Hydrostatic Value Research Articles

Pleasant Bayou Geopressured-Geothermal Reservoir Analysis—October 1991

Many sedimentary basins contain formations with pore fluids at pressures higher than hydrostatic value; these formations are called geopressured. The pore pressure is generally well in excess of hydrostatic and the fluids are saline, hot, and contain dissolved methane. The U.S. Department of Energy (DOE) has drilled and tested deep wells in the Texas-Louisiana Gulf Coast region to evaluate the geopressured-geothermal resource. Geological information for the Pleasant Bayou geopressured resource in southeast Texas is most extensive among the reservoirs tested. Testing of the DOE well (Pleasant Bayou No. 2) was conducted during 1979–1983; testing resumed in May 1988. A numerical simulator is employed to synthesize and integrate the geological information, formation rock and fluid properties data from laboratory tests, and well data from the earlier (1979–1983) and the ongoing testing (1988–1991) of the well. A reservoir simulation model has been constructed which provides a detailed match to the well test history to date.

Deformation potentials of CdTe epilayers from piezo and wavelength modulation reflectivity spectra analysis

We present investigations by means of differential spectroscopy on strained epilayers of CdTe 〈001〉 grown on Cd 0.96Zn 0.04Te substrate and 〈111〉 grown on GaAs substrate. While wavelength modulation is not selective, piezomodulation quenches the heavy-hole-related structures of reflectivity of CdTe epilayers and enhances the light-hole-related ones. This fact depends on deformation potentials and we can deduce from spectra analysis the following values: b = −0.99 eV and d = −2.76 eV using the hydrostatic potential value a = −2.74 eV.

On the ellipticity of the core-mantle boundary from Earth nutations and gravity

A change in the core free nutation period from its hydrostatic value of 466d to about 433d has been inferred from analysis of both earth's annual nutation amplitude from Polaris VLBI data (Herring et al., 1986) and surface gravity in the diurnal tidal band (Zürn et al., 1986; Neuberg et al., 1986). Gwinn et al. (1986) interpret this shift as due to an excess nonhydrostatic ellipticity ed, equivalent to a change in the equatorial minus polar radius of 0.5 km. In this paper, the effect of a layer at the core-mantle boundary (CMB) on σf(and hence ed) is examined. Although the potential effect of this layer on σfis found to be large, constraints imposed from gravimetry limit changes in edto 10%. In addition, the annual nutation has a significant out-of-phase component. Mantle solid friction accounts for a large fraction of the out-of-phase nutation.

Predicting Product Lethality in Hydrostatic Retorts

ABSTRACTThe spore inactivation potential associated with diminishing cooling water temperature and gradient pressure conditions characteristic of the exit water legs of commercial hydrostatic retorts was investigated. Ball's formula for relating process temperatures to lethality failed to exploit this component of the hydrostatic regimen. Hayakawa's computer method, employing theoretical jc/fc parameters (i.e., jc= 2.04 and fc= fh,), more nearly approximated the total hydrostatic process sterilization value. A numerical heat transfer model, based on retort thermocouple data and documented factory sterilizer temperature profiles, accurately predicted the complementary lethality attending the changing environmental temperature events of the hydrostatic cooling process. The ordered pressure decline imposed by the exit leg delayed but did not eliminate product convection currents. Our conduction model did not account for this phenomenon and thus occasionally overstated total lethality by 7.5 to 8.6%.

Pleural liquid pressure in dogs measured using a rib capsule.

We have developed a minimally invasive method for measuring the hydrostatic pressure in the pleural space liquid. A liquid-filled capsule is bonded into a rib and a small hole is cut in the parietal pleura to allow direct communication between the liquid in the capsule and the pleural space. The pressure can be measured continuously by a strain gauge transducer connected to the capsule. The rib capsule does not distort the pleural space or require removal of intercostal muscle. Pneumothoraces are easily detected when they occur inadvertently on puncturing the parietal pleura. We examined the effect of height on pleural pressure in 15 anesthetized spontaneously breathing dogs. The vertical gradients in pleural pressure were 0.53, 0.42, 0.46, and 0.23 cmH2O/cm height for the head-up, head-down, supine, and prone body positions, respectively. These vertical gradients were much less than the hydrostatic value (1 cmH2O/cm), indicating that the pleural liquid is not in hydrostatic equilibrium. In most body positions the magnitudes of pleural liquid pressure interpolated to midchest level were similar to the mean transpulmonary (surface) pressure determined postmortem. This suggests that pleural liquid pressure is closely related to the lung static recoil.

Glacier Flexure and the Position of Grounding Lines: Measurements By Tiltmeter on Rutford Ice Stream, Antarctica

Two methods were used to locate the grounding line on the Rutford Ice Stream. The first method determined where the glacier was floating in hydrostatic equilibrium, while the second method measured the flexing close to the grounding line due to ocean tides. The ratio of surface elevation to ice thickness of the glacier goes through the hydrostatic equilibrium value 1 to 2 km downstream of where tidal flexing was recorded. This behaviour can be explained if the upward pressure of the sea at the base of the ice is augmented by a vertical shear-stress gradient within the glacier to overcome its weight. Simple el as tie-beam theory matches the flexure profile data if a modified elastic modulus and effective thickness are used. Tiltmeters can he used to monitor the position of the grounding line if the geometry of the flexing region can be defined.

Glacier Flexure and the Position of Grounding Lines: Measurements By Tiltmeter on Rutford Ice Stream, Antarctica

Two methods were used to locate the grounding line on the Rutford Ice Stream. The first method determined where the glacier was floating in hydrostatic equilibrium, while the second method measured the flexing close to the grounding line due to ocean tides. The ratio of surface elevation to ice thickness of the glacier goes through the hydrostatic equilibrium value 1 to 2 km downstream of where tidal flexing was recorded. This behaviour can be explained if the upward pressure of the sea at the base of the ice is augmented by a vertical shear-stress gradient within the glacier to overcome its weight. Simple el as tie-beam theory matches the flexure profile data if a modified elastic modulus and effective thickness are used. Tiltmeters can he used to monitor the position of the grounding line if the geometry of the flexing region can be defined.

Geophysical observations pertaining to solid-state convection in the terrestrial planets

We present a broad-based review of the observational evidence that pertains to or otherwise implies solid-state convection to be occurring (or have occurred) in the interiors of the terrestrial planets. For the Earth, the motion of the plates is prima facie evidence of large-scale mantle convection. Provided we understand upper-mantle thermal conductivity correctly, heat flow beneath the old ocean basins may be too high to be transported conductively from the upper mantle through the base of the lithosphere and therefore convection on a second smaller scale might be operative. The horizontal scale of plate dimensions implies, due to typical cell aspect ratios observed in convection, that the motion extends to the core-mantle boundary. Improved global data coverage and viscoelastic modeling of isostatic rebound due to Pleistocene deglaciation imply a uniform mantle viscosity, and thus indicate that whole-mantle convection could exist. Additionally, there is some seismic evidence of lithospheric penetration to depths deeper than 700 km. We discuss some salient features and assumption boundedness of arguments for convection confined to the upper mantle and for convection which acts throughout the mantle since the vertical length scale has a profound effect upon the relevance of geophysical observations. The horizontal form of mantle convection may be fully three-dimensional with complex planform and, therefore, searching for correlative gravity patterns in the ocean basins may not be useful without additional geophysical constraints. Many long-wavelength gravity anomalies may arise from beneath the lithosphere and must be supported dynamically, although thermal convection is not a unique explanation. Topography is an additional geophysical constraint, but for wavelengths greater than a few hundred kilometers, a general lack of correlation exists between oceanic residual gravity and topography, except at specific locations such as Hawaii. Theoretical calculations predict a complex relationship between these two observational types. Oceanic gravity data alone shows no regular planform and there is no correlation with any small-scale convective pattern predicted by laboratory experiments. All of the observational evidence argues against Martian plate tectonics occurring now or over much of the history of this planet, but lack of plate tectonics is not an argument against interior convection. The Tharsis uplift on Mars may have resulted from convective processes in the mantle, and the present-day gravity anomaly associated with Tharsis must be supported by the finite strength of the lithosphere or by mantle convection. Stresses imparted by the present topographic load would be greater than a kilobar, in excess of long-term finite strength. Observed fracture patterns are probably a direct result of this load, and the key question concerns the level of resultant strain relief. The global topographic and geomorphic dichotomy between the northern and southern hemisphere required a solid-state flow process to create the accompanying center-of-figure to center-of-mass offset. Lunar heat flow values, in analogy with oceanic heat flow on the Earth, strongly imply a convective mechanism of heat transport in the interior which, based on seismic Q values, is limited to the lower mantle. The presence of moonquakes in this region does not preclude solid-state convective processes. Lunar conductivity profiles provide no information on convection because of the difficulty in conductivity modeling, uniqueness of models, and the uncertainty in the conductivity-temperature relationship. The excess oblateness of the lunar figure over the hydrostatic value does not require convective support; in fact, such a mechanism is unlikely. The presence of a dipole magnetic field on Mercury does not provide a constraint on mantle convection unless its existence can be inextricably linked to a molten core. The non-hydrostatic shape of the equatorial figure, required for the observed 3 2 resonance between Mercury's rotational and orbital periods, is most likely related to surface processes, as opposed to convection. The 3n 2 resonance implies escape from a 2 n resonance and, therefore, is related to the question of a molten core. Further dynamical data is needed to constrain interior models. Interpretation of limited radar imagery for the surface of Venus is enigmatic in terms of plate tectonics and therefore interior convection. Linear tensional and possibly compressional features are observed, but there are also crustal regions which appear to show large impact structures and are thus geologically old and may not have been recycled.

Some aspects of core formation in Mercury

Evidence for a large metallic core in Mercury is all indirect; the internal magnetic field may imply a convective dynamo; the surface geology is suggestive of large-scale differentiation; and thermal history calculations based on cosmochemical models for Mercury predict core formation. The presence of a core will not be confirmed by an accurate measure of J 2, probably two orders of magnitude larger than the hydrostatic value. Core infall on Mercury would be accompanied by an increase in planetary radius of 17 km, an increase in the mean internal temperature of 700°K, and substantial melting of the mantle. If Mercury's core differentiated from an originally homogeneous planet, such an event must predate most of the present surface. Subsequent to core formation, Mercury's radius has decreased by about 2km due primarily to cooling of the lithosphere, in agreement with the estimate by Strom and others of the amount of planetary contraction based on photogeologic measurements of length, dip and throw on the global system of lobate scarps. A convective dynamo mechanism for Mercury's magnetic field is in apparent conflict with cosmochemical models that do not predict a substantial source of heat, most probably radiogenic, in Mercury's core. Without such a heat source, the core would solidify within about 1 b.y. after core infall, producing an unacceptably large contraction in Mercury's radius.

Gas dynamics of semidetached binaries. II - The vertical structure of the stream

The letter considers the three-dimensional dynamics of the stream in semidetached binaries undergoing Roche-lobe overflow. Results of an earlier communication are generalized to include the dynamic effects in the direction perpendicular to the orbital plane. It is found that the scale height of the stream characteristically exceeds its corresponding hydrostatic value by a significant factor because the inertia of the gas prevents it from responding instantaneously to the changing gravitational field. This effect is important for the interpretation of observations relating to stream-disk impacts in cataclysmic variables and in binary X-ray sources of low total mass.

Die Physiologie der orthostatischen Regulation

The arterial blood pressure is integrated into a feedback control system and practically depends on three parameters, i. e. blood volume, heart dynamics, and peripheral resistance. When circulation is disturbed in the orthostatic, the correcting elements heart and vessels have to adapt themselves according to this demand. By standing up, the hydrostatic pressure in the arterial vessels increases rapidly in the lower body regions. The initial increase of the hydrostatic pressure will be stopped by the valves in the venous system. By means of a higher arteriovenous pressure gradient the blood flow into the lower body regions increases more than 100%. The blood flow fills the venous system within 1-2 min successively from downward to upward and opens the valves. The venous pressure in the feet can rise to the full hydrostatic value of 100 mm Hg. This change of pressure causes a volume increase of approximately 200 cm3 regarding both legs of healthy persons. In this way the circulatory blood quantity is reduced. The heart is able to put out shortly an increased cardiac output by loading off the central blood volume (lung and end-systolic volume), in order to compensate orthostatic demand. After a long upright position the cardiac output is falling under the starting value and heart frequency increases. By sympathetic stimulation the peripheral resistance increases as well.

The electric field in the solar coronal exosphere and the solar wind

The solar coronal exosphere (fixed at a level where the mean free path is comparable with the scale height) is shown to act like the sheath in a laboratory discharge that builds up an excess positive charge and electric field. Equality of flux for the charged particles (protons and electrons) at the exosphere is assumed. The exospheric electric potential (for a coronal temperature of 10 6 ° K ) is found to be about 325 V, which makes the protons virtually weightless. The exospheric sheath potential accelerates the thermal protons to a velocity of 258 km/sec with which they coast to the earth. The proton density in transit varies approximately as the inverse square law, and is 3 cm -3 near the earth. Higher velocities and densities are obtained for higher coronal temperatures. An estimate of the exospheric transition region is obtained by applying the hydrodynamic theory of ambipolar diffusion in a gravitational field to the “observed” coronal density distribution. It is found that the ratio of the electric to the gravitational force on the proton builds up from its hydrostatic value of 1 2 at 2·4R ⊚ to 1 at 8R ⊚ from the solar center.