Borehole (Downhole or THP) pressure survey based on the varying pressure response to the varying 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:
| (1) | q=q_0 \cdot \cos \left(\frac{2 \pi \, t}{T} \right) |
| (2) | p=p_0 \cdot \cos \left(\frac{2 \pi \, t}{T} + \delta \right) |
where
L | distance between the pint of flow variation and point of pressure response, this is going to be well radius L=r_w for Self-Pulse Test and distance between generating and receiving well L= \sqrt{ \left({\bf r}_{\rm Generator} - {\bf r}_{\rm Receiver} \right ) ^2} for Pressure Pulse Interference Test | ||
|---|---|---|---|
| phase shift related to the pressure response delay to the flowrate variation | ||
| pressure response to the flowrate variation | ||
| transmissbility | ||
| pressure diffusivity |
In case of non-harmonic the pressure pulse response is being matched by numerical model.