Experiment Study of Magnetic Fluid Boundary in Seals

Magnetic fluid seals are widely used technical applications of magnetic fluid. This paper presents a numerical simulation model to obtain the boundary of magnetic fluid in seals. The magnetic field in the seal is solved by finite element method, and the boundary is calculated by using Navier-Stokes equations in magnetic fluid. In order to observe the surface and obtain the seal capacity, the plane magnetic fluid seal experiment is carried out. The relationship between the seal capacity and the magnetic fluid volume is presented. The seal capacity which is obtained by the theoretical analysis has well congruence with the result of the experiment. The displacement of boundary with the pressure difference is quantitatively depicted.

Destruction of hydrocarbon reservoirs due to tectonic modifications: Conceptual models and quantitative evaluation on the Tarim Basin, China

The Tarim Basin in China is a complicated superimposed basin with four periods of hydrocarbon accumulations and three periods of modifications due to tectonic movements, forming complicated hydrocarbon reservoirs, many of which have gone through reservoir migration, reservoir scale reformation, reservoir damage and phase alterations a result of the tectonic events. Due to the complexity, the hydrocarbon exploration in this region has low success drilling rate. It is of great importance to study the destruction to the early hydrocarbon accumulations by the tectonic movements and quantitatively evaluate the remaining resource for understanding the current hydrocarbon distribution and guiding the exploration. This study analyzed six periods of large tectonic events in the Tarim Basin, and found the destroyed hydrocarbon volume was mainly controlled by four geological factors, including the ratio of the destroyed to the original hydrocarbon amount, tectonic event number and sequence, and the cap seal capacity. Larger ratio of destroyed hydrocarbon, less tectonic event number, later sequence and stronger cap seal capacity lead to more hydrocarbons preserved through the tectonic events. Based on the geological analysis, we established quantitative relationships among the destroyed hydrocarbon volume by the tectonic events (Ql), the volume of primary hydrocarbon accumulation (Q0), the ratio of destroyed hydrocarbon (Kl), the tectonic event number (n) and sequence (i), and cap seal capacity (fc). Using these relationships and the calibrated geological parameters, we delineated the hydrocarbon accumulation and destruction history and quantified the hydrocarbon loss due to the tectonic events for both the Tazhong area and the whole Tarim Basin. In the Tazhong area, four major accumulation events occurred at 510 Ma, 298 Ma, 227 Ma and 38 Ma with each accumulation underwent 68%, 59%, 28% and 0% of hydrocarbon loss due to later tectonic events. In total, over 60% of the original hydrocarbon reserves have been destroyed in the Tarim Basin, with an estimate of ca. 1.9 billion tons remaining hydrocarbons in the Tazhong area. At present, more than 95% oil and gas reservoirs and over 93% high quality exploration wells are located in the areas with high remaining resource potential predicted in this study, whereas 70% non-commercial production wells are located outside. Overall, this work shows that a careful evaluation of the damage to reservoirs from tectonic events can considerably enhance the success rate of hydrocarbon exploration.

Advances in high-pressure rotary sealing

Some types of rotating equipment employ a high-pressure lubricant between a pair of polymeric rotary seals. In hydraulic swivels, the lubricant transmits pressure between relatively rotatable components. In other equipment, such as an oilfield rotating control device (RCD), one seal excludes a high-pressure process fluid, whilst another retains the high-pressure lubricant. This article describes advancements in the life and pressure capacity of such seals.

The 2.1 Ga-old injectite network of the Franceville Basin, Gabon: Architecture, origin and implications on manganese mineralization

Detailed sedimentological investigations on numerous outcrops and drill-core sections in the 2.1-Ga-old Franceville basin, Gabon, provide evidence for a large-scale injectite network. The injectites were formed by the injection of sands through a thickness of about 150m of the FB1 Member, and now cover a minimum area of 70km2 corresponding to the Bangombé plateau, but are also recognized close to Franceville 35km farther south-east. The injectite lithology corresponds to a mud- or carbonate-supported sandstone characterized by a loose and uncompacted fabric contrasting with the host-rock. Because the injectites are often parallel to subparallel to the stratification, they were misinterpreted as depositional beds by previous authors. At outcrop, the injectite bodies exhibit sill, dyke, wing and protrusive geometries emplaced during early burial within poorly compacted material, with partial wall erosion and dissociation. The source of the sand material is attributed to a channel-levee turbidite depositional system located in the lower part of the FB1 Member. These deposits were buried by a thick biochemical muddy cap deposited during a starvation phase, which increased the seal capacity of the system. This type of architecture has a high potential to develop compaction disequilibrium during burial. Moreover, in the case of the Francevillian injectites, the abundance of microbial organic matter favoured early methane degassing and lateral charging of the sand reservoir. The overpressure in the channels was periodically released during early burial, through the effect of rapid sedimentary and tectonic loading, and possible seismic activity. The fluidized sand was injected according to a symmetrical wing pattern. Thus, the injected masses caused a local decrease in the grade of the lateritic manganese ore deposit of the Bangombé plateau.

Impact of Solid Surface Energy on Wettability of CO2-brine-Mineral Systems as a Function of Pressure, Temperature and Salinity

CO2 storage refers to the methods employed to inject CO2 in depleted oil and gas reservoirs and deep saline aquifers for long term storage of CO2 with the objective to reduce the anthropogenic CO2 emissions. Wettability and interfacial tension are two important multiphase parameters which are used to characterize the flow behavior of CO2 in reservoirs. Numerous studies have reported wettability data of CO2-brine systems on various rock forming minerals as function of pressure, temperature and salinity. However, the associated trends have not been physically well-understood and require considerable attention which is objective of our present work.In this work, we apply Neumann's equation of state method to our measured contact angle data for CO2-brine-mica systems and contact angle data of CO2-brine-quartz from Sarmadivaleh et al., 2015.Our results indicate that for mica, solid-CO2 interfacial tension decrease with pressure and salinity and increase with temperature. Moreover, solid-liquid interfacial tension decrease with temperature and decrease with salinity. For quartz, although the solid-CO2 interfacial tension decrease with pressure and increase with temperature, yet solid-liquid interfacial tension increase with temperature which explains the increase in contact angle with temperature for quartz. Overall, we find that results are in accordance with wettability data as function of pressure, temperature and salinity. We thus conclude that hotter reservoirs with lower injection pressure and lower brine salinities exhibit relatively better water wetting state and hence better seal capacity leading to higher CO2 storage potential. We also conclude that solid surface energy approach adequately explains the dependency of wettability on pressure, temperature and salinity.

Non-uniform Distribution of Magnetic Fluid in Multistage Magnetic Fluid Seals

Magnetic fluid, a new type of magnetic material, is a colloidal liquid constituted of nano-scale ferromagnetic particles suspended in carrier fluid. Magnetic fluid sealing is one of the most successful applications of magnetic fluid. As a new type of seal offering the advantages of no leakage, long life and high reliability, the magnetic fluid seal has been widely utilized under vacuum- and low-pressure-differential conditions. In practical applications, for improved pressure capacity, a multistage sealing structure is always used. However, in engineering applications, a uniform distribution of magnetic fluid under each tooth often cannot be achieved, which problem weakens the overall pressure capacity of the seals. In order to improve the pressure capacity of magnetic fluid seals and broaden their applications, the present study theoretically and experimentally analyzed the degree of non-uniform distribution of multistage magnetic fluid seals. A mathematical model reflecting the relationship between the pressure capacity and the distribution of magnetic fluid under a single tooth was constructed, and a formula showing the relationship between the volume of magnetic fluid and its contact width with the shaft was derived. Furthermore, the relationship of magnetic fluid volume to capacity was analyzed. Thereby, the causes of non-uniform distribution could be verified: injection of magnetic fluid; the assembly of magnetic fluid seals; the change of magnetic fluid silhouette under pressure loading; the magnetic fluid sealing mechanism of pressure transmission, and seal failure. In consideration of these causes, methods to improve the pressure capacity of magnetic fluid seals was devised (and is herein proposed).