Lapses

If the original field development plan was not based on a 3-D seismic survey (which would be a commonly used tool for new fields nowadays), then it would now be normal practice to shoot a 3-D survey for development purposes. The survey would help to provide definition of the reservoir structure and continuity (faulting and the extension of reservoir sands), which is used to better locate the development wells. In some cases time-lapse 3-D seismic 4D surveys carried out a number of years apart, see Section 2) is used to track the displacement of fluids in the reservoir. 

Hydrocarbon-water contact movement in the reservoir may be determined from the open hole logs of new wells drilled after the beginning of production, or from a thermal decay time (TDT) log run in an existing cased production well. The TDT is able to differentiate between hydrocarbons and saline water by measuring the thermal decay time of neutrons pulsed into the formation from a source in the tool. By running the TDT tool in the same well at intervals of say one or two years (time lapse TDTs), the rate of movement of the hydrocarbon-water contact can be tracked. This is useful in determining the displacement in the reservoir, as well as the encroachment of an aquifer. 

Figure Bl.19.7. A series of time-lapse STM topographic images at room temperature showing a 40 mn x 40 mn area of Au(l 11). The time per frame is 8 mm, and each took about 5 min to scan. The steps shown are one atomic unit in height. The second frame shows craters left after tip-sample contact, which are two and three atoms deep. During a 2 h period the small craters have filled completely with diflhismg atoms, while the large craters continue to fill. (Taken from [29], figure 1.)...

Many experimental techniques now provide details of dynamical events on short timescales. Time-dependent theory, such as END, offer the capabilities to obtain information about the details of the transition from initial-to-final states in reactive processes. The assumptions of time-dependent perturbation theory coupled with Fermi s Golden Rule, namely, that there are well-defined (unperturbed) initial and final states and that these are occupied for times, which are long compared to the transition time, no longer necessarily apply. Therefore, truly dynamical methods become very appealing and the results from such theoretical methods can be shown as movies or time lapse photography. 

In applying minimal END to processes such as these, one finds that different initial conditions lead to different product channels. In Figure 1, we show a somewhat truncated time lapse picture of a typical trajectory that leads to abstraction. In this rendering, one of the hydrogens of NHaD" " is hidden. As an example of properties whose evolution can be depicted we display interatomic distances and atomic electronic charges. Obviously, one can similarly study the time dependence of various other properties during the reactive encounter. 

When the actual temperature-decline-with-altitude is greater than 9.8°C/1000 m, the atmosphere is unstable, the Cj s become larger, and the concentrations of poUutants lower. As the lapse rate becomes smaUer, the dispersive capacity of the atmosphere declines and reaches a minimum when the lapse rate becomes positive. At that point, a temperature inversion exists. Temperature inversions form every evening in most places. However, these inversions are usuaUy destroyed the next morning as the sun heats the earth s surface. Most episodes of high poUutant concentrations are associated with multiday inversions. 

Fig. 8. Characteristic plume patterns where (--) represents dry-adiabatic lapse rate and (—), air (a) fanning (b) fumigation (c) lofting and (d) looping.

The nonwovens iadustry also uses a saline repeUency test, especiaUy for medical fabrics. Fabrics are evaluated for the lapsed time before wetting when a 115-mm column of water ia a mason jar is appUed to the surface (INDA Standard Test 80.5-92). 

Constant vigilance is required to prevent lapses in such administrative procedures. 

Lapse Rate and Atmospheric Stability Apart from mechanical interference with the steady flow of air caused by buildings and other obstacles, the most important fac tor that influences the degree of turbulence and hence the speed of diffusion in the lower air is the varia-... 

From the viewpoint of air pollution, both stable surface layers and low-level inversions are undesirable because they minimize the rate of dilution of contaminants in the atmosphere. Even though the surface layer may be unstable, a low-level inversion will act as abarrier to vertical mixing, and contaminants will accumulate in the surface layer below the inversion. Stable atmospheric conditions tend to be more frequent and longest in persistence in the autumn, but inversions and stable lapse rates are prevalent at all seasons of the year. 

FIG. 25-4 Stability criteria with measured lapse rate. 

ADIABATIC LAPSE RATE ATMOSPHERIC LAPSE RATE... 

FIG. 25-5 Characteristic lapse rates under inversion conditions. 

Weak lapse—coning (slightly unstable or neutral)... 

Inversion below, lapse aloft—lofting (transition from unstable to stable)... 

This condition occurs during transition from lapse to inversion and should be observed most frequently near sunset it maybe very transitory or persist for several hours. The shaded zone of strong effluent concentration is caused by trapping by the inversion of effluent carried into the stable layer by turbulent eddies that penetrate the layer for a short distance. 

Lapse below, inversion aloft—fumigation (transition from stable to unstable)... 

This occurs when the nocturnal inversion is dissipated by heat from the morning sun. The lapse layer usually starts at the ground and works its way upward (less rapidly in winter than in summer). Fumigation may also occur in sea-breeze circulations during late morning or early afternoon. The shaded zone of strong concentration is that portion of the plume which has not yet been mixed downward. 

FIG. 25-6 Lapse-rate characteristics of atmospheric-diffusion transport of stack emissions. 

Most accidents do not occur because we do not know how to prevent them but because we do not use the information that is available. The recommendations made after an accident are forgotten when the people involved have left the plant the procedures they introduced are allowed to lapse, the equipment they installed is no longer used, and the accident happens again. The following actions can prevent or reduce this loss of information. 

This time allows the fault current to reach its peak and therefore all the equipment, devices and components protected by sucb a device must be suitable for the full fault level of the system. While the tripping lime is usually in milliseconds the duration of fault, /sc- S considered as one or three seconds. The longer duration than necessary is to account for the various time lapses that may occur... 

Low-frequency potential deviations have to be taken into account with increased corrosion rate if the protection criterion according to Eq. (2-39) occasionally lapses. It is insufficient if only the average value of the potential over time remains more negative than the protection potential [38]. 

Thus air cools as it rises and warms as it descends. Since we have assumed an adiabatic process, -ATIAz defines the dry adiabatic process lapse rate, a constant equal to 0.0098 K/m, is nearly 1 K/lOO m or 5.4°F/1000 ft. 

If an ascending air parcel reaches saturation, the addition of latent heat from condensing moisture will partially overcome the cooling due to expansion. Therefore, the saturated adiabatic lapse rate (of cooling) is smaller than y. ... 

Comparing the temperature of this parcel to that of the surrounding environment (Fig. 17-6), it is seen that in rising from 100 to 300 m, the parcel undergoes the temperature change of the dry adiabatic process lapse rate. The dashed line is a dry adiabatic line or dry adiabat. Suppose that... 

Fig. 17-6. Temperature of a parcel of air forced to rise 200 m compared to the superadiabatic environmental lapse rate. Since the parcel is still warmer than the environment, it will continue to rise.

---