The general form of pressure dynamics:
| (1) | p(t, {\bf r}) = p_i + \frac{qB}{4 \pi \sigma} \left[ - 2 S + F \left(\frac{r^2}{4 \chi t} \right) \right] |
suggest that isobar
| (2) | p(t, {\bf r}) = p_i + \frac{qB}{4 \pi \sigma} \left[ - 2 S + F \left(\frac{r^2}{4 \chi t} \right) \right] = \rm const |
will be honouring the following equation:
| (3) | \frac{r^2}{4 \chi t} = \rm const |
or
| (4) | r(t) = r_w + 2 \sqrt{\chi t} |
which means it will be moving with the phase velocity (see also Formation Pressure Dynamics):
| (5) | u_{p= {\rm const}} = \sqrt{\frac{\chi}{t}} |
and slowing down in time.
The practical range for this velocity is around 3 · 10-6 m/s (circa 100 metres per year) which is much higher than actual fluid propagation in typical subsurface reservoirs.
This makes pressure pulsation an effective reservoir scanning technique.