Predicting correct pore-pressure is important for drilling applications. Wellbore stability problems, kicks, or even blow-outs can be avoided with a good estimate of porepressure. Conventional pore-pressure estimation methods are based on one-dimensional compaction theory and depend on a relationship between porosity and vertical effective stress. Strike-slip or reverse faulting environments especially require a different way to determine pore-pressure, since the overburden is not the maximum stress. This study proposes a method which better accounts for the three-dimensional nature of the stress field and provides improved estimates of pore-pressure. We apply the mean total stress estimate to estimate pore-pressure. Pore pressure is then obtained by modifying Eaton’s pore-pressure equations, which require either resistivity or sonic log data. The method was tested in the Snorre Field in the Norwegian North Sea, where the field changes from strike-slip to reverse stress state. Eaton’s resistivity and sonic equations were used to predict pore-pressure in this region by replacing the vertical stress by the mean total stress estimate. Results suggest that the modified Eaton method with resistivity log data gives better results for the area than the conventional method. The ratio of maximum horizontal stress to minimum horizontal stress throughout each well should be known for best results.

It has generally been assumed that porosity reduction during mechanical compaction of a sediment is controlled by the increase in vertical effective stress. But the theory of mechanical compaction shows that it is the mean effective stress which controls porosity reduction. According to published data, horizontal stresses increase with overpressure, as well as with depth, so mean stress and vertical stress profiles are poorly correlated in overpressured sections. In this study, a new methodology was developed whereby mudrock pore pressures were estimated principally by comparison of void ratios calculated from wireline log response with hydrostatic mean effective stress (the mean effective stress assuming the pore pressure is hydrostatic). These pressure estimates in the low permeability units were compared to the direct measurements in the aquifer units and an interpretation is made as to the origin of the excess pressure. The results of analysis of seven wells from SE Asia are presented including one study where seismic velocity analysis and basin modelling were performed to assess the pore pressure. The main conclusions of the study are: The proposed new methodology for estimating shale pore pressure from void ratio and mean effective stress analysis appears to be more consistent with the data and represents an improvement on previous methodologies using porosity and vertical effective stress or depth. Analysis of the mudrocks in this study indicates that the shales often appear to have significantly higher pressures than the adjacent aquifer units. The results of using mean (as opposed to vertical) effective stress analysis indicates that the pressure profiles in the wells studied, the profiles disequilibrium compaction can account for all or nearly all of the encountered overpressures. Evidence has been found for significant overpressure generated by fluid expansion in one of the seven wells studied.« Further work to refine the Breckels and Van Eekelen (1982) relationship between overpressure and horizontal stress is proposed to improve the accuracy of the methodology used in this study.

A systematic study of how mudstone permeability impacts reservoir pore pressure is important to understand the regional fluid field within sedimentary basins and the control of sediment properties on subsurface pressure. I develop a 2D static model to predict reservoir overpressure from information estimated from the bounding mudstones and structural relief. This model shows that close to a dipping reservoir, the mudstone permeability is high in the up-dip location and low in the down-dip location. This characteristic mudstone permeability variation causes the depth where reservoir pressure equals mudstone pressure (equal pressure depth) to be shallower than the mid-point of the reservoir structure. Based on the 2D static model, I constructed a nomogram to determine the equal pressure depth by considering both farfield mudstone vertical effective stress and reservoir structural relief. I find the equal pressure depth becomes shallower with decreasing vertical effective stress, increasing reservoir structural relief, and increasing mudstone compressibility. Pressure predicted by the static model agrees with pressure predicted by a more complete model that simulates the evolution of the basin and is supported by field observations in the Bullwinkle Basin (Green Canyon 65, Gulf of Mexico). This study can be applied to reduce drilling risk, analyze trap integrity, and facilitate safe and efficient exploration. / text

Blast neurotrauma represents a significant mode of traumatic injury to the brain. The incidence of blast neurotrauma is particularly high amongst military combat personnel and can be debilitating and endure clinically for years after injury is sustained. Mechanically, blast represents a unique and complex loading paradigm associated with compressive shock waves that propagate out from an explosive event and interact with the head and other organs through high-rate loading. When subjected to such insult, brain cells undergo characteristic injury responses which include neuroinflammation, oxidative stress, edema and persistent glial activation. These features of the injury have emerged as important mediators of the chronic brain damage that results from blast. Astrocytes have emerged as a potential therapeutic target because of their ubiquitous roles in brain homeostasis, tissue integrity and cognitive function. This glial subtype has a characteristic reactive response to mechanical trauma of various modes. In this work, custom in vitro injury devices were used to characterize functional models of astrocyte reactivity to high-rate insult to study mechano-stimulation mechanisms associated with the reactive phenotype. The working hypothesis was that high-rate overpressure exposure would cause metabolic aberrations, cell junction changes, and adhesion signal transduction activation, all of which would contribute to astrocyte response and reactivity. Astrocyte cultures were exposed to a 20 psi high-rate overpressure scheme using an underwater explosion-driven device. Astrocytes experienced dynamic energetic fluctuations in response to overpressure which were followed by the assumption of a classically defined reactive phenotype. Results indicated specific roles for cationic transduction, cell junction dynamics (gap junction and anchoring junctions) and downstream signal transduction mechanisms associated with adhesion alterations in onset of the astrocyte reactive phenotype. Investigation into adhesion signaling regulation by focal adhesion kinase in 2D and 3D cultures was also explored to better understand cellular reactivity as a function of extracellular environment. Additionally, another underwater in vitro device was built to study combination effects from overpressure and fluid shear associated with insult. Overall, the combined studies offer multiple mechanisms by which to explore molecular targets for harnessing astrocytes' potential for repair after traumatic injury to the brain. / PHD / Blast neurotrauma represents a significant mode of traumatic injury to the brain. The incidence of blast neurotrauma is particularly high amongst military combat personnel in which close to 80% of the injuries sustained in combat are attributed to explosive mechanisms. This injury, like other traumatic brain injuries, can be debilitating and result in altered quality of life for years after injury is sustained. There is a critical need to understand how brain cells are injured by and respond to blast loading in order to develop effective therapeutic strategies. The following work approaches this problem through the use of cellular models of blast-type insult. Custom injury devices were used to develop models of brain cell reactive response to high-rate insult based on experimental simulations of blast neurotrauma. In particular, a sub-type of brain cells called astrocytes were studied. Astrocytes have emerged as a potential therapeutic target because of their ubiquitous roles in brain homeostasis, tissue integrity and cognitive function. The working hypothesis was that high-rate overpressure exposure would cause metabolic aberrations, cell junction changes, and adhesion signal transduction activation, all of which would contribute to astrocyte response and reactivity. Astrocytes experienced dynamic energetic fluctuations in response to overpressure which were followed by the assumption of a classically defined reactive phenotype. Results indicated specific roles for cationic transduction, cell anchorage and downstream signaling mechanisms associated with adhesion alterations in onset of the astrocyte reactive phenotype. Investigation into adhesion signaling regulation by focal adhesion kinase in 2D and 3D cultures was also explored to better understand cellular reactivity as a function of extracellular environment. Additionally, another underwater cell injury device was built to study combination effects from overpressure and fluid shear associated with insult. Overall, the combined studies offer multiple mechanisms by which to explore molecular targets for harnessing astrocytes’ potential for repair after traumatic injury to the brain.

The Northern Carnarvon Basin is the richest petroleum province in Australia. About 50 gas/condensate and oil fields, associated mainly with Jurassic source rocks, have been discovered in the sub-basins and on the Rankin Platform since 1964. The basin is located at the southern end of the North West Shelf of Australia. It can be mainly subdivided into the Exmouth, Barrow, Dampier and Beagle Sub-basins, the Rankin Platform and Exmouth Plateau. The sub-basins are rift-related grabens and half-grabens developed during the Jurassic to the earliest Cretaceous and contain over 10 kilometres of Mesozoic and Cainozoic sedimentary rocks, among which are several thousand meters of Jurassic rocks. The formations of the Jurassic and the lower part of the Barrow Group of Early Cretaceous age in the sub-basins of the Northern Carnarvon Basin were found to be overpressured with excess pressures of 5-29 MPa at depths of 2900-3600 m indicated by repeat formation tests (RFTs) and drill stem tests (DSTs). The characteristics of organic matter, thermal history and thermal maturity, pressure seal and overpressure evolution in the sub-basins are crucial to a proper understanding of the nature and dynamic processes of hydrocarbon generation and migration in the basin. Based on organic geochemical data, the important source rocks in the basin are Jurassic organic-rich fine-grained rocks including the Murat Siltstone, the rift-related Athol Formation and Dingo Claystone. The Mungaroo Formation of the Middle-Upper Triassic contains gas-generating source rocks. These formations recognised to be organic rich based on 1256 values of the total organic carbon content (TOC, %) from 17 wells. Average TOC values (calculated from samples with TOC < 15 %) are about 2.19 % in the Mungaroo Formation, about 2.09 % in the Murat Siltstone and about 1.74 % in the Athol Formation and Dingo Claystone. / Data from kerogen element analysis, Rock-Eval pyrolysis, visual kerogen composition and some biomarkers have been used to evaluate the kerogen type in the basin. It appears that type III kerogen is the dominant organic-matter type in the Triassic and Jurassic source rocks, while the Dingo Claystone may contain some oil-prone organic matter. The vitrinite reflectance (Ro) data in some wells of the Northern Carnarvon Basin are anomalously low. As a major thermal maturity indicator, the anomalously low Ro data seriously hinder the assessment of thermal maturity in the basin. This study differs from other studies in that it has paid more attention to Rock-Eval Tmax data. Therefore, problems affecting Tmax data in evaluating thermal maturity were investigated. A case study of contaminated Rock-Eval data in Bambra-2 and thermal modelling using Tmax data in 16 wells from different tectonic subdivisions were carried out. The major problems for using Tmax data were found to be contamination by drilling-mud additives, natural bitumen and suppression due to hydrogen index (HI) > 150 in some wells. Although the data reveal uncertainties and there is about ±3-10 % error for thermal modelling by using the proposed relationship of Ro and Tmax, the "reliable" Tmax data are found to be important, and useful to assess thermal maturity and reduce the influence of unexpectedly low Ro data. / This study analyzed the characteristics of deep overpressured zones and top pressure seals, in detail, in 7 wells based on the observed fluid pressure data and petrophysical data. The deep overpressured system (depth greater than 2650-3000 m) in the Jurassic formations and the lower part of the Barrow Group is shown by the measured fluid pressure data including RFTs, DSTs and mud weights. The highly overpressured Jurassic fine-grained rocks also exhibit well-log responses of high sonic transit times and low formation resistivities. The deep overpressured zone, however, may not necessarily be caused by anomalously high porosities due to undercompaction. The porosities in the deep overpressured Jurassic rocks may be significantly less than the well-log derived porosities, which may indicate that the sonic-log and resistivity-log also directly respond to the overpressuring in the deep overpressured fine-grained rocks of the sub-basins. Based on the profiles of fluid pressure and well-log data in 5 wells of the Barrow Sub-basin, a top pressure seal was interpreted to be consistent with the transitional pressure zone in the Barrow Sub-basin. This top pressure seal was observed to consist of a rock layer of 60-80 % claystone and siltstone. The depths of the rock layer range from 2650 m to 3300 m with thicknesses of 300-500 m and temperatures of 110-135 °C. Based on the well-log data, measured porosity and sandstone diagenesis, the rock layer seems to be well compacted and cemented with a porosity range of about 2-5 % and calculated permeabilities of about 10-19 to 10-22 M2. / This study performed thermal history and maturity modelling in 14 wells using the BasinMod 1D software. It was found that the thermal maturity data in 4 wells are consistent with the maturity curves predicted by the rifting heat flow history associated with the tectonic regime of this basin. The maximum heat flows during the rift event of the Jurassic and earliest Cretaceous possibly ranged from 60-70 mW/m2 along the sub-basins and 70-80 mW/m2 on the southern and central Exmouth Plateau. This study also carried out two case studies of thermal maturity and thermal modelling within the deep overpressured system in the Barrow and Bambra wells of the Barrow Sub-basin. These case studies were aimed at understanding whether overpressure has a determinable influence on thermal maturation in this region. It was found that there is no evidence for overpressure-related retardation of thermal maturity in the deep overpressured system, based on the measured maturity, biomarker maturity parameters and 1D thermal modelling. Therefore, based on the data analysed, overpressure is an insignificant factor in thermal maturity and h hydrocarbon generation in this basin. / Three seismic lines in the Exmouth, Barrow and Dampier Sub-basins were selected and converted to depth cross-sections, and then 2D geological models were created for overpressure evolution modelling. A major object of these 2D geological models was to define the critical faults. A top pressure seal was also detected based on the 2D model of the Barrow Sub-basin. Two-dimensional overpressure modelling was performed using the BasinMod 2D software. The mathematical 2D model takes into consideration compaction, fluid thermal expansion, pressure produced by hydrocarbon generation and quartz cementation. The sealed overpressured conditions can be modelled with fault sealing, bottom pressure seal (permeabilities of 10-23 to 10-25 M2 ) and top pressure seal (permeabilities of 10-19 to 10-22 m2). The modelling supports the development of a top pressure seal with quartz cementation. The 2D modelling suggests the rapid sedimentation rates can cause compaction disequilibrium in the fine-grained rocks, which may be a mechanism for overpressure generation during the Jurassic to the Early Cretaceous. The data suggest that the present-day deep overpressure is not associated with the porosity anomaly due to compaction disequilibrium and that compaction may be much less important than recurrent pressure charges because most of the porosity in the Jurassic source rocks has been lost through compaction and deposition rates have been very slow since the beginning of the Cainozoic. / Three simple 1D models were developed and applied to estimate how rapidly the overpressure dissipates. The results suggest that the present day overpressure would be almost dissipated after 2 million years with a pressure seal with an average permeability of 10-22 M2 (10-7 md). On the basis of numerous accumulations of oil and gas to be expelled from the overpressured Jurassic source rocks in the basin and the pressure seal modelling, it seems that the top pressure seal with permeabilities of 10-19 to 10-22 M2 (10-4 to 10-7 md) is not enough to retain the deep overpressure for tens of millions of years without pressure recharging. Only if the permeabilities were 10-23 m2 (10-8 md) or less, would a long-lived overpressured system be preserved. This study suggests that hydrocarbon generation, especially gas generation and thermal expansion, within sealed conditions of low-permeability is a likely major cause for maintaining the deep overpressure over the past tens of millions of years. Keywords: Thermal history; Deep overpressure; Type III kerogen; Rock-Eval Tmax; Thermal maturity; Palaeoheatflow modelling; Pressure seal; 2D deep overpressure modelling; Pressure behaviour modelling; Overpressure generation; Northern Carnarvon Basin.

Geological carbon dioxide (CO₂) storage in deep geological formations can only lead to significant reductions in anthropogenic CO₂ emissions if large amounts of CO₂ can be stored safely. Determining the storage capacity, which is the volume of CO₂ stored safely, is essential to determine the feasibility of geological CO₂ storage. One of the main constraints for the storage capacity is the physical mechanisms of fluid flow in heterogeneous formations, which has not been studied sufficiently. Therefore, I consider two related problems: a) the evolution of injection-induced overpressure that determines the area affected by CO₂ storage and b) the rate of buoyant fluid flow along faults that determines the leakage of CO₂. I use a layered model of a sandstone reservoir embedded in mudrocks to quantify the increase in storage capacity due to dissipation of overpressure into the mudrocks. I use a model of a fault surface with flow barriers to constrain the reduction in the buoyancy-driven leakage flux across the fault. Using the layered model with injection at constant rate, I show that the pressure evolution in the reservoir is controlled by the amount of overpressure dissipated into ambient mudrocks. A main result of this study is that the pressure dissipation in a layered reservoir is controlled by a single dissipation parameter, M, that is identified here for the first time. I also show that lateral pressure propagation in the storage formation follows a power-law governed by M. The quick evaluation of the power-law allows a determination of the uncertainty in the estimate of the storage capacity. To reduce this uncertainty it is important to characterize the petrophysical properties of the mudrocks surrounding the storage reservoir. The uncertainty in mudrock properties due to its extreme heterogeneity or limited data available can cause large variability in these estimates, which emphasizes that careful characterization of mudrock is required for a reliable estimate of the storage capacity. The cessation of the injection operation will reduce overpressure near the injector, but regional scale pressure will continue to diffuse throughout the whole formation. I have been able to show that the maximum radius of the pressure plume in the post-injection period is approximately 3.5 times the radius of the pressure plume at the cessation of injection. Two aquifers can be hydraulically connected by a fault cutting across the intermediate aquitard. If the upper aquifer contains denser fluid, an exchange flow across the fault will develop. The unstable density stratification leads to a fingering pattern with localized zones of upwelling and downwelling along the fault. Due to the small volume of the fault relative to the aquifers, the exchange-flow will quickly approach a quasi steady state. If the permeability of the fault plane is homogeneous, the average number of the quasi-steady plume fingers, (nu), scales with the square root of the Rayleigh number Ra and the exchange flux measured by dimensionless convective flux, the Sherwood number, Sh, is a linear function of Ra. The dispersive flux perpendicular to the flow direction induces the formation of wider fingers and subsequently the less convective flux parallel to the flow direction. In the flow system with larger Ra, even the same increase in transverse dispersivity [alpha]T causes stronger impact of the mechanical dispersion on the vertical exchange flow so that (nu) and Sh reduce more with larger [alpha]T . Both measured characteristics, however, follow the same scaling for the non-dispersive homogeneous case by using a modified Rayleigh number, Ra*, considering the mechanical dispersion. The presence of flow barriers along the fault triggers unsteady exchange flow and subsequently controls the growth of the plume fingers. If the barriers are sufficiently wide to dominate the flow system, they create preferential pathways for exchange flow that determines the distribution of the quasi-steady fingers, and (nu) converges to a constant value. In addition, wider barriers induce substantial lateral spreading and enhance the efficiency of structural trapping, and reduce the exchange rate but still follows a linear relationship function of the effective Rayleigh number, Raeff , defined by the vertical effective permeability. This study is motivated by geological CO₂ storage in brine-saturated aquifer, but the effect of geological heterogeneity is also important in many other geological and engineering applications, in particular the risk assessment of the injection operations or the migration of hydrocarbons in tectonic-driven or hydraulically developed faults in reservoirs. Better understanding of fluid flow in geologically heterogeneous formations will allow more precise estimate of the reservoir capacity as well as more efficient operation of injection or production wells. / text

When CO₂ is injected in deep saline aquifers on the scale of gigatonnes, pressure buildup in the aquifer during injection will be a critical issue. Because fracturing, fault activation and leakage of brine along pathways such as abandoned wells all require a threshold pressure (Nicot et al., 2009); operators and regulators will be concerned with the spatial extent of the pressure buildup. Thus a critical contour of overpressure is a convenient proxy for risk. The location of this contour varies depending on the target aquifer properties (porosity, permeability etc.), the geology (presence of faults, abandoned wells etc.), and boundary conditions. Importantly, the extent also depends on relative permeability (Burton et al., 2008). First we describe ways of quantifying the risk due to pressure buildup in an aquifer with a constant pressure boundary, using the three-region injection model to derive analytical expressions for a specific contour of overpressure at any given time. All else being the same, the two-phase-region mobilities (and hence relative permeability characteristics) provide a basis for the ranking of storage formations based on risk associated with pressure elevation during injection. The pressure buildup during CO₂ injection will depend strongly upon the boundary conditions at the boundary of the storage formation. An analytical model for pressure profile in the infinite-acting aquifer is developed by combining existing water influx models in traditional reservoir engineering (Van-Everdingen and Hurst model, Carter-Tracy model) to the current problem for describing brine efflux from the storage aquifer when CO₂ injection creates a "three-region" saturation distribution. We determine evolution of overpressure with time for constant pressure, no-flow and infinite-acting boundary conditions, and conclude that constant pressure and no-flow boundary conditions give the most optimistic and pessimistic estimates of risk respectively. Compositional reservoir simulation results, using CMG-GEM simulator are presented, to show the effect of an isolated no-flow boundary on pressure buildup and injectivity in saline aquifers. We investigate the effect of multiple injection wells on single-phase fluid flow on aquifer pressure buildup, and demonstrate the use of an equivalent injection well concept to approximate the aquifer pressure profile. We show a relatively inexpensive method of predicting the presence of unanticipated heterogeneities in the formation, by employing routine measurements such as injection rate and injection pressure to track deviation in the plume path. This idea is implemented by combining Pro-HMS (probabilistic history matching software, that carries out geologically consistent parameter estimation), and a CMG-GEM model which has been tuned to the physics of the CO₂-brine system. / text

Perdas de água em redes de distribuição acontecem por diversas razões, uma delas, o excesso de pressão, pode ser prevenido através da divisão das redes em Distritos de Medição e Controle. Este método vem sendo utilizado há algum tempo como modo de prevenir sobrepressão na rede, aumentando a confiabilidade e vida útil das tubulações e dispositivos do sistema. Atualmente, alguns autores propõem diferentes tipos de metodologias para uma eficiente definição de Distritos de Medição e Controle. Neste trabalho foi criada e aplicada uma metodologia baseada no estudo de uma área (Setor Aracy) na cidade de São Carlos - SP guiado por análise topográfica. A rede de distribuição do setor de abastecimento foi analisada indicando um subdimensionamento em alguns trechos, assim como, foi concluído que já existe uma setorização na área que não foi guiada por análise topográfica e sim por implantação dos loteamentos. Um estudo de setorização que tem como objetivo o gerenciamento de pressões deve ser norteado por análise da topografia do local juntamente com dispositivos gerenciadores de pressão (válvulas, boosters etc). / Water losses in network distribution systems may happen due to many reasons, one of them, the overpressure, can be prevented through the partitioning of these networks in District Metered Areas. This method has been used for some time as a way of preventing network overpressure, enhancing the reliability and lifespan of pipes and system devices. Currently, some authors propose different methodologies to an efficient delimitation of the District Metered Areas. In this work, a methodology was conceived and applied based on the study of an area (Aracy Sector) in the city of São Carlos - SP guided by topographic analysis. The distribution network of the supply sector was analyzed indicating an undersize in some pipes, as well as, it was concluded that a sectorization already exists in the area that is not guided by topographic analysis, but by the implementation of the allotments. A sectorization study that aims to manage pressures should be guided by topographic analysis of the site, together with pressure management devices (valves, boosters etc).

The high ozone depletion and global warming potentials of fluorocarbon refrigerants have resulted in prohibitions and restrictions in many markets. Hydrocarbon refrigerants have low environmental impacts and are successfully used in domestic refrigerators and car air conditioners but replacing fluorocarbons in centrifugal chillers for air conditioning applications is unknown. Hydrocarbon replacements need a heat transfer correlation for refrigerant in flooded evaporators and predictions for operating conditions, capacity and performance. Safety precautions for large quantities of hydrocarbon refrigerants are needed and control of overpressure in plantrooms requires accurate prediction. Reliable correlations exist for forced convection in a single phase flow, condensation outside tubes and evaporation off sprayed tubes. For flooded evaporators this thesis proposes a new correlation for forced convection boiling of any refrigerant. An enhancement factor is combined with a modified Chen coefficient using recent pool boiling and forced convection correlations outside tubes. This correlates within typically a factor of two to known boiling literature measurements for CFC-113, CFC-11, HCFC-123, HFC-134a and HC-601. The operating conditions, capacity and performance of replacement hydrocarbons in centrifugal chillers were predicted using fluorocarbon performance as a model. With the new heat transfer correlation hydrocarbon predictions for flooded evaporators were made. For any fluorocarbon refrigerant there exists a replacement mixture of hydrocarbons which with a rotor speed increase about 40% gives the same cooling capacity in the same centrifugal chiller under the same operating conditions. For example replacing HCFC-123 in a flooded evaporator with HC-601/602 [90.4/9.6] and increasing the rotor speed by 43% will increase the coefficient of performance by 4.5% at the same cooling capacity. The maximum plantroom overpressure considered was from leakage and ignition of a uniform air/refrigerant mixture with maximum laminar burning velocity. Flow was modelled using a turbulence viscosity due to Launder and Spalding and turbulent deflagration using a reaction progress variable after Zimont. These partial differential equations were solved approximately for two and three dimensional geometries using finite volume methods from the Fluent program suite. Simple overpressure predictions from maximum flame area approximations agreed with Fluent results within 13.7% promising safe plantroom design without months of computer calculation.

<p>This thesis work has been performed at the department of diagnosis and dependability at Volvo Car Company, Torslanda. The background of this project is based on interest in ascertaining how different factors possibly can affect a diagnosis method, which has been developed to find leaks in the fuel tank and evaporation system. According to the OBD II requirements leaks with an orifice diameter larger or equal to 0,5 mm, must be detected. The idea of the diagnosis method is to create an over pressure in the system with an air-pump. The current through the pump is measured and correlates to the power consumed by the pump. As the power is a function of the pressure difference over the pump, the pump current correlates to the pressure in the tank. Thus, the pump current can be used as a measure of the impenetrability. Changes in the system pressure, not caused by the pump, are accordingly disturbances to the method. </p><p>The object of this work was to develop mathematical models, describing the lapse where the system is pressurized by the pump under the influence of different physical factors. The model is for instance considering variations in temperature and height, flow resistance in lines and valves, component characteristics, fuel evaporation, leaks etc. Furthermore the pump current is treated by the diagnosis evaluation algorithm with purpose to judge whether there is a leak in the system. </p><p>The model has been implemented in Matlab/Simulink and it can consequently be used in dynamic simulations according to the over pressure leakage detection concept. Numerical experiments can be done in purpose to examine how changes in environmental conditions or component characteristics will affect the diagnosis method. Good agreement has been found between measurements and simulated results. The diagnosis function produces correct decisions under different conditions with disparity in leak sizes, additionally confirming the reliability of the model.</p>