Showing papers on "Overpressure published in 2003"

Brittle-failure controls on maximum sustainable overpressure in different tectonic regimes

Abstract: Formation or reactivation of brittle faults and fractures within low-permeability rocks capping regions of overpressured crust creates drainage conduits limiting the degree of overpressuring. Maximum sustainable overpressure is therefore affected by the local state of stress within the capping layer and by any existing architecture of faults and fractures. Reshear of existing cohesionless faults that are favorably oriented for frictional reactivation within the stress field provides the lower limiting bound to overpressures and inhibits development of other brittle structures. Formation of drainage conduits by hydraulic extension fracturing is important only in the case of intact caprock under low differential stress. Brittle-failure-mode plots demonstrate that maximum overpressure is inversely related to the level of differential stress and that high overpressures are easier to sustain in compressional regimes. Changes in the regional stress state in areas of overpressuring (for example, during tectonic inversion) may induce significant fluid redistribution.

A Loudness Calculation Procedure Applied to Shaped Sonic Booms

Abstract: The economic viability of a supersonic commercial transport airplane would be much enhanced if it could fly supersonically over land Efforts to design an airplane to produce a minimized sonic boom at the ground require knowledge of the impact of sonic booms on people Loudness, being a fundamental and well-understood characteristic of human hearing, was chosen as a means of quantifying the magnitude of sonic boom impact on people This paper describes in detail a procedure that can be used to calculate the loudness of sonic booms The procedure is applied to a wide range of sonic booms, both classical N-waves and a variety of other shapes of booms The loudness of N-waves is controlled by overpressure and the associated rise time The loudness of shaped booms is highly dependent on the characteristics of the initial shock A comparison of the calculated loudness values indicates that shaped booms may have significantly reduced loudness relative to N-waves having the same peak overpressure This result implies that a supersonic transport designed to yield minimized sonic booms may be substantially more acceptable than an unconstrained design

Overpressuring mechanisms in the Yinggehai Basin, South China Sea

Abstract: Yinggehai Basin is an elongate Cenozoic rift basin on the northwestern margin of the South China Sea continental shelf. Its thick (17 km) basin fill is characterized by high geothermal gradient and high overpressure. Overpressure associated with nonequilibrium compaction mainly occurs at depths more than 2800 m at the basin center and more than 4000 m at the basin margin because the shallow-buried Neogene and Quaternary strata lack effective seals. This regional overpressure distribution, however, is disrupted at basin center where high overpressure occurs in permeable formations at a depth as shallow as 1400 m on top of a series of deep-seated faults and fractures. We studied the processes and mechanisms of overpressuring via numerical modeling that couples basin filling, sediment compaction, and thermal and pressure fields to approach the origin of the shallow high overpressure. Model results indicated that an increase of fluid volume due to natural-gas generation by organic cracking is not large enough to generate the overpressure because of the limited amount of organic matter. The shallow overpressure has probably been generated allogenically. Deep open faults have served as vertical hydraulic conduits and channeled the deep high pressure into shallow permeable formations.

The origin of overpressure in ‘old’ sedimentary basins: an example from the Cooper Basin, Australia

Abstract: Overpressure in ‘old’ sedimentary basins that have not undergone rapid, recent sedimentation cannot be easily explained using traditional burial-driven mechanisms. The last significant burial event in the Cooper Basin, Australia, was the Late Cretaceous deposition of the Winton Formation (98.5–90 Ma). Maximum temperature in the basin was attained during the Late Cretaceous, with cooling beginning prior to 75 Ma. Hence, overpressure related to rapid burial or palaeomaximum temperatures (e.g. hydrocarbon generation) must have developed prior to 75 Ma. Retaining overpressure for 75 Ma in ‘old’ basins such as the Cooper Basin requires extremely low seal permeabilities. An alternative explanation is that overpressure in the Cooper Basin has been generated because of an increase in mean stress associated with an increase in horizontal compressive stress since Late Cretaceous times. Structural observations and contemporary stress data indicate that there has been an increase in mean stress of approximately 50 MPa between Late Cretaceous times to that presently measured at 3780 m. The largest measured overpressure in the Cooper Basin is 14.5 MPa at 3780 m in the Kirby 1 well. Hence, disequilibrium compaction driven by increasing mean stress can explain the magnitude of the observed overpressure in the Cooper Basin. Increases in mean stress (tectonic loading) may be a feasible mechanism for overpressure generation in other ‘old’ basins that have undergone a recent increase in horizontal stress (e.g. Anadarko Basin).

Regional And High-resolution 3D Pore-pressure Prediction In Deep-water Offshore West Africa

Abstract: Using both a regional and a high-resolution (HR), automated 3D velocity analysis method and the appropriate rock models, we predict a regressive pore-pressure system in a deep-water basin, offshore West Africa. The onset of overpressure takes place at the seafloor. The pressure gradient increases slowly but almost continuously, then rapidly to a maximum value, and then gradually reverses back to a lower value. The pressure profile follows certain geologic time horizons and structures very closely. Radial canyons on the seafloor significantly affect the porepressure profile. The high-resolution study provides velocity and pore pressure in more detail than the regional study.

Overpressure valve for the content of a package

Abstract: An overpressure valve for a packaging container is disposed on the inside of the packaging material comprising the packaging container The overpressure valve comprises a base plate, a diaphragm, and a connecting element The overpressure valve is relatively simple in construction and can be produced economically

Overpressure fluid flow and rapid accumulation of natural gas in Yinggehai Basin

Abstract: A new style of overpressure fluid flow,namely late-stage overpressure fluid flow, was found and verified in Yinggehai Basin on the basis of comprehensive study of the formation pressure structure, distribution and development mechanism of diapers, and the effects of overpressure fluid flow. Different from the overpressure fluid flow model of Cartwright, the overpressure fluid flow in Yinggehai Basin was in a closed system in the early stage and expulsed in a focused manner through diapers in the late stage. The focused flow of overpressure fluids resulted in the late-stage, episodic and rapid accumulation of natural gases. The trap of DFl-1 gas field was formed in the Quaternary, and the minimum average injection rate of the DFl-1 gas field was estimated to be up to 140 cubic meters per day. The inter-reservoir compositional heterogeneities,the transient state thermal effects resulted from fluid activities and the strong migration fractionation reflected the non-continuous fluid flows,rapid changes in temperature-pressure conditions during fluid migration and inter-action of multi-stage injected fluids, which could become the effective parameters for identifying episodic fluid migration.

Simple and safe method for determining explosion limits at elevated pressures

Abstract: A simple and safe method for determining the explosion limits at elevated pressures and temperatures is developed by using a small explosion test cell with a pressure balancing and containment design. Tests at elevated pressure are achieved by balancing the test-cell pressure and the containment-vessel pressure. If the vapor in the test cell is flammable and ignites, the overpressure will rupture the test cell but remain confined safely by the containment vessel. The method successfully achieved explosion-limit measurement at pressures up to 5.5 MPa with all the equipment components rated at a pressure of only 13.9 MPa. Results are presented for hydrogen and methane at ambient condition and elevated pressures, and shown to be in good agreement with the data in the literature. Preliminary results on the upper explosion limits of cyclohexane at cyclohexane oxidation conditions are also reported. The method will greatly benefit the study of explosion limits at elevated pressures and the safety of hydrocarbon/air oxidation processes.

Tank-venting system in a motor vehicle and method for checking the operability of the tank-venting system

Abstract: A method checks the operability of a tank-venting system for a motor vehicle having an internal combustion engine. The tank-venting system includes a fuel tank ( 10 ), an adsorption filter ( 20 ) and a filter line ( 12 ) connecting the adsorption filter to the fuel tank. The adsorption filter ( 20 ) has a venting line ( 22 ) and a switchover/check valve ( 70 ) is provided for closing off the venting line ( 22 ). The system includes a tank-venting valve ( 90 ) and a valve line ( 24 ) connecting the tank-venting valve to the adsorption filter. In the method, an overpressure relative to atmospheric pressure is introduced into the tank-venting system utilizing a drivable pressure source ( 50 ). An operating characteristic variable of the pressure source is detected while introducing the overpressure to determine the pressure course. A conclusion is drawn as to the presence of a leak from the pressure course. The overpressure is reduced by opening the tank-venting valve ( 90 ) and simultaneously closing said switchover/check valve ( 70 ).

Measurements and modeling of the shallow pore pressure regime at the Sigsbee Escarpment Successful prediction of overpressure and ground-truthing with borehold measurements

Abstract: Editor's note: The material in this paper was prepared and presented (OTC Paper 15201) at the 2003 Offshore Technology Conference, 5–8 May in Houston, Texas, U.S., and is published with permission. Shallow overpressures and shallow water flow (SWF) are significant hazards to deepwater drilling and facilities. In this paper we demonstrate how a combination of geomorphology, hydrogeology, and seismic interpretation has been successfully used in infer shallow overpressures, to develop a testable hypothesis of pore pressure distribution, and to delineate where to collect in-situ data. In-situ pore pressure measurements provide ground-truth data that can validate the model and be used to evaluate the hazards that internally driven failure might pose for facilities development. Several slope failures on the Sigsbee Escarpment in the Mad Dog and Atlantis field areas show a geomorphology distinct from “top-down” slope failures. Specifically, these slumps have steep, amphitheater-shaped headscarps, shallowly sloping bases, sharp inflection points with the surrounding seafloor at both the top and bottom of the headscarp, a linear trend in map view, and linear side walls. These geomorphic characteristics suggest that the slumps are formed by internally driven failure, and that the slumps grow retrogressively by headward migration. Within the Mad Dog and Atlantis field areas, Mad Dog Slump 8 and Atlantis Slump A are the best examples of this morphology; in this paper we will focus our attention on Mad Dog Slump 8 due to its proximity to planned facilities. The types of slope failures discussed in this paper are found on many margins worldwide. Their characteristic morphology indicates that the primary mechanism of slope failure is due to internal forcing (overpressure, weakening), rather than by downslope erosional flow. Internally driven slope failures can provide clues about the shallow overpressure regime, and provide exploration targets. Because the ocean is at constant head, and …

Inverse Method for Identification of Acoustic Sources at Launch Vehicle Liftoff

Abstract: At liftoff, launch vehicles are subjected to a very severe overpressure and to an acoustic environment that can induce loads acting on payloads in the low-frequency domain (frequencies lower than 40 Hz). The overpressure starts at ignition of solid-rocket motors. This overpressure phase is followed by the acoustic phase. The liftoff acoustic environment is generated by the rocket exhausts and by their impingement on the launch pad. For a numerical prediction of the acoustic environment, the European Aeronautic Defence and Space Company has developed an inverse method via a time domain boundary integral equations approach that uses an optimal control method, with direct and adjoint equations. The corresponding discrete schemes are highly accurate and unconditionally stable. As an industrial application, the identification of acoustic sources is shown, on the liftoff acoustic environment of ARIANE 5. With the sources from acoustic pressure measurements on the upper part of the ARIANE 5 vehicle and on the pylons around the launch pad having been localized and characterized in the time domain, the complete environment is recovered. By integration of the resulting acoustic pressures over all surfaces of the launchers, the loads created by the liftoff acoustic field can be estimated.

Discussion on mechanisms and controls on the formation of sand intrusions

Abstract: D. M. D. James writes: I congratulate the authors on a very clear and comprehensive account of a widespread and complex phenomenon of increasing economic importance. However, presumably for didactic ease, they have made some simplifications that I feel are counterproductive for full physical understanding. It is not entirely clear from the paper that sand intrusions require a concatenation of source/seal properties that on the face of it are very rare. These are that the source sand bed must have a negligible grain cohesion typical of burial at very low vertical effective stress (not shallow depth, necessarily) and that the seal must have effectively negligible permeability, typical of burial at very high vertical effective stress (and often associated with high cohesion). In most basins sands that can be fluidized are interbedded with ‘leaky‘ shales of high permeability (for shales) that do not sustain high overpressure during normal compaction. However, such high overpressure is vital because the intrusion is powered by a pressure decline at source that provides the mechanical energy to strain elastically the intrusion walls and to drive the ascent of the fluidized sand against frictional resistance. This cannot happen if fracture takes place when fluid pressure reaches a value merely equal to that of the horizontal stress (as illustrated by the authors in their figs 6 and 8) as this lies on the closure gradient of any fracture, not its inception gradient. How then can the requisite overpressure for fracture initiation and propagation be attained at the shallow depths normally associated with low vertical effective stress? Of the obvious ways around this problem, the development of zero permeability diagenetic or clathrate seals seems unlikely to be a universal solution. More likely, and not mentioned in the paper, is that the source pressure builds up at such a high …

Safety device for use as overpressure protection for a trapped volume space

Abstract: The invention is a safety device for a trapped volume space for use as overpressure protection made of a housing forming a chamber within a trapped volume space having a incompressible fluid, a compressible material disposed in the chamber, and a pressure relief component in communication with the compressible material and the incompressible fluid, wherein the pressure relief component is adapted to break at a predetermined point thereby increasing the trapped volume space by compressing the compressible material and resulting in a reduced pressure in the trapped volume space.

Biological effect of shock waves on rat brain: pathological evaluation by compact Ho:YAG-laser-induced cavitational shock wave generator

Abstract: To introduce shock wave as a new treatment modality for the lesions in the vicinity of brain and skull, pressure-dependent brain damages after exposure of shock wave were investigated. A novel compact Ho:YAG laser-induced cavitational shock wave generator (diameter: 15 mm, weight: 20g) was used intstead of clinical lithotriptors due to their wide distribution of shock waves. In the first part, we have developed and investigated characteristics of present generator by means of high-speed photography, shadowgraphy, and pressure measurement. Generation of localized shock wave without harmful effect of laser was observed after irradiation of Ho:YAG laser in the brass tube with internal water supply. Mechanical effect of accompanying laser-induced liquid jet was mitigated after placement of latex diaphragm with acrylic water reservoir. Maximum overpressure of generated shock wave was 15 MPa before placement of diaphragm, and 5 MPa after placement of diaphragm. In the second part, shock wave-induced brain damages were investigated in 5 male Sprague-Dawley rats. While subarachnoid hemorrhage could be observed between 1 and 5 MPa, intracerebral hemorrhage, and laceration of tissue were also observed above 5 MPa. We therefore conclude that overpressure of exposing shock wave over brain surface should be managed under 1 MPa.

An Introduction to Detonation and Blast for the Non-Specialist

Abstract: : Blast effects can play a significant role in target damage. This report gives an overview of how blast waves are formed and describes methods for scaling blast overpressure. The aim is to provide a concise overview of blast for the non specialist.

Development of Overpressure in the Tertiary Damintun Depression, Liaohe Basin, Northern China

Abstract: The Damintun depression is one of the four depressions in the Liaohe basin in northern China, and is a rift basin developed in the Paleogene. This paper discusses in detail the characteristics of pressure and fluid potential of the Damintun depression based on a synthesis of the data from boreholes, well tests and seismic surveys. Data from sonic logs, well tests and seismic velocity measurements are used to study the pressure characteristics of the areas. From the sonic log data, shales can be characterized as normally pressured, slightly overpressured or highly overpressured; from the well test data, the pressure-depth gradient in oil-producing intervals implies hydrostatic pressure in general. Most seismic profiles in the Damintun depression are of sufficiently high quality for seismic velocities to be measured. The fluid pressures, excess pressures and pressure coefficients in 47 representative seismic profiles are predicted using formula calculation methods, and further transformed to fluid potentials. The resultant pressure profiles show normal pressure, moderate overpressure and intense overpressure increasing with depth. The pressure evolution can be divided into three stages as initial generation, partial dissipation and re-accumulation. Fluid potential is the principal factor controlling hydrocarbon migration in a reservoir. Its distribution varies with depth; above the T4 interface a gravity-flow dominates, whereas beneath it a compaction flow dominates. The development of overpressure in the Damintun depression has a crucial influence on the distribution of fluid potentials, which agrees with that of overpressure in general. The results of the fluid potential analysis indicate that the areas of Dongshenpu-Xinglongpu and the southwestern part of the depression are most favorable for hydrocarbon migration and accumulation.

Shock waves propagation inside tunnels

Abstract: We accomplish numerical simulation for flow field o f chemical explosion inside tunnels by means of three dimensional numerical sim ulation, formulas of shock wave peak overpressure and duration are obtained, the verification is accomplished through comparison with experiment results.

Risking Basin Analysis Results

Abstract: The work presented here uses a basin analysis code, developed for Excel, to handle burial history, fluid flow, fracturing, overpressure development with time, erosion events, kerogen breakdown to o...

Linear-Theory-Based Shape Optimization for Sonic Boom Minimization

Abstract: An overpressure ground signature with more than two shocks is proposed for sonic boom minimization. A procedure coupling linear-theory-based sonic boom theory with a state-of-the-art optimization tool is presented. The method is used to reshape a candidate supersonic aircraft for a reduced initial shock pressure rise.

Characteristics of Overpressure Systems and Their Significance in Hydrocarbon Accumulation in the Yinggehai and Qiongdongnan Basins,China

Abstract: Overpressure systems are widely developed in the central depression and paleo-uplift in the Yinggehai and Qiongdongnan basins They can be divided into three types according to the origin of abnormally high formation pressure in the reservoirs, ie the autochthonous, vertically-transmitted and laterally-transmitted types The autochthonous overpressure system results from rapid disequilibrium sediment loading and compaction In the allochthonous overpressure system, the increase of fluid pressure in sandstone originates from the invasion of overpressured fluid flowing vertically or laterally through the conduit units The autochthonous overpressure system occurs in the deep-lying strata of Neogene age in the central depression of the Yinggehai and Qiongdongnan basins The vertically transmitted overpressure system is developed in the shallow strata of Late Miocene and Pliocene ages in the diapiric zone of the central Yinggehai basin, and the laterally transmitted overpressure system occurs in the Oligocene strata of paleo-uplifts, such as the structure of Ya-211 in the Qiongdongnan basin The results indicate that the autochthonous overpressure system is generally a closed one, which is unfavorable for the migration and accumulation of hydrocarbons In the allochthonous overpressure system, hydrocarbon accumulation depends on the relationship between the formation of overpressure systems and the spatial location and duration of hydrocarbon migration The interval overlying the overpressure system is usually a favorable hydrocarbon accumulation zone if the duration of fluid expulsion coincides with that of hydrocarbon accumulation

Thermobaric munitions and their medical effects

Abstract: Thermobaric munitions are those munitions that, by design, produce more heat and overpressure than conventional explosives by exploding a vapour in the blast zone. Their main use initially was in airborne fuel- air explosive bombs. Whilst the United States has concentrated on airborne weapons, Russia has produced thermobaric weapons and warheads, from airborne bombs to rifle grenades. Their medical effect is principally primary blast and they affect organs where there is a tissue interface of varying densities, such as the lungs, bowel and inner ear. Damage manifests itself in the severity and onset of occurrence, depending on distance from the blast and orientation of the victim, and can be diagnosed by simple investigative techniques. (author abstract)

Simulation Analysis of Indoor Gas Explosion Damage

Abstract: The influence factors and process of indoor gas explosion are studied with AutoReaGas explosion simulator. The result shows that venting pressure has great influence on the indoor gas explosion damage. The higher the venting pressure is, the more serious the hazard consequence will be. The ignition location has also evident effect on the gas explosion damage. The explosion static overpressure would not cause major injury to person and serious damage to structure in the case of low venting pressure (lower than 2 kPa). The high temperature combustion after the explosion is the major factor to person injury in indoor gas explosion accidents.