Borehole (Downhole or THP) pressure survey based on the pressure response to the periodic flow rate variations (also called "cycles" or "pulses" ).

The usual practise is to create 3 - 5 pulses.

The pressure response is recorded in

• the same well where the flowrate is varying ( and in this case is called Self-Pulse Test) 

or

• in the offset well (an in this case is called Pressure Pulse Interference Test)

In case of harmonic pulsations and sufficiently long pressure-rate delay and a simple diffusion model (single-bed homogeneous reservoir without boundary) the test data can be approximated by analytical model:

q=q_0 \cdot \cos \left(\frac{2 \pi \, t}{T} \right)

p=p_0 \cdot \cos \left(\frac{2 \pi \, t}{T}  + \delta \right)

where

\delta = \frac{\pi}{8} + \frac{L}{\sqrt{\chi \, T}}

p_0 = \frac{q_0}{\sigma} ...

\sigma = \left< \frac{k}{\mu} \right> h

\chi = \left< \frac{k}{\mu} \right> \frac{1}{c_t \, \phi}