Compressible fluids static pressure

A static bottom hole pressure survey (SBHP) is useful for determining the reservoir pressure near the well, undisturbed by the effects of production. This often cannot be achieved by simply correcting a surface pressure measurement, because the tubing contents may be unknown, or the tubing contains a compressible fluid whose density varies with pressure (which itself has an unknown profile). 

Pressure Safety Valve (PSV) A safety valve is a spring loaded valve actuated by static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used with compressible fluids. 

For compressible fluids flowng through nozzles and orifices use Figures 2-17 and 2-18, using hL or AP as differential static head or pressure differential across taps located one diameter upstream at 0.5 diameters dow nstream from the inlet face of orifice plate or nozzle, when values of C are taken from Figures 2-17 and 2-18 [3]. For any fluid ... 

Simmer the audible or visible escape of fluid between the seat/disk of a pressure-relieving valve at an inlet static pressure below the popping pressure, but at no measurable capacity of flow. For compressible fluid service. 

Chatter, simmer or flutter Abnormal, rapid reciprocating motion of the movable parts of a PRV in which the disc makes rapid contacts with the seat. This results in audible and/or visible escape of compressible fluid between the seat and the disc at an inlet static pressure around the set pressure and at no measurable capacity, damaging the valve rapidly. 

In the first set of experiments, the known effect of static pressure on cavitation was utilized. It is known that cavitation in fluids and porous media can be suppressed at high pressures. This effect is believed to occur due to the dissolution or collapse of the gaseous nuclei under the influence of pressure. Sonophoresis experiments were performed using skin compressed at 30 atm (between two smooth glass plates soaked in water placed in a compression press for two hours prior to sonophoresis experiments). They found that while application of ultrasound (IMHz, 2W/cm continuous) enhances estradiol permeability of the normal human epidermis by 13-fold, the corresponding enhancement for compressed skin is only about 1.75-fold. 

Kita T, Uosaki Y, Moriyoshi T. Static relative permittivity of some compressed fluids. In Taniguchi Y, Senoo M, Hara K, eds. High Pressure Liquids and Solutions. Amsterdam Elsevier, 1994 181-198. 

A common scheme for measuring the liquid depth in tajnks is shown in Fig. 2.37. Compressed air or nitrogen bubbles slowly through a jdip tube into the liquid. The gas flow rate is so low that the gas may be considered a static fluid. The pressure gauge is 6 ft above the end of the dip tube. 

Static methods. In which the system of interest is enclosed in a magnetically stirred variable volume cell [64, 76] which in some cases contains a window. The temperature and pressure within the cell are accurately metered. The cell volume may be changed either using a mercury piston or a mechanical piston and samples of the fluid phases present may be obtained, if required, under conditions of constant temperature and pressure by suitably reducing the cell volume. In the windowed cell version [76] sampling is unnecessary for binary systems since the cell may be charged with known amounts of the two components and conditions adjusted to obtain trace presence only of one of the phases. In this way the dew- and bubble-point curves for binary systems may be established and similarly the solubilities of solids in compressed fluids may be determined. 

In general the net macroscopic pressure tensor is determined by two different molecular effects One pressure tensor component associated with the pressure and a second one associated with the viscous stresses. For a fluid at rest, the system is in an equilibrium static state containing no velocity or pressure gradients so the average pressure equals the static pressure everywhere in the system. The static pressure is thus always acting normal to any control volume surface area in the fluid independent of its orientation. For a compressible fluid at rest, the static pressure may be identified with the pressure of classical thermodynamics as may be derived from the diagonal elements of the pressure tensor expression (2.189) when the equilibrium distribution function is known. On the assumption that there is local thermodynamic equilibrium even when the fluid is in motion this concept of stress is retained at the macroscopic level. For an incompressible fluid the thermodynamic, or more correctly thermostatic, pressure cannot be deflned except as the limit of pressure in a sequence of compressible fluids. In this case the pressure has to be taken as an independent dynamical variable [2] (Sects. 5.13-5.24). 

This equation applies to any incompressible or compressible static fluid. For an incompressible hquid, pressure varies linearly with depth. For compressible gases, p is obtained by integration accounting for the variation of p with z. 

In principle, this is the same as for single-phase flow. For example in steady, fully developed, isothermal flow of an incompressible fluid in a straight pipe of constant cross section, friction has to be overcome as does the static head unless the pipe is horizontal, however there is no change of momentum and consequently the accelerative term is zero. In the case of compressible flow, the gas expands as it flows from high pressure to low pressure and, by continuity, it must accelerate. In Chapter 6 this was noted as an increase in the kinetic energy. 

PRESSURE. If a body of fluid is at rest, the forces are in equilibrium or the fluid is in static equilibrium. The types of force that may aci on a body are shear or tangential force, tensile force, and compressive force. Fluids move continuously under the action of shear or tangential forces. Thus, a fluid at rest is free in each part from shear forces one fluid layer does not slide relative to an adjacent layer. Fluids can be subjected to a compressive stress, which is commonly called pressure. The term may be defined as force per unit area. The pressure units may be dynes per square centimeter, pounds per square foot, torr. mega-Pascals, etc. Atmospheric pressure is the force acting upon a unit area due to the weight of the atmosphere. Gage pressure is the difference between the pressure of the fluid measured (at some point) and atmospheric pressure. Absolute pressure, which can be measured by a mercury barometer, is the sum of gage pressure plus atmospheric pressure. 

Kg/p = Vp — (4/3)V. This new parameter (sometimes thought of as the P-wave velocity of an equivalent fluid, for which G = 0) can be determined directly from static compression data V = Kg/p = (1 + Tay)(bP/bp)p. The bulk sound velocity possesses another desirable feature, in that it can also be constrained indirectly through chemical equilibrium experiments. Chemical equilibria describe free energy minima the pressure dependence of free energy is described by the molar volume, and the pressure dependence of volume (or density) is described by Kp and hence V. Thus, experimental determinations of equilibrium phase boundaries can... 

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