Pressure regimes

Normal pressure regimes follow a hydrostatic fluid gradient from surface, and are approximately linear. Abnormal pressure regimes include overpressured and underpressured fluid pressures, and represent a discontinuity in the normal pressure gradient. Drilling through abnormal pressure regimes requires special care. 

Assuming a normal pressure regime, at a given depth below ground level, a certain pressure must exist which just balances the overburden pressure (OBP) due to the... 

In a normal pressure regime the pressure in a hydrocarbon accumulation is determined by the pressure gradient of the overlying water (dP / dD), which ranges from 0.435 psi/ ft (10 kPa/m) for fresh water to around 0.5 psi/ft (11.5 kPa/m) for salt saturated brine. At any depth (D), the water pressure (PJ can be determined from the following equation, assuming that the pressure at the surface datum is 14.7 psia (1 bara) ... 

In order to contain normal or abnormal pressures, a pressure seal must be present. In hydrocarbon reservoirs, there is by definition a seal at the crest of the accumulation, and the potential for abnormal pressure regimes therefore exists. 

As data of the binary diflfiision coefficient Dam(P> tne not available in many cases, one has to resort to taking the solvent self-diflfiision coefficient Dy p,T) which requires rescaling in the low-pressure regime according to... 

Borkoveo M and Berne B J 1985 Reaotion dynamios in the iow pressure regime the Kramers modei and ooiiision modeis of moieouies with many degrees of freedom J. Chem. Phys. 82 794-9... 

P(lc) only affects T) in tire intennediate pressure regime [40.104], and has no affect on the high- and... 

Equation (A3.13.54) legitimates the use of this semi-classical approximation of the molecule-field interaction in the low-pressure regime. Since /7j(t) is explicitly time dependent, the time evolution operator is more... 

Figure 4.15. Shock pressure versus specific volume for calcia and fused quartz indicating three regimes fused quartz, low-pressure regime is fused quartz, mixed phase regime, and high-pressure regime representing stishovite. In the case of calcia, the low-pressure phase is the B1 structure, mixed phase is indicated, and the high-pressure phase regime is in the B2 structure.

M. L. Bernard et al, CRAcadSci, Ser C, 272 (26), 2112-15 (1972) CA.75, 101675 (1971) A generalization of the previously described (Bernard et al, 1971) ablation theory (for AP) combustion to include AP-based solid propints provides satisfactory fits to the exptl data of M. Summerfield et al (1960), with reproduction of the two distinct pressure regimes observed in the combustion of AP-based powders between 0 and 100 bars. The solid binding agent is assumed to be easily pyrolyzable, with each mol producing several combustible gaseous mols, as in the case of pyrolytically degrading polymers... 

In the normal pressure regime, where the number of collisions is very high (according to the previous section 10 s L at 1 bar), the denominator will be dominated by the second term, and hence we find the normal result that the overall rate is first order in the concentration of A. However, at low enough pressures, the first term of the denominator becomes dominant. Suppose that A and M are the same species, then the rate of the unimolecular reaction from A to P becomes d[P] k+lT[A][A]... 

The observation of negative apparent activation energy can most simply be interpreted in terms of the competition between the adsorption and desorption of methylacetylene on the surface. This qualitative explanation is illustrated in Figure 3, where the steady-state production of trimethylbenzene is compared with the TPD trace of methylacetylene. The fall off in steady state cyclotrimerization rate matches the tail of the desorption spectrum and illustrates the role of reactant desorption at higher temperatiu-es controlling the availability of alkyne monomers and thus the overall cyclotrimerization rate in this temperatime/pressure regime. 

The approximations to use depend upon the pressure regime and the values of the equilibrium constants. This oxide is an insulator under normal conditions, and so, in the middle region of the diagram, Schottky equilibrium is dominant, that is, > Ke and the electroneutrality equation is approximated by... 

In general only one of these options will be preferred in a particular partial pressure regime depending upon the values of the various equilibrium constants. 

Detailed experimental studies on rock-forming minerals (see Chakraborty and Ganguly, 1991, and references therein) have shown that the pressure effect on elemental diffusivity cannot be neglected in petrologic studies, in which highly variable pressure regimes are commonly involved. 

This temperature may be somewhat enhanced at high-pressure regimes in light of the observed positive deviations from Vegard s law (Ganguly et al., 1993). 

---