Seal Unit Research Articles

Impact of alteration corridors on karst reservoir organisation and evolution of groundwater flow path: An example from the southern border of the Larzac Causse, southern France

All the features of karstic reservoirs result from the chemical and/or mechanical erosion of an initial rock volume, which modifies the initial petrophysical properties (i.e., porosity and permeability). The spatial distribution and organisation of the karst system in a carbonate massif are often overlooked in studies on karst hydrological functioning. However, these parameters are key to understand and accurately model dynamic flow. This contribution aims at characterising the nature and impact of alteration corridors on the organisation and evolution of the karstic reservoir and its present-day functioning. We focus on characterising the specific impact of the late onset of pocket valley regressive erosion on the organisation of the present-day drainage system. We used a 3D approach to correlate field observations on the surface and in caves, with remote sensing. The expression of alteration corridors is analysed in a 40 km2 area on the southern border of the Larzac Causse. This Jurassic carbonate massif is affected over its entire thickness by a network of vertically elongated alteration corridors containing dissolution-collapse breccia, mainly oriented in a N-S direction. Ghost-rock karstification played a significant part in the karstic reservoir structure and evolution. Alteration corridors result from the in-situ dissolution of the bedrock along an initial jointing pattern. The dissolution-collapse breccia corridors correspond to ghost-rock corridors selectively emptied of their alterite, under the effect of a hydraulic gradient. The vertically elongated structure of alteration corridors that cross-cut the Jurassic sequence enables fluid circulation from an upper to a lower aquifer, which were initially separated by a Toarcian marly seal unit. The subsequent initiation of pocket valleys led to the rapid evacuation of the residual alterite contained in ghost-rock corridors, under the influence of gravity. These alteration corridors determine the position of present-day pocket valley springs and enhance the regressive erosion dynamics, that progressively capture a north-east flowing watershed (Vis River). Finally, residual alterites are evacuated below the overflow spring altitude during high-flow events by flooding/dewatering of galleries. Such mechanisms of alterite evacuation provide insight into i) the part of the karstic reservoir that is connected to the spring, and ii) the dynamics of the associated flows. This study suggests that corridor networks constitute a substantial volume of porous and permeable materials that plays a major role in the present-day groundwater flow path. Such features should be considered valuable drilling targets for water exploration when located below the piezometric level.

Quantifying the impact of heat in support seal configuration for aero engines

AbstractLeakage, deformations, power loss, heat generation in the support seal system and other issues are typical when support seals are developed. The design of the support seal system has progressively evolved over recent decades as part of an ongoing effort to provide effective cooling for the aero engine secondary air system. In particular, oil heat management in the oil chamber has strict requirements, which limit the heat generation of the support seal system. The potential of supporting seal research with an oil system is investigated in this work. The combination of the CFD/FEA method and quantifying the heat generation entering the oil chamber allows for improvements not just to the individual buffer air seal unit, but the oil seal together. The analysis relies on the combination of quantifying heat generation entering the oil chamber to provide a mutual influence of neighbouring labyrinth seals. The mutual influence requires further analysis, considering the thermal deformation of the rotor/stator to provide further accurate geometry parameters in preliminary seal designs. The experimental test was conducted to verify the preliminary CFD-FEA loosely coupled analysis result, which reveals that in a turbine support seal system, the radius of the buffer air seal has a significant influence on the leakage flow rate and power loss of the oil seal, which should take into account the integral influence of the pressure difference of the oil seal caused by the radius change of the buffer air seal and the running clearance of the oil seal.

Triassic evaporites and the structural architecture of the External Hellenides and Albanides (SE Europe): controls on the petroleum and geoenergy systems of Greece and Albania

A combination of well data, seismic information on thrusting and tectonic shortening, plus analyses of the nature and depth of the Mesozoic units related to main detachment horizons (Triassic evaporites, flysch), are used to review, and further update the complex structural styles of the External Hellenides and Albanides Orogenic Belts, SE Europe. In the study area, the late Alpine orogenic evolution resulted in a structural architecture characterised by the successive westward thrusting of tectonic nappes (Gavrovo/Kruja, Ionian), with an imbricate tectonic style prevailing in all external zones. In the internal and central Ionian zone, imbricate thrusts and duplex structures are recorded, especially where about 24 km of stacked Mesozoic–Tertiary successions have been formed in Albania. Triassic evaporites, up to 3.5 km thick, acted as a detachment horizon for the internal deformation of the Ionian and Pre-Apulia zones (1.7–1.8 km thick in Greece), whereas the flysch unit of Upper Eocene–Oligocene (External Hellenides) and Oligocene–Aquitanian (Albanides) contributed to the deformation of the Ionian zone. In the Ionian zone, Triassic evaporites are laterally continuous and act as an effective seal unit when thrusted above Mesozoic carbonate/Tertiary units. Most of the oil and gas fields, oil shows and surface seeps have been developed in association with the relative more complex structure styles in the internal and the central Ionian zone of Albania and Greece. The Triassic evaporite detachment is detected at depths of 8–22 km in Albania, and about 5 km to 12–13 km in Greece. Thin and probably combination of thin- and thick-skinned deformation (SW Greece) of the Meso-Cenozoic succession above the Triassic evaporite and Permian sequences better depicts the complex structural architecture of the External Hellenides and Albanides, later affected by strike-slip tectonics and extensional deformation active since the Early Pliocene times. The main source rock levels, Lower Cretaceous shale/carbonate, Toarcian Posidonia and Triassic shales, are common in the Albanides and the Hellenides forelands. The thickness and Total Organic Carbon of these levels significantly increase in Albania, whereas trapping mechanism is almost the same and the Triassic evaporites play a significant role in both forelands. The hydrocarbon migration primarily followed developed thrust faults and important halokinesis, to charge fractured Cretaceous–Eocene carbonate reservoirs in the overthrust unit (Ionian zone), likely beneath the thrusted anticlinal belts. These sub-thrust structural models are related to the evaporites. Sub-thrust plays, referred to the autochthonous units (Apulia, Pre-Apulia/Paxos, Sazani zones), may also present reservoir potential in Albania and Western Greece. Upper Miocene and Pliocene deposits (sands) record reservoir potential in stratigraphic traps and good caprock characteristics in the Peri-Adriatic depression (Albania), whereas Messinian evaporites and clays may document seal potential for Upper Miocene sands in the southern areas of the Ionian Sea (Kyparissiakos Gulf, SW Kythira).

Cool seal unit obstruction as an unusual cause of pump exchange of centrifugal pump EVAHEART

Cool seal unit obstruction as an unusual cause of pump exchange of centrifugal pump EVAHEART

Gas hydrate petroleum systems: What constitutes the “seal”?

The gas hydrate petroleum system (GHPS) approach, which has been used to characterize gas hydrates in nature, uses three distinct components: a methane source, a methane migration pathway, and a reservoir that not only contains gas hydrate, but also acts as a seal to prevent methane loss. Unlike GHPS, a traditional petroleum system (PS) approach further distinguishes between the reservoir, a unit with generally coarser sediment grains, and a separate overlying seal unit with generally finer sediment grains. Adopting this traditional PS distinction in the GHPS approach facilitates assessments of reservoir growth and production potential. The significance of the seal for the formation of a gas hydrate reservoir as well as for efficiency in methane extraction from the reservoir as an energy resource is evident in findings from recent offshore field expeditions, such as India’s second National Gas Hydrate Program expedition (NGHP-02). In regard to gas hydrate-bearing reservoir formations, the NGHP-02 gas chemistry data indicate a primarily microbial methane source. Fine-grained seal sediment in contact with coarser grained reservoir sediment can facilitate that microbial methane production. Logging-while-drilling and sediment core data also indicate that the overlying fine-grained seal sediment is less permeable than the underlying, highly gas hydrate-saturated reservoir sediment. The overlying seal’s capacity to act as a low-permeability boundary is important not only for preventing methane migration out of the reservoir over time, but also for preventing water invasion into the reservoir during methane extraction from the reservoir. Ultimately, the presence of an overlying, fine-grained, low-permeability “seal” influences how gas hydrate initially forms in a coarse-grained reservoir and dictates how efficiently methane can be extracted as an energy resource from the gas hydrate reservoir via depressurization.

The status of harbour seals (Phoca vitulina) in the UK

Abstract Estimates of population size and trends are essential for effective conservation and management of wildlife populations. For harbour seals (Phoca vitulina), these data are required to fulfil statutory reporting obligations under national and international regulations. Aerial survey counts of harbour seals hauled out during their annual moult were used to estimate population sizes and trends at UK, regional (seal management unit, SMU) and local (Special Area of Conservation, SAC) scales. Results indicate that the current UK harbour seal population is similar to estimates from the late 1990s, but there were significant declines in some subpopulations and increases in others. Fitted trends suggest that the UK harbour seal population can be divided into three geographically coherent groups: South‐east populations (South‐East and North‐East England SMUs) have shown continuous increases punctuated by phocine distemper virus epidemics in 1988 and 2002; north‐east populations (East Scotland, Moray Firth, North Coast and Orkney, and Shetland SMUs) have declined since the late 1990s; north‐west populations (West Scotland, Western Isles, and South‐West Scotland SMUs) have remained stable or increased. Similar geographical population substructure is evident in recent population genetics results. Trends within SACs generally match SMU trends since 2002. Of the nine SACs designated for harbour seals, four declined (in East Scotland, Moray Firth, and North Coast and Orkney SMUs), four remained stable (in Shetland and West Scotland SMUs), and one increased (in South‐East England SMU). Large changes in relative abundance have resulted from differences in regional trends. For example, in 1996–1997 the West Scotland and North Coast and Orkney SMUs each held ~27% of the Great Britain population but now hold ~50% and ~4% respectively; in 1980, the South‐East England SMU population was ~50% that of the Wadden Sea population, but by 2016 it was equivalent to <20% of the Wadden Sea count.

Calcareous nannofossil assemblages of the Late Cretaceous Fiqa Formation, north Oman

Abstract. This study presents the first detailed calcareous nannofossil assemblage data from the Late Cretaceous succession of the subsurface Aruma Basin, north Oman. The taxonomic description and documentation of assemblage composition are based on extensive quantitative analysis of ditch cuttings and side-wall samples from eight hydrocarbon exploration wells across north Oman. The samples studied from those wells cover the Coniacian to earliest Maastrichtian deep marine shales and marls of the subsurface Fiqa Formation. These fine-grained siliciclastic deposits often yield moderately to well-preserved nannofossil assemblages, especially in the Campanian intervals. Consequently, diverse assemblages have been recorded from the Fiqa Formation, with a total diversity of ∼200 species, including two new species, Staurolithites ormae sp. nov. and Chiastozygus fahudensis sp. nov., which are illustrated and described. Extensive imaging of this diversity is provided here, as are stratigraphic distributions of the main components from a key reference well in north Oman, W-4. Poorly described groups such as Staurolithites are closely investigated and their utility for stratigraphic applications is highlighted. Relative abundances of nannofossil taxa with strong palaeoenvironmental preferences have revealed new insights into the palaeo-productivity of the basin. High-fertility species like Discorhabdus ignotus, Biscutum constans and Zeugrhabdotus erectus show substantial variations in abundance throughout the Fiqa Formation, reflecting long-term shifts in the productivity conditions of the basin. This is supported by abundance patterns of Watznaueria barnesiae and Micula staurophora that show a broadly inverse correlation with the high-fertility species. The Fiqa Formation represents a key regional seal unit for the Cretaceous hydrocarbon reservoirs of Oman, as well as being a productive unit elsewhere in the Arabian Peninsula. Beyond the Aruma Basin of Oman, this study will provide a key reference point for future biostratigraphic or palaeoenvironmental analyses of the Late Cretaceous calcareous nannofossil assemblages across the Middle East and other southern Tethyan areas.

Recurrent slope failure enhancing source rock burial depth and seal unit competence in the Pearl River Mouth Basin, offshore South China Sea

High-quality 3-D seismic data are used to assess the significance of mass-transport deposits (MTDs) to the evolution of the Pearl River Mouth Basin (South China Sea). Basal shear surfaces and lateral margins of seven recurrent MTDs are mapped to reveal a general NE-SW transport direction throughout the Late Miocene-Quaternary. A key result of our analysis is the perceived relationship between the recurrence of slope instability in the study area and the Dongsha Tectonic Event. Using borehole data to constrain the ages of interpreted MTDs, we show that tectonic uplift in the northern South China Sea led to slope oversteepening in the Late Miocene (between 10.5Ma and 5.5Ma), preconditioning it to fail recurrently for more than10Ma. Interpreted MTDs are shown to enhance burial depths of source and reservoir units, and improve seal competence in lower-slope areas. Conversely, upper slope regions record important erosion and reduced sealing capacity in Late Cenozoic strata. As a result, we postulate that the thickness variations imposed by MTDs on Late Miocene-Quaternary strata have important implications to petroleum plays in the South China Sea.

An Analysis of Mechanical Seal Failure of HTM Pump and its Improvement

Regarding the issue of short service life of mechanical seal of HITM pump in polyester production, this paper analyzes its causes, carries out the modeling, theoretical analysis, and discussion concerning the temperature flow field of seal faces, and puts forward the measure for improving the mechanical seal unit.

New insights from 3D geological models at analogue CO 2 storage sites in Lincolnshire and eastern Scotland, UK

Summary Subsurface 3D geological models of aquifer and seal rock systems from two contrasting analogue sites have been created as the first step in an investigation into methodologies for geological storage of carbon dioxide in saline aquifers. Development of the models illustrates the utility of an integrated approach using digital techniques and expert geological knowledge to further geological understanding. The models visualize a faulted, gently dipping Permo-Triassic succession in Lincolnshire and a complex faulted and folded Devono-Carboniferous succession in eastern Scotland. The Permo-Triassic is present in the Lincolnshire model to depths of −2 km OD, and includes the aquifers of the Sherwood Sandstone and Rotliegendes groups. Model-derived thickness maps test and refine Permian palaeogeography, such as the location of a carbonate reef and its associated seaward slope, and the identification of aeolian dunes. Analysis of borehole core samples established average 2D porosity values for the Rotliegendes (16%) and Sherwood Sandstone (20%) groups, and the Zechstein (5%) and Mercia Mudstone (<10%) groups, which are favourable for aquifer and seal units respectively. Core sample analysis has revealed a complex but well understood diagenetic history. Re-interpretation of newly reprocessed seismic data in eastern Scotland has significantly reduced interpretative uncertainty of aquifer and seal units at depths of up to −6 km OD in a complex faulted and folded Devono-Carboniferous succession. Synthesis of diverse data in the 3D geological model defines a set of growth folds and faults indicative of active Viséan to Westphalian dextral-strike slip, with no major changes in structural style throughout the Carboniferous, in contrast to some published tectonic models. Average 2D porosity values are 14–17% in aquifer units and <2% in the seal unit, with a ferroan dolomite cement occluding porosity at depth.

Development of an All-in-One Type Adsorption Heat Pump for Heating Application

The present research of adsorption heat pump system for heating application mainly focuses on its miniaturization and high output. When the adsorption heat pump is downsized the heat energy is insufficient to meet heating application. In addition, a large amount of low-temperature heat energy in industry has not been utilized but discharged into the atmosphere as waste heat. To improve energy efficiency and reduce carbon dioxide emission, it is important to effectively utilize the low-temperature heat source which is usually discarded as waste heat. In order to solve the problem between the miniaturization and the high output, a miniature all-in-one type adsorption heat pump which can effectively utilize waste heat is designed. In this design, a heat exchanger coated with adsorption material is used as an adsorber or desorber, and another heat exchanger is used as an evaporator or condenser. A seal unit is formed by assembling two heat exchangers into a vacuum tight container and is connected to the surroundings only by hydraulic piping. Moreover, the adsorbent is a functional adsorbent material-zeolite (AQSOA FAM-Z02, Mitsubishi Plastics) which can be regenerated by utilizing the low-temperature heat energy between 75 and 100°C. In this paper the design and experimental performance of this all-in-one type adsorption heat pump are described.

Development of an All-in-One Type Adsorption Heat Pump for Heating Application

The present research of adsorption heat pump system for heating application mainly focuses on its miniaturization and high output. When the adsorption heat pump is downsized the heat energy is insufficient to meet heating application. In addition, a large amount of low-temperature heat energy in industry has not been utilized but discharged into the atmosphere as waste heat. To improve energy efficiency and reduce carbon dioxide emission, it is important to effectively utilize the low-temperature heat source which is usually discarded as waste heat. In order to solve the problem between the miniaturization and the high output, a miniature all-in-one type adsorption heat pump which can effectively utilize waste heat is designed. In this design, a heat exchanger coated with adsorption material is used as an adsorber or desorber, and another heat exchanger is used as an evaporator or condenser. A seal unit is formed by assembling two heat exchangers into a vacuum tight container and is connected to the surroundings only by hydraulic piping. Moreover, the adsorbent is a functional adsorbent material-zeolite (AQSOA FAM-Z02, Mitsubishi Plastics) which can be regenerated by utilizing the low-temperature heat energy between 75 and 100°C. In this paper the design and experimental performance of this all-in-one type adsorption heat pump are described.

Complementary products and devices

The design of a contactless seal for use in collars of pump impellers of high-speed units is described. A cup with an unconventional scheme of loading and deforming (straining) of the cup body has been used in the design of the seal unit. At low differential pressures, the cup seal functions as a conventional cup seal, but at high differential pressures it turns into a slit seal. The maximum positive effect in terms of influence on the dynamic characteristics of the rotor is achieved at fixed ratios of the dimensions of the deformed cup and parts that form the seal unit. The data obtained by comparative experimental study of the cup-slit and conventional seal units are provided. Use of cup-slit seals having fluoroplastic (Teflon) cups in oxygen pumps will help reduce expenditures for finding a solution to the problem of safe operation of such pumps.

Hand tool machine with a seal unit with different sealing fields

Hand tool machine with a seal unit with different sealing fields

Application of acoustic emission technology for detecting the onset and duration of contact in liquid lubricated mechanical seals

The continuous quest for higher efficiency has led machinery to be designed closer to their limits and with minimum clearances in order to reduce leakage and consequently increase efficiency. This is particularly the case in the seal industry, where the inappropriate selection or deterioration of seals can greatly influence the life and efficiency of machinery. Typically, a mechanical seal unit consists of rotating and stationary parts separated by a fluid film. The aim of this investigation was to assess the applicability of Acoustic Emission (AE) technology for detecting the onset and duration of seal-to-seal contact; a possible result of breakdown of the separating film. It was concluded that the AE technology successfully identified the onset and duration of seal-to-seal contact.

Patents

Wellhead seal unit Seal shaft shutoff device Gasket seal for a fixed window and the production method Intumescent seal Shaft seal Thermal seal between manifold and nozzle Gasket for alkali battery Vehicle door seal Gate valve seal assembly Mechanical seal with plastic bellows Improved valve seal for rotary valve engine Seal for microlitre plate and methods of use Glass-scraper seal including magnetic elements for vehicle windows that can be opened Contoured seal facing jaws in vertical form fill and seal packaging system PTFE shaft seal and manufacturing method Drink-through lid seal

Effects of Compression, Staging, and Braid Angle on Braided Rope Seal Performance

Future turbine engines and industrial systems will be operating at increased temperatures to achieve more demanding efficiency and performance goals. In the highest temperature sections of the engine new material systems such as ceramics and intermetallics are being considered to withstand the harsh thermal environment. Components constructed of these low expansion-rate materials experience thermal strains and a resulting reduction of life when rigidly attached to high expansion-rate, superalloy support structures. Seals are being designed to both seal and to serve as compliant mounts allowing for relative thermal growths between high temperature but brittle primary structures and the surrounding support structures. Previous seal research yielded several braided rope seal designs which demonstrated the ability to both seal and serve as a compliant mount. The hybrid seal was constructed of an all-ceramic (alumina-silica) core overbraided with a superalloy wire sheath (cobalt based superalloy). The all ceramic seal was constructed of an all-ceramic (alumina-silica) core overbraided with multiple ceramic (alumina-silica) sheath layers. Program goals for braided rope seals are to improve flow resistance and/or seal resilience. To that end, the current report studies the test results of: baseline and modified hybrid seals; two stage hybrid and two stage all-ceramic seal configurations; and single stage hybrid and single stage all-ceramic seal configurations for a range of seal crush conditions. Hybrid seal modifications include increasing the sheath braid angle and core coverage. For the same percent seal cross-sectional crush, results show that increasing the hybrid seal braid angle increased seal stiffness and seal unit load, resulting in flows approximately one third of the baseline hybrid seal flows. For both hybrid and all-ceramic seals, two stage seal configurations significantly outperformed single stage configurations. Two stage seal flows were at least 30% less than the single stage seal flows for the same seal crush. Furthermore, test results of single stage seals indicate that for both all-ceramic and hybrid seals, a specific seal crush condition exists at which minimum flows are achieved (i.e. increasing seal crush beyond a certain point does not result in better flow performance). Flow results are presented for a range of pressures and temperatures from ambient to 1300 F, before and after scrubbing. Compression tests results show that for both all-ceramic and hybrid seals, seal preload and stiffness increase with seal crush, but residual seal interference remains constant.

In this issue…

WE LEAD THIS ISSUE with an interesting assessment (by J. K. Seedhouse and A. Racey of British Gas) of the sealing quality of the Triassic Mercia Mudstone Group in the East Irish Sea Basin. Hydrocarbons here are reservoired in the fluvial and aeolian sandstones of the Lower Triassic Sherwood Sandstone Group, a syn‐rift succession up to about one km thick. Both natural gas and crude oil are sourced from underlying Namurian shales, and are produced commercially at a number of relatively small fields located offshore NW England. A regional top‐seal is provided by the post‐rift Mercia Mudstones; however, the quality of this seal is very variable across the basin. In terms of general stratigraphy, the Mercia Mudstone Group is composed of alternating halite‐and mudstone‐rich units, which together reach a maximum thickness of over 3,000 m. Where a halite‐dominated unit directly overlies the reservoir sandstones, a very efficient seal is formed. However, halite‐rich units are limited in their areal distribution; where they are absent, mudstone‐dominated intervals may overlie the reservoir section, providing a seal of very variable quality. This paper reports on the factors which control the variation in seal integrity of the mudstone‐dominated units.The authors make use of downhole pressure data from a number of wells to give a first indication of Mercia Mudstone Group seal integrity. Pore pressures at the top of the oil column are seen to increase markedly, as would be expected, if the overlying sealing unit is halite‐dominated. The pressure build‐up is more variable where mudstones overlie the reservoir interval. In a second stage of the investigation, cores of the sealing interval from two wells and two onshore boreholes were logged in detail. Mercury‐injection porosimetry was used to assess the pore framework of selected core‐plug samples. The results indicate that variations in capillary entry pressures are the most important control on seal integrity in the mudstone‐dominated units. The authors also briefly assess other controls, including the presence of fractures in the seal unit, variable hydrocarbon saturation in the mudstones' pores, and variations in seal thickness across the basin.

Petroleum Geology of the Upper Jurassic and Lower Cretaceous, Baltimore Canyon Trough, Western North Atlantic Ocean (1)

Numerous hydrocarbon shows, including a noncommercial gas and gas-condensate accumulation, occur in the Baltimore Canyon Trough within sandstone units deposited in prograding coastal-plain and transitional-marine environments located updip of an Oxfordian/Kimmeridgian carbonate shelf edge. The coastal-plain and transitional-marine facies are overlain by a fine-grained deltaic complex dominated by delta-plain shales which collectively form a regionally extensive top seal unit. This deltaic complex prograded into a back-reef lagoon during aggradation of lower Kimmeridgian through Berriasian shelf-margin carbonates. Wells drilled seaward of the continental shelf edge (>1500 m water depth) tested large structural/stratigraphic closures along the downdip termination of the Upper Jurassic/Lower Cretaceous carbonate shelf edge but encountered no significant hydrocarbon shows. Reservoir rocks in these wells consist of (1) oolite grainstone, which was deposited within a shoal-water complex located at the Aptian shelf edge, and (2) coral-stromatoporoid grainstone and boundstone, which formed an aggraded shelf-margin complex located at the late Kimmeridgian through Berriasian shelf edge. Structural closures having reservoir and top seals are present in both updip and downdip trends. Hydrocarbon shows in wells along the shelf interior trend indicate the presence of mature source beds, at least locally. The absence of hydrocarbon shows in downdip carbonate reservoirs and around the Schlee Dome, however, suggests charge/migration mechanisms within the fetch areas of these objectives have failed. Failure of charge can be due to (1) absence of mature source rocks, (2) absence of migration pathways from source rocks to reservoirs, and/or (3) absence of top seals at the time of hydrocarbon migration. Continued development of play concepts in the Baltimore Canyon Trough, therefore, requires identification and mapping of potential source-rock intervals and construction of hydr carbon expulsion models to time hydrocarbon generation relative to trap formation.